Antlamebic Action of 5-Chloro-7-Diethylaminomethyl-8-Quinolinol and of other Substituted 8-Quinolinols in Vitro and in Experimental Animals

Paul E. Thompson Research Laboratories, Parke, Davis & Company, Detroit 32, Michigan

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J. W. Reinertson Research Laboratories, Parke, Davis & Company, Detroit 32, Michigan

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Anita Bayles Research Laboratories, Parke, Davis & Company, Detroit 32, Michigan

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D. A. McCarthy Research Laboratories, Parke, Davis & Company, Detroit 32, Michigan

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Edward F. Elslager Research Laboratories, Parke, Davis & Company, Detroit 32, Michigan

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Summary

In a search for more effective amebicides, 98 substituted 8-quinolinols were tested against Endamoeba histolytica; all were examined in vitro, 63 against intestinal amebiasis in rats, 14 against intestinal amebiasis in dogs, and 4 against hepatic amebiasis in hamsters.

Many of the compounds were effective in vitro and against intestinal infections, but none of those tested against hepatic infections was encouragingly effective in nontoxic doses. Consideration of the manifest structure-activity relationships showed that activity was associated with a wide variety of substituents, particularly in the 5-, 6- or 7-position of the 8-quinolinol nucleus. Many of the active compounds did not contain iodine, thus casting doubt on the existing theory that iodine per se is responsible for the activity of the various iodinated-8-quinolinols in clinical use as amebicides.

Although most of the compounds were less active in vitro in the presence of gastric mucin than in its absence, many of them still were active in vivo. Therefore, susceptibility to mucin binding alone does not appear to be an adequate basis for rejecting compounds at the in vitro level. Good correlation was observed between high activity in vitro and therapeutic effect in vivo.

5-Chloro-7-diethylaminomethyl-8-quinolinol proved to be one of the most promising compounds. Its chemotherapeutic effects and toxicity in several species of animals are described, and a few observations are presented on its physiological disposition in animals.

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