Effects of the converting enzyme inhibitor quinapril on autonomic function in normotensive and essential hypertensive subjects

The lack of reflex tachycardia observed after quinapril administration suggests some specific influence on autonomic function. Twelve healthy volunteers and 12 patients with essential hypertension were given a single oral 20-mg dose of quinapril and a single dose of matching placebo, in a double-blind crossover design. Blood pressure and heart rate were monitored noninvasively on a beat-to-beat basis for eight hours and indexes of autonomic function at the time of maximum effect were measured. Identical results were obtained in both normotensives and hypertensives. Neither the pressor nor the chronotropic responses to the isometric exercise and the cold pressor test were influenced by quinapril. During dynamic exercise the increments in heart rate and systolic blood pressure were unchanged by quinapril. In the orthostatic test quinapril did not significantly alter the heart rate ratio. Similarly, the heart rate response to deep breathing and apneic facial immersion showed no significan...