Acute Toxicities of Rotenone and Mixed Pyrethrins in Mammals

Abstract

Rotenone and pyrethrum are proposed as harmless substitutes for inorganic insecticides, 1 and mixed pyrethrins are recommended as anthelmintics 2 and as scabicides. 3 The only critical report on the toxicity of rotenone in mammals is by Haag, 4 who indicates that there is little if any danger of acute intoxication following the ingestion of foodstuffs sprayed with rotenone. Chevalier 2 states that pyrethrum orally produces no untoward effects even when given to children.

In order to ascertain the probable toxic range of rotenone∗ or mixed pyrethrins† after absorption into the body, these drugs were given intraperitoneally or orally to guinea pigs, rats, and mice in 0.1-14% dilutions in ethylene glycol or petroleum oil, respectively, Animals were observed for one month. Controls, given the solvents alone, were unaffected over the period of observation.

1. Rotenone injected intraperitoneally killed half or more of the animals in doses of 2 to 10 mg. per kg. (Table I). Death occurred within 30 minutes in 50% of the fatalities, and within 14 days in the remainder. Toxic symptoms noted were: respiratory depression, incoordination, clonic convulsions, muscle tremors, and death due to respiratory failure. At necropsy one-third of the dead animals show'ed pulmonary congestion; no peritonitis or ulceration at the site of the injection were encountered.

Orally, the drug was given in powder form in gelatine capsules to guinea pigs, and in a 1% dilution in ethylene glycol by rubber tube to lightly anesthetized rats. The average minimal killing dose was 75 to 100 mg. per kg., and, as on intraperitoneal injection, was more toxic for rats than for guinea pigs (Table I). Thirty per cent of the fatalities occurred in 4 to 24 hours, 50% in 24 to 48 hours', and the rest in 3 to 10 days. Seventy per cent of the dead animals showed pulmonary congestion of varying degrees, and in 40% the mucosa of the stomach was reddened or sloughed. The animals surviving lost up to 10% of their initial weight in 3 days, but gradually regained it.