Hypertension is a major potential problem among the increasing number of older persons in the population, threatening their health and shortening their life expectancy due particularly to stroke and congestive heart failure (CHF). Controlled studies have shown that antihypertensive drug therapy reduces the incidence of severe CHF, stroke and cardiovascular mortality in the elderly. Special consideration should be given to altered drug metabolism, altered responses to drugs, and concomitant medications when pharmacotherapy is instituted in the elderly. Angiotensin-converting enzyme (ACE) inhibitors are acceptable in the hypertensive older patient as first-line therapy for all grades of hypertension and as second-line therapy for the patient with CHF. Use of ACE inhibitors avoids many of the symptoms and metabolic disturbances associated with beta-blockers and diuretics. Quinapril is a new non-sulphydryl ACE inhibitor whose active metabolite, quinaprilat, has a relatively short accumulation half-life compared with enalapril and lisinopril but has an enhanced affinity for the converting enzyme, allowing rapid excretion of the drug while retaining a 24-hour antihypertensive effect with once-daily dosing. Quinapril is a valuable addition to the ACE inhibitor class, with demonstrated efficacy and safety in the older patient.

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Patients with mild to moderate hypertension (diastolic blood pressure > or = 95 and < or = 115 mmHg) and renal dysfunction entered one of two studies to assess the safety of efficacious daily doses of quinapril on renal function and blood pressure. Twenty-four patients with moderate renal impairment (MRI) (creatinine clearance > 30 and < or = 60 ml/min) entered 24 weeks of open-label quinapril treatment; 31 patients with chronic renal failure (CRF) (creatinine clearance < 30 ml/min) entered 16 weeks of open-label quinapril treatment. Patients with MRI initially received quinapril 5 mg once daily (qd) followed by titration to a maximum dosage of 40 mg/day (furosemide optional at 40 mg only). Patients with CRF initially received quinapril 2.5 mg qd and were titrated up to 20 mg/day (furosemide optional). Open-label quinapril treatment resulted in significant decreases in mean systolic (SBP) and diastolic (DBP) blood pressure. The 20 patients with MRI and the 28 with CRF who completed the open-label phase were then randomly assigned to continue active drug or to receive placebo in a 4-week, double-blind, drug-withdrawal phase. During the double-blind withdrawal phase, placebo-treated patients had significant increases in mean SBP and DBP from the end of open label. Creatinine clearance was essentially unchanged following open-label quinapril treatment or quinapril withdrawal. In conclusion, in patients with mild to moderate hypertension and renal dysfunction, quinapril in dosages of 5-40 mg qd for patients with MRI and 2.5 to 20 mg qd for patients with CRF significantly reduces blood pressure without adversely affecting renal function.

Overall response to quinaprilat in ambulatory blood pressure monitoring and clinic blood pressure measurements was not statistically or clinically different from the response to oral quinapril therapy during baseline. Withdrawal from quinapril resulted in clinically significant increases in all blood pressure measurements compared with baseline therapy; the differences between placebo and quinaprilat therapy were statistically and clinically significant. Two patients treated with quinaprilat withdrew due to hypotension; one patient required a dosage reduction. Parenteral quinaprilat safely maintained blood pressure control whereas placebo control did not during the 72-h interruption of quinapril.