Effects of N-acetylcysteine on fetal development and on phenytoin teratogenicity in mice

The teratogenicity of phenytoin may result from its enzymatic bioactivation to a reactive intermediate, which interacts irreversibly with fetal tissues. Since glutathione (GSH) is involved in the detoxification of many reactive intermediates, N-acetylcysteine (NAC), a glutathione precursor, was evaluated for its effects on murine fetal development and phenytoin teratogenicity. NAC, 100 to 275 mg/kg, was given intraperitoneally (ip) or per os (po), or as 266 to 410 mg/kg in the drinking water, at various times before or after phenytoin, 65 to 75 mg/kg ip, on gestational days 12 and 13. Dams were killed on gestational day 19, fetal resorptions were noted, and fetuses were examined for anomalies. Significant reductions in phenytoin-induced fetal weight loss and cleft palates were observed when NAC was given by gavage 6 hours after phenytoin or in the drinking water with the lower dose of phenytoin. NAC administered in the drinking water also reduced the incidence of resorptions produced by the higher dose of phenytoin and enhanced postpartum survival in fetuses exposed to 65 or 75 mg/kg phenytoin (P less than .05). Conversely, the incidence of resorptions increased when NAC was given by gavage at other times before or after phenytoin, by single or repetitive ip injections, or in high concentrations in the drinking water (P less than .05). When given with the higher dose of phenytoin, NAC administered via the drinking water significantly increased the incidence of phenytoin-induced cleft palates and fetal weight loss (P less than .05). Similar results were obtained with a single ip injection of NAC and a lower dose of phenytoin. Thus, when given orally, NAC can partially reduce phenytoin teratogenicity and embryopathy. However, altering the route of NAC administration, or increasing the dose of phenytoin and/or NAC, enhanced phenytoin embryotoxicity, and NAC alone at higher doses had embryopathic effects.