[Pharmacokinetics of glycerol trinitrate]

The absorption, distribution and elimination of glyceryl trinitrate (GTN) in the human are extremely rapid processes. Enzymatic denitration occurs not only in the liver, but also in blood and other organs. The terminal half-life is 2-6 minutes, and clearance about 30 l/min. A large distribution volume indicates that GTN is taken up by peripheral tissues with the consequence that the concentration at the site of action is greater than in blood. The denitrated and glucuronidated metabolites make only a minor contribution to the anti-anginal effect. Within the therapeutic range there is a linear relationship between the applied dose and concentration in blood and this relationship is independent of the mode of application. GTN plasma concentration may fluctuate during prolonged infusions and transdermal application. GTN measurement on multiple plasma samples collected during the dosage interval are therefore required to obtain a reliable estimate of the steady state concentration. Individual dosage regimens are necessary to optimize therapy.