<prompt> GTN is given sub-lingually, why?To avoid first pass metabolismRapid effectGastric irritationTo avoid side effects  <response>: 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. 