Toxicity of Eugenol

Abstract

Summary

The LD50 for pure eugenol, administered to rats by stomach tube, and without subsequent reaspiration, was estimated to be 1.8 ml (1.93 g/kg). Any use of this datum as a guide to safe dosage in man, however, may take cognizance of the fact that the conditions of the rodent studies are considerably more severe than any which might be encountered in clinical studies. In the first place, the rat experiments employed eugenol per se, whereas work with dog and man is done with aqueous emulsions of the irritant. Furthermore, the rat retains all of the eugenol administered, because of its inability to vomit, whereas dog and man can reject part of the irritant in this manner if the dose is excessive, and this affords an additional factor of safety.

The salient features of the toxic manifestations of eugenol in the rat were as follows: Paralysis occurred initially in the hind legs and the lower jaw. The forelimbs were unaffected unless general prostration or coma ensued. In those animals in which the acute symptoms subsided, the animals remained lethargic, showed signs of urinary incontinence and frequently hematuria, and gave evidence of impaired function of the hind legs for several days. Gross and microscopic observations of the tissues suggested that profound changes in fluid distribution had occurred in response to acute irritation of the gastrointestinal tract. The net impression of the effect of the eugenol, from the microscopic evidence, was essentially that of circulatory collapse with resultant congestion.