• Type: SNRI
  • Dosage Forms:
  • Routes of Administration: Oral
  • Common Trade Names: Effexor

Adult Dosing

  • Extended release: 37.5-225mg PO daily
  • Immediate release: 75-375mg PO daily in 2-3 divided doses

Pediatric Dosing

Safety/efficacy not established

Special Populations

  • Pregnancy Rating: C
  • Lactation risk: Infant risk cannot be ruled out
  • Renal dosing: decrease dose by 25-50%
  • Hepatic dosing: decrease dose by 25-50%


  • Allergy to class/drug
  • MAOI use concomitantly or within past 14 days


  • Sodium channel blocking properties, similar to TCA toxicity and should be treated similarly:
    • Sodium bicarbonate for QRS prolongation
    • Benzodiazepines for seizures
  • QTc prolongation

Adverse Reactions


  • Seizure
  • Neuroleptic malignant syndrome, serotonin syndrome
  • GI bleed
  • Hepatitis
  • Hyponatremia
  • Exacerbation of depression, suicidality, mania


  • Constipation, nausea, xerostomia, anorexia, weight loss
  • Dizziness, insomnia, somnolence, dream disorder, tremor, anxiety, blurred vision
  • Sweating
  • Hypertension
  • Sexual dysfunction


  • Half-life: 5-11h
  • Metabolism: Hepatic, CYP2D6
  • Excretion: Mostly renal

Mechanism of Action

  • Inhibits serotonin, norepinephrine and dopamine reuptake


See Also


  1. Whyte IM et al. Relative toxicity of venlafaxine and selective serotonin reuptake inhibitors in overdose compared to tricyclic antidepressants. QJM: An International Journal of Medicine, Volume 96, Issue 5, 1 May 2003, Pages 369–374.