Rest and exercise hemodynamic and adrenergic responses to enalapril, hydrochlorothiazide, and combination treatment in patients with systemic hypertension.

The effects of enalapril (10-20 mg twice daily), hydrochlorothiazide (25-50 mg twice daily), and combination enalapril-hydrochlorothiazide therapy (10-20 mg enalapril/25-50 mg hydrochlorothiazide in combination tablet twice daily) were evaluated and compared to no therapy (control) in eight patients with mild to moderate hypertension at rest and during treadmill exercise. All active treatments reduced standing blood pressure in patients at rest compared to the control group (p less than 0.05); however, none produced significant reductions of standing blood pressure in patients at peak exercise. Standing heart rates of patients at rest and at peak exercise were not changed with active therapy. However, standing heart rate in patients at rest was lower with enalapril than with hydrochlorothiazide and combination therapy (p less than 0.05). Heart rate of patients on hydrochlorothiazide was higher than with control and other therapies at Stage I of exercise (p less than 0.01). Supine norepinephrine levels in patients at rest were elevated with both hydrochlorothiazide and combination therapy when compared to that in patients with enalapril and control (p less than 0.05). Treatment with enalapril alone produced no changes in plasma catecholamine levels compared to control. There were no differences between control and all treatment regimens in peak exercise levels of catecholamines. Thus, enalapril, hydrochlorothiazide, and combination therapy, although effective in lowering resting blood pressure, may not be effective in blunting the blood-pressure response to exercise. The drugs do not appear to have any significant effects on catecholamine levels in patients at peak exercise.