Antiallergic activity of picumast dihydrochloride in several animal species

Picumast dihydrochloride (3,4-dimethyl-7-[4-(4-chlorobenzyl)piperazine-1-yl]propoxycoumarin dihydrochloride) was compared with cromoglycate, ketotifen and mepyramine as an inhibitor of allergic and anaphylactoid reactions. 1. In guinea-pigs, pretreatment with picumast dihydrochloride given intravenously, orally or by inhalation prevented bronchospasm induced by antigen or histamine. The fraction of the bronchospasm remaining after mepyramine pretreatment was further reduced by picumast dihydrochloride. 2. Systemic administration of picumast dihydrochloride inhibited antigen-induced conjunctivitis, whereas mepyramine and ketotifen were inactive. 3. Intravenous and oral pretreatment with picumast dihydrochloride inhibited the antigen-induced mast cell degranulation in rat mesentery. The effective doses of cromoglycate given intravenously were twice as high as those of picumast dihydrochloride. Picumast dihydrochloride did not inhibit antigen-induced bronchoconstriction in rats. 4. The cutaneous reaction induced with Ascaris antigen in atopic monkeys was insensitive to the antihistaminic action of ketotifen, whereas it was inhibited by low doses of picumast dihydrochloride. Both compounds suppressed skin reactions induced by histamine. 5. Picumast dihydrochloride decreased IgE production in atopic high responder mice. It did not prevent autoimmune nephritis in NZB/W mice. 6. In rats, picumast dihydrochloride did not reduce cotton pellet granuloma, nor adjuvant arthritis. The inhibition of carrageenin oedema is presumably due to its anti-oedematous properties rather than to an antiproliferative activity. In conclusion, the inhibition of allergic and anaphylactoid reactions by picumast dihydrochloride can be attributed to a combined inhibition of liberation and action of histamine and other mediators.