This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Autacoids, Subject name: Pharmacology
Fexofenadine is metabolic product of 
Select and explain. 
A. Loratidine, B. Astemizole, C. Cetrizine, D. Terfenadine
D: Terfenadine
Answer: D: Terfenadine 
Explanation: Terfenadine acts as a peripherally-selectiveantihistamine, or antagonist of the histamine H1 receptor. It is a prodrug, generally completely metabolized to the active form fexofenadine in the liver by the enzyme cytochrome P450 3A4. Due to its near complete metabolism by the liver immediately after leaving the gut, terfenadine normally is not measurable in the plasma. Terfenadine itself, however, is cardiotoxic at higher doses, while its major active metabolite is not. Refer kDT 6/e p158