Phenytoin teratogenic effects

As with carbamazepine, phenytoin also causes idiosyncratic toxic effects, including hematological and connective tissue toxicities, hepatotoxicity, and teratogenicity (89). Although some of these toxicities have been hypothesized to be caused by P450 oxidative metabolism (92,93) or peroxidase-mediated reactions (94,95), mechanisms for these toxic effects in humans are unknown. 

Adverse effects These are primarily related to CNS and Gl disturbances. They include impaired concentration, dizziness, ataxia, diplopia, somnolence, nervousness, and confusion, as well as nausea and weight loss. Renal stones have been reported in 1.5 percent of patients. Topiramate is teratogenic in animals, and should be avoided during pregnancy. Inducers of drug metabolism such as phenytoin and carbamazepine decrease topiramate serum concentrations by approximately 50 percent. Topiramate decreases ethinyl estradiol concentrations of oral contraceptive preparations, and individuals should supplement the amount of ethinyl estradiol. 

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