GTN is given sub-lingually, why?

Ans: a (To avoid first pass metabolism) Ref: Goodman & Gilman, 11th ed, p. 3SUBLINGUAL ADMINISTRATIONVenous drainage from the mouth is to the superior vena cava, which protects highly soluble drugs like nitroglycerin from rapid hepatic first-pass metabolism. If a tablet of nitroglycerin were swallowed, the accompanying hepatic metabolism would be sufficient to prevent the appearance of any active nitroglycerin in the systemic circulation.