Drug Absorption in Gastrointestinal Disease and Surgery

Abstract

It is well recognized that drug absorption from the gastrointestinal tract is influenced by gastric and intestinal motility, surface area available for absorption, and physicochemical properties of the drug. Disease and surgery have been shown to alter these factors. Consequently, drug absorption can be altered as well, and these affect drug therapy. Apparently this effect is variable, but the variability may be due in part to the complexities of performing studies in this area. For example, many patient factors as well as drug characteristics must be considered. In addition, appropriate interpretation of results requires that intravenous data be collected if changes in absorption are based on bioavailability. At this time, the alterations in drug absorption due to gastrointestinal disease and surgery are of unknown or little clinical significance; nevertheless, clinicians should be aware that the possibility of malabsorption exists and anticipate any monitoring of or alterations in therapy that may have to be made.

A systematic review of drug absorption following bariatric surgery and its theoretical implications

“… Drug disintegration is the first step required for drug absorption and is necessary in order for a drug to become soluble within the gastrointestinal milieu. This step, which may even vary considerably across different preparations of the same drug, is often the rate‐limiting step in the absorption of most solid dosage forms (14). One factor that promotes drug disintegration is gastric mixing and this may be substantially reduced by such restrictive bariatric procedures as gastric banding, gastroplasty, gastric bypass, sleeve gastrectomy and some forms of biliopancreatic diversion.…”

“…Pharmacokinetically, reduced gastric emptying would be expected to reduce the rate but not the overall magnitude of drug absorption – therefore, AUC levels should remain unchanged. Studies examining the effect of non‐bariatric procedures that limit gastric emptying on drug absorption have demonstrated a reduced rate of drug absorption with a variable effect on overall drug absorption (14).…”

Enterocytic CYP3A4 in a paediatric population: developmental changes and the effect of coeliac disease and cystic fibrosis

“…The limited number of pharmacokinetic studies carried out in patients with coeliac disease have been reviewed, indicating a complex interplay of factors and the importance of adequate study design [40]. For example, conflicting data are available in adults for propranolol, which is metabolized by several cytochromes P450 and by direct glucuronidation.…”

Pregabalin Assay in a Patient with Widespread Neuropathic Pain and Late Onset Gluten Intolerance: Table 1

“…The wide spectrum of effects of different drugs precludes the application of universal rules and guidelines in drug therapy in most cases of malabsorption. Drugs, dosage forms, and various interactions should be considered individually [34], and if malabsorption exists, monitoring of therapy should be considered with venous blood assays if changes in absorption are based on bioavailability [35]. To date, this is the first assay of pregabalin in celiac disease.…”