Venlafaxine

Indications

Venlafaxine is used for: Depression, Anxiety, Panic disorder, Social anxiety disorder

Adult Dose

Oral Depression Adult: Conventional tab: Initially, 75 mg/day in 2 or 3 divided doses, may increase in increments of up to 75 mg/day at intervals of 4 days or more. Max: 375 mg/day. Extended-release: Initially, 37.5-75 mg once daily; in patients initiated at 37.5 mg once daily, may increase to 75 mg once daily after 4-7 days; dose may then be increased in increments of up to 75 mg/day at intervals of 4 days or more. Max: 225 mg/day. Panic disorder Adult: Extended-release: Initially, 37.5 mg once daily for a wk, may increase to 75 mg once daily after 7 days; increase in increments of up to 75 mg/day at intervals of 7 days or more. Max: 225 mg/day. Anxiety Adult: Extended-release: Initially, 37.5-75 mg once daily; in patients initiated at 37.5 mg once daily, may increase to 75 mg once daily after 4-7 days; dose may then be increased in increments of up to 75 mg/day at intervals of 4 days or more. Max: 225 mg/day. Hepatic impairment: Mild to moderate: Reduce dose by 50%.

Child Dose

Attention Deficit Disorder <40 kg: 12.5 mg/day PO initially; increase by 12.5 mg/week; not to exceed 50 mg/day divided twice daily >40 kg: 12.5 mg/day PO initially; increase by 25 mg/week; not to exceed 75 mg/day divided three times daily Depression Children: 37.5 mg/day PO initially Adolescents: 37.5-75 mg/day PO initially Maintenance: Children, 75-150 mg/day; adolescents, 150-300 mg/day

Renal Dose

Renal impairment: GFR <30 mL/min and patient requiring haemodialysis: Reduce dose by 50%.

Administration

Take with food

Contra Indications

Uncontrolled hypertension; high risk of serious ventricular arrhythmia.

Precautions

History of MI or unstable cardiac disease, seizure; hypomania or mania, increased intraocular pressure or at risk of acute narrow-angle glaucoma, at risk of bleeding. Renal and hepatic impairment. Gradual dose reduction is recommended rather than abrupt withdrawal. Pregnancy and lactation. Patient Counselling May impair ability to drive or operate machinery. Monitoring Parameters Monitor BP and heart rate regularly, cholesterol, mental status for depression. Closely observe for clinical worsening, suicidality and unusual changes in behaviour. Monitor for emergence of serotonin syndrome. In short-term studies, antidepressants increased the risk of suicidal thinking and behavior in children, adolescents, and young adults (<24 years) taking antidepressants for major depressive disorders and other psychiatric illnesses Lactation: Enters milk; not recommended

Pregnancy-Lactation

Pregnancy category: C Lactation: Enters milk; not recommended

Interactions

Increased risk of serotonin syndrome w/ TCA, SSRI, SNRI, lithium, sibutramine, tramadol. May increase serum levels w/ CYP3A4 inhibitors (e.g. ketoconazole, atazanavir, clarithromycin). May increase serum levels of haloperidol. May decrease serum levels of indinavir. May increase bleeding risk w/ aspirin, NSAIDs, warfarin and other anticoagulants. Potentially Fatal: Increased risk of serotonin syndrome w/ MAOIs, linezolid and methylene blue.

Side Effects

Side effects of Venlafaxine : >10% Headache (25-38%), Nausea (21-58%), Insomnia (15-24%), Asthenia (16-20%), Dizziness (11-24%), Ejaculation disorder (2-19%), Somnolence (12-26%), Dry mouth (12-22%), Diaphoresis (7-19%), Anorexia (15-17%), Nervousness (17-26%), Anorgasmia (5-13%) 1-10% Weight loss (1-6%), Abnormal vision (4-6%), Hypertension (2-5%), Impotence (4-6%), Paresthesia (2-3%), Tremor (1-10%), Vasodilation (2-6%), Vomiting (3-8%), Weight gain (2%), Flatulence (3-4%), Pruritus (1%), Yawning (3-8%), Dyspepsia (5-7%), Twitching (1-3%), Mydriasis (2%) <1% Angioedema, Agranulocytosis, Anemia, Anuria, Aneurism, Bacteremia, Myasthenia, Syncope, Suicide ideation/attempt Potentially Fatal: Blood dyscrasias, Stevens-Johnson syndrome, hepatitis.

Mode of Action

Venlafaxine and its active metabolite O-desmethylvenlafaxine selectively inhibit the neuronal reuptake of serotonin, norepinephrine and to a lesser extent dopamine. It has minimal affinity for muscarinic, histamine, or ?1-adrenergic receptors. It appears to be as effective as standard antidepressants but w/ a lower incidence of anticholinergic, sedative and CV side effects.