The effect of captopril on autonomic reflexes in human hypertension.
The effects of acute administration of captopril on heart rate, blood pressure and physiological responses to head-up tilt, hand-grip, exercise and Valsalva manoeuvre were studied in 25 hypertensive subjects (10 untreated, 15 previously treated). After chronic administration for 8-12 weeks the effect on heart rate, blood pressure and the response to head-up tilt were studied again in 15 of these subjects. After the first dose of captopril (0.5 mg/kg), both systolic and diastolic blood pressures fell significantly, with no change in heart rate. Head-up tilting produced a significant increase in heart rate without any alteration in the blood pressure; hand-grip produced a significant increase in heart rate and blood pressure. These responses and exercise-induced tachycardia were unaltered by captopril. There was a significant reduction in the Valsalva ratio. After chronic administration the hypotensive efficacy was maintained for 10-12 h after the last dose, suggesting that twice daily dosage may be sufficient. There was a significant reduction in the basal supine heart rate by captopril. Head-up tilt produced the same physiological changes as in the acute study. These findings suggest that captopril has a vagotonic effect, possibly associated with resetting of baroceptor mechanisms. This could be one explanation for the hypotensive effect of captopril even in low-renin states.
D001341:Autonomic Nervous System / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects*; D002216:Captopril / Q000008:administration & dosage / Q000494:pharmacology*; D006339:Heart Rate / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000188:drug therapy* / Q000503:physiopathology; D011187:Posture; D011311:Pressoreceptors / Q000187:drug effects; D012018:Reflex / Q000187:drug effects; D014630:Vagus Nerve / Q000187:drug effects; D014636:Valsalva Maneuver
D002216:Captopril