Comparison of gastrointestinal pH in dogs and humans: implications on the use of the beagle dog as a model for oral absorption in humans.

Gastrointestinal pH as a function of time was recorded for 4 beagle dogs and 10 human subjects using radiotelemetric pH measuring equipment. Results indicated that in the quiescent phase, gastric pH in the dogs (mean = 1.8 +/- 0.07 SEM) was significantly (p less than 0.05) higher than in humans (1.1 +/- 0.15). No significant difference in the time for the pH monitoring device to empty from the stomach was noted for the two species (99.8 +/- 27.2 min for dogs, 59.7 +/- 14.8 min for humans, p greater than 0.05). The fasting intestinal pH in dogs was consistently higher than in humans, with an average canine intestinal pH of 7.3 +/- 0.09 versus 6.0 +/- 0.14 for humans. The implication of these observations for extrapolation of drug absorption data from dogs to humans are discussed.