Anti-anginal and anti-ischemic efficacy of conventional and slow release formulations of isosorbide-5-mononitrate in angina pectoris.

Isosorbide-5-mononitrate is an active metabolite of isosorbide dinitrate and is nearly 100% bioavailable after oral administration. Following administration of single oral doses of 10 to 50 mg, isosorbide-5-mononitrate exerts beneficial hemodynamic, anti-ischemic and anti-anginal effects within 30 to 45 minutes and the effects persist for several hours. During sustained therapy with conventional formulation, persistent anti-ischemic and anti-anginal effects have been reported when the drug is given in a dose of 20 mg two or three times a day. However, tolerance to anti-anginal and anti-ischemic effects develops rapidly if used in higher doses of 50 mg three times a day. Tolerance to anti-anginal effects within 20 hours of administration of a single oral dose of 100 mg, slow release isosorbide-5-mononitrate has been reported. Further, no improvement in exercise tolerance or ST segment depression could be documented at 4, 20 or 24 hours after therapy for one week with either 50 or 100 mg slow release isosorbide-5-mononitrate once a day. From the available reports, the most effective way to prescribe isosorbide-5-mononitrate for angina pectoris appears to be the conventional formulation in a dose of 20 mg two or three times a day.