Bravo capsule system optimizes intragastric pH monitoring over prolonged time: Effects of ghrelin on gastric acid and hormone secretion in the rat

Gastroprotectants in small animal veterinary practice - a review of the evidence. Part 1: cyto-protective drugs

Diverse drugs with presumed cytoprotective effect have been used therapeutically in small animal veterinary practice for various gastro-intestinal conditions such as oesophagitis, gastric ulceration, gastritis or chronic gastro-enteropathies. Their efficacy has been doubted in human medicine, raising similar questions in the veterinary field. The aim of this review was to assess the current evidence on the efficacy and safety of these drugs in dogs and cats. Through a systematic review of the literature, we identified 37 articles on the use of misoprostol, sucralfate and other gastroprotectants in dogs and cats. There was evidence to support use of misoprostol in the prevention of aspirin-induced gastroduodenal mucosal injury in dogs, and for use of sucralfate in the prevention of acid-induced oesophagitis in cats. However, the overall quality of evidence supporting the use of these drugs in small animal patients was poor. In contrast, there was evidence of important adverse effects, especially drug interaction and gastro-intestinal signs. We therefore recommend prescribing these drugs with caution until further well-conducted studies reveal a useful gastroprotectant effect.

Evaluation of Acid Tolerance of Drugs Using Rats and Dogs Controlled for Gastric Acid Secretion

We attempted to establish animal models to evaluate the effects of drug degradation in the stomach on oral bioavailability. In addition, we assessed the utilization of animal studies in determining the need for enteric-coated formulations. In order to control the gastric pH in rats and dogs, appropriate dosing conditions were investigated using pentagastrin and rabeprazole, which stimulate and inhibit gastric acid secretion. Using animals controlled for gastric acid secretion, the area under curve (AUC) ratios (AUC with rabeprazole/AUC with pentagastrin) of all compounds unstable under acidic conditions were evaluated. The AUC ratios of omeprazole and erythromycin, which are administered orally to humans, as enteric-coated tablets, were greater than 1.9 in the rats and dogs controlled for gastric acid secretion. On the contrary, the AUC ratios of clarithromycin, azithromycin, and etoposide (commercially available as a standard immediate-release form) were less than 1.3 each. In conclusion, in vivo models using rats and dogs were optimized to evaluate the effects of gastric acid on the oral bioavailability of drugs, and demonstrated that in vivo models can lead to a better understanding of the oral bioavailability, with respect to the formulation development.

The type 2 CCK/gastrin receptor antagonist YF476 acutely prevents NSAID-induced gastric ulceration while increasing iNOS expression

YF476 differs from the proton pump inhibitor (PPI) esomeprazole in mode of action by antagonizing the type 2 receptor of cholecystokinin/gastrin (CCK-2R). YF476 protection against diclofenac-induced gastric ulcers was compared to esomeprazole and correlated with plasma levels of hormones related to gastric pH (gastrin, ghrelin, and somatostatin), gastric gene expression of these hormones, their receptors, and inducible nitric oxide synthase (iNOS). YF476 or esomeprazole pretreatments were followed by diclofenac. Four hours later, gastric tissue was excised and analyzed for ulcer index. An intragastrically implanted Bravo capsule measured pH for 5 days during YF476 plus pentagastrin treatment. Changes in gene expression were assayed for gastrin, ghrelin, and somatostatin; their receptors; and iNOS. YF476 acutely (within 4 h) protected against diclofenac-induced gastric ulcers equivalent to esomeprazole. Gastric pH recorded during 5 days in the presence of pentagastrin was 1.83 (±0.06). YF476 raised pH to 3.67 (±0.09) and plasma ghrelin, gastrin, and somatostatin increased. YF476 increased gene expression of somatostatin receptor and gastrin, while ghrelin receptor decreased; transcripts coding ghrelin, somatostatin, and CCK-2R remained unchanged. In the presence of diclofenac, esomeprazole increased expression of all these transcripts and that of iNOS, while YF476 yielded only decreased CCK-2R and increased iNOS transcripts. YF476 is a potential new preventative treatment for patients at risk of nonsteroidal antiinflammatory drug (NSAID)-induced ulceration. Gastric gene expressions of ghrelin, gastrin, and somatostatin and their receptors differ between esomeprazole and YF476. Despite these differences and different modes of action to raise gastric pH, both drugs acutely increase iNOS, suggesting iNOS expression parallels pH.