Elantan long (EL) is the only long-acting isosorbide mononitrate formulation based on a controlled membrane principle. 30% of the dose is available for immediate release and the remaining 70% is gradually released over time. After oral administration, isosorbide mononitrate EL has a quick onset of action (30 minutes) and effects are evident for up to 17 hours. The antianginal effects of once-daily isosorbide mononitrate EL 50 to 100mg were generally similar to those of conventional isosorbide mononitrate or isosorbide dinitrate 10 to 20mg twice or 3 times daily, or sustained-release nifedipine 20mg twice or 3 times daily. Patients tended to show a better response with once-daily isosorbide mononitrate EL 50mg than with bupranolol 100mg. Patients showed significantly greater improvement in some quality-of-life indices with once-daily isosorbide mononitrate EL than with twice or 3 times daily regimens of conventional isosorbide mononitrate or isosorbide dinitrate. Tolerance did not develop after 13 months of once-daily administration of isosorbide mononitrate EL. No rebound increase in incidence of ischaemic episodes was observed after discontinuation of the drug.