Gastric pH and gastric residence time in fasted and fed conscious cynomolgus monkeys using the Bravo® pH system

Purpose. To measure fasted and fed gastric pH and gastric residence time (GRT) in Cynomolgus monkeys using Bravo((R)) radiotelemetry capsules. Methods. Continuous pH measurements were recorded with Bravo((R)) capsules, which were either attached to the monkeys' stomach or administered as free capsules. Meals (either slurry or standard), were administered at designated times with monkeys chair-restrained during slurry meal ingestion. Results. From the attached capsule studies, the fasted gastric pH (similar to 1.9-2.2) was consistent among monkeys. Under fasted conditions, pH spikes were infrequently observed (once every 7.9 min to 3.6 h) with peaks reaching pH 9.4 and having short durations (< 1 min). After feeding, the gastric pH rose quickly and remained alkaline for approximately 4.5-7.5 h before returning to baseline. Although significantly different (p < 0.05), there was overlap between the fasted (153 +/- 87 min) and fed (436 +/- 265 (slurry) and 697 +/- 193 (standard) min) GRT due to considerable inter- and intra-subject variability. Conclusions. Fasted gastric pH was similar between monkeys and literature human values. After a meal, the monkey gastric pH was elevated for a longer duration than that in human. The monkey GRT appears longer than that observed in human under both fasted and fed conditions, although this is likely dependent on the Bravo((R)) capsule size.