Pharmacology: Pharmacokinetics: Losartan potassium (KENZAR) is readily absorbed from the gastrointestinal tract following oral administration. It undergoes first pass metabolism to form an active carboxylic acid metabolite which has a greater pharmacological activities. Peak plasma concentration is achieved in about 1 hour after an oral dose. It is 98% bound to plasma protein. It is excreted in urine and in feces as unchanged drug and metabolites. Following oral dose, about 4% of the dose is excreted unchanged in urine and about 6% in urine as the active metabolite.