Objective: To compare the antihypertensive effects and incidence of side effects of two formulations of nifedipine: a prolonged action (PA) tablet bid and a gastrointestinal therapeutic system (GITS) tablet once daily.
Design: Patients with controlled hypertension (diastolic blood pressure less than 90 mmHg) on nifedipine-PA 10 mg (n = 74) or 20 mg (n = 99) bid were enrolled into an open label study consisting of six weeks of previous nifedipine-PA followed by six weeks of nifedipine-GITS therapy. Nifedipine-GITS was increased from 30 mg to 60 mg daily if the patient's diastolic blood pressure increased by at least 10 mmHg compared with the value after six weeks of nifedipine-PA.
Main results: Blood pressure after six weeks of nifedipine-PA 10 mg (142 +/- 1/86 +/- 1 mmHg) decreased (P < 0.01) after conversion to nifedipine-GITS 30 mg (137 +/- 1/84 +/- 1 mmHg). Blood pressure values for nifedipine-PA 20 mg patients were unchanged after conversion to nifedipine-GITS; 74 patients received nifedipine-GITS 30 mg and 14 patients required titration up to nifedipine-GITS 60 mg daily. Sixteen patients withdrew on nifedipine-PA and five withdrew on nifedipine-GITS, mostly for reasons unrelated to drug therapy. Twenty-three patients experienced adverse events on nifedipine-PA versus 20 patients on nifedipine-GITS therapy.
Conclusions: Patients whose hypertension is controlled by nifedipine-PA 10 or 20 mg bid can be successfully converted to nifedipine-GITS with most patients remaining normotensive on 30 mg daily.