Venlafaxine

Therapeutic Class
 Antidepressant, Serotonin/Norepinephrine Reuptake Inhibitor
Indications

Treatment of major depressive disorder, generalized anxiety disorder (GAD), social anxiety disorder (social phobia), panic disorder, Obsessive-compulsive disorder (OCD); hot flashes; neuropathic pain (including diabetic neuropathy); attention attention-deficit/hyperactivity disorder (ADHD); post-traumatic stress disorder (PTSD).
Adult Doses

Depression
Oral:
Immediate-release tablets: Initial: 75 mg/day, administered in 2 or 3 divided doses; may increase in ≤75 mg/day increments at intervals of ≥4 days as tolerated (maximum daily dose: 225-375 mg)
Extended-release capsules or tablets: Initial: 37.5-75 mg once daily; in patients who are initiated at 37.5 mg once daily, may increase to 75 mg once daily after 4-7 days; dose may then be increased by ≤75 mg/day increments at intervals of ≥4 days as tolerated (maximum daily dose: 225 mg)

Generalized anxiety disorder & Social anxiety disorder
Extended-release capsules or tablets: Initial: 37.5-75 mg once daily; in patients who are initiated at 37.5 mg once daily, may increase to 75 mg once daily after 4-7 days; dose may then be increased by ≤75 mg/day increments at intervals of ≥4 days as tolerated (maximum daily dose: 225 mg)

Panic disorder
37.5 mg once daily for first 7 days, then increased to 75 mg daily; increase by up to 75 mg at intervals of at least 7 days as needed. Max: 225 mg daily.

Social anxiety disorder: Oral: Extended-release capsules or tablets: 75 mg once daily (maximum daily dose: 75 mg); no evidence that doses >75 mg/day offer any additional benefit

Obsessive-compulsive disorder (unlabeled use): Oral: Titrate to usual dosage range of 150-300 mg/day; however, doses up to 375 mg/day have been used; response may be seen in 4 weeks.

Neuropathic pain (unlabeled use): Oral: Dosages evaluated varied considerably based on etiology of chronic pain, but efficacy has been shown for many conditions in the range of 75-225 mg/day; onset of relief may occur in 1-2 weeks, or take up to 6 weeks for full benefit .

Diabetic neuropathy (unlabeled use): Oral: 75-225 mg/day.

Hot flashes (unlabeled use): Oral: Doses of 37.5-75 mg/day have demonstrated significant improvement of vasomotor symptoms after 4-8 weeks of treatment; in one study, doses >75 mg/day offered no additional benefit (Evans, 2005; Loprinzi, 2000); however, higher doses (225 mg/day) may be beneficial in patients with perimenopausal depression.

Attention-deficit disorder (unlabeled use): Oral: Initial: Doses vary between 18.75 to 75 mg/day; may increase after 4 weeks to 150 mg/day; if tolerated, doses up to 225 mg/day have been used.

Post-traumatic stress disorder (PTSD) (unlabeled use): Oral: Extended release formulation: 37.5-300 mg/day.

Alzheimer’s dementia-related depression (unlabeled use):
Immediate-release tablets: Initial: 25 mg/day; may increase at weekly intervals to maximum of 375 mg/day in divided doses

Extended-release capsules: Initial: 37.5 mg/day; may increase at weekly intervals to maximum of 225 mg/day

Note: When discontinuing this medication after more than 1 week of treatment, it is generally recommended that the dose be tapered. If venlafaxine is used for 6 weeks or longer, the dose should be tapered over 2 weeks when discontinuing its use.

maximum daily dose: 225-375 mg
Pediatric Doses

Attention-deficit/hyperactivity disorder: 
Children and Adolescents: Oral: Initial: 12.5 mg/day
Children <40 kg: Increase by 12.5 mg/week to maximum of 50 mg/day in 2 divided doses.
Children ≥40 kg: Increase by 25 mg/week to maximum of 75 mg/day in 3 divided doses.
Mean dose: 60 mg or 1.4 mg/kg administered in 2-3 divided doses
Doses in Renal impairment
CrCl (ml/min) Dosage Recommendation
10-30 Reduce dose by 50% and give once daily.
<10 No data available
Doses in Hepatic impairment

Moderate: Reduce dose by 50% and give once daily.
Severe: no data available.
Contraindications

<18 yr. Lactation. Uncontrolled hypertension; high risk of serious ventricular arrhythmia.
Boxed Warning

Antidepressants increase the risk of suicidal thinking and behavior in children, adolescents, and young adults (18-24 years of age) with major depressive disorder (MDD) and other psychiatric disorders.
Warnings / Precautions

Moderate to severe renal or hepatic impairment. Conditions which may be worsened by increase in heart rate. History of MI, bleeding disorder, epilepsy, hypomania or mania. Raised Intraocular pressure or risk at angle-closure glaucoma. May impair performance of skilled tasks, driving or machinery operation. Monitor BP and serum cholesterol regularly. Monitor closely during early therapy until depression improves due to increased risk of suicide. Avoid abrupt withdrawal. Withdraw gradually over at least 1-2 wk and monitor for withdrawal symptoms e.g. fatigue, headache, nausea, vomiting, palpitations. Discontinue if seizure develops or increase in seizure frequency. Elderly, pregnancy.
Adverse Reactions

Nausea, vomiting, anorexia, dry mouth, constipation, orthostatic hypotension, tremour, sweating, rash, anxiety, dizziness, fatigue, headache, syncope, insomnia, somnolence, constipation, hyponatraemia, sexual dysfunction, dyspepsia, visual disturbances, mydriasis, increased cholesterol concentrations, increased LFT. Aggressive behaviour (especially at the start and when stoppping therapy).
Potentially Fatal: Blood dyscrasias, Stevens-Johnson syndrome, hepatitis.
Overdose Reactions

Symptoms: Sweating, dizziness, somnolence, ECG changes, cardiac arrhythmias and seizures. Management: Treatment is symptomatic and supportive. Activated charcoal may reduce absorption if > 12.5 mg/kg has been ingested and presented within 1 hr of ingestion. Dialysis, haemoperfusion, exchange perfusion and increase in urine production unlikely useful.
Drug Interactions

Risk of serotonin syndrome with triptans, linezolid, lithium, tramadol. Increased risk of anticholinergic side effects and serotonin syndrome with TCA, SSRI. Decreased indinavir concentration with concurrent use. Increased INR with warfarin. Possible risk of serotonin syndrome with metoclopramide, and amoxicillin with clavulanate combinations.
Potentially Fatal: Increased risk of serotonin syndrome with MAOI, do not use within at least 14 days of discontinuing MAOI treatment and start MAOI at least 7 days after stopping venlafaxine. Increased risk of serotonin syndrome with sibutramine.
See Below for More venlafaxine hydrochloride Drug Interactions
Food Interactions

Ethanol: May increase CNS depression; monitor for increased effects with coadministration. Caution patients about effects.

Herb/Nutraceutical: Avoid valerian, St John's wort, SAMe, kava kava, tryptophan (may increase risk of serotonin syndrome and/or excessive sedation)
Mechanism of Actions

Venlafaxine and its active metabolite, O-desmethylvenlafaxine (ODV), are potent inhibitors of neuronal serotonin and norepinephrine reuptake and weak inhibitors of dopamine reuptake. Venlafaxine and ODV have no significant activity for muscarinic cholinergic, H1-histaminergic, or alpha2-adrenergic receptors. Venlafaxine and ODV do not possess MAO-inhibitory activity.
Metabolism

Substrate of CYP2C9 (minor), 2C19 (minor), 2D6 (major), 3A4 (major); Inhibits CYP2B6 (weak), 2D6 (weak), 3A4 (weak)
Pharmacodynamics

Absorption: Oral: ≥92%; food has no significant effect on absorption or formation of active metabolite

Distribution: Vdss: Venlafaxine 7.5 ± 3.7 L/kg, ODV 5.7 ± 1.8 L/Kg

Protein binding: Venlafaxine 27% ± 2%, ODV 30% ± 12%

Metabolism: Hepatic via CYP2D6 to active metabolite, O-desmethylvenlafaxine (ODV); other metabolites include N-desmethylvenlafaxine and N,O-didesmethylvenlafaxine

Bioavailability: Oral: ~45%

Half-life elimination: Venlafaxine: 5 ± 2 hours; ODV: 11 ± 2 hours; prolonged with cirrhosis (venlafaxine: ~30%, ODV: ~60%), renal impairment (venlafaxine: ~50%, ODV: ~40%), and during dialysis (venlafaxine: ~180%, ODV: ~142%)

Time to peak:

Immediate release: Venlafaxine: 2 hours, ODV: 3 hours

Extended release: Venlafaxine: 5.5 hours, ODV: 9 hours

Excretion: Urine (~87%; 5% of total dose as unchanged drug; 29% of total dose as unconjugated ODV; 26% of total dose as conjugated ODV; 27% of total dose as minor inactive metabolites)
Monitoring

Blood pressure should be regularly monitored, especially in patients with a high baseline blood pressure; may cause mean increase in heart rate of 4-9 beats/minute; cholesterol; mental status for depression, suicide ideation (especially at the beginning of therapy or when doses are increased or decreased), anxiety, social functioning, mania, panic attacks; height and weight should be monitored in children
Administration

Should be taken with food.

Extended-release formulations: Swallow capsule or tablet whole; do not crush or chew.
Pregnancy Category

C: Drug Pregnancy Category Animal reproduction studies have shown an adverse effect on the fetus and there are no adequate and well-controlled studies in humans, but potential benefits may warrant use of the drug in pregnant women despite potential risks.
Lactation

Enters breast milk/not recommended
Storage Conditions

Oral: Store below 30°C.
ATC Classification
 N06AX16
GenericPedia Classification
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    Storage

    Oral: Store below 30°C.
    Available As
  • Venlafaxine 150 mg
  • Venlafaxine 25 mg
  • Venlafaxine 37.5 mg
  • Venlafaxine 50 mg
  • Venlafaxine 75 mg

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