Radiotelemetering studies of jejunal pH before and after vagotomy and gastro-enterostomy

Physiochemical and physiological mechanisms for the effects of food on drug absorption: the role of lipids and pH

Drugs are absorbed after oral administration as a consequence of a complex array of interactions between the drug, its formulation, and the gastrointestinal (GI) tract. The presence of food within the GI tract impacts significantly on transit profiles, pH, and its solubilization capacity. Consequently, food would be expected to affect the absorption of co-administered drugs when their physicochemical properties are sensitive to these changes. The physicochemical basis by which ingested food/lipids induce changes in the GI tract and influence drug absorption are reviewed. The process of lipid digestion is briefly reviewed and considered in the context of the absorption of poorly water-soluble drugs. The effect of food on GI pH is reviewed in terms of location (stomach, upper and lower small intestine) and the temporal relationship between pH and drug absorption. Case studies are presented in which postprandial changes in bioavailability are rationalized in terms of the sensitivity of the physicochemical properties of the administered drug to the altered GI environment.

Factors controlling colonic motility: colonic pressures and transit after meals in patients with total gastrectomy, pernicious anaemia or duodenal ulcer

The motor responses of the proximal colon, sigmoid, and rectum to the ingestion of a standard meal have been compared in patients with total gastrectomy, pernicious anaemia, or duodenal ulcer. Colonic pressure activity increased during and after food in all the patients, but this was only once associated with propulsive activity. The results suggest that the postprandial pressure activity in the sigmoid colon is greater after total gastrectomy than in the other two groups. It is concluded that entry of food into the upper small intestine is the most important factor in initiating the colonic pressure response to food, since this response does not require the presence of the stomach, acid, antral gastrin, or of vagal innervation.