Primaclone (PMC) is a drug used in the management of seizures in humans and dogs. PMC was tested for its effects on fertility and reproduction in Swiss CD-1 mice according to the Continuous Breeding Protocol. It was administered via feed. Based on results of an extended dose-finding study which included mating, delivery of 1 litter and data collection on the 4 day survival rate of pups (Task 1), the following dose levels were chosen to investigate effects on fertility and reproduction: 0.015% (-24 mg/kg), 0.05% (-78 mg/kg), and 0.15% (-233 mg/kg). Male and female mice (F0) were continuously exposed for a 7-day precohabitation and a 98-day cohabitation period (Task 2).
Treated male and female body weights in Task 2 were always within 10% of control values. Feed consumption was similar in F0 control and treated animals. Fertility and reproduction in F0 animals were not affected. Only the cumulative days to litter value for the 5th litter of the low dose level (0.015% PNC) animals was significantly increased, a finding of questionable biological importance. All other parameters were similar to controls.
The F1 pups from the last litter in the control and highest dose groups were weaned. Body weights in the treated groups were higher than controls at weaning, but were similar thereafter. Mating, pregnancy and fertility indices for F1 mice were similar to control values, while absolute and relative liver weights were increased for both sexes. Estrous cycle length was increased by approximately 7% in F1 females exposed to 0.15% PMC. Overall, PMC produced mild reproductive toxicity at doses that also caused some systemic changes. These data show that PMC is not a selective reproductive toxicant in Swiss CD-1 mice at concentrations of up to 0.15% in the diet.