Cholestatic liver dysfunction after long-term phenytoin therapy.

Cholestatic jaundice developed in a 64-year-old woman who had received phenytoin sodium for more than 40 years. Discontinuation of phenytoin therapy resulted in resolution of the hepatic abnormalities, which recurred on rechallenge, strongly suggesting a causal relation to the drug. Phenytoin therapy was discontinued again, with complete resolution of the hepatic abnormalities. The liver biopsy specimen obtained during therapy showed cholestasis compatible with obstruction of the biliary tree, although an obstructive process was never demonstrated. The biochemical abnormalities and histologic features observed most likely represent an unusual response to phenytoin therapy.