The pharmacokinetics, antihistamine and concentration-effect relationship of ebastine in healthy subjects

1. The kinetics and effects of ebastine 10 and 50 mg were studied after oral dosing in healthy subjects. 2. The parent drug was extensively metabolised during the first pass to its carboxylic acid derivative, carebastine. 3. The pharmacokinetics of carebastine were linear over the dose range studied and the terminal elimination half-life was 10.6 +/- 2.6 and 12.5 +/- 1.9 h respectively after 10 and 50 mg of ebastine. 4. Antihistamine (H1-receptor) activity was examined with intradermal histamine (2 micrograms). Oral ebastine reduced the histamine wheal area for up to 24 h and also reduced subjective local pain. 5. Antihistamine activity correlated well with plasma levels of carebastine in individual subjects. 6. Ebastine appears to have potential as an antihistamine for once a day dosing.