DURATION OF INHIBITORY EFFECT OF TERFENADINE ON HISTAMINE-INDUCED SKIN WHEALS

Background: The duration of inhibitory effect of terfenadine on histam ine-induced skin wheals has been reported differently by different wor kers. Objective: The present study was carried out to study the durati on of inhibitory effect of terfenadine on histamine-induced skin wheal s. Methods: In nine normal, healthy adult volunteers, baseline skin re activity was established by performing intradermal skin tests with his tamine and normal saline on three consecutive days. The effect of two regimens of terfenadine was evaluated: 1-day treatment with 60 mg bid and 1-week treatment with the same dosage. Skin tests were performed e veryday following the treatment until the wheal size had recovered to within 90% of the baseline value. Results: The mean duration of inhibi tion with the 1-day treatment was 70.66 +/- 17.47 hours while that fol lowing the 1-week treatment was 78.66 +/- 20.00 hours (P >.05). The in hibition was about 40% at 24 hours and 17% at 48 hours with 1-day trea tment while it was 37% and 18%, respectively, with 1-week treatment. I n individual subjects, the duration of inhibitory effect varied from 3 6 to 84 hours with 1-day treatment and 60 to 108 hours with 1-week tre atment. Conclusion: The study showed that terfenadine has no significa nt cumulative antihistaminic effect on repeated dosing. It is suggeste d that terfenadine should be stopped at least three days before perfor ming skin tests for type I hypersensitivity.