Isosorbide-5-mononitrate is a longer acting active metabolite than the parent drug, isosorbide dinitrate (ISDN), with a half-life of around 4 hours. In coronary heart disease, myocardial infarction and in heart failure it causes a typical nitrate action on the central hemodynamics, but due to a complete systemic availability with high and predictable systemic drug levels, a drug action with a lower interindividual variability than with ISDN is to be expected. There is a close correlation between serum level and effect. The antianginal exercise tolerance increasing and unwanted effects as well as the development of tolerance to the drug action are comparable with those of ISDN. This naturally long-acting metabolite in ISDN works usually with a standard dosage of 20 mg twice daily.