Comparison of 24-hour ambulatory blood pressure data in hypertensive patients switched from nifedipine-GITS to nifedipine-CC

Study Objective. To evaluate 24-hour blood pressure control and frequency o f adverse effects in patients with mild to moderate hypertension switched f rom 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 moni tored 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 takin g 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 fro m 7:00 A.M.-10:00 P.M.), nighttime blood pressure load (percentage of value s > 120/80 mm Hg from 10:00 P.M.-7:00 A.M.), diurnal blood pressure variati on, average 24-hour blood pressure, daytime blood pressure, nighttime blood pressure, mean blood pressure for the first 4 hours, and last 8 hours of t he dosing interval were measured. Adverse effects such as headache, dizzine ss, and edema were also reported. Measurements and Main Results. No differences in average 24 hour-blood pres sure readings were observed but significant differences in blood pressure c ontrol 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 h ours. This could explain the lack of differences in average 24-hour blood p ressure values between formulations. Of the 20 patients, 20% experienced in creased headaches, 20% showed signs of increased peripheral edema, and 10% reported occasional dizziness after switching agents. Three patients discon tinued Nif-CC, two as ordered by their primary care physician and one on hi s own due to headache. Conclusion. This study suggests that patients switched from Nif-GITS to Nif -CC could experience increased blood pressure during the night or toward th e end of the dosing interval. They could also experience adverse effects su ch as headache, edema, and dizziness, which could result in more physician visits and put patients with other disease states such as coronary heart di sease at increased risk.