There is no experience with CARDURA XL overdosage. Overdosage experience with the doxazosin IR is limited. Two adolescents who each intentionally ingested 40 mg doxazosin IR with diclofenac or paracetamol were treated with gastric lavage with activated charcoal and made full recoveries. A two-year-old child who accidentally ingested 4 mg doxazosin IR was treated with gastric lavage and remained normotensive during the five-hour emergency room observation period. A six-month-old child accidentally received a crushed 1 mg tablet of doxazosin IR and was reported to have been drowsy. A 32-year-old female with chronic renal failure, epilepsy, and depression intentionally ingested 60 mg doxazosin IR (blood level 0.9 μg/mL; normal values in hypertensives=0.02 μg/mL); death was attributed to a grand mal seizure resulting from hypotension. A 39-year-old female who ingested 70 mg doxazosin IR, alcohol, and Dalmane® (flurazepam) developed hypotension which responded to fluid therapy. The most likely manifestation of overdosage would be hypotension, for which the usual treatment would be intravenous infusion of fluid, keeping the patient in the supine position, and in certain circumstances, the administration of vasopressors. As doxazosin is highly protein bound, dialysis would not be indicated.
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 trials of another drug and may not reflect the rates observed in clinical practice.
The incidence of adverse reactions was derived from two controlled efficacy and safety trials involving 1473 BPH patients. In Study 1, CARDURA XL (n=317) was compared to doxazosin IR tablets (n=322) and to placebo (n=156). In Study 2, CARDURA XL (n=350) was compared just to doxazosin IR tablets (n=330). In both of these studies, CARDURA XL was initiated at a dose of 4 mg, which could be increased by the investigator to 8 mg after seven weeks if an adequate response was not seen. Similarly, doxazosin IR was begun at a dose of 1 mg, which was increased in all patients to 2 mg after 1 week, followed by the option to increase to 4 mg after 4 weeks, and 8 mg after 7 weeks.
The most commonly reported adverse reactions leading to discontinuation in the CARDURA XL group were: dizziness, dyspnea, asthenia, headache, hypotension, postural hypotension, and somnolence. The rates of discontinuation for adverse reactions were 6%, 7% and 3% in the CARDURA XL, doxazosin IR, and placebo groups, respectively.
Table 1 lists the incidence rates of adverse reactions derived from all reported adverse events in the two controlled studies (Studies 1 and 2) combined, at a rate greater than placebo and in 1% or more of patients treated with CARDURA XL.
TABLE 1 : Adverse Reactions, Derived from All
Adverse Events Exceeding Placebo Rate and Occurring in ≥ 1% of BPH
Patients Treated with CARDURA XL
| Body System | CARDURA XL (N = 666) |
Doxazosin IR (N = 651) |
Placebo (N = 156) |
| BODY AS A WHOLE | |||
| Abdominal Pain | 1.8% | 2.3% | 0.6% |
| Asthenia | 3.9% | 6.9% | 1.3% |
| Headache | 6.0% | 5.1% | 4.5% |
| CARDIOVASCULAR | |||
| Hypotension | 1.7% | 1.8% | 0.0% |
| Postural Hypotension | 1.2% | 2.2% | 0.6% |
| DIGESTIVE | |||
| Dyspepsia | 1.4% | 1.2% | 0.0% |
| Nausea | 1.2% | 2.3% | 0.6% |
| MUSCULOSKELETAL | |||
| Myalgia | 1.4% | 0.5% | 0.0% |
| NERVOUS | |||
| Dizziness | 5.3% | 9.1% | 1.9% |
| Somnolence | 1.5% | 1.2% | 0.0% |
| Vertigo | 1.5% | 4.1% | 0.6% |
| RESPIRATORY | |||
| Dyspnea | 1.2% | 1.2% | 0.0% |
| Respiratory Tract Infection | 4.8% | 4.5% | 1.9% |
| UROGENITAL | |||
| Urinary Tract Infection | 1.4% | 0.8% | 0.6% |
Additional adverse events reported with CARDURA XL, reported by less than 1% of patients, and those of clinical interest include: Cardiovascular System: angina pectoris, syncope, tachycardia, chest pain, palpitations; Digestive System: diarrhea; Musculoskeletal System: arthralgia; Nervous System: libido decreased; Urogenital System: impotence, dysuria.
In general, the adverse events reported in the open-label safety extension, in approximately 295 BPH patients treated for up to 37 weeks, were similar in type and frequency to the events described above in the controlled trials.
Postmarketing ExperienceThe following adverse events have been identified during post-approval use of doxazosin. 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.
Autonomic Nervous System: priapism; Cardiovascular System: cerebrovascular accidents, dizziness postural, myocardial infarction; Central and Peripheral Nervous System: hypoesthesia, paresthesia; Endocrine System: gynecomastia; Gastrointestinal System: gastrointestinal obstruction, vomiting; General Body System: fatigue, hot flushes, malaise; Heart Rate/Rhythm: bradycardia, cardiac arrhythmias; Hematopoietic: leukopenia, purpura, thrombocytopenia; Liver/Biliary System: abnormal liver function tests, hepatitis, hepatitis cholestatic, jaundice; Musculoskeletal System: muscle cramps, muscle weakness; Psychiatric: agitation, anorexia, nervousness; Respiratory System: bronchospasm aggravated; Skin Disorders: alopecia, urticaria, skin rash, pruritus; Special Senses: blurred vision, Intraoperative Floppy Iris Syndrome ; Urinary System: hematuria, micturition disorder, micturition frequency, nocturia, polyuria.
There have been rare reports of gastrointestinal irritation and gastrointestinal bleeding with use of another drug in this non-deformable sustained release formulation, although causal relationship to the drug is uncertain.
Administration of CARDURA XL to patients with symptomatic BPH resulted in a statistically significant improvement in maximum urinary flow rate.
The pharmacokinetics of CARDURA XL is different from that of doxazosin IR. CARDURA XL provides a controlled release of doxazosin over a 24-hour period.
Absorption: Pharmacokinetic parameters describing absorption following 4 and 8 mg CARDURA XL daily doses are reported in Table 2 below. The relative bioavailability of CARDURA XL compared with doxazosin IR was 54% at the 4 mg dose and 59% for the 8 mg dose.
TABLE 2 : Mean (±SD) Plasma Concentration of
Doxazosin at Steady State in Healthy Volunteers: Pharmacokinetic Parameters
| Parameter | CARDURA XL (4 mg) | CARDURA XL (8 mg) |
| Cmax (ng/mL) | 10.1 ± 5.6 | 25.8 ± 12.1 |
| AUC (0 - ∞) | 183 ± 85.5 | 472 ± 170.8 |
| Tmax (h) | 8 ± 3.7 | 9 ± 4.7 |
Food Effect: As illustrated in Figure 1, the plasma C max and AUC were approximately 32% and 18% higher, respectively, after CARDURA XL was administered in the fed state compared with the fasted state. In order to provide the most consistent exposure, CARDURA XL should be administered with breakfast.
Figure 1: Mean (+SD) Plasma
Concentration of Doxazosin Following Single Oral Doses of 8 mg CARDURA XL (Fed
and Fasted)
GI Retention Time Effect: Markedly reduced GI retention times (e.g., short bowel syndrome) may influence the pharmacokinetics of CARDURA XL and possibly result in lower plasma concentrations. Conversely, markedly prolonged GI retention times (e.g., chronic constipation) can increase systemic exposure to doxazosin and potentially result in increased adverse reactions.
Distribution: At the plasma concentrations achieved by therapeutic doses, approximately 98% of the circulating drug is bound to plasma proteins.
Metabolism: Doxazosin is extensively metabolized in the liver. In vitro studies suggest that the primary pathway for elimination is via CYP 3A4; however, CYP 2D6 and CYP 2C9 metabolic pathways also exist to a lesser extent. No in vivo drug interaction studies have been performed with CARDURA XL. Although several active metabolites of doxazosin have been identified, the pharmacokinetics of these metabolites has not been characterized.
Excretion: In a study of two subjects administered radiolabeled doxazosin IR 2 mg orally and 1 mg intravenously on two separate occasions, approximately 63% of the dose was eliminated in the feces and 9% of the dose was found in the urine. On average, only 4.8% of the dose was excreted as unchanged drug in the feces and only a trace of the total radioactivity in the urine was attributed to unchanged drug. The apparent elimination half-life of CARDURA XL is 15-19 hours.
CARDURA XL is not indicated for use in females and is not indicated for the treatment of hypertension. The limited available data with CARDURA XL in pregnant women are not sufficient to inform a drug-associated risk for major birth defects and miscarriage. No adverse developmental outcomes were observed in animal reproduction studies with oral administration of doxazosin to pregnant rats and rabbits at doses of up to 10 and 4 times, respectively, the 12 mg/day recommended dose. Postnatal development was delayed in rats at a dose of 8 times the 12 mg/day recommended dose.
DataAnimal Data
Radioactivity was found to cross the placenta following oral administration of labeled doxazosin to pregnant rats. Studies in pregnant rabbits and rats at daily oral doses of up to 41 and 20 mg/kg, respectively (plasma drug concentrations of 10 and 4 times, respectively, the human AUC exposures with a 12 mg/day therapeutic dose), during organogenesis have revealed no evidence of adverse developmental effects. A dosage regimen of 82 mg/kg/day in the rabbit was associated with reduced fetal survival. In peri-and postnatal studies in rats, postnatal development at maternal doses of 40 or 50 mg/kg/day of doxazosin (about 8 times human AUC exposure with a 12 mg/day therapeutic dose) was delayed, as evidenced by slower body weight gain and slightly later appearance of anatomical features and reflexes.
Included as part of the PRECAUTIONS section.
PRECAUTIONS Postural HypotensionPostural hypotension with or without symptoms (e.g., dizziness) may develop within a few hours following administration of CARDURA XL. However, infrequently, symptomatic postural hypotension has also been reported later than a few hours after dosing. As with other alpha-blockers, there is a potential for syncope, especially after the initial dose or after an increase in dosage strength. Patients should be warned of the possible occurrence of such events and should avoid situations where injury could result should syncope occur. Care should be taken when CARDURA XL is administered to patients with symptomatic hypotension or patients who have had a hypotensive response to other medications.
Cataract SurgeryIntraoperative Floppy Iris Syndrome (IFIS) has been observed during cataract surgery in some patients on or previously treated with alpha 1 blockers. This variant of small pupil syndrome is characterized by the combination of a flaccid iris that billows in response to intraoperative irrigation currents, progressive intraoperative miosis despite preoperative dilation with standard mydriatic drugs, and potential prolapse of the iris toward the phacoemulsification incisions. The patient's surgeon should be prepared for possible modifications to their surgical technique, such as the utilization of iris hooks, iris dilator rings, or viscoelastic substances. There does not appear to be a benefit from stopping alpha 1 blocker therapy prior to cataract surgery.
Gastrointestinal DisordersAs with any other non-deformable material, caution should be used when administering CARDURA XL to patients with preexisting severe gastrointestinal narrowing (pathologic or iatrogenic). There have been rare reports of obstructive symptoms in patients with known strictures in association with the ingestion of another drug in this non-deformable extended release formulation. Markedly increased GI retention times, as may occur in patients with chronic constipation, can increase systemic exposure to doxazosin and thereby potentially increase adverse reactions.
Prostate CancerCarcinoma of the prostate causes many of the same symptoms associated with BPH and the two disorders frequently co-exist. Carcinoma of the prostate should therefore be ruled out prior to commencing therapy with CARDURA XL.
PDE-5 InhibitorsConcomitant administration of CARDURA XL with a PDE-5 inhibitor can result in additive blood pressure lowering effects and symptomatic hypotension. Pharmacodynamic interactions between CARDURA XL and antihypertensive medications or other vasodilating agents have not been determined.
Patients With Hepatic ImpairmentCARDURA XL is not recommended for patients with severe hepatic impairment and should be administered with caution to patients with mild or moderate hepatic impairment.
Patients With Coronary InsufficiencyPatients with congestive heart failure, angina pectoris, or acute myocardial infarction within the last 6 months were excluded from the Phase 3 studies. If symptoms of angina pectoris should newly appear or worsen, CARDURA XL should be discontinued.
CYP 3A4 InhibitorsCaution should be exercised when concomitantly administering CARDURA XL with a strong CYP 3A4 inhibitor, such as atanazavir, clarithromycin, indinavir, itraconazole, ketoconazole, nefazodone, nelfinavir, ritonavir, saquinavir, telithromycin, or voriconazole.
PriapismRarely (probably less frequently than once in every several thousand patients), alpha-1 antagonists, including doxazosin, have been associated with priapism (painful penile erection, sustained for hours and unrelieved by sexual intercourse or masturbation). Because this condition can lead to permanent impotence if not promptly treated, patients must be advised about the seriousness of the condition.
Patient Counseling InformationSee FDA-approved patient labeling (PATIENT INFORMATION)
Postural HypotensionPatients should be told about the possible occurrence of symptoms related to postural hypotension, such as dizziness or syncope, when beginning therapy or when increasing dosage strength of CARDURA XL. Patients should be cautioned about driving, operating machinery, or performing hazardous tasks during this period, until the drug's effect has been determined.
PriapismInform the patient about the possibility of priapism as a result of treatment with CARDURA XL extended release tablets and other similar medications. Patients should be informed that this reaction is extremely rare, but if not brought to immediate medical attention, can lead to permanent erectile dysfunction.
Tablet AdministrationPatients should be informed that CARDURA XL extended release tablets should be swallowed whole. Patients should not chew, divide, cut, or crush tablets.
Dosing IntervalCARDURA XL should be taken each day with breakfast.
Tablet EliminationPatients should not be concerned if they occasionally notice in their stool something that looks like a tablet. In the CARDURA XL extended release tablet, the medication is contained within a nonabsorbable shell designed to release the drug at a controlled rate. When this process is completed, the empty tablet is eliminated from the body.
Nonclinical Toxicology Carcinogenesis, Mutagenesis, Impairment Of Fertility Carcinogenesis And MutagenesisDoxazosin mesylate was not carcinogenic to rats or mice when administered daily for 2 years at doses up to 40 mg/kg/day or 120 mg/kg/day, respectively. Systemic drug exposures, as measured by AUC, were approximately 34fold in rats and 16-fold in mice above the exposures at the maximum human recommended dose (MHRD) of 8 mg CARDURA XL.
Doxazosin base was not mutagenic in the in vitro bacterial Ames assays, the chromosomal aberration assay in human lymphocytes, or the mouse lymphoma assay. Doxazosin was not clastogenic in the in vivo mouse micronucleus assay. Doxazosin mesylate has not been evaluated for genotoxicity.
Fertility In MalesStudies in rats after oral administration of doxazosin base showed reduced fertility in males, which was reversible after two weeks of treatment termination at doxazosin base exposure of 13-fold above the human exposure (AUC) at the MHRD of 8 mg CARDURA XL. There have been no reports of any effects of doxazosin on male fertility in humans.
Use In Specific Populations Pregnancy Risk SummaryCARDURA XL is not indicated for use in females and is not indicated for the treatment of hypertension. The limited available data with CARDURA XL in pregnant women are not sufficient to inform a drug-associated risk for major birth defects and miscarriage. No adverse developmental outcomes were observed in animal reproduction studies with oral administration of doxazosin to pregnant rats and rabbits at doses of up to 10 and 4 times, respectively, the 12 mg/day recommended dose. Postnatal development was delayed in rats at a dose of 8 times the 12 mg/day recommended dose.
DataAnimal Data
Radioactivity was found to cross the placenta following oral administration of labeled doxazosin to pregnant rats. Studies in pregnant rabbits and rats at daily oral doses of up to 41 and 20 mg/kg, respectively (plasma drug concentrations of 10 and 4 times, respectively, the human AUC exposures with a 12 mg/day therapeutic dose), during organogenesis have revealed no evidence of adverse developmental effects. A dosage regimen of 82 mg/kg/day in the rabbit was associated with reduced fetal survival. In peri-and postnatal studies in rats, postnatal development at maternal doses of 40 or 50 mg/kg/day of doxazosin (about 8 times human AUC exposure with a 12 mg/day therapeutic dose) was delayed, as evidenced by slower body weight gain and slightly later appearance of anatomical features and reflexes.
Lactation Risk SummaryCARDURA XL is not indicated for use in females and is not indicated for the treatment of hypertension. Doxazosin is present in human milk. There is no information on the effects of CARDURA XL on the breastfeed infant or the effects on milk production.
Pediatric UseThe safety and effectiveness of CARDURA XL in pediatric patients have not been established.
Geriatric UseThe incidence of hypotension with CARDURA XL use appears to be age related and more prevalent in patients 70 years or older. At steady state, increases of 27% in maximum plasma concentrations (C max ) and 34% in the area under the concentration-time curve (AUC) were seen in the elderly ( > 65 years old) compared to the young.
Of the 666 patients with BPH who received CARDURA XL in the two controlled clinical efficacy and safety studies, 325 patients (49%) were 65 years of age or older. One hundred thirty-six patients treated with CARDURA XL (20%) were > 70 years of age. In these two studies, the cumulative incidence of hypotension appeared to be age related. The reason for an increased incidence of hypotension in patients older than 70 years of age may be related to a modest increase in systemic exposure to doxazosin , to an increased propensity to orthostasis in the elderly, or to an enhanced sensitivity to vasodilatory agents in the elderly. The incidence of hypotension reported as an adverse reaction was higher in patients 70 years of age and older (4/136; 2.9%) as compared to patients < 70 years of age (7/530; 1.3%).
Hepatic ImpairmentSince there is no clinical experience in patients with severe hepatic impairment, use in these patients is not recommended. CARDURA XL should be administered with caution to patients with mild or moderate hepatic impairment.
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 trials of another drug and may not reflect the rates observed in clinical practice.
The incidence of adverse reactions was derived from two controlled efficacy and safety trials involving 1473 BPH patients. In Study 1, CARDURA XL (n=317) was compared to doxazosin IR tablets (n=322) and to placebo (n=156). In Study 2, CARDURA XL (n=350) was compared just to doxazosin IR tablets (n=330). In both of these studies, CARDURA XL was initiated at a dose of 4 mg, which could be increased by the investigator to 8 mg after seven weeks if an adequate response was not seen. Similarly, doxazosin IR was begun at a dose of 1 mg, which was increased in all patients to 2 mg after 1 week, followed by the option to increase to 4 mg after 4 weeks, and 8 mg after 7 weeks.
The most commonly reported adverse reactions leading to discontinuation in the CARDURA XL group were: dizziness, dyspnea, asthenia, headache, hypotension, postural hypotension, and somnolence. The rates of discontinuation for adverse reactions were 6%, 7% and 3% in the CARDURA XL, doxazosin IR, and placebo groups, respectively.
Table 1 lists the incidence rates of adverse reactions derived from all reported adverse events in the two controlled studies (Studies 1 and 2) combined, at a rate greater than placebo and in 1% or more of patients treated with CARDURA XL.
TABLE 1 : Adverse Reactions, Derived from All
Adverse Events Exceeding Placebo Rate and Occurring in ≥ 1% of BPH
Patients Treated with CARDURA XL
| Body System | CARDURA XL (N = 666) |
Doxazosin IR (N = 651) |
Placebo (N = 156) |
| BODY AS A WHOLE | |||
| Abdominal Pain | 1.8% | 2.3% | 0.6% |
| Asthenia | 3.9% | 6.9% | 1.3% |
| Headache | 6.0% | 5.1% | 4.5% |
| CARDIOVASCULAR | |||
| Hypotension | 1.7% | 1.8% | 0.0% |
| Postural Hypotension | 1.2% | 2.2% | 0.6% |
| DIGESTIVE | |||
| Dyspepsia | 1.4% | 1.2% | 0.0% |
| Nausea | 1.2% | 2.3% | 0.6% |
| MUSCULOSKELETAL | |||
| Myalgia | 1.4% | 0.5% | 0.0% |
| NERVOUS | |||
| Dizziness | 5.3% | 9.1% | 1.9% |
| Somnolence | 1.5% | 1.2% | 0.0% |
| Vertigo | 1.5% | 4.1% | 0.6% |
| RESPIRATORY | |||
| Dyspnea | 1.2% | 1.2% | 0.0% |
| Respiratory Tract Infection | 4.8% | 4.5% | 1.9% |
| UROGENITAL | |||
| Urinary Tract Infection | 1.4% | 0.8% | 0.6% |
Additional adverse events reported with CARDURA XL, reported by less than 1% of patients, and those of clinical interest include: Cardiovascular System: angina pectoris, syncope, tachycardia, chest pain, palpitations; Digestive System: diarrhea; Musculoskeletal System: arthralgia; Nervous System: libido decreased; Urogenital System: impotence, dysuria.
In general, the adverse events reported in the open-label safety extension, in approximately 295 BPH patients treated for up to 37 weeks, were similar in type and frequency to the events described above in the controlled trials.
Postmarketing ExperienceThe following adverse events have been identified during post-approval use of doxazosin. 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.
Autonomic Nervous System: priapism; Cardiovascular System: cerebrovascular accidents, dizziness postural, myocardial infarction; Central and Peripheral Nervous System: hypoesthesia, paresthesia; Endocrine System: gynecomastia; Gastrointestinal System: gastrointestinal obstruction, vomiting; General Body System: fatigue, hot flushes, malaise; Heart Rate/Rhythm: bradycardia, cardiac arrhythmias; Hematopoietic: leukopenia, purpura, thrombocytopenia; Liver/Biliary System: abnormal liver function tests, hepatitis, hepatitis cholestatic, jaundice; Musculoskeletal System: muscle cramps, muscle weakness; Psychiatric: agitation, anorexia, nervousness; Respiratory System: bronchospasm aggravated; Skin Disorders: alopecia, urticaria, skin rash, pruritus; Special Senses: blurred vision, Intraoperative Floppy Iris Syndrome ; Urinary System: hematuria, micturition disorder, micturition frequency, nocturia, polyuria.
There have been rare reports of gastrointestinal irritation and gastrointestinal bleeding with use of another drug in this non-deformable sustained release formulation, although causal relationship to the drug is uncertain.
DRUG INTERACTIONS CYP 3A4 InhibitorsNo in vivo drug interaction studies were conducted with CARDURA XL.
In vitro studies suggest that doxazosin is a substrate of CYP 3A4. Caution should be exercised when concomitantly administering CARDURA XL with a strong CYP 3A4 inhibitor, such as atanazavir, clarithromycin, indinavir, itraconazole, ketoconazole, nefazodone, nelfinavir, ritonavir, saquinavir, telithromycin, or voriconazole.
Antihypertensive MedicationsPharmacodynamic interactions between CARDURA XL and antihypertensive medications or other vasodilating agents have not been determined.
PDE-5 InhibitorsConcomitant administration of CARDURA XL with a PDE-5 inhibitor can result in additive blood pressure lowering effects and symptomatic hypotension.
