Emetic Action of Nitrogen Mustard (Mechlorethamine Hydrochloride) in Dogs and Cats

Abstract

The early emetic response (within 4 hr.) after intravenous injection of the nitrogen mustard, methyl-bis (beta-chlorethyl) amine hydrochloride, was compared in dogs and cats. The emetic effect of the drug in dogs differed from that in cats in the following respects: a) the dose of 0.5 mg/kg was uniformly effective in dogs whereas the lowest uniformly effective dose in cats was 5.0 mg/kg. b) Dogs were completely protected against the emetic effect, up to 10.0 mg/kg, by chronic ablation of the medullary emetic chemoreceptor trigger zone (CT zone), whereas cats were not. Cats were completely protected against the emetic effect by abdominal deafferentation accomplished by transthoracic vagotomy in combination with either spinal cord transection at T4 or dorsal rhizotomy of spinal segments T5 to T10. The dose-response curve for emesis after nitrogen mustard in the cat was shifted towards a higher dose level by acute decerebration. A forebrain facilitatory role was further supported by a protective effect, against the mustard-induced vomiting, afforded by chronic frontal lobectomy in the cat. Attention is directed to the similarity in emetic actions of nitrogen mustard and x-radiation, including parallel species differences between dogs and cats.