Safety and Efficacy of a Mandatory Formulary Switch From Nifedipine GITS to Amlodipine

OBJECTIVE: To analyze retrospectively the effects on blood pressure (BP) control of a mandatory switch from nifedipine in the gastrointestinal therapeutic system (GITS) to amlodipine. DESIGN: Retrospective review of a randomized sample of medical records to assess the safety and efficacy of the medication change. All outpatient pharmacy prescriptions (n=525) had been converted over the course of a year by the patients' clinicians to amlodipine when the current refills for nifedipine GITS had expired. We reviewed a randomized sample of patients' medical records (n=182). SETTING: The Brockton/West Roxbury Veterans Administration Medical Center. PATIENTS: Patients on a stable dose of nifedipine GITS for three months or more before switching and on a stable dose of amlodipine for three months or more. MAIN OUTCOME MEASURES: The average of at least two outpatient BP measures was used as a measure of efficacy. RESULTS: Of the 86 patients who fulfilled the study criteria, 72 (84%) converted directly to amlodipin...