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Clinical pharmacy 2024/2025 Level 3 Pharm D Pharmacology 1 (PO 502)

7- α-adrenergic blocking agents

Examples and Prazosin, doxazosin, and terazosin ➔ competitive block of α1

MOA adrenoceptors
treat mild to moderate hypertension ➔ in combination with
Uses
propranolol and//or a diuretic for additive effects.
➢ ↓ peripheral vascular resistance ➔ ↓ arterial blood pressure by causing

relaxation of both arterial and venous smooth muscle.
Action
➢ Postural hypotension (excessive vasodilation in legs) may occur in

some individuals.
 Reflex tachycardia and first-dose syncope ➔ universal adverse
effects (avoided by decrease the dose)

➔ Concomitant use of β-blocker ➔ blunt the short-term effect of
reflex tachycardia (especially in myocardial infarction)
S/E
 Because of the side-effect profile ➔ tolerance (increase dose to

reach the same effect), and the advent of safer antihypertensive ➔
 α-blockers ➔ seldom used as monotherapy in treatment of
hypertension.
➢ cause only minimal changes in cardiac output, renal blood flow, and

glomerular filtration rate.
Advantages
➢ long-term tachycardia does not occur, but salt and water retention dose

(overcome by diuretics)

NOTE

Tamsulosin ➔ α1-blockers with greater selectivity for prostate muscle ➔ treatment of
benign prostatic hyperplasia.

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