Zinc and copper metabolism in phenytoin therapy

The effect of phenytoin (PHT) on the metabolism of zinc (Zn) and copper (Cu) has been studied during treatment for epilepsy. Eleven previously untreated epileptics were followed from the start of therapy together with 20 patients on long-term therapy. In eight untreated epileptic males low serum concentrations of Zn (S-Zn) were found. At the start of therapy increased S-Zn and S-Cu concentrations were noted. After 1 month of therapy S-Zn was at pretherapy levels but S-Cu was still increased. No changes in the urinary excretion of the metals or in the CSF-Zn concentrations were registered. In the patients on long-term therapy S-Zn was unchanged while S-Cu and S-ceruloplasmin were increased significantly compared with age- and sex-matched controls. It is postulated that the drug may cause a relative zinc deficiency through a chelate binding between Zn and PHT and/or an increased absorption and accumulation of Cu. These effects may be of importance in the development of intoxication symptoms and may also influence the effectiveness of seizure control.