Use of quinapril in the elderly patient. Quinapril hydrochloride is a nonsulfhydryl angiotensin converting enzyme (ACE) inhibitor that has been extensively tested and found effective when administered once-a-day to hypertensive patients of both sexes and all degrees of hypertension and cardiac compromise, including those with left ventricular hypertrophy, with and without congestive heart failure. Observations with earlier ACE inhibitors led to reports that this class of drugs was relatively ineffective in older hypertensive patients. To ascertain the role of quinapril (greater than or equal to 10 mg/day) in older patients, its blood pressure-lowering effects in 1,175 hypertensive patients less than or equal to 65 years of age were compared with those in 304 patients greater than 65 years of age. An excellent response was observed in patients greater than 65 years of age with mild to moderate hypertension (diastolic BP, 95 to 105 mm Hg) and moderate to severe hypertension (diastolic BP, 106 to 115 mm Hg). The reductions in blood pressure achieved with quinapril were at least comparable to those obtained in the younger hypertensives, and were numerically (but not statistically) greater in the mild to moderate group (-14 mm Hg v-12 mm Hg). In addition, the percentage of patients who experienced adverse experiences was lower in the greater than 65 group than in the less than or equal to 65 group (15% v 19%). The main adverse experiences reported included dizziness, headache, cough, fatigue, and hypotension. These findings indicate that quinapril is at least as safe and effective in older hypertensives as in younger patients. 