Seldane (Terfenadine (Removed from market 1998)) Drug Information: Overdosage and Contraindications

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May 27, 2012

Seldane

Hay Fever »

What is hay fever? What are the symptoms and signs?

Hay fever is a misnomer. Hay is not a usual cause of this problem, and it does not cause fever. Early descriptions of sneezing, nasal congestion, and eye irritation while harvesting field hay promoted this popular term. Allergic rhinitis is the correct term used to describe this allergic reaction, and many different substances cause the allergic symptoms noted in hay fever. Rhinitis means "irritation of the nose" and is a derivative of rhino, meaning nose. Allergic rhinitis which occurs during a specific season is called "seasonal allergic rhinitis." When it occurs throughout the year, it is called "perennial allergic rhinitis." Rhinosinusitis is the medical term that refers to inflammation of the nasal lining as well as the lining tissues of the sinuses. This term is sometime used because the two conditions frequently occur together.

Symptoms of allergic rhinitis, or hay fever...

Read the Hay Fever article »

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Seldane

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Please Note: This Brand Name drug is no longer available in the US.
(Generic versions may still be available.)

OVERDOSE

Signs and symptoms of overdosage may be absent or mild (e.g., headache, nausea, confusion); but adverse cardiac events including cardiac arrest, ventricular arrhythmias including torsades de pointes and QT prolongation have been reported at overdoses of 360 mg or more and occur more frequently at doses in excess of 600 mg, and QTc prolongations of up to 30% have been observed at a dose of 300 mg b.i.d. Seizures and syncope have also been reported. USE OF DOSES IN EXCESS OF 60 MG B.I.D. IS NOT RECOMMENDED. (See BOXED WARNING, CLINICAL PHARMACOLOGY, and ADVERSE REACTIONS).

In overdose cases where ventricular arrhythmias are associated with significant QTc prolongation, treatment with antiarrhythmics known to prolong QTc intervals is not recommended.

Therefore, in cases of overdosage, cardiac monitoring for at least 24 hours is recommended and for as long as QTc is prolonged, along with standard measures to remove any unabsorbed drug. Limited experience with the use of hemoperfusion (n=1) or hemodialysis (n=3) was not successful in completely removing the acid metabolite of terfenadine from the blood.

Treatment of the signs and symptoms of overdosage should be symptomatic and supportive after the acute stage.

Oral LD₅₀ values for terfenadine were greater than 5000 mg/kg in mature mice and rats. The oral LD₅₀was 438 mg/kg in newborn rats.

CONTRAINDICATIONS

CONCOMITANT ADMINISTRATION OF TERFENADINE WITH KETOCONAZOLE (NIZORAL) OR ITRACONAZOLE (SPORONOX) IS CONTRAINDICATED. TERFENADINE IS ALSO CONTRAINDICATED IN PATIENTS WITH DISEASE STATES OR OTHER CONCOMITANT MEDICATIONS KNOWN TO IMPAIR ITS METABOLISM, INCLUDING SIGNIFICANT HEPATIC DYSFUNCTION, AND CONCURRENT USE OF CLARITHROMYCIN, ERYTHROMYCIN, OR TROLEANDOMYCIN. QT PROLONGATION HAS BEEN DEMONSTRATED IN SOME PATIENTS TAKING TERFENADINE IN THESE SETTINGS, AND RARE CASES OF SERIOUS CARDIOVASCULAR EVENTS, INCLUDING DEATH, CARDIAC ARREST, AND TORSADES DE POINTES, HAVE BEEN REPORTED IN THESE PATIENT POPULATIONS. (See WARNINGS and DRUG INTERACTIONS).

Terfenadine is contraindicated in patients with a known hypersensitivity to terfenadine or any of its ingredients.

Last reviewed on RxList: 12/8/2004
This monograph has been modified to include the generic and brand name in many instances.