Pharmacology: Pharmacokinetics: The principal pharmacological action of Isosorbide-5-mononitrate is relaxation of vascular smooth muscle, producing significant vasodilator activity, the strongest effect being exerted on the venous system and a lesser effect on the arterial circulation. As a consequence, the heart has less work to perform against diminished resistance and therefore oxygen requirement is reduced.
Isosorbide-5-mononitrate is readily absorbed from the gastro-intestinal tract and does not undergo first-pass hepatic metabolism and bioavailability is nearly 100%. The rate of absorption is slowed by food but overall bioavailability is unchanged. Kinetics of Isosorbide-5-mononitrate are not significantly influenced by advancing age, hepatic or renal disease.
Isosorbide-5-mononitrate is widely distributed with a large apparent volume of distribution. It undergoes nearly total elimination in the liver by denitration and conjugation to form Isosorbide and Isosorbide glucoronide as inactive metabolites. Only 2% of Isosorbide mononitrate is excreted unchanged in the urine with an elimination half-life of around 5 hours.