Prolonged inhibition of meal-stimulated acid secretion and gastrin release following single subcutaneous administration of octreotide (SMS 201-995) in man

Effects of octreotide on healing of intestinal anastomosis following small bowel obstruction in rats

PURPOSE

Octreotide is an analog of somatostatin, with the same biologic effects but a longer half-life than somatostatin. The purpose of this experimental study was to search the effects of octreotide on the healing of bowel anastomosis and to observe the anatomic and physiologic changes in the obstructed bowel.

METHODS

Two groups of ten male Wistar albino rats (average weight, 250 grams) were used in this study. One group was the octreotide group, and the other was the control group. In both groups, the basal diameters of jejunum were measured before ligation of the bowel 20 cm from the duodenum. Octreotide was administered subcutaneously (7 micrograms/kg/day, in two equal doses) in the first group, and the same volume of saline was used in the control group. Diameters of the obstructed segments were measured, and sodium and potassium levels, obtained from the luminal fluid of the obstructed bowel, were recorded 48 hours following the first operation. Dilated segments were resected, and end-to-end intestinal anastomoses were performed. In rats sacrificed on the fourth and seventh days following the second operation, bursting pressures of the anastomotic and hydroxyproline levels in tissue samples taken from the anastomosis were measured.

RESULTS

The diameter of the obstructed bowel increased significantly in the control group (P < 0.05). Sodium and potassium losses were significantly less in the octreotide group (P < 0.001 for sodium; P < 0.01 for potassium). In histopathologic examination, ischemic changes were more evident in the control group (P < 0.05). Anastomotic bursting pressure differences were not significant on the fourth postoperative day (P > 0.05), but differences were significant on the seventh postoperative day (P < 0.05). Anastomotic tissue hydroxproline synthesis on the fourth and seventh postoperative days of the octreotide and control groups did not show significant difference (P > 0.05).

CONCLUSION

In this experimental model, it appears that octreotide attenuates the ischemic changes and electrolyte losses in the obstructed bowel.

Somatostatin analogue treatment inhibits post-resectional adaptation of the small bowel in rats

Post-resectional hyperplasia is the phenomenon in which residual small bowel increases in size and absorptive capacity after segmental enterectomy. This experiment studied the effect of somatostatin analogue therapy on the development of two structural parameters of post-resectional hyperplasia in rats subjected to 40% proximal small bowel resection. Octreotide acetate-treated rats failed to develop increased villus height (902 +/- 50 microns) relative to saline-treated rats (1,103 +/- 98 microns). Augmentation of residual intestinal weight was also significantly impaired in analogue-treated rats (92 +/- 3 versus 118 +/- 5 mg/cm). We conclude that somatostatin analogue treatment during the early postoperative period does impair the growth of residual bowel in rats. These findings raise concern regarding the use of this drug for postoperative patients who have undergone massive small bowel resection in whom the process of post-resectional adaptation may be critical to allow sustenance with enteral nutrition.

Prolonged inhibition of acid secretion causes hypergastrinaemia without altering pH inhibition of gastrin release in humans

Hypergastrinaemia induced by potent inhibitors of acid secretion is thought to occur as a result of the elimination of the inhibitory effects of intragastric acid on gastrin release. The present study was designed to determine if the mechanisms responsible for feedback inhibition of gastrin release and acid secretion by intragastric acid are preserved during four weeks of varying degrees of drug-induced acid inhibition. Forty-eight healthy male volunteers were randomly assigned to one of four treatments for four weeks: 10 mg omeprazole o.m., 20 mg omeprazole o.m., 40 mg omeprazole o.m. or 150 mg ranitidine b.d. Gastrin release and acid secretion in response to peptone meals maintained at pH 2.5 and pH 5.5 by intragastric titration, and 24-hour gastrin profiles in response to standard meals were determined before treatment, at the fourth week of treatment and two weeks after discontinuing treatment. As expected, omeprazole produced dose-related effects on acid secretion and gastrin concentrations that were largely reversed after treatment was discontinued. Gastrin release in response to pH 5.5 peptone meals remained significantly greater than gastrin release in response to pH 2.5 meals during treatment with all doses of omeprazole. The ratio of pH 5.5/pH 2.5 peptone meal-stimulated gastrin release was approximately 1.5, and remained constant for all treatment groups throughout the study period. These data indicate that four weeks of drug induced hypochlorhydria causes an apparent increase in overall G-cell function, but it does not interfere with normal feedback inhibition of gastrin release and acid secretion mediated by intragastric acidity.