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Forearm vascular α 1 ‐adrenergic blockade by verapamil
Author(s) -
Abernethy Darrell R,
Winterbottom Lisa M
Publication year - 1990
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.1990.104
Subject(s) - phenylephrine , verapamil , vasoconstriction , medicine , forearm , brachial artery , vasodilation , plethysmograph , vascular resistance , anesthesia , propranolol , hemodynamics , phentolamine , blood pressure , surgery , calcium
With use of direct brachial artery infusion and measurement of forearm blood flow and vascular resistance by strain gauge plethysmography, the effect of verapamil on phenylephrine‐induced vasoconstriction was determined. Seven healthy men (age range, 19 to 47 years; weight range, 68 to 108 kg; mean blood pressure, 74 to 100 mm Hg; five nonsmokers) were systemically β‐blocked with intravenous administrations of 10 mg propranolol. Each subject then received ascending doses of phenylephrine (0.191 to 7.6 μg/min) alone and with concurrent verapamil (19.1 μg/min) by brachial arterial infusion. Dose‐ratio during verapamil infusion compared with control was 8.1 ( p < 0.05). No change in slope of the phenylephrine dose‐response curve was noted; however, consistent with the dose ratio, verapamil shifted the curve to the right with a decrease in the y intercept determined by linear regression (60.0 versus 40.3 mm Hg ml/100 ml forearm volume/min; p < 0.05). Verapamil‐induced attenuation of forearm vasoconstriction elicited by phenylephrine indicates that, in humans, in vivo verapamil forearm vasodilating effects are, in part, a result of α 1 ‐adrenergic blockade. Clinical Pharmacology and Therapeutics (1990) 47 , 755–759; doi: 10.1038/clpt.1990.104