Magazine article Drug Topics

New Antihistamine Approved for Long-Term Application

Magazine article Drug Topics

New Antihistamine Approved for Long-Term Application

Article excerpt

A newly approved prescription antihistamine has reached the market. Cetirizine (Zyrtec) is approved for long-term use against allergic rhinitis and chronic urticaria in adults and children over the age of 12 (for more on cetirizine, see page 68). It is also approved for use against chronic idiopathic urticaria-hives that cannot be attributed to a specific allergenic cause.

Other prescription antihistamines are not approved for long-term use, said Linda B. Ford, M.D., an allergist and immunologist in Omaha, Neb., and clinical instructor of pediatrics at the University of Nebraska.

The new drug, an oral H, receptor antagonist, will be competing against several other oral antihistamines, among them three nonsedating prescription products-terfenadine (Seldane, Hoechst Marion Roussel), astemizole (Hismanal, Janssen), and loratadine (Claritin, Schering-Plough)-as well as a sedating one, acrivastine/ pseudoephedrine (Semprex-D, Glaxo Wellcome).

Pfizer, the manufacturer of Zyrtec, is not describing cetirizine as nonsedating. Because sedation has been reported as a side effect, the labeling for cetirizine warns users to be cautious when driving a car or operating dangerous machinery. And alcohol or other central nervous system depressants may increase this effect.

The key issue with cetirizine is that it does not appear to have drug interactions the way that terfenadine and astemizole do, said Dianne Tharp, R.Ph., director of pharmacy services at Revco D.S., in Twinsburg, Ohio. Combinations of cetirizine and erythromycin, azithromycin, or ketoconazole also do not appear to create arrhythmias.

Terfenadine and astemizole carry boxed warnings in their labeling against concomitant use with ketoconazole, erythromycin, and other drugs. Use of terfenadine and astemizole has also been associated with ventricular arrhythmias.

"There are no cardiac warnings for [cetirizine] and no significant drug interactions," Tharp said. "This is a key point."

No significant drug-drug interactions have been reported for cetirizine with azithromycin, pseudoephedrine, ketoconazole, or erythromycin, according to Pfizer's labeling. While no interactions have been seen with low doses of theophylline, 400-mg doses of theophylline have caused a small decrease (16%) in cetirizine clearance. Larger doses of theophylline may have a greater effect.

Cetirizine does not prolong QTc significantly in tests of healthy adults who are given up to six times the maximum daily dose for a week.

Because it is approved for long-term use, cetirizine is indicated for both perennial and seasonal allergic rhinitis, Ford said. …

Search by... Author
Show... All Results Primary Sources Peer-reviewed

Oops!

An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.