A COMPARISON OF RESULTS ESTIMATED BY GUINEA PIG METHOD AND PIGEON METHOD IN THE BIOASSAY OF COMMERCIAL DIGITOXIN

Since 1954 in authors' laboratory, various digitalis preparations, including digitalis leaves, tablets and tinctures and digitoxin and its injections, were assayed by both guineapig method and pigeon (lethal dose) method, using standardized digitalis powder as reference standard. It was found that results of digitalis leaf preparations obtained by guinea pig method and those by pigeon method were reasonably agreeable; while the results of digitoxin preparations obtained by guinea pig method were always significantly lower than those obtained by pigeon method. In this paper, these facts were again shown, when 6 digitalis leaf preparations and 7 commercial digitoxin preparations were investigated. In digitoxin preparations, the potency estimated by pigeon method could be 2.36 times greater than that estimated by guinea pig method. The authors ascribed the difference to the inadequate standard preparation employed in the assay, as digitalis purpurea consisting of chiefly purpurea glycosides A and B being different in the mode of action to digitoxin (commercial) which was chiefly degraded product of purpurea glycoside A. They concluded that in bioassay of digitoxin against a digitalis standard, a suitable authorised method should be strictly followed; and the 4 methods employing different kinds of animals recommended by British Pharmacopeia 1953 and quoted by Bristish Pharmacopeia Codex 1954 for digitoxin would make confusions.