Immediate cardiovascular responses to oral prazosin--effects of concurrent beta-blockers.

Abstract

Initiation of prazosin therapy may be complicated by the first-dose response of acute postural hypotension and tachycardia. The effects of beta-blocker on the responses to oral prazosin were studied in eight normotensive men. After 1 mg oral prazosin there was a marked postural fall in blood pressure to a lowest mean standing systolic pressure of 88 +/- 7 mm Hg (mean +/- SD), associated with a tachycardia of 117 +/- 13 bpm, and an increase in mean plasma norepinephrine concentration to 9.6 +/- 7.9 nmole/l. There was a linear relationship (r = 0.93) between plasma prazosin concentration and hypotensive effect. Concurrent propranolol 80 mg or primidolol 100 mg (a cardioselective beta-blocker) increased the severity and duration of the postural hypotensive response, with lowest mean systolic blood pressure (BP) of 79 +/- 7 and 75 +/- 9 mm Hg. There was no effect on the orthostatic release of norepinephrine but there was attenuation of the postural tachycardia. Concurrent beta-adrenergic blocking therapy, selective or nonselective, intensifies the immediate postural hypotensive response to the initial dose of prazosin.

• Authors: H L Elliott, K McLean, D J Sumner, P A Meredith, J L Reid
• Journal: Clinical pharmacology and therapeutics (Clin Pharmacol Ther) Vol. 29 Issue 3 Pg. 303-9 (Mar 1981) ISSN: 0009-9236 [Print] United States
• PMID: 6110503 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Adrenergic beta-Antagonists
• Catecholamines
• Quinazolines
• Prazosin

Topics

• Administration, Oral
• Adrenergic beta-Antagonists (administration & dosage, pharmacology)
• Adult
• Blood Pressure (drug effects)
• Catecholamines (blood)
• Dose-Response Relationship, Drug
• Drug Therapy, Combination
• Heart Rate (drug effects)
• Humans
• Hypotension, Orthostatic (chemically induced)
• Male
• Prazosin (administration & dosage, adverse effects, blood)
• Quinazolines (adverse effects)