Gastric pH and gastric residence time in fasted and fed conscious cynomolgus monkeys using the Bravo pH system.
OBJECTIVE
To measure fasted and fed gastric pH and gastric residence time (GRT) in Cynomolgus monkeys using Bravo radiotelemetry capsules.


METHODS
Continuous pH measurements were recorded with Bravo 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 (~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 capsule size.
Chen
Emile P
EP
Department of Preclinical Drug Metabolism and Pharmacokinetics, GlaxoSmithKline, King of Prussia, PA 19406, USA. emile.p.chen@gsk.com
Mahar Doan
Kelly M
KM
Portelli
Samm
S
Coatney
Robert
R
Vaden
Vernal
V
Shi
Wei
W
D000818:Animals; D002214:Capsules; D003627:Data Interpretation, Statistical; D005215:Fasting / Q000502:physiology*; D005502:Food; D005745:Gastric Acidity Determination / Q000295:instrumentation*; D005746:Gastric Emptying / Q000502:physiology*; D005753:Gastric Mucosa / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D008252:Macaca fascicularis; D008297:Male; D013686:Telemetry / Q000379:methods*
D002214:Capsules