Paroxetine

Aka: Paroxetine, Paxil, Paroxetine hydrochloride, Pexeva, Paroxetine mesylate

1. Mechanism
   1. Selective Serotonin Reuptake Inhibitor (SSRI)
2. Indications
   1. Major Depression
   2. Comorbid Generalized anxiety or Panic Attacks
   3. Obsessive Compulsive Disorder
   4. Suppression of premature ejaculation
   5. Social Anxiety Disorder or Social Phobia
   6. Post-Traumatic Stress Disorder
3. Pregnancy Risk
   1. Category D
   2. Neonatal withdrawal risk
      1. Sanz (2005) Lancet 365:482-7
   3. Increased Atrial and Ventricular Septal Defects
      1. Associated with first trimester exposure
      2. Associated with a two fold increased risk
      3. (2006) Obstet Gynecol 108:1601-3
4. Background
   1. Cost: $81 per month
5. Preparations
   1. Paxil (Paroxetine hydrochloride)
      1. Generic Paxil is available in United States in 2003
      2. Tablets (lower doses scored): 10, 20, 30, and 40 mg
      3. Oral Suspension: 10 mg/5 ml
   2. Paxil CR Tablets: 12.5, 25, and 37.5 mg
      1. Marketed as reducing GI upset with standard Paxil
      2. Must be swallowed whole without chewing
   3. Pexeva (Paroxetine mesylate)
      1. Likely has similar activity to Paxil but not proven
      2. Significantly less expensive than Paxil
6. Dosing: Paxil
   1. Start
      1. Adults: 20 mg PO qhs
      2. Elderly: 10 mg qd
   2. Titrate
      1. Adults: Increase by 10 mg every 2 weeks
   3. Maximum: 60 mg PO qhs
7. Mechanism
   1. Selective Serotonin Reuptake Inhibitor (SSRI)
   2. Increased Norepinephrine reuptake inhibitor activity
   3. Increased Anticholinergic activity
8. Pharmacokinetics
   1. Half Life: 1 day (shorter than most other SSRIs)
9. Drug Interactions
   1. Inhibits Cytochrome P450-2D6
   2. Raises Warfarin (Coumadin) levels and associated INR
   3. Raises Tricyclic Antidepressant levels
   4. Highly protein bound
      1. Interacts with other protein bound medications
   5. Allow 2 week wash-out prior to starting MAO inhibitor
10. Adverse Effects
    1. Anticholinergic side effects (Sedation, Constipation)
       1. Avoid in elderly with cognitive disorders
    2. Sedating on the Sedation to excitation continuum
       1. Most sedating of the SSRIs (administer at bedtime)
       2. Some patients may have paradoxical activation
    3. Sexual Dysfunction (inhibits nitric oxide synthetase)
       1. See Antidepressant Induced Sexual Dysfunction
       2. More common than with Fluoxetine or Sertraline
    4. Dysesthesia (skin Paresthesias)
    5. Dry Mouth
    6. Constipation
    7. Antidepressant Withdrawal on stopping medication
       1. Reduce dose by 10 mg per day every 5-7 days
       2. Taper down to 5-10 mg before discontinuing
    8. Less anxiety (more Anxiolytic) than other SSRIs
       1. Similar to Serzone on this spectrum
    9. Weight gain
       1. More common than with Fluoxetine or Sertraline
11. Precautions
    1. Use caution in Pediatric Depression
       1. Use may be associated with higher Suicide Risk
12. Resources
    1. Paxil Website (GlaxoSmithKline)
       1. http://www.paxil.com