MODIFICATION OF PARATHION TOXICITY TO WAX MOTH LARVAE BY CHLORCYCLIZINE, AMINOPYRINE OR PHENOBARBITAL

LC50 parathion doses for 5th and 6th instar wax moth larvae (Galleria mellonella) were 152.309 ± 1.644 and 163.982 ± 1.115 μg parathion per gram larval medium, respectively. Pretreatment of 6th instar larvae with sublethal doses of chlorcyclizine dihydrochloride, aminopyrine or phenobarbital in the larval medium reduced the mortality due to parathion. Chlorcyclizine (0.5 g/100 g larval medium) decreased the toxicity due to the LC50 parathion dose for 6th instar larvae to 32, 20, 4, and 10% mortality when fed for 2, 4, 8, and 10 days, respectively. The 2-day pretreatment protection lasted only 24 hours whereas the longer times protected the larvae for up to 72 hours. Phenobarbital was somewhat more effective than aminopyrine. Both, however, offered protection against parathion if the time of exposure was increased. The data suggest that the protective effect is neither immediate nor permanent and that it depends upon the dosage and length of drug pretreatment. © 1969.