Effects of Emetic and Cathartic Agents on the Gastrointestinal Tract and the Treatment of Toxic Ingestion

Abstract

Emetic drugs and saline cathartics produce direct or reflex changes in gastrointestinal motility. The changes in gastrointestinal smooth muscle function may be important in the rapid oral or rectal expulsion of gastrointestinal contents, effects which serve as a basis for emetic and cathartic drug use in the treatment of toxic ingestion. Because of difficulties in recording gastrointestinal smooth muscle contractile activity from the intact, unanesthetized animal or man, relatively few studies have attempted to characterize the changes in gastrointestinal motility preceding vomiting. Limited results from past studies and the results of more recent studies employing improved technology suggest that pharmacological activation of the emetic reflex is accompanied by characteristic movements of the stomach and small intestine. The gastric response consists of initial muscle relaxation and an expansion of gastric volume. The intestine responds with a contraction, which begins in the distal ileum and migrates orad over the entire small intestine immediately before active retching. The changes in gastric and intestinal motility may be initiated by structures in the central nervous system and may be an important component of the emetic reflex. This article urges more active research to characterize the gastrointestinal emetic response and to investigate more generally the therapeutic value of emesis in the treatment of toxic ingestion. Emphasis should be placed on the clinically important emetic drugs apomorphine and syrup of ipecac. Studies comparing the efficiency of removal of gastrointestinal contents, resultant blood levels of orally administered drugs with and without emesis, differences in the gastrointestinal emetic response between agents and the pharmacology of the gastrointestinal emetic response should be performed. Studies should also be conducted to determine the pharmacology of the emetic sensory receptors in the gastrointestinal tract and the intraluminal physical-chemical or gastrointestinal physiological factors influencing gastrointestinal emetic sensory receptor activation. The results would demonstrate the value of emesis in various poison cases and help establish criteria for use and selection of emetic drugs. No less experimental attention should be devoted to the cathartic drugs. There are no experimental studies which demonstrate unequivocally that when given alone saline cathartics reduce the extent of oral drug or poison absorption, or that saline cathartics enhance the antidotal effectiveness of activated charcoal. More studies should be performed to evaluate the effectiveness of saline cathartics in limiting drug absorption, while considering their potential to alter the antidotal actions of activated charcoal through chemical means, or by alteration of gastrointestinal physiological function. New procedures to achieve gastrointestinal decontamination or enhance drug elimination should also be evaluated. Whole intestinal lavage with newly developed iso-osmotic solutions that neither induce absorption nor secretion may be of value. High-dose, repeated administration of activated charcoal during the postabsorptive phase of drug or poison ingestion may enhance elimination. Whole intestinal lavage with non-absorbable solutions containing activated charcoal may prove more effective than currently established protocols for saline cathartic drug use in the treatment of toxic ingestion.