Pharmacodynamics of the new H1-antagonist 3-amino-9,13b-dihydro-1H-dibenz[c,f]imidazo[1,5-a]azepine hydrochloride in volunteers.

The inhibitory effects of 3-amino-9,13b-dihydro-1H-dibenz[1,5-a]azepine hydrochloride (WAL 801 CL), a new H1-receptor antagonist, on histamine-induced skin wheals were studied in 9 volunteers. The study was a double-blind, randomized (Latin square) change-over, intraindividual comparison of the effects of single doses of 2,6 and 18 mg WAL 801 CL and of placebo and 2 mg ketotifen on skin wheals induced by intradermal injections of 5 micrograms hystamine 1, 2, 4, 6 and 8 h after administration of the drugs. The injection of 5 micrograms was also made prior to each drug administration. The effects on psychological performance and the subjective state were also evaluated. The following tests were employed: simple visual reaction time (RT), critical flicker fusion frequency (C3F) and von Zerssen's self-rating scale Bf-S, assessing state of mood. There was a washout period of at least 72 h between each course of treatment. A decrease in the size of the histamine wheal was observed 1 h after WAL 801 CL and was maintained for at least 8 h. The reduction in the size of the histamine wheal was between 44% (2.0 mg) and 71% (18.0 mg). After ketotifen a marked decrease in the wheal area was observed between 4 and 8 h after administration of the drug, with maximum histamine antagonism of 59% after 6 h. The inhibitory effects of 6 and 18 mg WAL 801 CL and 2 mg ketotifen were statistically significant compared with placebo. 8 of 9 subjects felt tired (subjective report) after ketotifen, corresponding changes could be detected by Zerssen's state of mood scale Bf-S, but not by other psychological performance measures (RT, C3F).(ABSTRACT TRUNCATED AT 250 WORDS)

Antihistamine activity and central effects of WAL 801 CL in man.

The tolerability and antihistaminic activity of WAL801 CL, a new, peripherally acting H1-receptor antagonist, have been evaluated in a double-blind, placebo-controlled, within-subject cross-over study. WAL801 CL 8 mg b.d. was given to 10 healthy volunteers for 15 days. It resulted in a distinct reduction in histamine wheal size and a decreased bronchoconstrictor response to histamine inhalation. No cardiovascular side effects were observed. Transient and slight fatigue was observed in 3 subjects. Psychological tests, such as simple visual reaction time, critical flicker fusion frequency and mood self rating scale, showed that WAL801 CL had no sedative side effects and that it did not alter psychomotor performance.