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Immediate cardiovascular responses to oral prazosin—Effects of concurrent β‐blockers
Author(s) -
Elliott Henry L,
McLean Kathleen,
Sumner David J,
Meredith Peter A,
Reid John L
Publication year - 1981
Publication title -
clinical pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.941
H-Index - 188
eISSN - 1532-6535
pISSN - 0009-9236
DOI - 10.1038/clpt.1981.40
Subject(s) - prazosin , medicine , orthostatic vital signs , blood pressure , propranolol , tachycardia , norepinephrine , anesthesia , heart rate , cardiology , antagonist , receptor , dopamine
Initiation of prazosin therapy may be complicated by the first‐dose response of acute postural hypotension and tachycardia. The effects of β‐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 (x̄ ± 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 β‐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 β‐adrenergie blocking therapy, selective or nonselective, intensifies the immediate postural hypotensive response to the initial oral dose of prazosin. Clinical Pharmacology and Therapeutics (1981) 29, 303–309; doi: 10.1038/clpt.1981.40