Terfenadine is an antihistamine formerly used for the treatment of allergic conditions. It was brought to market by Hoechst Marion Roussel and was marketed under various brand names, including Seldane in the United States, Triludan in the United Kingdom, + some more technical info Terfenadine acted as a peripheral H1 receptor antagonist with little central nervous system penetration, administered orally as a non-sedating antihistamine. It underwent extensive first-pass hepatic metabolism, primarily via cytochrome P450 3A4, to a major carboxylate metabolite that is pharmacologically active. Clinically relevant safety concerns emerged from parent compound accumulation when CYP3A4 was inhibited by concomitant drugs or grapefruit juice, producing blockade of cardiac hERG potassium channels, QT interval prolongation and risk of torsades de pointes; these findings led to market withdrawal in most countries. Typical prewithdrawal formulations were immediate-release tablets and capsule dosage forms; analytical methods for quality control included HPLC and LC-MS assays for assay, related substances, and degradation profiling.
Parent: Terfenadine
Parent: Terfenadine
Parent: Terfenadine
Parent: Terfenadine
Parent: Terfenadine
Typical quality control specifications applied in development and legacy dossiers limited related compounds and impurities to conservative levels to ensure safety and purity: assay of terfenadine drug substance commonly required ≥98.0% purity, individual specified related compounds commonly limited to ≤0.5% each, total specified related compounds limited to ≤2.0%, individual unspecified impurities often held to ≤0.10% each, and total impurities commonly limited to ≤1.0%. Known related substances and process or degradation impurities reported in analytical work included oxidative metabolites, N-oxide species, desalkyl and demethyl variants, and the carboxylic acid metabolite fexofenadine; in well-controlled processes these are typically present at trace levels below the individual limits above. These figures represent typical industry specification ranges used for legacy antihistamine drug substances and should be confirmed against current regulatory submissions and product-specific control strategies.
Terfenadine was used orally as a non-sedating H1 antihistamine to relieve symptoms of allergic rhinitis and urticaria; use ceased following safety findings related to cardiac arrhythmia risk.
No, terfenadine and fexofenadine are distinct chemical entities; fexofenadine is the primary active carboxylate metabolite produced from terfenadine metabolism and it lacks the same cardiac electrophysiology liability, which is why fexofenadine was developed as a safer alternative.
Terfenadine has been withdrawn or discontinued for systemic use in most countries because of its potential to cause QT prolongation and torsades de pointes when plasma levels were elevated by CYP3A4 inhibitors; it is not generally available as a marketed prescription product now.
Fexofenadine, the active metabolite, effectively replaced terfenadine as a safer oral H1 antihistamine; other second generation antihistamines such as loratadine and cetirizine are also used as alternatives.
