Drug surveillance study of amlodipine in patients with hypertension not controlled with drug therapy: NORCON study

Abstract

Objective: This study was undertaken to assess the efficacy and tolerability of amlodipine as monotherapy and in combination therapy in patients with uncontrolled hypertension despite pharmacologic treatment. Methods: This observational, open, prospective, parallel, controlled, multicenter, comparative, postmarketing drug surveillance study included hypertensive outpatients (systolic blood pressure [SBP] ≥ 140 mm Hg and/or diastolic blood pressure [DBP] ≥ 90 mm Hg) whose hypertension was uncontrolled despite pharmacologic treatment. Randomly selected primary care physicians chose the patients and assigned them to the group (amlodipine monotherapy or amlodipine as part of a 2-drug antihypertensive regimen) they considered more appropriate. Each patient was to have ≥3 visits during the 4-month follow-up period. The initial dosage of amlodipine was 5 mg once daily; this dosage could be increased to 10 mg once daily to achieve control of hypertension. Main outcome measures included optimum and suboptimum control of hypertension and incidence of adverse events. Results: A total of 2628 patients (1838 [69.9%], amlodipine monotherapy; 790 [30.1%], combination therapy) participated in this study. Of these patients, 2406 had DBP ≥ 90 mm Hg at baseline. Only 29 patients had DBP > 90 mm Hg and SBP < 140 mm Hg. By the end of the study, 28.6% of the 2442 patients for whom data were available had achieved the optimum therapeutic goal (SBP < 140 mm Hg and DBP < 90 mm Hg). A total of 156 patients (5.9%) experienced adverse events, 93.0% mild (edema, headache, flushing) and 7.0% serious. In 78.3% of cases the prescribing physician considered the adverse event to be related to treatment, but none of the 13 serious adverse events in 11 patients were considered to be related to amlodipine. No significant difference in the incidence of adverse events was found between the patients receiving monotherapy and those receiving combination therapy. A significantly higher percentage of nondiabetic patients than diabetic patients experienced optimum control ( P < 0.05). Conclusions: Amlodipine appears to be a well-tolerated and effective antihypertensive drug for use in monotherapy or a combination regimen in patients with uncontrolled hypertension despite pharmacologic treatment. Because the maximum dose (10 mg once daily) was not required in most patients and because combination therapy was often not needed, amlodipine may be a low-cost option for the treatment of hypertension.