NIFEDIPINE GASTROINTESTINAL THERAPEUTIC SYSTEM (GITS) FOR HYPERTENSIVE PATIENTS IN A PRIMARY-CARE SETTING - RESULTS OF THE EXTENDED-RELEASEADALAT CANADIAN TRIAL (EXACT)

Nifedipine gastrointestinal therapeutic system (GITS) is an extended-r elease dosage formulation that provides sustained blood concentrations of nifedipine over 24 hours. A 20-week, postmarketing surveillance st udy of the effectiveness and patient tolerability of nifedipine GITS 3 0 or 60 mg was conducted in the offices of 187 Canadian general practi tioners from September 1992 to March 1994. A total of 1700 patients pr eviously or newly diagnosed with mild-to-moderate essential hypertensi on (sitting diastolic blood pressure, 95 to 114 mm Hg) were included. The 20-week treatment period was completed by 1326 patients. Patients received nifedipine GITS 30 mg initially; the dose could be titrated u pward to 60 mg after 3 and 6 weeks. Of all patients entered, 605 (35.6 %) reported one or more adverse events. The three most frequently occu rring adverse events were headache (12.2%), peripheral edema (8.1%), a nd dizziness (2.9%). The frequency of adverse events was highest in th e first 3 weeks and decreased subsequently. The overall incidence of a dverse events was 29.8% in patients receiving 30 mg of nifedipine GITS and 25.3% in those receiving 60 mg; adverse events were the cause of study discontinuation in 12.3% of patients. The overall health status of patients as measured by the SF-36 questionnaire was comparable to t hat previously reported for healthy individuals. At baseline, mean (+/ -SE) systolic/diastolic blood pressure values for all patients were 16 0.1 +/- 0.4/97.4 +/- 0.2 mm Hg. Final blood pressure readings after 20 weeks of treatment in the 30-mg group (141.5 +/- 0.4/84.8 +/- 0.2 mm Hg) and the 60-mg group (146.6 +/- 0.8/88.8 +/- 0.4 mm Hg) were signif icantly decreased from baseline. At week 20, the 30-mg dose was suffic ient to maintain blood pressure in 74.5% of patients; 25.5% of patient s required 60 mg. Subgroup analysis revealed similar responses in pati ents who had received blood pressure medication before study initiatio n and those who had not. Response was also independent of age and type of previous antihypertensive therapy. In general medical practice, th e 30-mg and 60-mg doses of nifedipine GITS were both effective and wel l tolerated and had minimal or no negative effects on the overall heal th status of treated individuals.