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Drugs, Supplies and Delivery
Venlafaxine (Effexor)
Venlafaxine, commonly marketed under the brand name Effexor (not Lustral¹), is a serotonin-norepinephrine reuptake inhibitor (SNRI) used to treat major depressive disorder (MDD), anxiety disorders, and other psychiatric conditions. Known for its dual mechanism of action, venlafaxine is effective but requires careful management due to its dose-dependent side effects. This article synthesizes information from the British National Formulary (BNF), Lippincott Textbook of Pharmacology, and Lange Basic & Clinical Pharmacology to provide a detailed overview of venlafaxine, including its mechanism, uses, dosing, side effects, precautions, interactions, and availability.
Venlafaxine inhibits the reuptake of serotonin (5-HT) and norepinephrine (NE) at presynaptic neurons, increasing their availability in the synaptic cleft. This dual action enhances mood regulation and arousal:
- At lower doses (≤150 mg/day), it primarily blocks serotonin reuptake.
- At higher doses (>150 mg/day), it additionally inhibits norepinephrine reuptake (Lippincott Textbook of Pharmacology).
This SNRI activity differentiates it from SSRIs and contributes to its efficacy in treatment-resistant depression (Lange Basic & Clinical Pharmacology).
¹Note: Lustral® is a brand name for sertraline, an SSRI. Venlafaxine is marketed as Effexor® or Efexor®.
- Major Depressive Disorder (MDD):
- First-line treatment for acute episodes and maintenance therapy (BNF).
- Generalized Anxiety Disorder (GAD):
- Reduces excessive worry and physical symptoms.
- Social Anxiety Disorder (SAD):
- Alleviates fear of social interactions.
- Panic Disorder:
- Decreases frequency and severity of panic attacks (Lange Basic & Clinical Pharmacology).
- Adults:
- Initial Dose: 37.5–75 mg once daily (immediate-release) or 75 mg once daily (extended-release).
- Maintenance Dose: 75–225 mg/day; maximum 375 mg/day (immediate-release) or 225 mg/day (extended-release) (BNF).
- Elderly or Hepatically Impaired Patients:
- Start with 37.5 mg/day and titrate cautiously (Lippincott).
Administration:
- Take with food to reduce nausea.
- Extended-release capsules (Effexor XR®) must be swallowed whole; do not crush or chew.
- Common: Nausea, headache, dry mouth, insomnia, and sweating (BNF).
- Serious:
- Hypertension: Dose-dependent increase in blood pressure (monitor regularly).
- Serotonin Syndrome: Agitation, hyperthermia, and tachycardia (rare but life-threatening).
- Withdrawal Symptoms: Dizziness, irritability, and "brain zaps" if abruptly discontinued (Lange Basic & Clinical Pharmacology).
- QT Prolongation: Risk increases at high doses or with predisposing conditions (Lippincott).
- Contraindications:
- Concurrent use of MAO inhibitors (risk of serotonin syndrome).
- Uncontrolled hypertension or severe cardiovascular disease (BNF).
- Monitoring:
- Blood pressure at baseline and during dose escalation.
- Renal/hepatic function in impaired patients.
- Pregnancy/Lactation:
- BNF Category C: Use only if benefits outweigh risks; potential neonatal withdrawal.
- Excreted in breast milk—consult a specialist (Lippincott).
- MAO Inhibitors: Risk of serotonin syndrome; allow a 14-day washout period (BNF).
- Other Serotonergic Drugs (e.g., tramadol, triptans): Increased serotonin syndrome risk.
- CYP2D6 Inhibitors (e.g., fluoxetine, paroxetine): Raise venlafaxine levels; reduce dose by 50% if combined.
- NSAIDs/Anticoagulants: Elevated bleeding risk due to platelet inhibition (Lange Basic & Clinical Pharmacology).
Venlafaxine is the generic name. Brand names include Effexor® (immediate-release) and Effexor XR® (extended-release). Generic formulations are widely available as:
- Tablets: 25 mg, 37.5 mg, 50 mg, 75 mg, 100 mg.
- Capsules (XR): 37.5 mg, 75 mg, 150 mg.
- Oral Solution: 37.5 mg/5 mL (BNF).
