Appropriateness of nitrate use in a general medicine population

BACKGROUND: Nitrates are one of the most commonly prescribed drug groups for cardiac disease, especially for angina pectoris and congestive heart failure. The chronic efficacy of nitrates is limited by the development of tolerance, which can be attenuated by use of sustained-release preparations or administration of regular-release preparations asymmetrically. OBJECTiVE: To determine whether patients receiving isosorbide 5-mononitrate (ISMN) use the drug in a pharmacologically appropriate manner and whether they had been instructed in the prophylactic use of sublingual nitrates prior to effort. METHODS: We administered a questionnaire regarding details of nitrate use to 229 patients with ischemic heart disease using oral ISMN, prescribed prior to their current admission. The study was conducted in a 600-bed university-affiliated hospital. RESULTS: We found that only 15% of patients receiving regular-release ISMN were taking the drug asymmetrically. In contrast, 82.6% of the patients receiving sustained-release ISMN were using the drug properly. Only 38.1% of the patients treated with regular-release ISMN were treated with the dose recommended in the literature. Furthermore, of the 190 patients who reported experiencing effort angina, only 17.9% had been instructed in the prophylactic use of nitrates prior to effort. CONCLUSIONS: The majority of patients (85%) using regular-release ISMN were taking the medication in an inappropriate fashion, while most patients taking sustained-release preparations were using them properly. More than half the patients treated with regular-release ISMN were treated with doses exceeding the recommended dose. In addition, most patients experiencing effort angina had not been instructed regarding the prophylactic use of nitrates. These findings suggest that both physicians and pharmacists must be reminded of the continuing need to properly counsel patients regarding appropriate drug use.