Decreased phenytoin levels in antineoplastic therapy.

A case history is reported illustrating the difficulties which may be encountered in maintaining seizure control in patients being treated with antineoplastic therapy. The maintenance of therapeutic serum levels of phenytoin during combined cis-platinum and bleomycin sulfate therapy suggests an absorptive defect, possibly related to damage of the intestinal mucosa. This defect did not appear to alter the absorption of primidone or phenobarbital, since increased dosages were not necessary to maintain these drugs within therapeutic ranges.