Abstract
Study Objective. To evaluate 24-hour blood pressure control and frequency of adverse effects in patients with mild to moderate hypertension switched from nifedipine gastrointestinal therapeutic system (Nif-GITS) to nifedipine coat core (Nif-CC). Design. Open-label, prospective, switch study Setting. University-affiliated outpatient cardiology clinic. Subjects. Twenty patients with mild to moderate essential hypertension, who were taking Nif- GITS 30, 60, or 90 mg/day for 8 weeks or longer. Interventions. Patients stabilized with Nif-GITS 30, 60, or 90 mg were monitored over 24 hours with an ambulatory blood pressure monitor and were then switched to an equivalent dosage of Nif-CC. After 8 weeks ± 1 week taking Nif-CC, they were again monitored with a 24-hour blood pressure monitor. The 24-hour blood pressure load (percentage of values > 135/85 mm Hg for 24 hrs), daytime blood pressure load (percentage of values > 140/90 mm Hg from 7:00 A.M.-10:00 P.M.), nighttime blood pressure load (percentage of values > 120/80 mm Hg from 10:00 P.M.-7:00 A.M.), diurnal blood pressure variation, average 24-hour blood pressure, daytime blood pressure, nighttime blood pressure, mean blood pressure for the first 4 hours, and last 8 hours of the dosing interval were measured. Adverse effects such as headache, dizziness, and edema were also reported. Measurements and Main Results. No differences in average 24 hour- blood pressure readings were observed but significant differences in blood pressure control during the first 4 and last 8 hours of the dosing interval were seen. Systolic and diastolic blood pressures were higher after approximately 16 hours in patients switched from Nif-GITS to Nif-CC. Although Nif-CC caused a greater initial response, it was less effective than Nif- GITS after 16 hours. This could explain the lack of differences in average 24-hour blood pressure values between formulations. Of the 20 patients, 20% experienced increased headaches, 20% showed signs of increased peripheral edema, and 10% reported occasional dizziness after switching agents. Three patients discontinued Nif-CC, two as ordered by their primary care physician and one on his own due to headache. Conclusion. This study suggests that patients switched from Nif-GITS to NifCC could experience increased blood pressure during the night or toward the end of the dosing interval. They could also experience adverse effects such as headache, edema, and dizziness, which could result in more physician visits and put patients with other disease states such as coronary heart disease at increased risk.