Editor,—I read with interest the recent article by Parkman et al(Gut1998;42:243–50) who reported on the effects of H₂ receptor antagonists and omeprazole on interdigestive gastroduodenal motility and concluded that these drugs have a motor stimulant effect. This conclusion, however, could be invalidated by the unsatisfactory study design. The basal fasting period of 30 minutes prior to administration of the drug is very short when one considers that the mean duration of the cycle of the interdigestive migrating motor complex is at least three times as long1; the 30 minute observation period after drug administration is also quite short. Parkman and colleagues could have recorded the phase III that frequently occurs spontaneously when the stress caused by the insertion of the probe has lessened. In addition, omeprazole was given before the insertion of the manometric probe so that no control period was recorded in these subjects. These biases could raise some perplexing questions about the real effectiveness of these …