Terfenadine

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Terfenadine
Systematic (IUPAC) name
4-[4-(hydroxy-diphenyl-methyl)-1-piperidyl]- 1-(4-tert-butylphenyl)-butan-1-ol
Identifiers
CAS number	50679-08-8
ATC code	R06AX12
PubChem	5405
DrugBank	APRD00606
Chemical data
Formula	C₃₂H₄₁N O₂
Mol. mass	471.673 g/mol
Pharmacokinetic data
Bioavailability	?
Protein binding	70%
Metabolism	?
Half life	3.5 hours
Excretion	?
Therapeutic considerations
Pregnancy cat.	?
Legal status
Routes	?

Terfenadine is an antihistamine formerly used for the treatment of allergic conditions. It was marketed under various brand names including Seldane in the United States, Triludan in the United Kingdom, and Teldane in Australia. It was superseded by fexofenadine in the 1990s due to the risk of cardiac arrhythmia caused by QT interval prolongation.

Terfenadine is a prodrug, generally completely metabolised to the active form fexofenadine by intestinal CYP3A4. Terfenadine itself, however, has a cardiotoxic effect in higer doses. Toxicity is possible after years of continued use with no previous problems with changes in other medications such as erythromycin, or foods like grapefruit. The addition of or dosage change in these cytochrome P450-CYP3A4 inhibitors makes it harder for the body to metabolize and remove the drug leading to toxic effects on the heart's rhythm and electrical conduction.

In early 1997, the U.S. FDA recommended that the terfenadine-containing drugs be removed from the market and that physicians consider alternative medications for their patients. Seldane was formally removed from the U.S. market in late 1997 after the approval of Allegra, a drug by the same maker as Seldane that was not found to cause the potentially fatal heart condition.^[1] Terfenadine-containing drugs were subsequently removed from the Canadian market in 1999,^[2] though they remain available in the UK by prescription only.

[edit] References

v • d • e Antihistamines (primarily R06)

Aminoalkyl ethers	Bromazine/Bromodiphenhydramine • Carbinoxamine • Clemastine • Chlorphenoxamine • Diphenylpyraline • Diphenhydramine • Doxylamine • Orphenadrine • Phenyltoloxamine

Substituted alkylamines	Brompheniramine • Chlorphenamine • Dexbrompheniramine • Dexchlorpheniramine • Dimetindene • Pheniramine • Talastine

Substituted ethylenediamines	Chloropyramine • Histapyrrodine • Mepyramine • Methapyrilene • Tripelennamine (Pyribenzamine)

Phenothiazine derivatives	Alimemazine • Hydroxyethylpromethazine • Isothipendyl • Mequitazine • Methdilazine • Oxomemazine • Promethazine

Piperazine derivatives	Buclizine • Cetirizine • Chlorcyclizine • Cinnarizine • Cyclizine • Hydroxyzine • Levocetirizine • Meclizine • Niaprazine • Oxatomide

Others for systemic use	Antazoline • Azatadine • Bamipine • Cyproheptadine • Deptropine • Dimebon • Ebastine • Epinastine • Ketotifen • Mebhydrolin • Mizolastine • Phenindamine • Pimethixene • Pyrrobutamine • Rupatadine • Triprolidine • selective (Acrivastine • Astemizole • Azelastine • Desloratadine • Fexofenadine • Loratadine • Terfenadine)

For topical use	Bamipine • Chloropyramine • Chlorphenoxamine • Clemastine • Dimetindene • Diphenhydramine • Isothipendyl • Mepyramine • Promethazine • Thenalidine

Antiallergic agents excluding corticosteroids	Antazoline • Azelastine

Other antiallergics	Emedastine • Epinastine • Ketotifen • Montelukast • Olopatadine