The rectal administration of lactulose.

A lactulose colonic washout (pH 4.5) was administered to six male patients with portal systemic encephalopathy. Estimation of blood ammonia levels and electroencephalography were performed before and after each treatment. Five patients recorded a significant fall in blood ammonia level as a result of lactulose therapy (P less than .025). In the sixth subject, an enema with buffered physiological saline, pH 4.5, induced a fall in ammonia which was not increased by subsequent lactulose solution. Improvement in the electroencephalogram was recorded in all periods where a lactulose colonic washout produced a fall in blood ammonia level.