Effects of antihypertensive drug therapy on responses to isometric exercise.

The increases in heart rate and blood pressure induced by a standard isometric handgrip (IHG) stress in normal men were similar in degree to the changes found in an age-matched group of men with untreated essential hypertension. In hypertensive patients whose blood pressure was controlled at normal levels with hydrochlorothiazide or guanethidine, drugs that act primarily at peripheral sites, the pressor increases with IHG were not different from those found in the untreated subjects. In contrast, significantly augmented pressor responses to IHG were observed in patients treated with propranolol, methyldopa, or clonidine, agents with central antihypertensive activity. The observed hyperresponsiveness to the peripherally mediated reflexes involved in the pressor effects of IHG may be associated with chronic reduction of central sympathetic outflow.