Alpha Blockers

Mechanism of action

  • α-blockers are pharmacological agents that act as neutral antagonists or inverse agonists of α-adrenergic receptors
  • Blocks Alpha-1 receptors in blood vessels (arteries and veins). By blocking these receptors, blood vessels will dilate (relax) and lower blood pressure.

Treatment

  • High blood pressure (hypertension)
  • Benign prostate hyperplasia
  • Raynaud syndrome
    • spasm of arteries causes periods of reduced blood flow
  • Scleroderma
    • Autoimmune diseases which cause changes to changes to the skin, blood vessels, muscles, and internal organs

Names of Selective α1-adrenergic Receptor Antagonists

  • Alfuxosin (Uroxatral, Xat, Xatral, Prostetrol and Alfural)
  • Doxazosin (Cardura)
    • Increased cardiac output during exercise at 50% VO2 Max (ACSM 2013)
    • No change of heart rate during exercise up to 50% VO2 Max (ACSM 2013)
    • Increase of heart rate during exercise at 75% VO2 Max (ACSM 2013)
  • Prazosin (Minipress)
    • Acute administration (ACSM 2013)
      • Increased heart rate during exercise
    • Chronic administration (ACSM 2013)
      • No change during exercise
  • Tamsulosin (Flomax)
  • Terazosin (Hytrin)
  • Silodosin (Rapaflo, Silodyx, Rapilif, Silodal, Sildoo, Urief, Thrupas, Urorec)

Effect on Exercise and Rest

  • No effect on heart rate (Niedfeldt 2002, ACSM 2013)
  • Decrease of systolic blood pressure (ACSM 2013)
  • No change of diastolic blood pressure (ACSM 2013)
  • No effect on stroke volume (Niedfeldt 2002)
  • No effect on cardiac output (Niedfeldt 2002)
  • Decrease in vascular resistance (Niedfeldt 2002)
  • No effect on plasma volume (Niedfeldt 2002)
  • Decreased exercise ischemia (ACSM 2013)
  • No effect on training (Niedfeldt 2002)
  • No effect on performance (ACSM 2013)

Potential Side Effect

  • First-dose hypotensive effect with alpha-1 blockers especially in elderly patients (Niedfeldt 2002)
  • Centrally acting agents may cause drowsiness, dry mouth, and impotence (Niedfeldt 2002)
  • Rebound hypertension can occur with abrupt discontinuation of clonidine (Catapres), an alpha agonist (Niedfeldt 2002)

Recommended Populations

  • Recommended for those with hyperlipidemia or benign prostatic hyperplasia (BPH) (Niedfeldt 2002)

Populations Not Recommend

  • Not recommended for men older than 55 (Niedfeldt 2002)

Banned Status

  • None

References

American College of Sports Medicine (2013). Guidelines for Exercise Testing and Prescription, William & Wilkins, 9, 402.

Niedfeldt MW (2002). Managing Hypertension in Athletes and Physically Active Patients. Am Fam Physician. 1;66(3):445-453.

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