The Effect of Selected Drugs on First-Stage Radioemesis in Beagle Dogs

An animal model of irradiation-induced emesis was developed by exposing the abdominal area of young beagle dogs to 800 rad. A 100% incidence of emesis occurred within 2 hr followed by a second wave of emesis, anorexia, and hemorrhagic diarrhea approximately 48 hr later. Seven individual drugs and one combination of two drugs were examined for antagonistic effects against the first-stage emesis. Chlorpromazine proved to be the most potent antagonist, while dimenhydrinate and diphenhydramine showed the same activity but to a lesser degree. Inactive drugs were phenytoin sodium, perphenazine (at a low dose), WR2721, and the combination of amphetamine plus scopolamine. Acetylsalicyclic acid adversely intensified the emesis. These results suggest that CNS-active agents are potentially more effective in counteracting first-stage emesis.