In postmarketing experience, overdose with venlafaxine was reported predominantly in combination with alcohol and/or other medicinal products. The most commonly reported events in overdose include tachycardia, changes in level of consciousness (ranging from somnolence to coma), mydriasis, convulsion, and vomiting. Other reported events include electrocardiographic changes (e.g., prolongation of QT interval, bundle branch block, QRS prolongation), ventricular tachycardia, bradycardia, hypotension, vertigo, and death.
Published retrospective studies report that venlafaxine overdosage may be associated with an increased risk of fatal outcomes compared to that observed with SSRI antidepressant products, but lower than that for tricyclic antidepressants. Epidemiological studies have shown that venlafaxine treated patients have a higher burden of suicide risk factors than SSRI patients. The extent to which the finding of an increased risk of fatal outcomes can be attributed to the toxicity of venlafaxine in overdosage, as opposed to some characteristics of venlafaxine-treated patients, is not clear. Prescriptions for venlafaxine should be written for the smallest quantity of the medicinal product consistent with good patient management in order to reduce the risk of overdose.
Recommended treatment
General supportive and symptomatic measures are recommended; cardiac rhythm and vital signs must be monitored. When there is a risk of aspiration, induction of emesis is not recommended. Gastric lavage may be indicated if performed soon after ingestion or in symptomatic patients. Administration of activated charcoal may also limit absorption of the active substance. Forced diuresis, dialysis, hemoperfusion and exchange transfusion are unlikely to be of benefit. No specific antidotes for venlafaxine are known.
Concomitant treatment with irreversible monoamine oxidase inhibitors (MAOIs) is contraindicated due to the risk of serotonin syndrome with symptoms such as agitation, tremor and hyperthermia.
Venlafaxine must not be initiated for at least 14 days after discontinuation of treatment with an irreversible MAOI.
Venlafaxine must be discontinued for at least 7 days before starting treatment with an irreversible MAOI.
Not applicable.
The most commonly (>1/10) reported adverse reactions in clinical studies were nausea, dry mouth, headache and sweating (including night sweats).
Adverse reactions are listed below by system organ class and frequency.
Frequencies are defined as: very common (>1/10), common (>1/100 to <1/10), uncommon (>1/1,000 to <1/100), rare (>1/10,000 to <1/1,000), not known (cannot be estimated from the available data).
| Body System | Very Common | Common | Uncommon | Rare | Not Known |
| Blood and lymphatic system disorders | Thrombocytopaenia, Blood disorder, (including agranulocytosis, aplastic anaemia, neutropaenia, pancytopaenia) | ||||
| Immune system disorders | Anaphylactic reaction | ||||
| Endocrine disorders | Syndrome of Inappropriate antidiuretic hormone secretion (SIADH) | ||||
| Metabolism and nutrition disorders | Decreased appetite | Hyponatraemia, | |||
| Psychiatric disorders | Confusional state, Depersonalization, Anorgasmia, Libido decreased, Nervousness, Insomnia, Abnormal dreams | Hallucination, Derealization, Agitation, Orgasm abnormal (female), Apathy, Hypomania, Bruxism | Mania | Suicidal ideation and suicidal behaviours**, Delirium, Aggression*** | |
| Nervous system disorders | Dizziness Headache* | Somnolence, Tremor, Paraesthesia, Hypertonia | Akathisia/ Psychomotor restlessness, Syncope, Myoclonus, Coordination abnormal, Balance disorder, Dysgeusia | Convulsion, | Neuroleptic Malignant Syndrome (NMS), Serotonergic syndrome, Extrapyramidal disorder, including dystonia and dyskinaesia, Tardive dyskinaesia |
| Eye disorders | Visual impairment, including vision blurred, Mydriasis, Accommodation disorder | Angle-closure glaucoma | |||
| Ear and labyrinth disorders | Tinnitus | Vertigo | |||
| Cardiac disorders | Palpitations | Tachycardia | Ventricular fibrillation, Ventricular tachycardia (including Torsade de Pointes) | ||
| Vascular disorders | Hypertension, Vasodilatation (mostly flush) | Orthostatic hypotension, | Hypotension, Bleeding (mucous membrane bleeding) | ||
| Respiratory, thoracic and mediastinal disorders | Yawning | Dyspnoea | Pulmonary eosinophilia | ||
| Gastrointestinal disorders | Nausea, Dry mouth | Vomiting Diarrhoea, Constipation | Gastrointestinal haemorrhage | Pancreatitis | |
| Hepatobiliary disorders | Hepatitis, Liver function test abnormal | ||||
| Skin and subcutaneous tissue disorders | Hyperhidrosis (including night sweats) | Angioedema, Photosensitivity reaction, Ecchymosis, Rash, Alopecia | Erythema multiforme, Toxic epidermal necrolysis, Stevens- Johnson syndrome, Pruritus, Urticaria | ||
| Musculoskeletal and connective tissue disorders | Rhabdomyolysis | ||||
| Renal and urinary disorders | Dysuria (mostly urinary hesitation), Pollakiuria | Urinary retention | Urinary incontinence | ||
| Reproductive system and breast disorders | Menstrual disorders associated with increased bleeding or irregular bleeding (e.g. menorrhagia, metrorrhagia), Ejaculation disorder, Erectile dysfunction | ||||
| General disorders and administration site conditions | Asthenia, Fatigue, Chills | ||||
| Investigations | Blood cholesterol increased | Weight increased, Weight decreased | Electrocardiogram QT prolonged, Bleeding time prolonged, Blood prolactin increased Discontinuation of venlafaxine (particularly when abrupt) commonly leads to withdrawal symptoms. Dizziness, sensory disturbances (including paraethesia), sleep disturbances (including insomnia and intense dreams), agitation or anxiety, nausea and/or vomiting, tremor, vertigo, headache and flu syndrome are the most commonly reported reactions. Generally, these events are mild to moderate and are self-limiting; however, in some patients, they may be severe and/or prolonged. It is therefore advised that when venlafaxine treatment is no longer required, gradual discontinuation by dose tapering should be carried out. Paediatric population In general, the adverse reaction profile of venlafaxine (in placebo-controlled clinical trials) in children and adolescents (ages 6 to 17) was similar to that seen for adults. As with adults, decreased appetite, weight loss, increased blood pressure, and increased serum cholesterol were observed. In paediatric clinical trials the adverse reaction suicidal ideation was observed. There were also increased reports of hostility and, especially in major depressive disorder, self-harm. Particularly, the following adverse reactions were observed in paediatric patients: abdominal pain, agitation, dyspepsia, ecchymosis, epistaxis, and myalgia. Reporting of suspected adverse reactions Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continued monitoring of the benefit/risk balance of the medicinal product. Healthcare professionals are asked to report any suspected adverse reactions via the Yellow Card Scheme; website: www.mhra.gov.uk/yellowcard |
Studies with venlafaxine in rats and mice revealed no evidence of carcinogenesis. Venlafaxine was not mutagenic in a wide range of in vitro and in vivo tests.
Animal studies regarding reproductive toxicity have found in rats a decrease in pup weight, an increase in stillborn pups, and an increase in pup deaths during the first 5 days of lactation. The cause of these deaths is unknown. These effects occurred at 30mg/kg/day, 4 times the human daily dose of 375mg of venlafaxine (on an mg/kg basis). The no-effect dose for these findings was 1.3 times the human dose. The potential risk for humans is unknown.
Reduced fertility was observed in a study in which both male and female rats were exposed to ODV. This exposure was approximately 1 to 2 times that of a human venlafaxine dose of 375mg/day. The human relevance of this finding is unknown.
- Treatment of major depressive episodes.
- For prevention of recurrence of major depressive episodes.
- Treatment of generalised anxiety disorder.
- Treatment of social anxiety disorder.
- Treatment of panic disorders, with or without agoraphobia.
Pharmacotherapeutic group: Other antidepressants - ATC code: NO6A X16.
Mechanism of action
The mechanism of venlafaxine's antidepressant action in humans is believed to be associated with its potentiation of neurotransmitter activity in the central nervous system. Preclinical studies have shown that venlafaxine and its major metabolite, O-desmethylvenlafaxine (ODV), are inhibitors of serotonin and noradrenaline reuptake. Venlafaxine also weakly inhibits dopamine uptake. Venlafaxine and its active metabolite reduce β-adrenergic responsiveness after both acute (single dose) and chronic administration. Venlafaxine and ODV are very similar with respect to their overall action on neurotransmitter reuptake and receptor binding.
Venlafaxine has virtually no affinity for rat brain muscarinic, cholinergic, H1-histaminergic or α1-adrenergic receptors in vitro. Pharmacological activity at these receptors may be related to various side effects seen with other antidepressant medicinal products, such as anticholinergic, sedative and cardiovascular side effects.
Venlafaxine does not possess monoamine oxidase (MAO) inhibitory activity.
In vitro studies revealed that venlafaxine has virtually no affinity for opiate or benzodiazepine sensitive receptors.
Major depressive episodes
The efficacy of venlafaxine immediate-release as a treatment for major depressive episodes was demonstrated in five randomised, double-blind, placebo-controlled, short-term trials ranging from 4 to 6 weeks duration, for doses up to 375mg/day. The efficacy of venlafaxine prolonged-release as a treatment for major depressive episodes was established in two placebo-controlled, short-term studies for 8 and 12 weeks duration, which included a dose range of 75 to 225mg/day.
In one longer-term study, adult outpatients who had responded during an 8-week open trial on venlafaxine prolonged-release (75, 150, or 225mg) were randomised to continuation of their same venlafaxine prolonged-release dose or to placebo, for up to 26 weeks of observation for relapse.
In a second longer-term study, the efficacy of venlafaxine in prevention of recurrent depressive episodes for a 12-month period was established in a placebo-controlled double-blind clinical trial in adult outpatients with recurrent major depressive episodes who had responded to venlafaxine treatment (100 to 200mg/day, on a b.i.d. schedule) on the last episode of depression.
Generalised anxiety disorder
The efficacy of venlafaxine prolonged-release capsules as a treatment for generalised anxiety disorder (GAD) was established in two 8-week, placebo-controlled, fixed-dose studies (75 to 225mg/day), one 6-month, placebo-controlled, fixed-dose study (75 to 225mg/day), and one 6-month, placebo-controlled, flexible-dose study (37.5, 75, and 150mg/day) in adult outpatients.
While there was also evidence for superiority over placebo for the 37.5mg/day dose, this dose was not as consistently effective as the higher doses.
Social anxiety disorder
The efficacy of venlafaxine prolonged-release capsules as a treatment for social anxiety disorder was established in four double-blind, parallel-group, 12-week, multi-center, placebo-controlled, flexible-dose studies and one double-blind, parallel-group, 6-month, placebo-controlled, fixed/flexible-dose study in adult outpatients. Patients received doses in a range of 75 to 225mg/day.
There was no evidence for any greater effectiveness of the 150 to 225mg/day group compared to the 75mg/day group in the 6-month study.
Panic disorder
The efficacy of venlafaxine prolonged-release capsules as a treatment for panic disorder was established in two double-blind, 12-week, multi-center, placebo-controlled studies in adult outpatients with panic disorder, with or without agoraphobia. The initial dose in panic disorder studies was 37.5mg/day for 7 days. Patients then received fixed doses of 75 or 150mg/day in one study and 75 or 225mg/day in the other study.
Efficacy was also established in one long-term double-blind, placebo-controlled, parallel-group study of the long-term safety, efficacy, and prevention of relapse in adult outpatients who responded to open-label treatment. Patients continued to receive the same dose of venlafaxine prolonged-release that they had taken at the end of the open-label phase (75, 150, or 225mg).
Venlafaxine is extensively metabolised, primarily to the active metabolite, O-desmethylvenlafaxine (ODV). Mean ± SD plasma half-lives of venlafaxine and ODV are 5±2 hours and 11±2 hours, respectively. Steady-state concentrations of venlafaxine and ODV are attained within 3 days of oral multiple-dose therapy. Venlafaxine and ODV exhibit linear kinetics over the dose range of 75mg to 450mg/day.
Absorption
At least 92% of venlafaxine is absorbed following single oral doses of immediate-release venlafaxine. Absolute bioavailability is 40% to 45% due to presystemic metabolism. After immediate-release venlafaxine administration, the peak plasma concentrations of venlafaxine and ODV occur in 2 and 3 hours, respectively. Following the administration of venlafaxine prolonged-release capsules, peak plasma concentrations of venlafaxine and ODV are attained within 5.5 hours and 9 hours, respectively. When equal daily doses of venlafaxine are administered as either an immediate-release tablet or prolonged-release capsule, the prolonged-release capsule provides a slower rate of absorption, but the same extent of absorption compared with the immediate-release tablet. Food does not affect the bioavailability of venlafaxine and ODV.
Distribution
Venlafaxine and ODV are minimally bound at therapeutic concentrations to human plasma proteins (27% and 30%, respectively). The volume of distribution for venlafaxine at steady-state is 4.4±1.6 L/kg following intravenous administration.
BiotransformationVenlafaxine undergoes extensive hepatic metabolism. In vitro and in vivo studies indicate that venlafaxine is biotransformed to its major active metabolite, ODV, by CYP2D6. In vitro and in vivo studies indicate that venlafaxine is metabolised to a minor, less active metabolite, N-desmethylvenlafaxine, by CYP3A4. In vitro and in vivo studies indicate that venlafaxine is a weak inhibitor of CYP2D6. Venlafaxine did not inhibit CYP1A2, CYP2C9, or CYP3A4.
Elimination
Venlafaxine and its metabolites are excreted primarily through the kidneys. Approximately 87% of a venlafaxine dose is recovered in the urine within 48 hours as either unchanged venlafaxine (5%), unconjugated ODV (29%), conjugated ODV (26%), or other minor inactive metabolites (27%). Mean ± SD plasma steady-state clearances of venlafaxine and ODV are 1.3±0.6 L/h/kg and 0.4±0.2 L/h/kg, respectively.
Special populations
Age and gender
Subject age and gender do not significantly affect the pharmacokinetics of venlafaxine and ODV.
CYP2D6 extensive/poor metabolisers
Plasma concentrations of venlafaxine are higher in CYP2D6 poor metabolisers than extensive metabolisers. Because the total exposure (AUC) of venlafaxine and ODV is similar in poor and extensive metabolisers, there is no need for different venlafaxine dosing regimens for these two groups.
Patients with hepatic impairment
In Child-Pugh A (mildly hepatically impaired) and Child-Pugh B (moderately hepatically impaired) subjects, venlafaxine and ODV half-lives were prolonged compared to normal subjects. The oral clearance of both venlafaxine and ODV was reduced. A large degree of intersubject variability was noted. There are limited data in patients with severe hepatic impairment.
Patients with renal impairment
In dialysis patients, venlafaxine elimination half-life was prolonged by about 180% and clearance reduced by about 57% compared to normal subjects, while ODV elimination half-life was prolonged by about 142% and clearance reduced by about 56%. Dosage adjustment is necessary in patients with severe renal impairment and in patients that require haemodialysis.
5.2 Pharmacokinetic properties
Venlafaxine is extensively metabolised, primarily to the active metabolite, O-desmethylvenlafaxine (ODV). Mean ± SD plasma half-lives of venlafaxine and ODV are 5±2 hours and 11±2 hours, respectively. Steady-state concentrations of venlafaxine and ODV are attained within 3 days of oral multiple-dose therapy. Venlafaxine and ODV exhibit linear kinetics over the dose range of 75mg to 450mg/day.
Absorption
At least 92% of venlafaxine is absorbed following single oral doses of immediate-release venlafaxine. Absolute bioavailability is 40% to 45% due to presystemic metabolism. After immediate-release venlafaxine administration, the peak plasma concentrations of venlafaxine and ODV occur in 2 and 3 hours, respectively. Following the administration of venlafaxine prolonged-release capsules, peak plasma concentrations of venlafaxine and ODV are attained within 5.5 hours and 9 hours, respectively. When equal daily doses of venlafaxine are administered as either an immediate-release tablet or prolonged-release capsule, the prolonged-release capsule provides a slower rate of absorption, but the same extent of absorption compared with the immediate-release tablet. Food does not affect the bioavailability of venlafaxine and ODV.
Distribution
Venlafaxine and ODV are minimally bound at therapeutic concentrations to human plasma proteins (27% and 30%, respectively). The volume of distribution for venlafaxine at steady-state is 4.4±1.6 L/kg following intravenous administration.
Metabolism
Venlafaxine undergoes extensive hepatic metabolism. In vitro and in vivo studies indicate that venlafaxine is biotransformed to its major active metabolite, ODV, by CYP2D6. In vitro and in vivo studies indicate that venlafaxine is metabolised to a minor, less active metabolite, N-desmethylvenlafaxine, by CYP3A4. In vitro and in vivo studies indicate that venlafaxine is a weak inhibitor of CYP2D6. Venlafaxine did not inhibit CYP1A2, CYP2C9, or CYP3A4.
Elimination
Venlafaxine and its metabolites are excreted primarily through the kidneys. Approximately 87% of a venlafaxine dose is recovered in the urine within 48 hours as either unchanged venlafaxine (5%), unconjugated ODV (29%), conjugated ODV (26%), or other minor inactive metabolites (27%). Mean ± SD plasma steady-state clearances of venlafaxine and ODV are 1.3±0.6 L/h/kg and 0.4±0.2 L/h/kg, respectively.
Special populations
Age and gender
Subject age and gender do not significantly affect the pharmacokinetics of venlafaxine and ODV.
CYP2D6 extensive/poor metabolisers
Plasma concentrations of venlafaxine are higher in CYP2D6 poor metabolisers than extensive metabolisers. Because the total exposure (AUC) of venlafaxine and ODV is similar in poor and extensive metabolisers, there is no need for different venlafaxine dosing regimens for these two groups.
Patients with hepatic impairment
In Child-Pugh A (mildly hepatically impaired) and Child-Pugh B (moderately hepatically impaired) subjects, venlafaxine and ODV half-lives were prolonged compared to normal subjects. The oral clearance of both venlafaxine and ODV was reduced. A large degree of intersubject variability was noted. There are limited data in patients with severe hepatic impairment.
Patients with renal impairment
In dialysis patients, venlafaxine elimination half-life was prolonged by about 180% and clearance reduced by about 57% compared to normal subjects, while ODV elimination half-life was prolonged by about 142% and clearance reduced by about 56%. Dosage adjustment is necessary in patients with severe renal impairment and in patients that require haemodialysis.
Suicide/suicidal thoughts or clinical worsening
Depression is associated with an increased risk of suicidal thoughts, self harm and suicide (suicide-related events). This risk persists until significant remission occurs. As improvement may not occur during the first few weeks or more of treatment, patients should be closely monitored until such improvement occurs. It is general clinical experience that the risk of suicide may increase in the early stages of recovery.
Other psychiatric conditions for which venlafaxine is prescribed can also be associated with an increased risk of suicide-related events. In addition, these conditions may be co-morbid with major depressive disorder. The same precautions observed when treating patients with major depressive disorder should therefore be observed when treating patients with other psychiatric disorders.
Patients with a history of suicide-related events, or those exhibiting a significant degree of suicidal ideation prior to commencement of treatment are known to be at greater risk of suicidal thoughts or suicide attempts, and should receive careful monitoring during treatment.
A meta-analysis of placebo-controlled clinical trials of antidepressant drugs in adult patients with psychiatric disorders showed an increased risk of suicidal behaviour with antidepressants compared to placebo in patients less than 25 years old. Close supervision of patients and in particular those at high risk should accompany drug therapy especially in early treatment and following dose changes.
Patients (and caregivers of patients) should be alerted about the need to monitor for any clinincal worsening, suicidal behaviour or thoughts and unusual changes in behaviour and to seek medical advice immediately if these symptoms present.
Paediatric population
Quilarex XR should not be used in the treatment of children and adolescents under the age of 18 years. Suicide-related behaviours (suicide attempt and suicidal thoughts), and hostility (predominantly aggression, oppositional behaviour and anger) were more frequently observed in clinical trials among children and adolescents treated with antidepressants compared to those treated with placebo. If, based on clinical need, a decision to treat is nevertheless taken; the patient should be carefully monitored for the appearance of suicidal symptoms. In addition, long-term safety data in children and adolescents concerning growth, maturation and cognitive and behavioural development are lacking.
Serotonin syndrome
As with other serotonergic agents, serotonin syndrome, a potentially life-threatening condition, may occur with venlafaxine treatment, particularly with concomitant use of other agents, that may affect the serotonergic neurotransmitter system (including triptans, SSRIs, SNRIs, lithium, sibutramine, St.John's Wort [Hypericum perforatum], fentanyl and its analogues, tramadol, dextromethorphan, tapentadol, pethidine, methadone and pentazocine), with medicinal agents that impair metabolism of serotonin such as MAOIs e.g. methylene blue, with serotonin precursors (such as tryptophan supplements) or with antipsychotics or other dopamine antagonists.
Serotonin syndrome symptoms may include mental status changes (e.g., agitation, hallucinations, coma), autonomic instability (e.g., tachycardia, labile blood pressure, hyperthermia), neuromuscular aberrations (e.g., hyperreflexia, incoordination) and/or gastrointestinal symptoms (e.g., nausea, vomiting, diarrhoea) Serotonin syndrome in its most severe form, can resemble NMS, which includes hyperthermia, muscle rigidity, autonomic instability with possible rapid fluctuation of vital signs and mental status changes.
If concomitant treatment with venlafaxine and other agents that may affect the serotonergic and/or dopaminergic neurotransmitter systems is clinically warranted, careful observation of the patient is advised, particularly during treatment initiation and dose increases.
The concomitant use of venlafaxine with serotonin precursors (such as tryptophan supplements) is not recommended.
.
Narrow-angle glaucoma
Mydriasis may occur in association with venlafaxine. It is recommended that patients with raised intraocular pressure or patients at risk for acute narrow-angle glaucoma (angle-closure glaucoma) be closely monitored.
Blood pressure
Dose-related increases in blood pressure have been commonly reported with venlafaxine. In some cases, severely elevated blood pressure requiring immediate treatment has been reported in postmarketing experience. All patients should be carefully screened for high blood pressure and preexisting hypertension should be controlled before initation of treatment. Blood pressure should be reviewed periodically, after initiation of treatment and after dose increases. Caution should be exercised in patients whose underlying conditions might be compromised by increases in blood pressure, e.g., those with impaired cardiac function.
Heart rate
Increases in heart rate can occur, particularly with higher doses. Caution should be exercised in patients whose underlying conditions might be compromised by increases in heart rate.
Cardiac disease and risk of arrhythmia
Venlafaxine has not been evaluated in patients with a recent history of myocardial infarction or unstable heart disease. Therefore, it should be used with caution in these patients.
In postmarketing experience, cases of QTc prolongation, Torsade de Pointes (TdP), ventricular tachycardia, and fatal cardiac arrhythmias have been reported with the use of venlafaxine, especially in overdose or in patients with other risk factors for QTc prolongation/TdP. The balance of risks and benefits should be considered before prescribing venlafaxine to patients at high risk of serious cardiac arrhythmia or QTc prolongation.
Convulsions
Convulsions may occur with venlafaxine therapy. As with all antidepressants, venlafaxine should be introduced with caution in patients with a history of convulsions, and concerned patients should be closely monitored. Treatment should be discontinued in any patient who develops seizures.
Hyponatraemia
Cases of hyponatraemia and/or the Syndrome of Inappropriate Antidiuretic Hormone (SIADH) secretion may occur with venlafaxine. This has most frequently been reported in volume-depleted or dehydrated patients. Elderly patients, patients taking diuretics, and patients who are otherwise volume-depleted may be at greater risk for this event.
Abnormal bleeding
Medicinal products that inhibit serotonin uptake may lead to reduced platelet function. Bleeding events related to SSRI and SNRI use have ranged from ecchymoses, hematomas, epistaxis, and petechiae to gastrointestinal and life-threatening haemorrhages. The risk of haemorrhage may be increased in patients taking venlafaxine. As with other serotonin-reuptake inhibitors, venlafaxine should be used cautiously in patients predisposed to bleeding, including patients on anticoagulants and platelet inhibitors.
Serum cholesterol
Clinically relevant increases in serum cholesterol were recorded in 5.3% of venlafaxine-treated patients and 0.0% of placebo-treated patients treated for at least 3 months in placebo-controlled clinical trials. Measurement of serum cholesterol levels should be considered during long-term treatment.
Co-administration with weight loss agents
The safety and efficacy of venlafaxine therapy in combination with weight loss agents, including phentermine, have not been established. Co-administration of venlafaxine and weight loss agents is not recommended. Venlafaxine is not indicated for weight loss alone or in combination with other products.
Mania/hypomania
Mania/hypomania may occur in a small proportion of patients with mood disorders who have received antidepressants, including venlafaxine. As with other antidepressants, venlafaxine should be used cautiously in patients with a history or family history of bipolar disorder.
Aggression
Aggression may occur in a small number of patients who have received antidepressants, including venlafaxine. This has been reported under initiation, dose changes and discontinuation of treatment.
As with other antidepressants, venlafaxine should be used cautiously in patients with a history of aggression.
Discontinuation of treatment
Withdrawal symptoms when treatment is discontinued are common, particularly if discontinuation is abrupt. In clinical trials, adverse events seen on treatment discontinuation (tapering and post-tapering) occurred in approximately 31% of patients treated with venlafaxine and 17% of patients taking placebo.
The risk of withdrawal symptoms may be dependent on several factors including the duration and dose of therapy and the rate of dose reduction. Dizziness, sensory disturbances (including paraesthesia), sleep disturbances (including insomnia and intense dreams), agitation or anxiety, nausea and/or vomiting, tremor and headache are the most commonly reported reactions. Generally these symptoms are mild to moderate; however, in some patients they may be severe in intensity. They usually occur within the first few days of discontinuing treatment, but there have been very rare reports of such symptoms in patients who have inadvertently missed a dose. Generally these symptoms are self-limiting and usually resolve within 2 weeks, though in some individuals they may be prolonged (2-3 months or more). It is therefore advised that venlafaxine should be gradually tapered when discontinuing treatment over a period of several weeks or months, according to the patient's needs.
Akathisia/psychomotor restlessness
The use of venlafaxine has been associated with the development of akathisia, characterised by a subjectively unpleasant or distressing restlessness and need to move often accompanied by an inability to sit or stand still. This is most likely to occur within the first few weeks of treatment. In patients who develop these symptoms, increasing the dose may be detrimental.
Dry mouth
Dry mouth is reported in 10% of patients treated with venlafaxine. This may increase the risk of caries, and patients should be advised upon the importance of dental hygiene.
Diabetes
In patients with diabetes, treatment with an SSRI or venlafaxine may alter glycaemic control. Insulin and/or oral antidiabetic dosage may need to be adjusted.
Drug-Laboratory Test Interactions
False-positive urine immunoassay screening tests for phencyclidine (PCP) and amphetamine have been reported in patients taking venlafaxine. This is due to lack of specificity of the screening tests. False positive test results may be expected for several days following discontinuation of venlafaxine therapy. Confirmatory tests, such as gas chromatography/mass spectrometry, will distinguish venlafaxine from PCP and amphetamine.
The excipient sunset yellow FCF (E110) included in the capsules shell may cause allergic reactions.
Since the capsules contain sucrose patients with rare hereditary problems of fructose intolerance, glucose-galactose malabsorption or sucrase-isomaltase insufficiency should not take this medicine.
Any psychoactive medicinal product may impair judgment, thinking, and motor skills. Therefore, any patient receiving venlafaxine should be cautioned about their ability to drive or operate hazardous machinery.
Posology
Major depressive episodes
The recommended starting dose for prolonged-release venlafaxine is 75mg given once daily. Patients not responding to the initial 75mg/day dose may benefit from dose increases up to a maximum dose of 375mg/day. Dosage increases can be made at intervals of 2 weeks or more. If clinically warranted due to symptom severity, dose increases can be made at more frequent intervals, but not less than 4 days.
Because of the risk of dose-related adverse effects, dose increments should be made only after a clinical evaluation. The lowest effective dose should be maintained.
Patients should be treated for a sufficient period of time, usually several months or longer.
Treatment should be reassessed regularly on a case-by-case basis. Longer-term treatment may also be appropriate for prevention of recurrence of major depressive episodes (MDE). In most of the cases, the recommended dose in prevention of recurrence of MDE is the same as the one used during the current episode.
Antidepressive medicinal products should continue for at least six months following remission.
Generalised anxiety disorder
The recommended starting dose for prolonged-release venlafaxine is 75mg given once daily. Patients not responding to the initial 75mg/day dose may benefit from dose increases up to a maximum dose of 225mg/day. Dosage increases can be made at intervals of 2 weeks or more.
Because of the risk of dose-related adverse effects, dose increments should be made only after a clinical evaluation. The lowest effective dose should be maintained.
Patients should be treated for a sufficient period of time, usually several months or longer. Treatment should be reassessed regularly, on a case-by-case basis.
Social anxiety disorder
The recommended dose for prolonged-release venlafaxine is 75mg given once daily. There is no evidence that higher doses confer any additional benefit.
However, in individual patients not responding to the initial 75mg/day, increases up to a maximum dose of 225mg/day may be considered. Dosage increases can be made at intervals of 2 weeks or more.
Because of the risk of dose-related adverse effects, dose increments should be made only after a clinical evaluation. The lowest effective dose should be maintained.
Patients should be treated for a sufficient period of time, usually several months or longer. Treatment should be reassessed regularly, on a case-by-case basis.
Panic disorder
It is recommended that a dose of 37.5mg/day of prolonged-release venlafaxine be used for 7 days. Dosage should then be increased to 75mg/day. Patients not responding to the 75mg/day dose may benefit from dose increases up to a maximum dose of 225mg/day. Dosage increases can be made at intervals of 2 weeks or more.
Because of the risk of dose-related adverse effects, dose increments should be made only after a clinical evaluation. The lowest effective dose should be maintained.
Patients should be treated for a sufficient period of time, usually several months or longer. Treatment should be reassessed regularly, on a case-by-case basis.
Use in elderly patients
No specific dose adjustments of venlafaxine are considered necessary based on patient age alone. However, caution should be exercised in treating the elderly (e.g., due to the possibility of renal impairment, the potential for changes in neurotransmitter sensitivity and affinity occurring with aging). The lowest effective dose should always be used, and patients should be carefully monitored when an increase in the dose is required.
Use in children and adolescents under the age of 18 years
Venlafaxine is not recommended for use in children and adolescents.
Controlled clinical studies in children and adolescents with major depressive disorder failed to demonstrate efficacy and do not support the use of venlafaxine in these patients.
The efficacy and safety of venlafaxine for other indications in children and adolescents under the age of 18 have not been established.
Use in patients with hepatic impairment
In patients with mild and moderate hepatic impairment, in general a 50% dose reduction should be considered. However, due to inter-individual variability in clearance, individualisation of dosage may be desirable.
There are limited data in patients with severe hepatic impairment. Caution is advised, and a dose reduction by more than 50% should be considered. The potential benefit should be weighed against the risk in the treatment of patients with severe hepatic impairment.
Use in patients with renal impairment
Although no change in dosage is necessary for patients with glomerular filtration rate (GFR) between 30-70 ml/minute, caution is advised. For patients that require haemodialysis and in patients with severe renal impairment (GFR < 30 ml/min), the dose should be reduced by 50%. Because of inter-individual variability in clearance in these patients, individualisation of dosage may be desirable.
Withdrawal symptoms seen on discontinuation of venlafaxine
Abrupt discontinuation should be avoided. When stopping treatment with venlafaxine, the dose should be gradually reduced over a period of at least one to two weeks in order to reduce the risk of withdrawal reactions. If intolerable symptoms occur following a decrease in the dose or upon discontinuation of treatment, then resuming the previously prescribed dose may be considered. Subsequently, the physician may continue decreasing the dose, but at a more gradual rate.
Method of administration
For oral use.
It is recommended that venlafaxine prolonged-release capsules be taken with food, at approximately the same time each day. Capsules must be swallowed whole with fluid and not divided, crushed, chewed, or dissolved.
Patients treated with venlafaxine immediate-release tablets may be switched to venlafaxine prolonged-release capsules at the nearest equivalent daily dosage. For example, venlafaxine immediate-release tablets 37.5mg twice daily may be switched to venlafaxine prolonged-release capsules 75mg once daily. Individual dosage adjustments may be necessary.
Venlafaxine prolonged-release capsules contain spheroids, which release the active substance slowly into the digestive tract. The insoluble portion of these spheroids is eliminated and may be seen in faeces.
No special requirements.
