Fexofenadine is metabolic product of

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