Developmental and reproduction toxicity of piperonyl butoxide part 2 developmental safety of piperonyl butoxide in the NZW rabbit.

Piperonyl butoxide (PBO) was developed in the 1940s. PBO increases the effectiveness of pyrethrins, thus it is called a synergist. Herein, the findings from a guideline developmental toxicity study in rabbits conducted in 1986 are reported. Inseminated New Zealand White rabbits were randomly assigned to a control and three treatment groups of 16 does each. Dose levels of 50, 100 and 200 mg/kg/day were selected based on a dosage-range study to avoid excessive maternal toxicity and administered orally (gavage) as a single daily dose on days 7-19 of gestation at a volume of 0.5 mL/kg. The control group received the vehicle only, Mazola® corn oil. Cesarean sections were performed on all surviving females on gestation day 29 and fetuses were evaluated. Survival for all study groups was 100%. Treatment-related maternotoxicity was manifested at the 100 and 200 mg/kg/day levels as decreased defecation and dose-related body weight losses during the treatment period (gestation days 7-13 and 7-19). The Cesarean section parameter values and fetal morphological observations of the treated groups did not differ significantly from the concurrent control group and were within the historical control range for this rabbit strain. No maternal or fetal adverse effects were seen at the 50 mg/kg/day dose level. Although maternal toxicity resulting from treatment was apparent at the 100 and 200 mg/kg/day dose levels, neither fetotoxicity nor teratogenicity were elicited in rabbits by piperonyl butoxide at dose levels as high as 200 mg/kg/day.

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