Ex vivo evaluation of degradation rates of metronidazole and olsalazine in distal ileum and in cecum: The impact of prandial state.

PURPOSE: Evaluate ex vivo the bacterial metabolism induced degradation rates of mesalamine (negative control), metronidazole and olsalazine in distal ileum and in cecum. METHODS: The contents of distal ileum and cecum were collected during colonoscopy under anaerobic conditions from twelve healthy adults in the fasted and in the fed state. To eliminate potential effects of enzymes that may exist in the fluid of lower intestine, each sample was ultracentrifuged and the precipitate was diluted with a volume of normal saline equivalent to that of the supernatant, after ultracentrifugation of intestinal contents from which the specific precipitate had been obtained. Degradation of the three model drugs in individual materials was evaluated anaerobically. RESULTS: Mesalamine was stable in all cases. Degradation rates of metronidazole and olsalazine were higher in cecum than in distal ileum, only in the fasted state; no trend could be observed in the fed state. Degradation rates of metronidazole and olsalazine were decreased in the fed state in the cecum; no trend could be observed in distal ileum. CONCLUSIONS: In the fasted state, bacterial activity is higher in cecum than in distal ileum. Food residues decrease bacterial metabolism degradation rates of drugs in cecum.

Characteristics of the Human Upper Gastrointestinal Contents in the Fasted State Under Hypo- and A-chlorhydric Gastric Conditions Under Conditions of Typical Drug - Drug Interaction Studies.

OBJECTIVE: Evaluate the impact of reduced gastric acid secretion after administration of two acid-reducing agents on the physicochemical characteristics of contents of upper gastrointestinal lumen of fasted adults. MATERIALS AND METHODS: Eight healthy male adults, fasted from food for 12 h, participated in a three-phase crossover study. Phase 1: No drug treatment prior to aspirations. Phase 2: Oral administration of 40 mg pantoprazole at ~9 am the last 3 days prior to aspirations and at ~7 am on aspiration day. Phase 3: Oral administration of 20 mg famotidine at ~7 pm prior to aspirations and at ~7 am on aspiration day. Samples from the contents of upper gastrointestinal lumen were aspirated for 50 min, after administration of 240 ml table water at ~9 am. RESULTS: Reduction of gastric acid secretion was accompanied by reduced buffer capacity, chloride ion concentration, osmolality and surface tension in stomach and by increased pH (up to ~0.7 units) in upper small intestine during the first 50 min post-water administration. The mechanism of reduction of acid secretion seems to be important for the buffer capacity in stomach and for the surface tension in upper gastrointestinal lumen. CONCLUSIONS: Apart from gastric pH, reduced acid secretion affects physicochemical characteristics of contents of upper gastrointestinal lumen which may be important for the performance of certain drugs/products in the fasted state.

Characterization of Contents of Distal Ileum and Cecum to Which Drugs/Drug Products are Exposed During Bioavailability/Bioequivalence Studies in Healthy Adults.

PURPOSE: Characterize the contents of distal ileum and cecum in healthy adults under conditions simulating the bioavailability/bioequivelance studies of drug products in fasted and fed state. METHODS: Twelve males participated in a two-phase crossover study. Phase I: subjects remained fasted overnight plus 4.5 h in the morning prior to colonoscopy. Phase II: subjects remained fasted overnight, consumed breakfast in the morning, and abstain from food until colonoscopy, 4.5 h after breakfast. Upon sampling, volume, pH and buffer capacity were measured; after ultracentrifugation, supernatant was physicochemically characterized and non-liquid particles diameter was measured. RESULTS: In distal ileum, pH is ~8.1 and size of non-liquid particles is ~200 µm, regardless of dosing conditions; in fed state, liquid fraction was lower whereas osmolality and carbohydrate content were higher. In cecum, the environment was similar with previously characterized environment in the ascending colon; in fasted state, size of non-liquid particles is smaller than in distal ileum (~70 µm). Fluid composition in distal ileum is different from cecum, especially in fasted state. CONCLUSION: Differences in luminal environment between distal ileum and cecum may impact the performance of orally administered products which deliver drug during residence in lower intestine. Dosing conditions affect cecal environment more than in distal ileum.