Antihistaminic Action of'Pyronil'.

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Abstract
Conclusions 1.'Pyronil', a new histamine antagonist, was found to possess an antihistaminic activity of remarkable degree and duration in 2 different test preparations. Its other pharmacological effects, aside from its ability to protect guinea pigs from anaphylactic shock, were unimportant. 2. In mice and guinea pigs'Pyronil'has a relatively low toxicity when administered orally, subcutaneously or intramuscularly, In mice by vein it was moderately toxic although apparently less toxic than many of the other antihistamincs in mice as judged from published lethal doses in the literature (8). In guinea pigs the ratio of toxic to therapeutic doses indicated a high margin of safety. In rabbits his compound has the same toxic dosage level as other antihistaminics. 3 Rats fed diets containing as high as 0.1% of the drug in the diet for 4 weeks gained weight comparable to the weight of control rats fed normal ration. Higher concentrations impaired growth but produced no visceral damage as shown by hematological and pathological studies. 4. Does given large daily doses of'Pyronil'for 4 weeks, aside from the presence of occasional red cells in the collecting tubules of the kidney, showed no significant pathological changes attributable to the drug.