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Venlafaxine

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Venlafaxine, Effexor, Venlafaxine Withdrawal

  • See Also
  1. Desvenlafaxine (Pristiq)
  2. Serotonin Norepinephrine Reuptake Inhibitor (SNRI)
  3. SNRI Overdose
  • Indications
  1. Major Depression including refractory cases
    1. Considered to be second-line agent
  2. Generalized Anxiety Disorder
  3. Obsessive Compulsive Disorder
  4. Post-Traumatic Stress Disorder
  • Mechanism
  1. Similar activity as Tricyclic Antidepressants
  2. Serotonin Norepinephrine Reuptake Inhibitor
    1. Selective Serotonin Reuptake Inhibitor (<150 mg/day)
    2. Both Serotonin and Norepinephrine Reuptake Inhibitor (>150 mg/day)
  3. Minimally inhibits Dopamine uptake
  • Pharmacokinetics
  1. Venlafaxine Regular Release
    1. Half life: 5 to 11 hours
  • Safety
  1. Unknown safety in Lactation
  2. Pregnancy Category C
  • Preparations
  • Venlafaxine
  1. Venlafaxine regular release (Effexor)
    1. Available as 25, 37.5, 75, 100 mg tablets (scored)
    2. Start: 25 mg PO tid
    3. Effective dose: 150-225 mg per day divided bid to tid
    4. Maximum dose: 375 mg per day
    5. Disadvantages: More adverse effects than Effexor XR
    6. Advantages: May be dosed once daily since metabolites offer similar duration to Effexor XR
  2. Venlafaxine extended release (Effexor XR)
    1. Available as 37.5, 75, 150 mg (capsules)
    2. Start: 37.5 to 75 mg orally daily
    3. Maximum: 225 mg orally daily
  3. Indications to decrease dose by 50% (or 25% if mild organ Impairment)
    1. Hepatic Impairment
    2. Renal Impairment or Hemodialysis
  • Adverse Effects
  • Prominent Withdrawal symptoms
  1. See also Antidepressant Withdrawal
  2. Symptoms start 1-3 days after stopping medication (mild symptoms may have onset within hours of missed pill)
    1. Dizziness
    2. Irritability
    3. Insomnia
    4. Headache
    5. Gastrointestinal upset
    6. Ataxia or Vertigo
    7. Paresthesias (including shock-like Sensations)
    8. Tachycardia
    9. Fever
  3. Effexor taper schedule
    1. Reduce dose 25 mg/day every 5-7 days
    2. Taper to 25-50 mg/day before stopping
  4. 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
  5. Alternatives to tapering with Effexor
    1. Start Sertraline (Zoloft) 50 mg orally daily on stopping Effexor
  • Adverse Effects (more common 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
  7. Photosensitivity
  8. Suicidal Ideation and self harm (children)
  9. Ocular changes
    1. Increased Intraocular Pressure (Exercise caution in Glaucoma)
    2. Mydriasis
  • Drug Interactions
  1. Minimal Cytochrome P450 interactions
  2. Metabolized by CYP2D6 and CYP3A4
  3. Avoid with MAO Inhibitors (including Linezolid)
  4. Exercise caution when combining with Cimetidine or Haloperidol
  5. Risk of Serotonin Syndrome (as with other SNRI and with SSRI)
    1. Monitor closely with Triptans
  • Resources
  1. Venlafaxine (DailyMed)
    1. https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=55889b3d-74c9-4638-9a14-6a4ca3a99f7f
  • References
  1. (2023) Med Lett Drugs Ther 62(1592): 25-32
  2. Olson (2020) Clinical Pharmacology, Medmaster Miami, p. 38-9
  3. Hamilton (2020) Tarascon Pocket Pharmacopoeia
  4. Mishler and Lovecchio (2017) Crit Dec Emerg Med 31(11): 15-20
  5. (1997) Am J Psych 154:1760 [PubMed]
  6. Sundberg (1995) Depression Primary Care, PGM, p. 45-57