Alpha Blockers in Hypertension Management

Alpha1 Blockers

• Cause vasodilation and reduce peripheral resistance and venous return
• Cause reflex sympathetic discharge, leading to tachycardia and salt and water retention
• Have favorable effects on plasma lipids
• Used as add-on therapy for resistant hypertension and primarily in hypertensive men with BPH
• Adverse effects: hypotension (first-dose effect, 50%), failure of ejaculation, and headache

Non-Selective Alpha Blockers

• Examples: Phentolamine and Phenoxybenzamine
• Used for pheochromocytoma
• Cause postural hypotension and reflex tachycardia

Combined Alpha1 and Beta Blockers

• Examples: Carvedilol and Labetalol
• Vasodilator β [α1/β] blockers
• Effective in black patients and used for hypertension with heart failure and PVD, pheochromocytoma-induced hypertension, hypertensive emergencies, and hypertension in pregnancy
• Adverse effects: bradycardia, AV block, asthma, and hypotension

Aldosterone Antagonists

• Competitively block mineralocorticoid receptors
• Administered orally with delayed onset but long duration of action
• Marked antihypertensive action
• Prolong survival in heart failure
• Adverse effects: gynecomastia, dysmenorrhea, and hyperkalemia

Sympatholytics

• Block sympathetic neural activation
• Used for moderate to severe hypertension
• Different sites of action and toxicity:
  • Centrally acting α2 agonists
  • Ganglionic blockers
  • Adrenergic neuron blockers
  • Alpha blockers
  • Beta blockers
  • Combined α1 and β blockers

Beta Blockers

• Most widely used antihypertensive drugs
• Less effective in black and older patients
• Four useful antihypertensive actions:
  • Decrease cardiac output
  • Depress RAAS
  • Reduce arterial resistance
  • Suppress reflex tachycardia
• Used for mild to moderate hypertension
• Used with vasodilators for severe hypertension
• Preferred in hypertension with:
  • CHD (angina, post-MI)
  • Heart failure (carvedilol)

Cardioselective Beta Blockers

• Examples: Bisoprolol, Carvedilol, Metoprolol, and Nebivolol
• Used in asthma, COPD, and PVD
• Adverse effects:
  • Bradycardia
  • AV blockade
  • Bronchoconstriction
  • Mask sign of hypoglycemia
  • Rebound hypertension and angina