Venlafaxine

Aka: Venlafaxine, Effexor, Desvenlafaxine, Pristiq

1. Indications
   1. Major Depression including refractory cases
      1. Considered to be second-line agent
   2. Generalized Anxiety Disorder
2. Mechanism
   1. Similar activity as Tricyclic Antidepressants
   2. Serotonin Norepinephrine Reuptake Inhibitor
      1. Selective Serotonin Reuptake Inhibitor (<150 mg/day)
      2. Norepinephrine Reuptake Inhibitor (>150 mg/day)
   3. Minimally inhibits Dopamine uptake
3. Pharmacokinetics
   1. Half life: 5 to 11 hours
4. Background
   1. Cost: $60 per month
5. Preparations
   1. Effexor Tablets (scored): 25, 37.5, 75, 100 mg
   2. Effexor XR Capsules: 37.5, 75, 150 mg
   3. Pristiq (Desvenlafaxine)
      1. Active metabolite of Effexor XR
      2. No added benefit over Effexor XR and with possibly more adverse effects
      3. Reference
         1. (2008) Prescriber's Letter 15(5): 28
6. Dosing: Effexor
   1. Start: 25 mg PO tid
   2. Effective dose: 150-225 mg per day divided bid to tid
   3. Maximum dose: 375 mg per day
   4. Disadvantages: More adverse effects than Effexor XR
   5. Advantages: May be dosed once daily since metabolites offer similar duration to Effexor XR
7. Dosing: Effexor XR (extended release)
   1. Start: 37.5 to 75 mg PO qd
   2. Maximum: 225 mg PO qd
8. Precautions: Prominent Withdrawal symptoms
   1. See also Antidepressant Withdrawal
   2. Dizziness, irritability and Insomnia
   3. Symptoms start 3 days after stopping medication
   4. Effexor taper schedule
      1. Reduce dose 25 mg/day every 5-7 days
      2. Taper to 25-50 mg/day before stopping
   5. Effexor XR taper schedule
      1. Reduce dose 37.5 to 75 mg per day every 7 days
      2. Taper to 37.5 mg/day before stopping
9. Adverse Effects (higher with regular release Effexor)
   1. Anticholinergic (less than Tricyclic Antidepressants)
      1. Dizziness
      2. Somnolence
      3. Dry Mouth
   2. Nausea or Vomiting
      1. May be severe and limit dosing
      2. Start therapy at 25 mg per day
   3. Increased Blood Pressure
      1. Only seen with total daily doses 300 mg or higher
   4. Less Sexual Dysfunction than Prozac, Zoloft, Paxil
      1. Sexual dysfunction in 10-15% of cases
      2. Similar to Luvox and Celexa
      3. See Antidepressant Induced Sexual Dysfunction
   5. More stimulating (anxiogenic) than sedating
      1. Agitation or Insomnia may occur
   6. Decreased appetite and Weight loss may occur
10. Drug Interactions
    1. Minimal Cytochrome P450 interactions
11. References
    1. (1997) Am J Psych 154:1760
    2. Sundberg (1995) Depression Primary Care, PGM, p. 45-57