Nitroglycerin half-life

Isosorbide is rapidly absorbed and undergoes rapid first-pass metaboHsm by the Hver. The bioavaUabUity of the subHngual and chewable tablets is 59% and 22%, respectively, for the regular tablet. Isosorbide is metabolized to isosorbide-2-mononitrate and isosorbide-5-mononitrate, both of which have pharmacologic activity. The elimination half-Hves of subHngual and po isosorbide dinitrate ate 1 and 4 h, respectively. Those of the 2- and 5-mononitrate metaboHtes are 1.5—3.1 h and 4—5.6 h, respectively. The two metaboHtes prolong the elimination half-life of the dinitrate. Adverse effects with isosorbide are similar to those described for nitroglycerin (99). 

Nitroglycerin is a lipid-soluble substance that is rapidly absorbed across the sublingual or buccal mucosa. Its onset of action occurs within 2 to 5 minutes, with maximal effects observed at 3 to 10 minutes. Little residual activity remains 20 to 30 minutes after sublingual administration. The plasma half-life of nitroglycerin, given... 

Although the above arguments provide useful general rules, there are many exceptions. Nitroglycerin has a biological half-life of less than 0.5 h. It is generally considered to be poorly absorbed and is rapidly... 

If absorption is slow, and the apparent absorption half-life is much longer than the elimination half-life, then the dose regimen can be based on the apparent half-life of the absorption phase. Changing the formulation is a relatively common approach that is taken for short-acting drugs to extend the duration of absorption. The elimination half-life of nitroglycerin is approximately 2 min. However, nitroglycerin from a transdermal formulation is slowly released, and therapeutic plasma concentrations can be maintained for 24 h. 

Bauer, J. A., and Fung, H.-L. (1993b). Effect of apparent elimination half-life on nitroglycerin-induced hemodynamic rebound in experimental heart failure. Pharm. Res. 10,1341-1445. 

Short Sublingual nitroglycerin or isosorbide dinitrate 10-30 minutes (isosorbide dinitrate has a somewhat longer half-life than nitroglycerin)... 

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