<unk>  acts as a peripherally-selective antihistamine, 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,<unk>  normally is not measurable in the plasma.<unk>  itself, however, is cardiotoxic at higher doses, while its major active metabolite is not.<unk> , in addition to its antihistamine effects, also acts as a potassium channel blocker (Kv11.1 encoded by the gene hERG). Since its active metabolite is not a potassium channel blocker, no cardiotoxicity is associated with fexofenadine. Sudden toxicity is possible even after years of use without problems as a result of an interaction with other medications such as erythromycin, or foods such as grapefruit. The addition of, or a dosage increase in, these CYP3A4 inhibitors makes it harder for the body to metabolize and remove<unk> . In larger plasma concentrations, it may lead to toxic effects on the heart's rhythm (e.g. ventricular tachycardia and torsades de pointes).
Terfenadine
Loratadine
Olopatadine
Budesonide
Desloratadine
Tralomethrin
Allergan
Roxadustat