Enprostil inhibits post-prandial gastrin release: a dose-response study

The effect of indomethacin-induced gastric mucosal injury on 24-h intragastric acidity and plasma gastrin concentration in healthy volunteers

AIMS

To determine the influences of prostaglandin inhibition by indomethacin on 24-h intragastric acidity and plasma gastrin concentration, related to gastric mucosal injury.

METHODS

A pre- and post-treatment study design was employed in 10 Helicobacter pylori negative healthy male subjects. All subjects underwent upper gastrointestinal endoscopy at least 3 days before and after 7 days dosing with indomethacin 50 mg t.d.s. Mucosal damage was scored according to the Lanza method, and biopsies were taken for H. pylori status and assay of mucosal concentrations of prostaglandin (PG)E2 and leukotriene (LT)B4. Before and on the last day of dosing, intragastric acidity was measured by continuous 24-h pH monitoring, and plasma gastrin levels determined by radioimmunoassay in blood samples collected over the same period.

RESULTS

All subjects completed the study and no serious adverse events were reported. The mucosal injury score increased significantly from 0 (0-2) to 3.4 (0-8) (mean and range of values, P < 0.05) after dosing with indomethacin. No differences were observed in 24-h mean pH or meal stimulated plasma gastrin concentrations. Mucosal PGE2 and LTB4 were unchanged 8-10 h after the last indomethacin dose.

CONCLUSIONS

Endogenous prostaglandins do not appear to alter intragastric acidity or gastrin secretion, in contrast to the PGE analogues, whose effects must be more pharmacological than physiological.

Effects of hypochlorhydria and hypergastrinemia on structure and function of gastrointestinal cells. A review and analysis

Since hypochlorhydria can induce hypergastrinemia, and gastrin has a trophic effect on some gastrointestinal cells, states that cause elevated plasma gastrin levels are of interest in terms of effects on cell growth and function. This article reviews the relationship between gastric mucosal cells during periods of acid stimulation and inhibition and analyses the effects of hypochlorhydria and hypergastrinemia on gastric and colonic cells and tumors. Hypochlorhydria releases the inhibitory effect of antral gastrin cells, inducing them to release gastrin in the presence of peptides or amino acids in the gastric lumen or in response to antral distension. Gastrin stimulates the oxyntic mucosa, which may lead to hyperplasia of enterochromaffin-like cells, resulting in enterochromaffin-like carcinoid tumors in aged rats and, rarely, in patients with chronic atrophic gastritis or gastrinomas. In addition to hypergastrinemia, other factors appear to be required for the progression of enterochromaffin-like hyperplasia to carcinoids; genetic factors may be involved. Gastrin elevations due to antisecretory drug therapy are indirectly proportional to the degree of acid inhibition and are reversible upon cessation of therapy. The gastrin levels during omeprazole therapy are similar to those caused by gastric vagotomy. Available evidence does not support a relationship between hypergastrinemia and the occurrence or growth of gastric carcinoma or colonic tumors.

Effect of enprostil on serum gastrin and pepsinogen A and C levels in patients on long-term treatment with omeprazole

BACKGROUND

Treatment of omeprazole induces profound inhibition of gastric acid secretion, resulting in hypergastrinaemia. In rats hypergastrinaemia induced by chronic administration of high doses of omeprazole resulted in ECL-cell hyperplasia and subsequent carcinoid formation. This finding may limit long-term therapy in man. The synthetic prostaglandin E2 analogue enprostil not only inhibits gastric acid secretion but also reduces serum gastrin in normal subjects and in peptic ulcer patients. The present study was undertaken to determine whether enprostil reduces serum gastrin in patients on long-term treatment with omeprazole.

METHODS

Eight patients with reflux oesophagitis treated with 40 mg omeprazole once daily for at least 3 months received 35 micrograms enprostil t.d.s. during a 5-day treatment course. Basal and postprandial serum gastrin concentrations and pepsinogen A and C levels were measured on the day before, the first and the final day, and on the day after cessation of treatment.

RESULTS

Enprostil significantly (P < 0.05) reduced basal serum gastrin from 65 +/- 15 pmol/L to 51 +/- 13 pmol/L on the first treatment day, and to 41 +/- 9 pmol/L on the final day. Enprostil also significantly (P < 0.05) reduced postprandial integrated serum gastrin from 6173 +/- 849 pmol.h/L to 4516 +/- 906 pmol.h/L and to 3532 +/- 706 pmol.h/L on the first and final treatment days, respectively. On the day after cessation of treatment basal (57 +/- 11 pmol/L) and postprandial integrated serum gastrin concentrations (5766 +/- 864 pmol.h/L) were not significantly different when compared to pretreatment values. Enprostil had no significant influence on serum pepsinogens A and C.

CONCLUSION

Short-term co-administration of enprostil lowers the serum gastrin levels in patients on long-term treatment with omeprazole.

Effect of synthetic prostaglandin E2 analog enprostil on omeprazole-induced hypergastrinemia and hyperpepsinogenemia

This study was undertaken to determine whether the synthetic prostaglandin E2 analog enprostil is able to inhibit basal and postprandial hypergastrinemia induced by omeprazole. We also studied the effect of omeprazole, enprostil, and the combination of both drugs on serum pepsinogen A and C levels. Eight normal subjects received in random order five-day courses of 40 mg omeprazole once a day, 35 micrograms enprostil three times a day, the combination of both drugs, and placebo. Omeprazole induced significant increases in basal and postprandial serum gastrin and in pepsinogen A and C levels. These increments persisted on the day after stopping treatment. Coadministration of enprostil inhibited omeprazole-induced basal hypergastrinemia and postprandial integrated serum gastrin, but not basal serum pepsinogen A and C, while the inhibition on the day after the treatment courses only reached statistical significance for the postprandial integrated serum gastrin concentration. It is concluded that enprostil inhibits omeprazole-induced basal and postprandial hypergastrinemia, with a tendency to protracted inhibition after stopping the drugs, and that enprostil does not significantly influence omeprazole-induced increases in pepsinogen A and C level. Coadministration of enprostil may be helpful in preventing pronounced hypergastrinemia in the few patients who show large serum gastrin increases during treatment with omeprazole.

Gastric acid secretion and intragastric acidity: measurement in health and disease

Gastric acid secretion tests have limited use in clinical practice. For practical purposes, a pH measurement on a fasting gastric aspirate will provide strong evidence of the presence or absence of achlorhydria. Tests of gastric acidity, in particular 24-h acidity studies, have provided considerable insight into normal and abnormal gastric physiology, and have largely determined the dosing regimens for the management of acid-peptic diseases. Acid tests may be simple to perform, so much so that they have been suggested as 'practicals' for student teaching (Nicol et al, 1991). However, reproducible and meaningful results require careful attention to detail, and the appropriate mathematical analysis is still subject to some debate. It is important that the presentation of the data should allow the reader to assess the response over the 24-h period, and also the range of individual responses. Despite the many years of research into gastric acid secretion, only recently have the effects of age, sex, diet, smoking and mental stress been identified. In addition, many data need to be reviewed in the light of the effects of H. pylori infection on gastrin release. H2-receptor antagonists had been studied extensively before and since their first clinical use in 1974, but surprisingly only recently have the issues of tolerance and rebound been defined. The 24-h intragastric acidity profile remains an essential study before the start of clinical trials on any new drug to be used for the treatment of acid-peptic diseases.

Eradication of Helicobacter pylori abolishes 24-hour hypergastrinaemia: a prospective study in healthy subjects

In a prospective study, eight young healthy subjects (five with an active H. pylori infection in the antral mucosa) were treated with a course of tripotassium dicitrato bismuthate, amoxycillin and metronidazole. The triple therapy eradicated infection when assessed 20-24 weeks later by antral biopsy (urease, histology, and 13C urea breath test [4 out of 5 subjects]). Twenty-four hour intragastric acidity and plasma gastrin concentration were measured before treatment, and 4-6 weeks and 20-24 weeks post-treatment. Treatment did not affect acidity in either the H. pylori-positive or H. pylori-negative groups, nor did it affect the plasma gastrin profile in the H. pylori-negative group. Eradication of H. pylori infection in five subjects caused a drop of the median integrated 24-hour plasma gastrin concentration from 558 pmol.h/L before treatment to 307 and 289 pmol.h/L at 4-6 and 20-24 weeks post-treatment, respectively. It is concluded that H. pylori infection is associated with 24-hour hypergastrinaemia, and that in apparently healthy subjects normal gastric physiology can be restored by eradication of the infection.

Upper gastrointestinal manifestations in rheumatoid arthritis patients: intrinsic or extrinsic pathogenesis?

Apart from the complication of gastrointestinal vasculitis it is not known whether the upper gastrointestinal (UGI) tract has any special disease characteristics in rheumatoid arthritis (RA). However, oesophageal motility disorders have been reported in 30% of RA patients. Hypergastrinaemia has been found in 23-43% of RA patients, usually in combination with a decreased gastric acid output. Another finding suggestive of a decreased secretory state, namely a decreased level of pepsinogen A, was found in RA patients with the sicca syndrome and in patients with active disease. The risk for peptic ulcer disease with regard to nonsteroidal anti-inflammatory drugs (NSAID) is possibly higher in RA patients than in patients with other rheumatic diseases. These findings suggest that in RA patients intrinsic factors play a role in the pathogenesis of the oesophageal motility disorders, in hypergastrinaemia and hypopepsinogenaemia and the related decreased gastric secretory state, and possibly in the increased susceptibility to NSAID-related ulcers. However, there are also indications that oesophageal motility disorders, hypergastrinaemia, and NSAID-related ulcers in RA are the result of extrinsic factors, mainly the use of NSAIDs. The effects of NSAIDs and gold compounds on infection with Helicobacter pylori, a possible pathogenetic factor in ulcer disease, is discussed. It is clear that the discussion about intrinsic and extrinsic factors as a cause of the UGI manifestations in RA remains an intriguing but difficult subject for further studies.

A comparison of low-dose maintenance treatment with enprostil against ranitidine in the prevention of duodenal ulcer recurrence

Enprostil, a prostaglandin E2 analogue, is effective in healing acute duodenal ulcer but its value in preventing recurrence, when given daily for maintenance therapy, is uncertain. In this three-centre study we compared enprostil and ranitidine maintenance therapy; the latter is known to reduce duodenal ulcer relapse rates. Patients whose duodenal ulcers had been healed by treatment with an H2-receptor antagonist were randomized to receive single-blind treatment with either 35 micrograms enprostil (n = 64) or 150 mg ranitidine (n = 64) at bedtime for periods of up to 1 year. Endoscopy was routinely performed at 3 months at one centre, and at 6 and 12 months at all three centres, or whenever ulcer symptoms recurred. Clinical assessment and laboratory investigations were performed every 3 months. Relapse, defined as recurrent ulcer with or without pain, or erosions with pain, was significantly greater in patients on enprostil, the comparative rates at 3, 6 and 12 months were: enprostil 23, 31 and 36% ranitidine 6, 12 and 17% (P = 0.013; P = 0.03 and P = 0.03, respectively). Thirty-one patients reported adverse events, the most common being headache (enprostil = 6, ranitidine = 2) and mild diarrhoea (enprostil = 6, ranitidine = 0). Four patients on enprostil were withdrawn for adverse events, although none terminated because of diarrhoea. There were no clinically significant changes in haematology or biochemistry. Enprostil may reduce duodenal ulcer relapse but at a dose of 35 micrograms nightly, it is less effective than 150 mg ranitidine nightly.