Use of terfenadine and contraindicated drugs.
OBJECTIVE
To assess changes in concurrent use of products containing terfenadine and contraindicated macrolide antibiotics (erythromycin, clarithromycin, troleandomycin) and imidazole antifungals (ketoconazole, itraconazole) following reports of serious drug-drug interactions and changes in product labeling.


METHODS
Retrospective review of computerized pharmacy claims.


METHODS
A large health insurer in New England.


METHODS
Health plan members with 1 or more paid pharmacy claims for products containing terfenadine between January 1990 and June 1994.


METHODS
Among persons with paid claims for terfenadine in any given month, percentage with a prescription for any contraindicated drug that alternatively was dispensed on the same day as ("same-day dispensing") or had therapy days that overlapped those of ("overlapping use") a prescription for terfenadine.


RESULTS
Concurrent use of terfenadine and contraindicated drugs declined over the study period. The rate of same-day dispensing declined by 84% from an average of 2.5 per 100 persons receiving terfenadine in 1990 to 0.4 per 100 persons during the first 6 months of 1994, while the rate of overlapping use declined by 57% (from 5.4 to 2.3 per 100 persons). Most cases involved erythromycin.


CONCLUSIONS
Despite substantial declines following reports of serious drug-drug interactions and changes in product labeling, concurrent use of terfenadine and contraindicated macrolide antibiotics and imidazole antifungals continues to occur.
Thompson
D
D
Policy Analysis Inc, Brookline, Mass, USA.
Oster
G
G
D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D000935:Antifungal Agents / Q000627:therapeutic use*; D017291:Clarithromycin / Q000627:therapeutic use; D000075202:Contraindications; D004347:Drug Interactions; D004363:Drug Utilization; D004917:Erythromycin / Q000627:therapeutic use; D006634:Histamine H1 Antagonists / Q000627:therapeutic use*; D006801:Humans; D017964:Itraconazole / Q000627:therapeutic use; D007654:Ketoconazole / Q000627:therapeutic use; D010593:Pharmaceutical Services; D011356:Product Labeling; D012189:Retrospective Studies; D016593:Terfenadine / Q000627:therapeutic use*; D014217:Troleandomycin / Q000627:therapeutic use
D000900:Anti-Bacterial Agents; D000935:Antifungal Agents; D006634:Histamine H1 Antagonists; D017964:Itraconazole; D004917:Erythromycin; D016593:Terfenadine; D014217:Troleandomycin; D017291:Clarithromycin; D007654:Ketoconazole