The effect of food on the absorption of slow-release isosorbide-5-mononitrate tablets

Long-acting isosorbide mononitrate

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.

Clinical pharmacokinetics of nitrates

The pharmacokinetics of organic nitrates are discussed with emphasis on the possible clinical relevance. For glyceryl trinitrate, the measurement of plasma concentrations is very difficult. Its pharmacokinetics are unusual, with a very rapid disappearance from plasma, and large intraindividual and interindividual variations. After oral administration, there seems to be a very extensive first-pass hepatic extraction and the plasma concentrations are often below the detection limit; after sublingual administration, glyceryl trinitrate appears in plasma. With transdermal glyceryl trinitrate controlled-release systems, plasma concentrations of glyceryl trinitrate can be maintained over 24 hours, although with fluctuations and important intraindividual and interindividual variability. After administration of glyceryl trinitrate via different routes, glyceryl dinitrates and mononitrates are present in plasma. The pharmacokinetics of isosorbide dinitrate are somewhat easier to understand. The substance disappears less rapidly from the plasma than does glyceryl trinitrate. After oral administration, there is also a hepatic first-pass extraction; the plasma concentrations can be prolonged by administering slow-release products. Sublingual administration leads to higher plasma concentrations than oral administration. Isosorbide dinitrate is metabolized in the organism to isosorbide 5-mononitrate and isosorbide 2-mononitrate, which both have vasodilator activity: after administration of isosorbide dinitrate, the mononitrates, and mainly the 5-mononitrate, reach very high concentrations in plasma. Isosorbide 5-mononitrate has been studied in its own right as an antianginal agent: it is completely absorbed after oral administration; it has a half-life of around 4 hours, and oral standard and controlled-release formulations have been extensively studied.(ABSTRACT TRUNCATED AT 250 WORDS)