Terfenadine

Terfenadine is indicated for the treatment of allergic rhinitis, hay fever, and allergic skin disorders.

Terfenadine competes with histamine for binding at H1-receptor sites in the GI tract, uterus, large blood vessels, and bronchial muscle. This reversible binding of terfenadine to H1-receptors suppresses the formation of edema, flare, and pruritus resulting from histaminic activity. As the drug does not readily cross the blood-brain barrier, CNS depression is minimal.

Adult (>12 year and >50 kg): 60-120 mg in the morning or 60 mg bid. Max: 120 mg daily.

Renal Impairment: CrCl <40: Half the usual daily dose

Increased risk of ventricular arrhythmia with triazole and imidazole antifungals, macrolide antibacterials, streptogramin antibacterials, SSRI, HIV-protease inhibitors and non-nucleoside reverse transcriptase inhibitors, arrhythmogenic drugs, diuretics, astemizole and zileutron.

Porphyria.

Anxiety, palpitations, insomnia, mild GI distubances, erythema multiforme and galactorrhoea.

Pregnancy Category C. Either studies in animals have revealed adverse effects on the foetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the foetus.

Child and elderly. Avoid in patients with cardiac or significant hepatic disease, electrolyte imbalance, or known or suspected prolongation of the QT interval. Lactation, pregnancy.

Non-sedating antihistamines.