Chronopharmacological Study of a Nonsedative H₁-blocking Agent (WAL 801 CL, Epinastine)

The dose-response relation (study I) and the effect of the timing of administration (study II) with respect to the antihistaminic activity of a Hi-blocking agent, WAL 801 CL (Epinastine), were investigated. In study I, a 10, 20, and 40 mg dose of WAL 801 CL or a placebo was administered to 11 healthy male volunteer students (X±SD = 23. 3 ±1.3 yrs) after breakfast (8: 30) by a double-blind fashion using the Latin square design, and the histamine intradermal reaction and psychomotor functions were subsequently examined. In study II, either 20 mg of WAL 801 CL or a placebo were administeredto 8 healthy male volunteer students (23.8±1.4 yrs) after breakfast (8:00) or after dinner (20:30) in the same way as in Study I, and the histamine intradermal reaction was subsequently examined. WAL 801 CL inhibited the histamine intradermal reaction dose-dependently, and no findings suggesting any effects on the CNS were observed. The inhibitory effect of WAL 801 CL on the histamine intradermal reaction tended to last longer when it was administered in the morning, while the effect tended to be stronger when it was administered in the evening, but the differences were not significant. Thus the results show that WAL 801 CL is a nonsedative Hi-blocking agent and that the timing of administration does not critically influence the antihistaminic activity of the drug.