The influence of alpha 1-adrenergic blockade on the acute antihypertensive effect of nifedipine.
The hypotensive effect of vasodilator monotherapy in hypertension is attenuated by a baroreceptor-mediated increase in the sympathetic release of noradrenaline. Nifedipine induces a rise in noradrenaline release, but it is not known to affect noradrenaline-induced vascular contraction of smooth muscle to a clinically significant degree. The haemodynamic and hormonal effects of a single sublingual dose of nifedipine 20 mg in 8 moderately hypertensive patients have been studied before and during postsynaptic alpha 1-blockade with prazosin. The antihypertensive effect of nifedipine was significantly increased by prazosin pretreatment (fall in mean arterial pressure 60 min after nifedipine: -16.7% with and -8.5% without prazosin), despite similar increases in plasma noradrenaline. Prazosin alone caused no change in supine blood pressure for 2 h after an oral dose of 2 mg. The findings are in keeping with the hypothesis that prazosin blocks a compensatory reaction to vasodilatation caused by nifedipine.
Sluiter
H E
HE
Huysmans
F T
FT
Thien
T A
TA
Koene
R A
RA
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000328:Adult; D000368:Aged; D000959:Antihypertensive Agents; D001794:Blood Pressure / Q000187:drug effects; D004347:Drug Interactions; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D008297:Male; D008875:Middle Aged; D009543:Nifedipine / Q000494:pharmacology*; D011224:Prazosin / Q000494:pharmacology; D013997:Time Factors
D000317:Adrenergic alpha-Antagonists; D000959:Antihypertensive Agents; D009543:Nifedipine; D011224:Prazosin