Blindness Induced by Double-blindedness

Like everything else under the sun, the new observation by McClain and colleagues (see p 901) that sorbitol solution is metabolized by intestinal bacteria is not entirely new. Similarly, their finding that sorbitol is effective in treating portal systemic encephalopathy (PSE), albeit subclinical, is not completely new either. These effects have been demonstrated indirectly in several studies in which sorbitol served as a control substance for comparison with lactulose. In the investigation reported by Elkington et al,¹in which sorbitol was compared with lactulose, sorbitol therapy induced a substantial decrease in stool pH although it caused no apparent clinical benefits. The mean pH of the stools of the seven patients before therapy was 7.0 and it was 5.2 after ingestion of lactulose. After sorbitol therapy, the mean pH was 6.4 and it reached levels as low as 5.4 and 5.6 in individual patients. In a controlled clinical comparison of