In 1990, the U.S. Food and Drug Administration noted risk factors for the development of serious ventricular arrhythmias in patients receiving terfenadine, the first nonsedating antihistamine for the treatment of allergic rhinitis. These risk factors included the use of terfenadine concomitantly with certain other medications. Specific update information about these contraindications was sent to all practicing physicians in 1992 and 1992 Physicians have been further warned about the potential for drug-drug interactions involving terfenadine through the publication of case reports, commentaries and clinical investigations. Currently, coadministration of terfenadine and erythromycin, clarithromycin, troleandomycin, itraconazole and ketoconazole is specifically contraindicated. Thompson and Oster conducted a retrospective review to determine if these guidelines are being followed.
The authors reviewed pharmacy records data from a four-year period after the initial drug warnings were issued. All patients with a paid claim for a terfenadine-containing medication were included, and their pharmacy records were reviewed to identify any periods in which terfenadine use overlapped with use of any of the contraindicated medications.
Over the course of the study, the use of terfenadine with contraindicated drugs decreased. The overlapping use of terfenadine and a contraindicated drug decreased from 5.4 instances per 100 persons in 1990 to 2.3 instances per 100 persons during the first six months of 1994. This represents a decrease of 57, percent. However, even by 1994, the rates of overlapping contraindicated drugs remained significantly high. Most of the cases of concurrent use involved terfenadine and erythromycin.
Although the rate of prescribing terfenadine with contraindicated drugs has declined since the initial FDA warnings, the authors conclude that concurrent use of terfenadine and contraindicated macrolide antibiotics and imidazole antifungals still continues to occur, placing patients at risk of serious drug-drug interactions. (Thompson D, Oster G. Use of terfenadine and contraindicated drugs. JAMA 1996;275:1339-41.)
COPYRIGHT 1996 American Academy of Family Physicians
COPYRIGHT 2004 Gale Group
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