The rat as a model to evaluate the gastric irritation potential of alkaline products.
Animal models historically used to assess the acute gastric irritation potential of accidental ingestion of consumer products include the dog, pig, rabbit, and cat. In looking at alternative methods that are of shorter duration and more cost-effective, the rat is being evaluated as a potential model. Acute gastric irritation is known to increase as the reserve alkalinity of the formulation increases. In initial experiments to assess the rat as a potential model, animals were dosed via oral gavage with 1 of 4 formulations ranging in reserve alkalinity from 4.0 to 10.8. Necropsies were performed at 15 and 60 min after dosing. Macroscopic and microscopic evaluations of the stomach revealed morphological differences in the various treatment groups that distinguish granular formulations having either a low (R.A. = 4.0), moderate (R.A. = 7.1), or higher (R.A. = 10.8) reserve alkalinity. Additionally, it was observed that the acute gastric changes in rats dosed with a liquid formulation having a low (R.A. = 4.2) reserve alkalinity were similar to those in rats dosed with a granular formulation having a moderate reserve alkalinity (R.A. = 7.1). This suggests that other factors such as types of ingredients, pH, and physical form influence the extent of acute gastric irritation and demonstrates that an evaluation of only reserve alkalinity is not sufficient to ensure the safety of these products. This preliminary work supports the rat as a potential model to assess the acute gastric irritation potential of alkaline formulations or substances.