Emetic dose of digitalis in pigeons as an index of the therapeutic dose in man.

Abstract

Emesis, as an index of digitaloid action, occurs promptly and characteristically after the intravenous administration of the digitaloid preparations in pigeons whose vomiting mechanism appears to be rather sensitive. The technique of determining the emetic dose is simple.

The digitaloid preparation is injected from an accurately graduated Luer (tuberculin) syringe into the wing vein of a pigeon of about 300 gm. body weight, held conveniently by an assistant. Then the pigeon is at once replaced into a cage for observation of vomiting, which is recognized by downward craning movements of the head preceded, sometimes by salivation and lachrymation and accompanied by ruffling of neck feathers, and, usually, flapping of the wings with occasional expulsion of gravel. Several such vomitings occur at the end of 5 to 10 minutes, depending on the dosage of the preparation used. Since the pigeons recover completely at the end of 2 to 3 days, they may be used over again for confirmation, and apparently as long as the wing veins permit further injections. The digitaloid preparations do not require previous evaporation, as in the case of most bioassay methods; but sodium chloride in isotonic concentration should be added to infusions, and tinctures should be diluted with about an equal part of 0.85 per cent sodium chloride before injection.

With this method the minimal emetic dose (M. E. D.) of a good tincture of digitalis (U. S. P.) is about the same as the full therapeutic or “minor toxicity” dose determined by Eggleston 1 for man, namely, 0.3 cc. (30 mg. digitalis) per kilo of body weight, or about 15 cc. for a 50 kilo man. Hence, it seems that the method should be valuable in determining the probable full therapeutic dose since emesis is one of the earliest signs of digitalis action in man; or, at least, it should be a valuable supplementary test to bioassays depending on fatal dosage.