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Duration of inhibitory effect of terfenadine on histamine-induced skin wheals
S K Chhabra1, P Singh, S Jhamb
1Department of Cardio-Respiratory Physiology, Vallabhbhai Patel Chest Institute, University of Delhi, India.
Background:
The duration of inhibitory effect of terfenadine on histamine-induced skin wheals has been reported differently by different workers.
Objective:
The present study was carried out to study the duration of inhibitory effect of terfenadine on histamine-induced skin wheals.
Methods:
In nine normal, healthy adult volunteers, baseline skin reactivity was established by performing intradermal skin tests with histamine 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 every day following the treatment until the wheal size had recovered to within 90% of the baseline value.
Results:
The mean duration of inhibition with the 1-day treatment was 70.66 +/- 17.47 hours while that following the 1-week treatment was 78.66 +/- 20.00 hours (P less than .05). The inhibition was about 40% at 24 hours and 17% at 48 hours with 1-day treatment while it was 37% and 18%, respectively, with 1-week treatment. In individual subjects, the duration of inhibitory effect varied from 36 to 84 hours with 1-day treatment and 60 to 108 hours with 1-week treatment.
Conclusion:
The study showed that terfenadine has no significant cumulative antihistaminic effect on repeated dosing. It is suggested that terfenadine should be stopped at least three days before performing skin tests for type I hypersensitivity.