Nifedipine Gastrointestinal Therapeutic System versus Nifedipine Coat-Core: Comparison of Efficacy via 24-Hour Ambulatory Blood Pressure Monitoring

Abstract

OBJECTIVE: To assess the comparable efficacy and adverse effect profile of two extended-release preparations of nifedipine — Gastrointestinal therapeutic system (GITS) and coat-core (CC) — In patients with mild-to-moderate hypertension. DESIGN: Single institution, single-blind, prospective study. SETTING: Dwight David Eisenhower Army Medical Center, Fort Gordon, GA. PATIENTS: Ninety-one patients who were taking nifedipine GITS as a sole antihypertensive agent were randomized to receive either GITS or CC. After 3 weeks, 24-hour ambulatory blood pressure monitoring was conducted and an adverse effect questionnaire was administered. The patients were then crossed over to the other treatment arm and monitoring was repeated after 3 weeks. MEASUREMENTS: Mean blood pressures, heart rates, and the percentage of readings exceeding 140 mm Hg systolic and 90 mm Hg diastolic were compared for the 24-hour period. Additionally, mean blood pressures at 4-hour intervals after drug administration and heart rate during the first 8 hours of the dosage interval were compared. RESULTS: Ninety-one patients enrolled, 79 completed the study, and 62 patients were included in the efficacy analysis. A statistically significant difference (p = 0.020) was shown only in the last 4-hour systolic blood pressure. However, this difference was small (122 ± 15 mm Hg with GITS vs. 126 ± 14 mm Hg with CC). There was no difference in the percentage of readings exceeding 140 mm Hg systolic or 90 mm Hg diastolic. Neither dosage nor treatment order had an effect on the results. Adverse effects were reported with a greater frequency during CC therapy (40 with CC vs. 22 with GITS; p = 0.006), but were generally transient. Discontinuation of the drug was necessary in 3 patients during the CC cycle. CONCLUSIONS: GITS and CC demonstrated clinically equivalent antihypertensive efficacy in the study population. The CC product may have a higher rate of adverse effects, but drug discontinuation was uncommon. Patients who are taking the GITS formulation of nifedipine as a sole antihypertensive agent can safely be switched to the CC preparation without a clinically important sacrifice in blood pressure control or a major increase in adverse effects that might lead to drug discontinuation. The results of this study cannot be extrapolated to patients with poorly controlled hypertension or with other conditions treated with nifedipine. At our military medical center or any cost-controlled institution, the reason to contemplate such a switch is clearly economic. We estimate that there are 600 patients at our institution receiving the GITS preparation, at an annual cost of $320 000. At the current market costs, a direct switch would lead to an annual savings of $120 000 for our institution. For patients currently taking the GITS nifedipine product, CC nifedipine offers adequate blood pressure control and is more cost effective.