Venlafaxine
Mechanism :
Venlafaxine selectively inhibits the neuronal re-uptake of serotonin, norepinephrine and to a lesser extent dopamine. It has minimal affinity for muscarinic, histamine or a1-adrenergic receptors. It appears to be as effective as standard antidepressants with a lower incidence of the anticholinergic side effects.
Indication :
Contraindications :
Uncontrolled hypertension; high risk of serious ventricular arrhythmia.
Dosing :
Its use in children <18 years is not recommended.
Anxiety:
Initial: 37.5-75 mg/day orally.
Maintenance: Children, 75-150 mg/day; adolescents, 150-300 mg/day.
Attention deficit disorder:
<40 kg:
12.5 mg/day oral, initially, increase by 12.5 mg weekly. Max: 50 mg/day in 2 divided doses.
>40 kg:
12.5 mg/day oral, initially, increase by 25 mg weekly. Max: 75 mg/day in 3 divided doses.
Adverse Effect :
Nausea, vomiting, anorexia, dry mouth, constipation, dyspepsia, orthostatic hypotension, tremor, sweating, anxiety, dizziness, fatigue, headache, syncope, insomnia, somnolence, aggressive behaviour (especially at the start and when stopping therapy), rash, visual disturbances, mydriasis, increased cholesterol concentrations, increased LFT, sexual dysfunction. Potentially fatal: Blood dyscrasias, Stevens-Johnson syndrome, hepatitis.
Interaction :
Triptans, Linezolid, Lithium, Tramadol: Risk of serotonin syndrome.
TCA, SSRI: Increased risk of anticholinergic side effects and serotonin syndrome.
Indinavir: Decreased indinavir concentration with concurrent use.
Warfarin: Increased INR with warfarin.
Metoclopramide, and Amoxicillin with Clavulanate Combinations: Possible risk of serotonin syndrome.
Monoamine Oxidase Inhibitors: Potentially Fatal Interaction: 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.
Sibutramine: Increased risk of serotonin syndrome with sibutramine.
Renal Dose :
Dose in Renal Impairment GFR (mL/min)
| 30-50 | Dose as in normal renal function |
| 10-30 | Reduce total dose by 50% and administer daily |
| <10 | Reduce total dose by 50% and administer daily |
Dose in Patients undergoing Renal Replacement Therapies
| CAPD | Not dialysed. Dose as in GFR<10 mL/min |
| HD | Not dialysed. Dose as in GFR<10 mL/min |
| HDF/High flux | Unknown dialysability. Dose as in GFR<10 mL/min |
| CAV/VVHD | Not dialysed. Dose as in GFR=10–30 mL/min |
Hepatic Dose :
Mild to moderate hepatic impairment: Decrease daily dose by 50%.
Severe hepatic impairment or hepatic cirrhosis: Decrease daily dose by 50% or even more.