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Alpha Adrenergic AntagonistAka: Prazosin, Minipress, Terazosin, Hytrin, Doxazosin, Cardura, Tamsulosin, Flomax

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  1. Indications
    1. Benign Prostatic Hypertrophy
    2. Hypertension (not Tamsulosin)
  2. Mechanism: General
    1. See Alpha Adrenergic Receptor (Alpha-1 antagonist)
  3. Mechanism: Benign Prostatic Hypertrophy
    1. Preparations used in Benign Prostatic Hypertrophy
      1. Terazosin (Hytrin)
      2. Doxazosin (Cardura)
      3. Tamsulosin (Flomax)
      4. Prazosin (Minipress)
    2. Rapid relaxation of smooth muscle tone
      1. Bladder neck
      2. Prostate Capsule
      3. Prostatic Urethra
    3. Relieves symptoms of urinary obstruction
      1. May see full effect within 2 weeks
    4. Does not effect size of prostate (unlike Proscar)
  4. Preparations
    1. Prazosin (Minipress)
      1. Dose: 1 mg PO bid-tid (Maximum 40 mg/day)
      2. Less expensive but not available for once daily dose
    2. Terazosin (Hytrin)
      1. Dose: 1 mg PO qhs (Maximum 20 mg/day)
    3. Doxazosin (Cardura)
      1. Dose: 1 mg PO qd (Maximum 16 mg/day)
    4. Phenoxybenzamine (Dibenzyline)
      1. Dose: 10 mg PO bid (Maximum 120 mg/day)
    5. Tamsulosin (Flomax)
      1. More expensive than other agents
      2. Dose 0.4 mg PO qd (maximum 0.8 mg/day)
      3. Highly selective alpha-1a blocker
        1. Does not effect Blood Pressure
        2. May be more effective in BPH than other agents
  5. Combination Alpha-Beta Antagonist (Labetalol or Trandate)
    1. Oral: 100 mg PO bid (Maximum: 2400 mg/day)
    2. Intravenous: 20 mg IV q10 minutes (Maximum: 200 mg)
  6. Adverse effects (Incidence: 7 to 9%)
    1. Dose at bed and slowly titrate to reduce side effects
    2. Cardiovascular adverse effects (not Tamsulosin)
      1. Dizziness
      2. Postural Hypotension
    3. Other adverse effects
      1. Fatigue
      2. Asthenia
  7. Precautions
    1. Avoid using as monotherapy for Hypertension
      1. Higher risk of CVA and CHF compared with other agents
      2. (2000) JAMA 283:1967
  8. References
    1. (1994) Med Lett Drugs Ther 36:15
    2. (1997) Med Lett Drugs Ther 39:1011
    3. Lee (2000) Ann Pharmacother 34:188
    4. Aldridge (1996) Lancet 348:602

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