Pharm

Selective Alpha-1a Antagonist

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Selective Alpha-1a Antagonist, Tamsulosin, Flomax, Alfuzosin, Uroxatral, Silodosin, Rapaflo

  1. Background
    1. Non-Selective Postsynaptic Alpha Adrenergic Antagonist (Terazosin, Doxazosin, Prazosin)
      1. Relatively weak antihypertensives, were often used for BPH
    2. Selective Alpha-1a Antagonist
      1. Developed for specific Alpha-1a activity with minimal antihypertensive effects
  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)
  • Preparations
  • Selective Alpha-1a Antagonists (Prostate specific agents)
  1. Precautions
    1. Still cause Orthostatic Hypotension, fall risk, Head Trauma and Fractures, despite selective nature
    2. Number needed to harm (NNH): 600 for fall-related hospitalizations, and 1600 for fall-related Fractures
    3. Welk (2015) BMJ 351:h5398 +PMID:26502947 [PubMed]
  2. Alfuzosin (Uroxatral, generic)
    1. Dose: 10 mg once daily
    2. Contraindicated in moderate to severe liver disease (and Exercise caution in renal disease)
  3. Silodosin (Rapaflo)
    1. Dose: 8 mg daily with food (4 mg daily if GFR 30-50 ml/min)
    2. Contraindicated when GFR <30 ml/min or severe liver disease (Child-Pugh Score 10 or more)
  4. Tamsulosin (Flomax, generic)
    1. Dose 0.4 mg orally daily (maximum 0.8 mg/day)