Which of the following is an active metabolite of another drug and is available as a separate drug for the treatment of angine?: (A) Isosorbide mononitrate, (B) Isosorbide dinitrate, (C) Nitroglycerine, (D) Propanolol
Answer is A. (Ref: KDT 6/e p525) It is a metabolite of isosorbide dinitrate and is also available as a separate drug. It undergoes least first pass metabolism.