Qsymia

Overdose

In the event of a significant overdose with Qsymia, if the ingestion is recent, the stomach should be emptied immediately by gastric lavage or by induction of emesis. Appropriate supportive treatment should be provided according to the patient's clinical signs and symptoms.

Acute overdose of phentermine may be associated with restlessness, tremor, hyperreflexia, rapid respiration, confusion, aggressiveness, hallucinations, and panic states. Fatigue and depression usually follow the central stimulation. Cardiovascular effects include arrhythmia, hypertension or hypotension, and circulatory collapse. Gastrointestinal symptoms include nausea, vomiting, diarrhea, and abdominal cramps. Fatal poisoning usually terminates in convulsions and coma. Manifestations of chronic intoxication with anorectic drugs include severe dermatoses, marked insomnia, irritability, hyperactivity, and personality changes. A severe manifestation of chronic intoxication is psychosis, often clinically indistinguishable from schizophrenia.

Management of acute phentermine intoxication is largely symptomatic and includes lavage and sedation with a barbiturate. Acidification of the urine increases phentermine excretion. Intravenous phentolamine has been suggested for possible acute, severe hypertension, if this complicates phentermine overdosage.

Topiramate overdose has resulted in severe metabolic acidosis. Other signs and symptoms include convulsions, drowsiness, speech disturbance, blurred vision, diplopia, mentation impaired, lethargy, abnormal coordination, stupor, hypotension, abdominal pain, agitation, dizziness, and depression. The clinical consequences were not severe in most cases, but deaths have been reported after poly-drug overdoses involving gram amounts of topiramate. A patient who ingested a dose between 96 and 110 grams topiramate was admitted to hospital with coma lasting 20 to 24 hours followed by full recovery after 3 to 4 days.

Activated charcoal has been shown to adsorb topiramate in vitro. Hemodialysis is an effective means of removing topiramate from the body.

Contraindications

Qsymia is contraindicated in the following conditions:

• Pregnancy
• Glaucoma
• Hyperthyroidism
• During or within 14 days following the administration of monoamine oxidase inhibitors
• Known hypersensitivity or idiosyncrasy to the sympathomimetic amines.

Undesirable effects

The following important adverse reactions are described below and elsewhere in the labeling:

• Fetal Toxicity:
• Elevation in Heart Rate
• Suicidal Behavior and Ideation
• Acute Angle Closure Glaucoma
• Mood and Sleep Disorders
• Cognitive Impairment
• Metabolic Acidosis

Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical studies of another drug and may not reflect the rates observed in practice.

The data described herein reflects exposure to Qsymia in two, 1-year, randomized, double-blind, placebo-controlled, multicenter clinical trials, and two Phase 2 supportive trials in 2318 adult patients (936 [40.4%] patients with hypertension, 309 [13.3%] patients with type 2 diabetes, 808 [34.9%] patients with BMI greater than 40 kg/m²) exposed for a mean duration of 298 days.

Adverse reactions occurring at a rate of greater than or equal to 5% and at a rate at least 1.5 times placebo include paraesthesia, dizziness, dysgeusia, insomnia, constipation, and dry mouth.

Adverse reactions reported in greater than or equal to 2% of Qsymia-treated patients and more frequently than in the placebo group are shown in Table 3.

Table 3: Adverse Reactions Reported in Greater Than or Equal to 2% of Patients and More Frequently than Placebo during 1 Year of Treatment – Overall Study Population

Reports of paraesthesia, characterized as tingling in hands, feet, or face, occurred in 4.2%, 13.7%, and 19.9% of patients treated with Qsymia 3.75 mg/23 mg, 7.5 mg/46 mg, and 15 mg/92 mg, respectively, compared to 1.9% of patients treated with placebo. Dysgeusia was characterized as a metallic taste, and occurred in 1.3%, 7.4%, and 9.4% of patients treated with Qsymia 3.75 mg/23 mg, 7.5 mg/46 mg, and 15 mg/92 mg, respectively, compared to 1.1% of patients treated with placebo. The majority of these events first occurred within the initial 12 weeks of drug therapy; however, in some patients, events were reported later in the course of treatment. Only Qsymia-treated patients discontinued treatment due to these events (1% for paraesthesia and 0.6% for dysgeusia).

The proportion of patients in 1-year controlled trials of Qsymia reporting one or more adverse reactions related to mood and sleep disorders was 15.8%, 14.5%, and 20.6% with Qsymia 3.75 mg/23 mg, 7.5 mg/46 mg, and 15 mg/92 mg, respectively, compared to 10.3% with placebo. These events were further categorized into sleep disorders, anxiety, and depression. Reports of sleep disorders were typically characterized as insomnia, and occurred in 6.7%, 8.1%, and 11.1% of patients treated with Qsymia 3.75 mg/23 mg, 7.5 mg/46 mg, and 15 mg/92 mg, respectively, compared to 5.8% of patients treated with placebo. Reports of anxiety occurred in 4.6%, 4.8%, and 7.9% of patients treated with Qsymia 3.75 mg/23 mg, 7.5 mg/46 mg, and 15 mg/92 mg, respectively, compared to 2.6% of patients treated with placebo. Reports of depression/mood problems occurred in 5.0%, 3.8%, and 7.6% of patients treated with Qsymia 3.75 mg/23 mg, 7.5 mg/46 mg, and 15 mg/92 mg, respectively, compared to 3.4% of patients treated with placebo. The majority of these events first occurred within the initial 12 weeks of drug therapy; however, in some patients, events were reported later in the course of treatments. In the Qsymia clinical trials, the overall prevalence of mood and sleep adverse reactions was approximately twice as great in patients with a history of depression compared to patients without a history of depression; however, the proportion of patients on active treatment versus placebo who reported mood and sleep adverse reactions was similar in these two subgroups. Occurrence of depression-related events was more frequent in patients with a past history of depression across all treatment groups. However, the placebo-adjusted difference in incidence of these events remained constant between groups regardless of previous depression history.

In the 1-year controlled trials of Qsymia, the proportion of patients who experienced one or more cognitive-related adverse reactions was 2.1% for Qsymia 3.75 mg/23 mg, 5.0% for Qsymia 7.5 mg/46 mg, and 7.6% for Qsymia 15 mg/92 mg, compared to 1.5% for placebo. These adverse reactions were comprised primarily of reports of problems with attention/concentration, memory, and language (word finding). These events typically began within the first 4 weeks of treatment, had a median duration of approximately 28 days or less, and were reversible upon discontinuation of treatment; however, individual patients did experience events later in treatment, and events of longer duration.

In the 1-year controlled trials of Qsymia, the incidence of persistent treatment-emergent decreases in serum bicarbonate below the normal range (levels of less than 21 mEq/L at 2 consecutive visits or at the final visit) was 8.8% for Qsymia 3.75 mg/23 mg, 6.4% for Qsymia 7.5 mg/46 mg, and 12.8% for Qsymia 15 mg/92 mg, compared to 2.1% for placebo. The incidence of persistent, markedly low serum bicarbonate values (levels of less than 17 mEq/L on 2 consecutive visits or at the final visit) was 1.3% for Qsymia 3.75 mg/23 mg, 0.2% for Qsymia 7.5 mg/46 mg dose, and 0.7% for Qsymia 15 mg/92 mg dose, compared to 0.1% for placebo. Generally, decreases in serum bicarbonate levels were mild (average 1-3 mEq/L) and occurred early in treatment (4-week visit), however severe decreases and decreases later in treatment occurred.

In the 1-year controlled trials of Qsymia, the incidence of persistent low serum potassium values (less than 3.5 mEq/L at two consecutive visits or at the final visit) during the trial was 0.4% for Qsymia 3.75 mg/23 mg, 3.6% for Qsymia 7.5 mg/46 mg dose, and 4.9% for Qsymia 15 mg/92 mg, compared to 1.1% for placebo. Of the subjects who experienced persistent low serum potassium, 88% were receiving treatment with a non-potassium sparing diuretic.

The incidence of markedly low serum potassium (less than 3 mEq/L, and a reduction from pre-treatment of greater than 0.5 mEq/L) at any time during the trial was 0.0% for Qsymia 3.75 mg/23 mg, 0.2% for Qsymia 7.5 mg/46 mg dose, and 0.7% for Qsymia 15 mg/92 mg dose, compared to 0.0% for placebo. Persistent markedly low serum potassium (less than 3 mEq/L, and a reduction from pre-treatment of greater than 0.5 mEq/L at two consecutive visits or at the final visit) occurred in 0.0% of subjects receiving Qsymia 3.75 mg/23 mg, 0.2% receiving Qsymia 7.5 mg/46 mg dose, and 0.1% receiving Qsymia 15 mg/92 mg dose, compared to 0.0% receiving placebo.

Hypokalemia was reported by 0.4% of subjects treated with Qsymia 3.75 mg/23 mg, 1.4% of subjects treated with Qsymia 7.5 mg/46 mg, and 2.5% of subjects treated with Qsymia 15 mg/92 mg compared to 0.4% of subjects treated with placebo. “Blood potassium decreased” was reported by 0.4% of subjects treated with Qsymia 3.75 mg/23 mg, 0.4% of subjects treated with Qsymia 7.5 mg/46 mg, 1.0% of subjects treated with Qsymia 15 mg/92 mg, and 0.0% of subjects treated with placebo.

In the 1-year controlled trials of Qsymia, there was a dose-related increase from baseline, peaking between Week 4 to 8, which declined but remained elevated over baseline over 1 year of treatment. The incidence of increases in serum creatinine of greater than or equal to 0.3 mg/dL at any time during treatment was 2.1% for Qsymia 3.75 mg/23 mg, 7.2% for Qsymia 7.5 mg/46 mg, and 8.4% for Qsymia 15 mg/92 mg, compared to 2.0% for placebo. Increases in serum creatinine of greater than or equal to 50% over baseline occurred in 0.8% of subjects receiving Qsymia 3.75 mg/23 mg, 2.0% receiving Qsymia 7.5 mg/46 mg, and 2.8% receiving Qsymia 15 mg/92 mg, compared to 0.6% receiving placebo.

In the 1-year controlled trials of Qsymia, the incidence of nephrolithiasis was 0.4% for Qsymia 3.75 mg/23 mg, 0.2% for Qsymia 7.5 mg/46 mg, and 1.2% for Qsymia 15 mg/92 mg, compared to 0.3% for placebo.

In the 1-year placebo-controlled clinical studies, 11.6% of Qsymia 3.75 mg/23 mg, 11.6% of Qsymia 7.5 mg/46 mg, 17.4% of Qsymia 15 mg/92 mg, and 8.4% of placebo-treated patients discontinued treatment due to reported adverse reactions. The most common adverse reactions that led to discontinuation of treatment are shown in Table 4.

Table 4: Adverse Reactions Greater Than or Equal To 1% Leading to Treatment Discontinuation (1-Year Clinical Trials)

The following adverse reactions have been reported during post approval use of phentermine and topiramate, the components of Qsymia. Because these reactions are reported voluntarily from a population of uncertain size it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure.

Suicidal ideation, Suicidal behavior

Acute angle closure glaucoma

Increased intraocular pressure

Urticaria

Elevation of blood pressure, Ischemic events

Euphoria, Psychosis, Tremor

Changes in libido, Impotence

Bullous skin reactions (including erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis), Pemphigus

Pancreatitis

Hepatic failure (including fatalities), Hepatitis

Hyperammonemia

Hypothermia

Maculopathy

Therapeutic indications

Qsymia is indicated as an adjunct to a reduced-calorie diet and increased physical activity for chronic weight management in adult patients with an initial body mass index (BMI) of

• 30 kg/m² or greater (obese), or
• 27 kg/m² or greater (overweight) in the presence of at least one weight related comorbidity such as hypertension, type 2 diabetes mellitus, or dyslipidemia

The effect of Qsymia on cardiovascular morbidity and mortality has not been established.

The safety and effectiveness of Qsymia in combination with other products intended for weight loss, including prescription and over-the-counter drugs and herbal preparations have not been established.

Pharmacodynamic properties

Typical actions of amphetamines include central nervous system stimulation and elevation of blood pressure. Tachyphylaxis and tolerance have been demonstrated with all drugs of this class in which these phenomena have been looked for.

The effect of Qsymia on the QTc interval was evaluated in a randomized, double-blind, placebo-and active-controlled (400 mg moxifloxacin), and parallel group/crossover thorough QT/QTc study. A total of 54 healthy subjects were administered Qsymia 7.5 mg/46 mg at steady state and then titrated to Qsymia 22.5 mg/138 mg at steady state. Qsymia 22.5 mg/138 mg [a supra-therapeutic dose resulting in a phentermine and topiramate maximum concentration (Cmax) of 4-and 3-times higher than those at Qsymia 7.5 mg/46 mg, respectively] did not affect cardiac repolarization as measured by the change from baseline in QTc.

Pharmacokinetic properties

Upon oral administration of a single Qsymia 15 mg/92 mg, the resulting mean plasma phentermine maximum concentration (Cmax), time to Cmax (Tmax), area under the concentration curve from time zero to the last time with measureable concentration (AUC0-t), and area under the concentration curve from time zero to infinity (AUC0-∞) are 49.1 ng/mL, 6 hr, 1990 ng•hr/mL, and 2000 ng•hr/mL, respectively. A high fat meal does not affect phentermine pharmacokinetics for Qsymia 15 mg/92 mg. Phentermine pharmacokinetics is approximately dose-proportional from Qsymia 3.75 mg/23 mg to phentermine 15 mg/topiramate 100 mg. Upon dosing phentermine/topiramate 15/100 mg fixed dose combination capsule to steady state, the mean phentermine accumulation ratios for AUC and Cmax are both approximately 2.5.

Upon oral administration of a single Qsymia 15 mg/92 mg, the resulting mean plasma topiramate Cmax, Tmax, AUC0-t, and AUC0-∞, are 1020 ng/mL, 9 hr, 61600 ng•hr/mL, and 68000 ng•hr/mL, respectively. A high fat meal does not affect topiramate pharmacokinetics for Qsymia 15 mg/92 mg. Topiramate pharmacokinetics is approximately dose-proportional from Qsymia 3.75 mg/23 mg to phentermine 15 mg/topiramate 100 mg. Upon dosing phentermine 15 mg/topiramate 100 mg fixed dose combination capsule to steady state, the mean topiramate accumulation ratios for AUC and Cmax are both approximately 4.0.

Phentermine

Phentermine is 17.5% plasma protein bound. The estimated phentermine apparent volume of distribution (Vd/F) is 348 L via population pharmacokinetic analysis.

Topiramate

Topiramate is 15 -41% plasma protein bound over the blood concentration range of 0.5 to 250 μg/mL. The fraction bound decreased as blood topiramate increased. The estimated topiramate Vc/F (volume of the central compartment), and Vp/F (volume of the peripheral compartment) are 50.8 L, and 13.1 L, respectively, via population pharmacokinetic analysis.

Phentermine

Phentermine has two metabolic pathways, namely p-hydroxylation on the aromatic ring and N-oxidation on the aliphatic side chain. Cytochrome P450 (CYP) 3A4 primarily metabolizes phentermine but does not show extensive metabolism. Monoamine oxidase (MAO)-A and MAO-B do not metabolize phentermine. Seventy to 80% of a dose exists as unchanged phentermine in urine when administered alone. The mean phentermine terminal half-life is about 20 hours. The estimated phentermine oral clearance (CL/F) is 8.79 L/h via population pharmacokinetic analysis.

Topiramate

Topiramate does not show extensive metabolism. Six topiramate metabolites (via hydroxylation, hydrolysis, and glucuronidation) exist, none of which constitutes more than 5% of an administered dose. About 70% of a dose exists as unchanged topiramate in urine when administered alone. The mean topiramate terminal half-life is about 65 hours. The estimated topiramate CL/F is 1.17 L/h via population pharmacokinetic analysis.

Fertility, pregnancy and lactation

Pregnancy Category X

Qsymia is contraindicated in pregnant women. The use of Qsymia can cause fetal harm and weight loss offers no potential benefit to a pregnant woman. Available epidemiologic data indicate an increased risk in oral clefts (cleft lip with or without cleft palate) with first trimester exposure to topiramate, a component of Qsymia. When multiple species of pregnant animals received topiramate at clinically relevant doses, structural malformations, including craniofacial defects, and reduced fetal weights occurred in offspring.

If this drug is used during pregnancy, or if a patient becomes pregnant while taking this drug, treatment should be discontinued immediately and the patient should be apprised of the potential hazard to a fetus.

There is a Qsymia Pregnancy Surveillance Program to monitor maternal-fetal outcomes of pregnancies that occur during Qsymia therapy. Healthcare providers and patients are encouraged to report pregnancies by calling 1-888-998-4887.

Oral clefts occur from the fifth through the ninth week of gestation. The lip is formed between the beginning of the fifth week to the seventh week of gestation, and the palate is formed between the beginning of the sixth week through the ninth week of gestation.

A minimum weight gain, and no weight loss, is currently recommended for all pregnant women, including those who are already overweight or obese, due to the obligatory weight gain that occurs in maternal tissues during pregnancy.

Qsymia can cause metabolic acidosis. The effect of topiramate-induced metabolic acidosis has not been studied in pregnancy; however, metabolic acidosis in pregnancy (due to other causes) can cause decreased fetal growth, decreased fetal oxygenation, and fetal death, and may affect the fetus' ability to tolerate labor.

Data evaluating the risk of major congenital malformations and oral clefts with topiramate (a component of Qsymia) exposure during pregnancy is available from the North American Anti-Epileptic Drug (NAAED) Pregnancy Registry and from several larger retrospective epidemiologic studies. The NAAED Pregnancy Registry suggested an estimated increase in risk for oral clefts of 9.60 (95% CI 3.60 -25.70). Larger retrospective epidemiology studies showed that topiramate monotherapy exposure in pregnancy is associated with an approximately two to five-fold increased risk of oral clefts (Table 5). The FORTRESS study, sponsored by the maker of Qsymia, found an excess risk of 1.5 (95% CI = -1.1 to 4.1) oral cleft cases per 1,000 infants exposed to topiramate during the first trimester.

Table 5: Summary of Studies Evaluating the Association of Topiramate in Utero Exposure and Oral Clefts and Major Congenital Malformations

Phentermine/Topiramate

Embryo-fetal development studies have been conducted in rats and rabbits with combination phentermine and topiramate treatment. Phentermine and topiramate co-administered to rats during the period of organogenesis caused reduced fetal body weights but did not cause fetal malformations at the maximum dose of 3.75 mg/kg phentermine and 25 mg/kg topiramate [approximately 2 times the maximum recommended human dose (MRHD) based on area under the curve (AUC) estimates for each active ingredient]. In a similar study in rabbits, no effects on embryo-fetal development were observed at approximately 0.1 times (phentermine) and 1 time (topiramate) clinical exposures at the MRHD based on AUC. Significantly lower maternal body weight gain was recorded at these doses in rats and rabbits.

A pre-and post-natal development study was conducted in rats with combination phentermine and topiramate treatment. There were no adverse maternal or offspring effects in rats treated throughout organogenesis and lactation with 1.5 mg/kg/day phentermine and 10 mg/kg/day topiramate (approximately 2 and 3 times clinical exposures at the MRHD, respectively, based on AUC). Treatment with higher doses of 11.25 mg/kg/day phentermine and 75 mg/kg/day topiramate (approximately 5 and 6 times maximum clinical doses based on AUC, respectively) caused reduced maternal body weight gain and offspring toxicity. Offspring effects included lower pup survival after birth, increased limb and tail malformations, reduced pup body weight and delayed growth, development, and sexual maturation without affecting learning, memory, or fertility and reproduction. The limb and tail malformations were consistent with results of animal studies conducted with topiramate alone.

Phentermine

Animal reproduction studies have not been conducted with phentermine. Limited data from studies conducted with the phentermine/topiramate combination indicate that phentermine alone was not teratogenic but resulted in lower body weight and reduced survival of offspring in rats at 5-fold the MRHD of Qsymia, based on AUC.

Topiramate

Topiramate causes developmental toxicity, including teratogenicity, at clinically relevant doses.

Qualitative and quantitative composition

Qsymia capsules are formulated in the following four strength combinations (phentermine mg/topiramate mg extended-release):

• 3.75 mg/23 mg [Purple cap imprinted with VIVUS, Purple body imprinted with 3.75/23]
• 7.5 mg/46 mg [Purple cap imprinted with VIVUS, Yellow body imprinted with 7.5/46]
• 11.25 mg/69 mg [Yellow cap imprinted with VIVUS, Yellow body imprinted with 11.25/69]
• 15 mg/92 mg [Yellow cap imprinted with VIVUS, White body imprinted with 15/92]

Qsymia is available as phentermine hydrochloride (expressed as the weight of the free base)/topiramate extended-release gelatin capsules in the following strengths and colors:

• 3.75 mg/23 mg [Purple cap imprinted with VIVUS, Purple body imprinted with 3.75/23]
• 7.5 mg/46 mg [Purple cap imprinted with VIVUS, Yellow body imprinted with 7.5/46]
• 11.25 mg/69 mg [Yellow cap imprinted with VIVUS, Yellow body imprinted with 11.25/69]
• 15 mg/92 mg [Yellow cap imprinted with VIVUS, White body imprinted with 15/92]

The capsules are supplied as follows:

Store at controlled room temperature, 15°C to 25°C (59°F to 77°F). Keep container tightly closed and protect from moisture.

VIVUS, Inc 351 East Evelyn Avenue Mountain View, CA 94041 USA. Issued: 09/2014

Special warnings and precautions for use

Included as part of the PRECAUTIONS section.

Qsymia can cause fetal harm. Data from pregnancy registries and epidemiology studies indicate that a fetus exposed to topiramate, a component of Qsymia, in the first trimester of pregnancy has an increased risk of oral clefts (cleft lip with or without cleft palate). If Qsymia is used during pregnancy or if a patient becomes pregnant while taking Qsymia, treatment should be discontinued immediately, and the patient should be apprised of the potential hazard to a fetus. Females of reproductive potential should have a negative pregnancy test before starting Qsymia and monthly thereafter during Qsymia therapy. Females of reproductive potential should use effective contraception during Qsymia therapy.

Because of the teratogenic risk associated with Qsymia therapy, Qsymia is available through a limited program under the REMS. Under the Qsymia REMS, only certified pharmacies may distribute Qsymia. Further information, is available at www.QsymiaREMS.com or by telephone at 1-888-998-4887.

Qsymia can cause an increase in resting heart rate.

A higher percentage of Qsymia-treated overweight and obese adults experienced heart rate increases from baseline of more than 5, 10, 15, and 20 beats per minute (bpm) compared to placebo-treated overweight and obese adults. Table 2 provides the numbers and percentages of patients with elevations in heart rate in clinical studies of up to one year.

Table 2: Number and Percentage of Patients with an Increase in Heart Rate at a Single Time Point from Baseline

The clinical significance of a heart rate elevation with Qsymia treatment is unclear, especially for patients with cardiac and cerebrovascular disease (such as patients with a history of myocardial infarction or stroke in the previous 6 months, life-threatening arrhythmias, or congestive heart failure).

Regular measurement of resting heart rate is recommended for all patients taking Qsymia, especially patients with cardiac or cerebrovascular disease or when initiating or increasing the dose of Qsymia. Qsymia has not been studied in patients with recent or unstable cardiac or cerebrovascular disease and therefore use is not recommended.

Patients should inform healthcare providers of palpitations or feelings of a racing heartbeat while at rest during Qsymia treatment. For patients who experience a sustained increase in resting heart rate while taking Qsymia, the dose should be reduced or Qsymia discontinued.

Antiepileptic drugs (AEDs), including topiramate, a component of Qsymia, increase the risk of suicidal thoughts or behavior in patients taking these drugs for any indication. Patients treated with Qsymia should be monitored for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior. Discontinue Qsymia in patients who experience suicidal thoughts or behaviors.

Avoid Qsymia in patients with a history of suicidal attempts or active suicidal ideation.

Pooled analyses of 199 placebo-controlled clinical studies (monotherapy and adjunctive therapy, median treatment duration 12 weeks) of 11 different AEDs across several indications showed that patients randomized to one of the AEDs had approximately twice the risk (adjusted Relative Risk 1.8, 95% Confidence Interval [CI] 1.2, 2.7) of suicidal thinking or behavior compared to patients randomized to placebo. The estimated incidence rate of suicidal behavior or ideation among 27,863 AED-treated patients was 0.43%, compared to 0.24% among 16,029 placebo-treated patients, representing an increase of approximately one case of suicidal thinking or behavior for every 530 patients treated. There were four suicides in AED-treated patients in the trials and none in placebo treated patients, but the number is too small to allow any conclusion about AED effect on suicide.

The increased risk of suicidal thoughts or behavior with AEDs was observed as early as 1 week after starting drug treatment with AEDs and persisted for the duration of treatment assessed. Because most trials included in the analysis did not extend beyond 24 weeks, the risk of suicidal thoughts or behavior beyond 24 weeks could not be assessed.

The risk of suicidal thoughts or behavior was generally consistent among drugs in the data analyzed. The finding of increased risk with AEDs of varying mechanisms of action and across a range of indications suggests that the risk applies to all AEDs used for any indication. The risk did not vary substantially by age (5 to 100 years) in the clinical trials analyzed.

A syndrome consisting of acute myopia associated with secondary angle closure glaucoma has been reported in patients treated with topiramate, a component of Qsymia. Symptoms include acute onset of decreased visual acuity and/or ocular pain. Ophthalmologic findings can include myopia, anterior chamber shallowing, ocular hyperemia (redness), and increased intraocular pressure. Mydriasis may or may not be present. This syndrome may be associated with supraciliary effusion resulting in anterior displacement of the lens and iris, with secondary angle closure glaucoma. Symptoms typically occur within 1 month of initiating treatment with topiramate but may occur at any time during therapy. The primary treatment to reverse symptoms is immediate discontinuation of Qsymia. Elevated intraocular pressure of any etiology, if left untreated, can lead to serious adverse events including permanent loss of vision.

Qsymia can cause mood disorders, including depression, and anxiety, as well as insomnia. Patients with a history of depression may be at increased risk of recurrent depression or other mood disorders while taking Qsymia. The majority of these mood and sleep disorders resolved spontaneously, or resolved upon discontinuation of dosing.

For clinically significant or persistent symptoms consider dose reduction or withdrawal of Qsymia. If patients have symptoms of suicidal ideation or behavior, discontinue Qsymia.

Qsymia can cause cognitive dysfunction (e.g., impairment of concentration/attention, difficulty with memory, and speech or language problems, particularly word-finding difficulties). Rapid titration or high initial doses of Qsymia may be associated with higher rates of cognitive events such as attention, memory, and language/word-finding difficulties.

Since Qsymia has the potential to impair cognitive function, patients should be cautioned about operating hazardous machinery, including automobiles, until they are reasonably certain Qsymia therapy does not affect them adversely. If cognitive dysfunction persists consider dose reduction or withdrawal of Qsymia for symptoms that are moderate to severe, bothersome, or those which fail to resolve with dose reduction.

Hyperchloremic, non-anion gap, metabolic acidosis (decreased serum bicarbonate below the normal reference range in the absence of chronic respiratory alkalosis) has been reported in patients treated with Qsymia.

Conditions or therapies that predispose to acidosis (i.e., renal disease, severe respiratory disorders, status epilepticus, diarrhea, surgery or ketogenic diet) may be additive to the bicarbonate lowering effects of topiramate. Concomitant use of Qsymia and a carbonic anhydrase inhibitor (e.g., zonisamide, acetazolamide, or dichlorphenamide) may increase the severity of metabolic acidosis and may also increase the risk of kidney stone formation. Therefore, if Qsymia is given concomitantly with another carbonic anhydrase inhibitor to a patient with a predisposing condition for metabolic acidosis the patient should be monitored for the appearance or worsening of metabolic acidosis.

Some manifestations of acute or chronic metabolic acidosis may include hyperventilation, nonspecific symptoms such as fatigue and anorexia, or more severe sequelae including cardiac arrhythmias or stupor. Chronic, untreated metabolic acidosis may increase the risk for nephrolithiasis or nephrocalcinosis, and may also result in osteomalacia (referred to as rickets in pediatric patients) and/or osteoporosis with an increased risk for fractures. The effect of Qsymia on growth and bone-related sequelae has not been systematically investigated in long-term, placebo-controlled trials.

Measurement of electrolytes including serum bicarbonate prior to starting Qsymia and during Qsymia treatment is recommended. In Qsymia clinical trials, the peak reduction in serum bicarbonate occurred by week 4, and in most subjects there was a correction of bicarbonate by week 56, without any change to study drug. However, if persistent metabolic acidosis develops while taking Qsymia, reduce the dose or discontinue Qsymia.

Qsymia can cause an increase in serum creatinine. Peak increases in serum creatinine were observed after 4 to 8 weeks of treatment. On average, serum creatinine gradually declined but remained elevated over baseline creatinine values. Elevations in serum creatinine often signify a decrease in renal function, but the cause for Qsymia-associated changes in serum creatinine has not been definitively established. Therefore, measurement of serum creatinine prior to starting Qsymia and during Qsymia treatment is recommended. If persistent elevations in creatinine occur while taking Qsymia, reduce the dose or discontinue Qsymia.

Weight loss may increase the risk of hypoglycemia in patients with type 2 diabetes mellitus treated with insulin and/or insulin secretagogues (e.g., sulfonylureas). Qsymia has not been studied in combination with insulin. Measurement of blood glucose levels prior to starting Qsymia and during Qsymia treatment is recommended in patients with type 2 diabetes. Decreases in medication doses for antidiabetic medications which are non-glucose-dependent should be considered to mitigate the risk of hypoglycemia. If a patient develops hypoglycemia after starting Qsymia, appropriate changes should be made to the antidiabetic drug regimen.

In hypertensive patients being treated with antihypertensive medications, weight loss may increase the risk of hypotension, and associated symptoms including dizziness, lightheadedness, and syncope. Measurement of blood pressure prior to starting Qsymia and during Qsymia treatment is recommended in patients being treated for hypertension. If a patient develops symptoms associated with low blood pressure after starting Qsymia, appropriate changes should be made to the antihypertensive drug regimen.

The concomitant use of alcohol or central nervous system (CNS) depressant drugs (e.g., barbiturates, benzodiazepines, and sleep medications) with phentermine or topiramate may potentiate CNS depression or other centrally mediated effects of these agents, such as dizziness, cognitive adverse reactions, drowsiness, light-headedness, impaired coordination and somnolence. Therefore, avoid concomitant use of alcohol with Qsymia.

Abrupt withdrawal of topiramate, a component of Qsymia, has been associated with seizures in individuals without a history of seizures or epilepsy. In situations where immediate termination of Qsymia is medically required, appropriate monitoring is recommended. Patients discontinuing Qsymia 15 mg/92 mg should be gradually tapered as recommended to reduce the possibility of precipitating a seizure.

Phentermine and topiramate, the components of Qsymia, are cleared by renal excretion. Therefore, exposure to phentermine and topiramate is higher in patients with moderate (creatinine clearance [CrCl] greater than or equal to 30 and less than 50 mL/min) or severe (CrCl less than 30 mL/min) renal impairment. Adjust dose of Qsymia for both patient populations.

Qsymia has not been studied in patients with end-stage renal disease on dialysis. Avoid use of Qsymia in this patient population.

In patients with mild (Child-Pugh score 5 -6) or moderate (Child-Pugh score 7 -9) hepatic impairment, exposure to phentermine was higher compared to healthy volunteers. Adjust dose of Qsymia for patients with moderate hepatic impairment.

Qsymia has not been studied in patients with severe hepatic impairment (Child-Pugh score 10 -15). Avoid use of Qsymia in this patient population.

Use of Qsymia has been associated with kidney stone formation. Topiramate, a component of Qsymia, inhibits carbonic anhydrase activity and promotes kidney stone formation by reducing urinary citrate excretion and increasing urine pH.

Avoid the use of Qsymia with other drugs that inhibit carbonic anhydrase (e.g., zonisamide, acetazolamide, or methazolamide).

Use of topiramate by patients on a ketogenic diet may also result in a physiological environment that increases the likelihood of kidney stone formation.

Increase fluid intake to increase urinary output which can decrease the concentration of substances involved in kidney stone formation .

Oligohidrosis (decreased sweating), infrequently resulting in hospitalization, has been reported in association with the use of topiramate, a component of Qsymia. Decreased sweating and an elevation in body temperature above normal characterized these cases. Some of the cases have been reported with topiramate after exposure to elevated environmental temperatures.

Patients treated with Qsymia should be advised to monitor for decreased sweating and increased body temperature during physical activity, especially in hot weather. Caution should be used when Qsymia is prescribed with other drugs that predispose patients to heat-related disorders; these drugs include, but are not limited to, other carbonic anhydrase inhibitors and drugs with anticholinergic activity.

Qsymia can increase the risk of hypokalemia through its inhibition of carbonic anhydrase activity. In addition, when Qsymia is used in conjunction with non-potassium sparing diuretics such as furosemide (loop diuretic) or hydrochlorothiazide (thiazide-like diuretic) this may further potentiate potassium-wasting. When prescribing Qsymia, patients should be monitored for hypokalemia.

Qsymia was associated with changes in several clinical laboratory analytes in randomized, double-blind, placebo-controlled studies.

Obtain a blood chemistry profile that includes bicarbonate, creatinine, potassium, and glucose at baseline and periodically during treatment.

See FDA-approved patient labeling (Medication Guide).

Advise patients of the following:

Qsymia is indicated for chronic weight management in conjunction with a reduced-calorie diet and increased physical activity.

Qsymia is only available through certified pharmacies that are enrolled in the Qsymia certified pharmacy network. Advise patients on how to access Qsymia through certified pharmacies. Additional information may be obtained via the website www.QsymiaREMS.com or by telephone at 1-888-998-4887.

Advise patients to tell healthcare provider(s) about all medications, nutritional supplements, and vitamins (including any weight loss products) that are being taken or may be taken while on Qsymia.

Advise patients to take Qsymia in the morning with or without food.

Advise patients to start treatment with Qsymia as follows:

• Take one Qsymia 3.75 mg/23 mg capsule once daily – in the morning -for the first 14 days
• After the first 14 days is complete, take one Qsymia 7.5 mg/46 mg capsule once daily – in the morning
• Do not take Qsymia 3.75 mg/23 mg and Qsymia 7.5/46 mg capsules together

If an increase in Qsymia dose is prescribed after medical evaluation, advise patients to increase the dose of Qsymia as follows:

• Take one Qsymia 11.25 mg/69 mg capsule once daily – in the morning -for 14 days
• After the 14 days is complete, take one Qsymia 15 mg/92 mg capsule once daily – in the morning
• Do not take Qsymia 11.25/69 mg and Qsymia 15 mg/92 mg capsules together

Advise patients to discontinue the Qsymia 15 mg/92 mg dose gradually by taking one Qsymia 15 mg/92 mg capsule every other day for at least one week before stopping in order to avoid a seizure.

Qsymia can cause fetal harm and patients should avoid getting pregnant while taking Qsymia

• Pregnancy testing is recommended before starting Qsymia and monthly thereafter during therapy.
• Advise patients about effective methods of contraception, as well as the importance of using effective contraception consistently during Qsymia therapy. Advise females who become pregnant during Qsymia therapy to stop Qsymia immediately and tell their healthcare provider(s).

Either discontinue nursing or discontinue Qsymia.

• Qsymia can increase resting heart rate.
• Advise patients to report symptoms of sustained periods of heart pounding or racing while at rest to their healthcare provider(s).

Qsymia can increase the risk of mood changes, depression, and suicidal ideation.

• Advise patients to tell their healthcare provider(s) immediately if mood changes, depression, and suicidal ideation occur.

Qsymia can increase the risk of acute myopia and secondary angle closure glaucoma.

• Advise patients to report symptoms of severe and persistent eye pain or significant changes in their vision to their healthcare provider(s).

Qsymia can cause dizziness, confusion, concentration, and word-finding difficulties, or visual changes.

• Advise patients to tell their healthcare provider(s) about any changes in attention, concentration, memory, and/or difficulty finding words.
• Advise patients not to drive or operate machinery until they have gained sufficient experience on Qsymia to gauge whether it adversely affects their mental performance, motor performance, and/or vision.

Qsymia can increase the risk of metabolic acidosis.

• Advise patients to tell their healthcare provider(s) about any factors that can increase the risk of acidosis (e.g. prolonged diarrhea, surgery, and high protein/low carbohydrate diet, and/or concomitant medications such as carbonic anhydrase inhibitors).

Weight loss may increase the risk of hypoglycemia in patients with type 2 diabetes mellitus treated with insulin and/or insulin secretagogues (e.g., sulfonylureas).

• Advise patients with type 2 diabetes mellitus on anti-diabetic therapy to monitor their blood glucose levels and report symptoms of hypoglycemia to their healthcare provider(s)

The concomitant use of alcohol or central nervous system (CNS) depressant drugs (e.g., barbiturates, benzodiazepines, and sleep medications) with phentermine or topiramate may potentiate CNS depression or other centrally mediated effects of these agents, such as dizziness, cognitive adverse reactions, drowsiness, light-headedness, impaired coordination and somnolence.

• Advise patients not to drink alcohol while taking Qsymia.

Abrupt withdrawal of topiramate, a component of Qsymia, has been associated with seizures in individuals without a history of seizures or epilepsy.

• Advise patients not to abruptly stop Qsymia without first talking to their healthcare provider(s)

Use of Qsymia has been associated with kidney stone formation.

• Advise patients to increase fluid intake to increase urinary output which can decrease the concentration of substances involved in kidney stone formation.
• Advise patients to report symptoms of severe side or back pain, and/or blood in their urine to their healthcare provider(s).

Oligohidrosis (decreased sweating) has been reported in association with the use of topiramate, a component of Qsymia. Decreased sweating and an elevation in body temperature above normal characterized these cases.

• Advise patients to monitor for decreased sweating and increased body temperature during physical activity, especially in hot weather.

No animal studies have been conducted with phentermine/topiramate, the combined products in Qsymia, to evaluate carcinogenesis, mutagenesis, or impairment of fertility. The following data are based on findings in studies performed individually with phentermine or topiramate, Qsymia's two active ingredients.

Phentermine was not mutagenic or clastogenic with or without metabolic activation in the Ames bacterial mutagenicity assay, a chromosomal aberration test in Chinese hamster lung (CHL-K1) cells, or an in vivo micronucleus assay.

Rats were administered oral doses of 3, 10, and 30 mg/kg/day phentermine for 2 years. There was no evidence of carcinogenicity at the highest dose of phentermine (30 mg/kg) which is approximately 11 to 15 times the maximum recommended clinical dose of Qsymia 15 mg/92 mg based on AUC exposure.

No animal studies have been conducted with phentermine to determine the potential for impairment of fertility.

Topiramate did not demonstrate genotoxic potential when tested in a battery of in vitro and in vivo assays. Topiramate was not mutagenic in the Ames test or the in vitro mouse lymphoma assay; it did not increase unscheduled DNA synthesis in rat hepatocytes in vitro; and it did not increase chromosomal aberrations in human lymphocytes in vitro or in rat bone marrow in vivo.

An increase in urinary bladder tumors was observed in mice given topiramate (20, 75, and 300 mg/kg) in the diet for 21 months. The elevated bladder tumor incidence, which was statistically significant in males and females receiving 300 mg/kg, was primarily due to the increased occurrence of a smooth muscle tumor considered histomorphologically unique to mice. Plasma exposures in mice receiving 300 mg/kg were approximately 2 to 4 times steady-state exposures measured in patients receiving topiramate monotherapy at the MRHD of Qsymia 15 mg/92 mg. The relevance of this finding to human carcinogenic risk is uncertain. No evidence of carcinogenicity was seen in rats following oral administration of topiramate for 2 years at doses up to 120 mg/kg (approximately 4 to 10 times the MRHD of Qsymia based on AUC estimates).

No adverse effects on male or female fertility were observed in rats at doses up to 100 mg/kg or approximately 4 to 8 times male and female MRHD exposures of Qsymia based on AUC.

Pregnancy Category X

Qsymia is contraindicated in pregnant women. The use of Qsymia can cause fetal harm and weight loss offers no potential benefit to a pregnant woman. Available epidemiologic data indicate an increased risk in oral clefts (cleft lip with or without cleft palate) with first trimester exposure to topiramate, a component of Qsymia. When multiple species of pregnant animals received topiramate at clinically relevant doses, structural malformations, including craniofacial defects, and reduced fetal weights occurred in offspring.

If this drug is used during pregnancy, or if a patient becomes pregnant while taking this drug, treatment should be discontinued immediately and the patient should be apprised of the potential hazard to a fetus.

There is a Qsymia Pregnancy Surveillance Program to monitor maternal-fetal outcomes of pregnancies that occur during Qsymia therapy. Healthcare providers and patients are encouraged to report pregnancies by calling 1-888-998-4887.

Oral clefts occur from the fifth through the ninth week of gestation. The lip is formed between the beginning of the fifth week to the seventh week of gestation, and the palate is formed between the beginning of the sixth week through the ninth week of gestation.

A minimum weight gain, and no weight loss, is currently recommended for all pregnant women, including those who are already overweight or obese, due to the obligatory weight gain that occurs in maternal tissues during pregnancy.

Qsymia can cause metabolic acidosis. The effect of topiramate-induced metabolic acidosis has not been studied in pregnancy; however, metabolic acidosis in pregnancy (due to other causes) can cause decreased fetal growth, decreased fetal oxygenation, and fetal death, and may affect the fetus' ability to tolerate labor.

Data evaluating the risk of major congenital malformations and oral clefts with topiramate (a component of Qsymia) exposure during pregnancy is available from the North American Anti-Epileptic Drug (NAAED) Pregnancy Registry and from several larger retrospective epidemiologic studies. The NAAED Pregnancy Registry suggested an estimated increase in risk for oral clefts of 9.60 (95% CI 3.60 -25.70). Larger retrospective epidemiology studies showed that topiramate monotherapy exposure in pregnancy is associated with an approximately two to five-fold increased risk of oral clefts (Table 5). The FORTRESS study, sponsored by the maker of Qsymia, found an excess risk of 1.5 (95% CI = -1.1 to 4.1) oral cleft cases per 1,000 infants exposed to topiramate during the first trimester.

Table 5: Summary of Studies Evaluating the Association of Topiramate in Utero Exposure and Oral Clefts and Major Congenital Malformations

Phentermine/Topiramate

Embryo-fetal development studies have been conducted in rats and rabbits with combination phentermine and topiramate treatment. Phentermine and topiramate co-administered to rats during the period of organogenesis caused reduced fetal body weights but did not cause fetal malformations at the maximum dose of 3.75 mg/kg phentermine and 25 mg/kg topiramate [approximately 2 times the maximum recommended human dose (MRHD) based on area under the curve (AUC) estimates for each active ingredient]. In a similar study in rabbits, no effects on embryo-fetal development were observed at approximately 0.1 times (phentermine) and 1 time (topiramate) clinical exposures at the MRHD based on AUC. Significantly lower maternal body weight gain was recorded at these doses in rats and rabbits.

A pre-and post-natal development study was conducted in rats with combination phentermine and topiramate treatment. There were no adverse maternal or offspring effects in rats treated throughout organogenesis and lactation with 1.5 mg/kg/day phentermine and 10 mg/kg/day topiramate (approximately 2 and 3 times clinical exposures at the MRHD, respectively, based on AUC). Treatment with higher doses of 11.25 mg/kg/day phentermine and 75 mg/kg/day topiramate (approximately 5 and 6 times maximum clinical doses based on AUC, respectively) caused reduced maternal body weight gain and offspring toxicity. Offspring effects included lower pup survival after birth, increased limb and tail malformations, reduced pup body weight and delayed growth, development, and sexual maturation without affecting learning, memory, or fertility and reproduction. The limb and tail malformations were consistent with results of animal studies conducted with topiramate alone.

Phentermine

Animal reproduction studies have not been conducted with phentermine. Limited data from studies conducted with the phentermine/topiramate combination indicate that phentermine alone was not teratogenic but resulted in lower body weight and reduced survival of offspring in rats at 5-fold the MRHD of Qsymia, based on AUC.

Topiramate

Topiramate causes developmental toxicity, including teratogenicity, at clinically relevant doses.

The effect of Qsymia on labor and delivery in humans is unknown. The development of Qsymia-induced metabolic acidosis in the mother and/or in the fetus might affect the fetus's ability to tolerate labor.

Qsymia may be present in human milk because topiramate and amphetamines (phentermine has pharmacologic activity and a chemic

Dosage (Posology) and method of administration

Determine the patient's BMI. BMI is calculated by dividing weight (in kilograms) by height (in meters) squared. A BMI conversion chart (Table 1) based on height [inches (in) or centimeters (cm)] and weight [pounds (lb) or kilograms (kg)] is provided below.

Table 1: BMI Conversion Chart

In adults with an initial BMI of 30 kg/m² or greater or 27 kg/m² or greater when accompanied by weight-related co-morbidities such as hypertension, type 2 diabetes mellitus, or dyslipidemia prescribe Qsymia as follows:

• Take Qsymia once daily in the morning with or without food. Avoid dosing with Qsymia in the evening due to the possibility of insomnia.
• Start treatment with Qsymia 3.75 mg/23 mg (phentermine 3.75 mg/topiramate 23 mg extended-release) daily for 14 days; after 14 days increase to the recommended dose of Qsymia 7.5 mg/46 mg (phentermine 7.5 mg/topiramate 46 mg extended-release) once daily.
• Evaluate weight loss after 12 weeks of treatment with Qsymia 7.5 mg/46 mg.
  If a patient has not lost at least 3% of baseline body weight on Qsymia 7.5 mg/46 mg, discontinue Qsymia or escalate the dose, as it is unlikely that the patient will achieve and sustain clinically meaningful weight loss at the Qsymia 7.5 mg/46 mg dose.
  To escalate the dose: Increase to Qsymia 11.25 mg/69 mg (phentermine 11.25 mg/topiramate 69 mg extended-release) daily for 14 days; followed by dosing Qsymia 15 mg/92 mg (phentermine 15 mg/topiramate 92 mg extended-release) once daily.
• Evaluate weight loss following dose escalation to Qsymia 15 mg/92 mg after an additional 12 weeks of treatment.
  If a patient has not lost at least 5% of baseline body weight on Qsymia 15 mg/92 mg, discontinue Qsymia as directed, as it is unlikely that the patient will achieve and sustain clinically meaningful weight loss with continued treatment.
• Qsymia 3.75 mg/23 mg and Qsymia 11.25 mg/69 mg are for titration purposes only.

• Discontinue Qsymia 15 mg/92 mg gradually by taking a dose every other day for at least 1 week prior to stopping treatment altogether, due to the possibility of precipitating a seizure.

In patients with moderate (creatinine clearance [CrCl] greater than or equal to 30 and less than 50 mL/min) or severe (CrCl less than 30 mL/min) renal impairment dosing should not exceed Qsymia 7.5 mg/46 mg once daily. Renal impairment is determined by calculating CrCl using the Cockcroft-Gault equation with actual body weight.

In patients with moderate hepatic impairment (Child-Pugh score 7 -9), dosing should not exceed Qsymia 7.5 mg/46 mg once daily.

Interaction with other medicinal products and other forms of interaction

Phentermine

Phentermine is not an inhibitor of CYP isozymes CYP1A2, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4, and is not an inhibitor of monoamine oxidases. Phentermine is not an inducer of CYP1A2, CYP2B6, and CYP3A4. Phentermine is not a P-glycoprotein substrate.

Topiramate

Topiramate is not an inhibitor of CYP isozymes CYP1A2, CYP2A6, CYP2B6, CYP2C9, CYP2D6, CYP2E1, and CYP3A4/5. However, topiramate is a mild inhibitor of CYP2C19. Topiramate is a mild inducer of CYP3A4. Topiramate is not a P-glycoprotein substrate.

Table 6: Effect of Phentermine/Topiramate on the Pharmacokinetics of Co-administered Drugs

Table 7: Effect of Co-administered Drugs on the Pharmacokinetics of Phentermine/Topiramate

Antiepileptic Drugs

Potential interactions between topiramate and standard antiepileptic (AED) drugs were assessed in controlled clinical pharmacokinetic studies in patients with epilepsy. The effects of these interactions on mean plasma AUCs are summarized in Table 8.

In Table 8, the second column (AED concentration) describes what happens to the concentration of the AED listed in the first column when topiramate is added. The third column (topiramate concentration) describes how the co-administration of a drug listed in the first column modifies the concentration of topiramate in experimental settings when topiramate was given alone.

Table 8: Summary of AED Interactions with Topiramate

Digoxin

In a single-dose study, serum digoxin AUC was decreased by 12% with concomitant topiramate administration. The clinical relevance of this observation has not been established.

Hydrochlorothiazide

A drug-drug interaction study conducted in healthy volunteers evaluated the steady-state pharmacokinetics of hydrochlorothiazide (HCTZ) (25 mg q24h) and topiramate (96 mg q12h) when administered alone and concomitantly. The results of this study indicate that topiramate Cmax increased by 27% and AUC increased by 29% when HCTZ was added to topiramate. The clinical significance of this change is unknown. The steady-state pharmacokinetics of HCTZ were not significantly influenced by the concomitant administration of topiramate. Clinical laboratory results indicated decreases in serum potassium after topiramate or HCTZ administration, which were greater when HCTZ and topiramate were administered in combination.

Pioglitazone

A drug-drug interaction study conducted in healthy volunteers evaluated the steady-state pharmacokinetics of topiramate and pioglitazone when administered alone and concomitantly. A 15% decrease in the area under the concentration-time curve during a dosage interval at steady state (AUCτ,ss) of pioglitazone with no alteration in maximum steady-state plasma drug concentration during a dosage interval (Cmax,ss) was observed. This finding was not statistically significant. In addition, a 13% and 16% decrease in Cmax,ss and AUCτ,ss respectively, of the active hydroxy-metabolite was noted as well as a 60% decrease in Cmax,ss and AUCτ,ss of the active keto-metabolite. The clinical significance of these findings is not known. When topiramate is added to pioglitazone therapy or pioglitazone is added to topiramate therapy, careful attention should be given to the routine monitoring of patients for adequate control of their diabetic disease state.

Glyburide

A drug-drug interaction study conducted in patients with type 2 diabetes evaluated the steady-state pharmacokinetics of glyburide (5 mg/day) alone and concomitantly with topiramate (150 mg/day). There was a 22% decrease in Cmax and a 25% reduction in AUC24 for glyburide during topiramate administration. Systemic exposure (AUC) of the active metabolites, 4-trans-hydroxyglyburide (M1), and 3-cis-hydroxyglyburide (M2), was reduced by 13% and 15%, and Cmax was reduced by 18% and 25%, respectively. The steady-state pharmacokinetics of topiramate were unaffected by concomitant administration of glyburide.

Lithium

In patients, the pharmacokinetics of lithium were unaffected during treatment with topiramate at doses of 200 mg/day; however, there was an observed increase in systemic exposure of lithium (27% for Cmax and 26% for AUC) following topiramate doses up to 600 mg/day. Lithium levels should be monitored when co-administered with high-dose topiramate.

Haloperidol

The pharmacokinetics of a single dose of haloperidol (5 mg) were not affected following multiple dosing of topiramate (100 mg every 12 hours) in 13 healthy adults (6 males, 7 females).

Amitriptyline

There was a 12% increase in AUC and Cmax for amitriptyline (25 mg per day) in 18 normal subjects (9 males, 9 females) receiving 200 mg/day of topiramate. Some subjects may experience a large increase in amitriptyline concentration in the presence of topiramate and any adjustments in amitriptyline dose should be made according to the patient's clinical response and not on the basis of plasma levels.

Sumatriptan

Multiple dosing of topiramate (100 mg every 12 hrs) in 24 healthy volunteers (14 males, 10 females) did not affect the pharmacokinetics of single-dose sumatriptan either orally (100 mg) or subcutaneously (6 mg).

Risperidone

When administered concomitantly with topiramate at escalating doses of 100, 250, and 400 mg/day, there was a reduction in risperidone systemic exposure (16% and 33% for steady-state AUC at the 250 and 400 mg/day doses of topiramate). No alterations of 9-hydroxyrisperidone levels were observed. Co-administration of topiramate 400 mg/day with risperidone resulted in a 14% increase in Cmax and a 12% increase in AUC12 of topiramate. There were no clinically significant changes in the systemic exposure of risperidone plus 9-hydroxyrisperidone or of topiramate; therefore, this interaction is not likely to be of clinical significance.

Propranolol

Multiple dosing of topiramate (200 mg/day) in 34 healthy volunteers (17 males, 17 females) did not affect the pharmacokinetics of propranolol following daily 160 mg doses. Propranolol doses of 160 mg/day in 39 volunteers (27 males, 12 females) had no effect on the exposure to topiramate, at a dose of 200 mg/day of topiramate.

Dihydroergotamine

Multiple dosing of topiramate (200 mg/day) in 24 healthy volunteers (12 males, 12 females) did not affect the pharmacokinetics of a 1 mg subcutaneous dose of dihydroergotamine. Similarly, a 1 mg subcutaneous dose of dihydroergotamine did not affect the pharmacokinetics of a 200 mg/day dose of topiramate in the same study.

Diltiazem

Co-administration of diltiazem (240 mg Cardizem CD®) with topiramate (150 mg/day) resulted in a 10% decrease in Cmax and a 25% decrease in diltiazem AUC, a 27% decrease in Cmax and an 18% decrease in desacetyl diltiazem AUC, and no effect on N-desmethyl diltiazem. Co-administration of topiramate with diltiazem resulted in a 16% increase in Cmax and a 19% increase in AUC12 of topiramate.

Venlafaxine

Multiple dosing of topiramate (150 mg/day) in healthy volunteers did not affect the pharmacokinetics of venlafaxine or O-desmethyl venlafaxine. Multiple dosing of venlafaxine (150 mg extended release) did not affect the pharmacokinetics of topiramate.