Immunoglobulin G in serum and cerebrospinal fluid from epileptic patients treated with phenytoin.

Concentrations of IgG and titres of IgG antibodies to rabbit erythrocytes were studied in serum and cerebrospinal fluid (CSF) from 21 phenytoin-treated patients; 11 of these had reduced serum IgA. The CSF IgG concentration was not reduced in any patient. A reduction of CSF IgG has been found earlier in phenytoin-treated patients, when other antisera to IgG were used for the determination of IgG concentration. The present findings therefore indicate that an alteration of the composition or quality of the CSF IgG is present in phenytoin-treated patients. 1 patient had a phenytoin-induced low serum concentration of IgG and IgA. In this patient the ratios CSF:serum were normal both for IgG concentration and for IgG antibodies to rabbit erythrocytes.