Simultaneous measurement of in vitro gastroduodenal prostaglandin E2 synthesis and degradation in peptic ulcer disease

Short-term sucralfate administration alters potassium diclofenac absorption in healthy male volunteers

AIMS

Since patients who regularly take NSAIDS may use sucralfate because of its cytoprotective properties, we examined the influence of this compound on the pharmacokinetics of diclofenac.

METHODS

Potassium diclofenac (105 mg) was administered orally to eighteen healthy male volunteers with or without a 5-day pre-treatment with sucralfate (2000 mg twice daily). Blood samples were collected at intervals post-dose and serum concentrations of diclofenac were determined by reverse-phase h.p.l.c.

RESULTS

Pre-treatment with sucralfate significantly decreased both the AUC(0,8 h) [2265 ng h ml-1 (geometric mean) (range 1815-2827) vs 1821 ng h ml-1 (1295-2562)] and the Cmax [1135 ng ml-1 (geometric mean) (range 898-1436) 701 ng ml-1 (501-981)] with no significant delay in absorption [tmax 1.0 h (median) (range 0.5-2.0) vs 1.0 h (0.5-4.0)].

CONCLUSIONS

The short-term treatment of healthy male volunteers with sucralfate decreases potassium diclofenac bioavailability. These findings suggest that either an appropriate increase in the diclofenac intake or the use of another gastric mucosa protector must be adopted.

Gastric bicarbonate secretion and release of prostaglandin E2 are increased in duodenal ulcer patients but not in Helicobacter pylori-positive healthy subjects

BACKGROUND

Duodenal ulcer (DU) patients have impaired proximal duodenal mucosal bicarbonate secretion at rest and in response to luminal acid with higher acid-stimulated mucosal release of prostaglandin (PG) E2 than healthy subjects. Our purpose was to determine whether this abnormality was present also in the stomach of DU patients.

METHODS

Simultaneous determinations of gastric and duodenal bicarbonate secretion and luminal release of PGE2 were performed in 16 healthy volunteers (5 Helicobacter pylori-positive) and 8 inactive DU patients (all H. pylori-positive).

RESULTS

In healthy volunteers the rates of gastroduodenal bicarbonate secretion and the release of PGE2 were not influenced by H. pylori status. In inactive DU patients the rates of basal (704 +/- 84 versus 356 +/- 40 mumol/h; mean +/- SEM) and vagally stimulated (modified sham feeding) (1724 +/- 376 versus 592 +/- 52 mumol/h) gastric bicarbonate secretion were higher (p < 0.05) than in the health, whereas the corresponding rates (339 +/- 42 versus 591 +/- 51 mumol/h and 543 +/- 99 versus 778 +/- 69 mumol/h) in duodenal bicarbonate secretion were lower (p < 0.05). In addition, inactive DU patients had higher basal (148 +/- 32 versus 53 +/- 5 ng/h) and stimulated (291 +/- 84 versus 131 +/- 25 ng/h) gastric release of PGE2, but only the basal release of PGE2 into the duodenum was significantly increased (20 +/- 3 versus 5 +/- 1 ng/h; p < 0.05).

CONCLUSION

Increased mucosal production of PGE2 may be responsible for the abnormally high gastric secretion of bicarbonate in inactive DU patients. The defective duodenal secretion of bicarbonate observed in these patients may be a consequence of previous ulceration rather than the mere presence of H. pylori infection.

Mucosal adaptation to indomethacin induced gastric damage in man--studies on morphology, blood flow, and prostaglandin E2 metabolism

The effect of 28 days' continuous administration of oral indomethacin on gastroduodenal morphology, gastric mucosal blood flow, and gastric mucosal prostaglandin E2 (PGE2) metabolism in man was studied to define further the mechanisms of mucosal injury induced by indomethacin. Indomethacin caused acute gastroduodenal damage in all cases, which was maximal at 24 hours of administration. With continued intake, mucosal adaptation occurs resulting in resolution of endoscopic mucosal damage. At the time of maximal mucosal damage, gastric mucosal blood flow was significantly reduced compared with values before treatment (p less than 0.001 in fundus and p less than 0.002 in antrum), with good correlation between the severity of damage and the magnitude of the reduction in blood flow (r = 0.76). Mucosal recovery was associated with a return of the blood flow to normal. PGE2 in mucosal homogenate was significantly reduced by indomethacin in both the fundus (p less than 0.01) and antrum (p less than 0.01) after 24 hours but there was no correlation between the magnitude of this reduction and the severity of mucosal damage (r = -0.34). Despite mucosal recovery by 28 days, PGE2 values remained significantly below those before treatment in both the fundus (p less than 0.01) and antrum (p less than 0.01). The PGE2 degradation capacity was not influenced by indomethacin. In conclusion, mucosal adaptation to acute damage by indomethacin occurs in man and seems independent of local PGE2 metabolism.

Prostaglandins and gastric ulcers: from seminal vesicle to misoprostol (Cytotec)

Misoprostol (Cytotec, G.D. Searle & Company, Chicago, IL) is the first of a new class of orally administered prostaglandin analog drugs to be marketed in the United States. Misoprostol was approved for the prevention of gastric mucosal ulcers associated with nonsteroidal anti-inflammatory drugs (NSAIDS) in high-risk patients. This represents a potentially important development in the pharmacotherapy of peptic ulcer disease. The purposes of this article are to review (1) the biochemistry, physiology, and pharmacology of prostaglandins, especially those synthesized by the stomach; (2) the potential role of prostaglandin deficiency in the pathophysiology of gastric ulcer disease; and (3) the role of prostaglandin analogs in the prevention and therapy of gastric ulcer disease and in other conditions. As the mechanism of action of these new drugs differs from that of the histamine H2-receptor antagonists (H2-blockers), prostaglandin analogs will, whenever possible, be compared with the H2-blockers [cimetidine (Tagamet), ranitidine (Zantac), nizatidine (Axid) and famotidine (Pepcid)], currently the cornerstone of peptic ulcer therapy in this country.

Duodenal and antral mucosal prostaglandin E2 synthesis in a study of normal subjects and all stages of duodenal ulcer disease treated by H2 receptor antagonists

We tested the hypothesis that the production of prostaglandin E2 (PGE2) is impaired in duodenal ulcer disease and affected by treatment and healing. This was investigated by a study of maximal PGE2 synthesis rates in duodenal and antral mucosal biopsies obtained at endoscopy. The patients were divided into three groups. Group (a): endoscopically normal controls (n = 56); group (b): treatment controls (non-DU disease: gastric ulcer or oesophagitis treated by histamine H2 receptor antagonists) (n = 41); and group (c): patients with DU disease (n = 183) further subdivided into group (c1) active ulcer not on treatment (n = 47), (c2) treated active ulcer (n = 35), (c3) healed ulcer on treatment (n = 86), and (c4) healed ulcer not on treatment (n = 15). Group (a) synthesised (mean (SD] 106.6 (39.0) pg PGE2/mg wt of tissue from the duodenal bulb and 129.9 (56.9) from the second part of the duodenum. No difference was found between group (a) and (b) at either site. Group (c1) ulcer rim made 49.8 (22.7) and at all stages ulcer rim and scar made less than the control duodenal bulb (p less than 0.02). Uninvolved duodenal bulb form groups (c1) (63.4 (31.0], (c2) (83.6 (38.5], and (c3) (81.5 (31.1], however, also made significantly less than controls (p less than 0.02) and a similar though non-significant trend was seen in group (c4). Biopsies from the second part of the duodenum did not synthesise significantly less than the control group but a similar trend was noticed at each stage of ulcer treatment. Biopsies of control antrum synthesised 124.5 (32.2) but only 93.7 (44.2) in group (cl) (p < 0.005). All stages of duodenal ulcer healing were associated with a decreased capacity to synthesise the major prostaglandin PGE2 at the ulcer site and the uninvolved duodenal bulb and, in acute untreated duodenal ulcer, the uninvolved antrum. This decreased capacity may be the consequence of the disease process itself and not secondary to the treatment, indicating a basic pathophysiological abnormality which may explain the characteristic tendency of the disease to relapse.

The relationship between plasma cortisol and gastric mucosa prostaglandin levels in rats with stress ulcers

A correlation between the levels of plasma cortisol, gastric mucosal prostaglandins and the degree of gastric ulceration produced by stress in rats was examined. Four groups of rats were evaluated. Group A, the cold stressed group; group B, their controls; group C, those receiving intraperitoneal indomethacin; and group D, those receiving intraperitoneal saline. Group A developed stress ulcers and their gastric mucosal prostaglandin levels (prostaglandin E2 (PGE2) and prostacyclin levels, as measured by its stable metabolite 6-keto-prostaglandin F1 alpha (6-keto-PGF-1 alpha, but not thromboxane) were significantly reduced when compared with their respective non-stressed controls. The plasma cortisol levels in both group A and B increased slightly in the first hour but there was no statistical difference between the two groups and there was no change at 2, 3 or 4 h of stress. Group C (indomethacin) also developed ulcers and had low gastric mucosal prostaglandin levels when compared with group D (saline). The plasma cortisol levels did not alter in either group C or D. It has been postulated that stress ulcers may involve the depletion of gastric mucosal prostaglandin levels which, in turn, may be a consequence of a higher plasma cortisol level. A decrease in gastric prostaglandins independent of any change of plasma cortisol levels was demonstrated in this study and the mechanism of production of stress gastric ulcers remains obscure.