Histamine H2-antagonists modify gastric emptying in the rat

Rational use of gastroprotectants in cats: An evidence-based approach

PRACTICAL RELEVANCE

Acid-related disorders including esophagitis and gastroduodenal ulceration are uncommon in the cat. However, when they occur, they can have devastating consequences and require targeted intervention, including the use of gastroprotectants. Careful consideration of the causes of esophagitis and gastroduodenal ulceration can help the clinician to determine which gastroprotectant to use, and when to begin and end gastroprotective therapy.

CLINICAL CHALLENGES

Gastroprotectants remain one of the most misused classes of drugs in veterinary and human medicine. There are very few studies evaluating the efficacy of gastroprotective agents in cats. Furthermore, goals for the degree of gastric acid suppression are extrapolated from studies performed in dogs and humans.

AIMS

This review provides a foundation for the logical approach to the choice of gastroprotectant as indicated by the disease process, and is aimed at all veterinarians who prescribe gastroprotectants for use in cats.

EVIDENCE BASE

The guidance provided in this review is supported by current literature, including consensus opinion from the American College of Veterinary Internal Medicine. Gaps in evidence for use of gastroprotectants in cats are filled by extrapolations from studies performed in dogs and humans.

Medical management of malignant bowel obstruction in patients with advanced cancer: 2021 MASCC guideline update

BACKGROUND

Malignant bowel obstruction (MBO) is a frequent complication in patients with advanced cancer, particularly colon or gynecological malignancies. MASCC previously published a guideline for symptom management of MBO in 2017. This is a 5-year update.

METHOD

A systematic search and review of relevant literature includes a review published in 2010 and 2017. The guideline update used the same literature search process as followed in 2015. The dates of the new search included 2015 up to February 2, 2021. The guidelines involved the pharmacologic management of nausea and vomiting in malignant bowel obstruction (MBO) only. Only randomized trials were included in the updated guideline as evidence. The evidence was reviewed by the panel and the MASCC criteria for establishing a guideline were followed using MASCC level of grading and category of evidence.

RESULTS

There was one systematic review and 3 randomized trials accepted as evidence from 257 abstracts. Octreotide is effective in reducing gastrointestinal secretions and colic and thereby reduces nausea and vomiting caused by MBO. Scopolamine butylbromide is inferior to octreotide in the doses used in the comparison study. Olanzapine or metoclopramide may be effective in reducing nausea and vomiting secondary to partial bowel obstructions. The panel suggests using either drug. Additional studies are needed to clarify benefits. Haloperidol has been used by convention as an antiemetic but has not been subjected to a randomized comparison. Ranitidine plus dexamethasone may be effective in reducing nausea and vomiting from MBO but cannot be recommended until there is a comparison with octreotide.

DISCUSSION

Octreotide remains the drug of choice in managing MBO. Ranitidine was used in one randomized trial in all participants and so its effectiveness as a single drug is not known until there is a randomized comparison with octreotide. Antiemetics such as metoclopramide and olanzapine may be effective, but we have very few randomized trials of antiemetics in MBO.

CONCLUSION

The panel recommends octreotide in non-operable MBO. Randomized trials are needed to clarify ranitidine and antiemetic choices.

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.

L-lysine dose dependently delays gastric emptying and increases intestinal fluid volume in humans and rats

BACKGROUND

Novel sensory inputs for the control of food intake and gastrointestinal (GI) function are of increasing interest due to the rapid increase in nutrition-related diseases. The essential amino acid L-lysine was demonstrated to have a selective impact on food intake, gastric emptying, and intestinal transit in rats, thus indicating a potential novel direct sensory input to assess dietary protein content and quality. The aim of this study was to assess translational aspects of this finding and to investigate the dose-dependent effect of L-lysine on human and rat GI function.

METHODS

L-lysine doses from 0-800 mg in rats and 0.5-7.5 g in humans were analyzed for their effect on gastric emptying and GI secretion. Human GI function was assessed non-invasively using magnetic resonance imaging (MRI), rat data were acquired using standard lethal measurement methods. L-lysine dose dependently delayed gastric emptying and stimulated GI secretion in rats as reflected by residual phenol red content and increased gastric wet weight.

KEY RESULTS

The dose-dependent delay in gastric emptying observed in rats was confirmed in humans with an increase in halftime of gastric emptying of 4 min/g L-lysine, p < 0.01. Moreover, a dose-dependent increase in intestinal fluid accumulation was observed (0.4 mL/min/g L-lysine, p < 0.0001). No effect on alkaline tide, glucose concentration, hematocrit, or visceral sensations was detected.

CONCLUSIONS & INFERENCES

This translational study demonstrates comparable dose-dependent effects of intragastric L-lysine on GI function in humans and rats and suggests a broader role for individual amino acids in the control of GI motility and secretion in vivo.

Simultaneous assessment of gastric emptying and secretion in rats by a novel computed tomography-based method

Gastric emptying and gastric secretion are two major physiological functions of the stomach. The assessment of these functions in particular in small animals is challenging; no method currently available allows the simultaneous measurement of both functions, and methods used are lethal or invasive and often limited by spatial, temporal, or quantitative resolution. Here, we report the establishment and validation of a quantitative noninvasive high-throughput computed tomography-based method to measure simultaneously gastric emptying and secretion in rats in vivo. The imaging strategy enables one to visualize stomach anatomy and to quantify stomach volume and stomach contrast agent content. The method was validated by comparing the results to classical lethal methods (stomach phenol red content and stomach wet weight). Additionally, we showed that the use of a mild anesthetic does not interfere with normal gastric function, thereby enabling high-resolution temporal studies within single animals. These combined advantages were applied to reevaluate the impact of cholecystokinin (CCK), histamine, and oral glucose solutions on gastric function with high temporal resolution. CCK inhibited gastric emptying completely for 20 min, leading to the accumulation of gastric juice in the stomach. The CCK antagonist devazepide blocked this effect. Histamine stimulated both gastric secretion and delayed emptying. Oral glucose solution emptied at a fixed rate of 24-31 cal/min and stimulated gastric secretion. These results confirm previous observations and add volumetric changes as a new dimension. As computed tomography scanners become broadly available, this method is an excellent approach to measure the combined gastric functional readout and to reduce the number of animals used.

Xiaotan Tongfu granules contribute to the prevention of stress ulcers

AIM: To investigate the efficacy and potential mechanism of Xiaotan Tongfu granules (XTTF) in stress ulcers.

METHODS: One hundred sixty rats were randomly divided into 4 groups (n = 10) as follows: the model group (MP group), the control group (CP group), the ranitidine group (RP group) and the XTTF granule group (XP group). Rats in the MP group received no drugs, rats in the CP group received 0.2 mL of a 0.9% sodium chloride solution via oral gavage, and rats in the RP and XP groups received the same volume of ranitidine (50 mg/kg) or XTTF granule (4.9 g/kg). The cold-restraint stress model was applied to induce stress ulcers after 7 consecutive days of drug administration. Afterwards, rats were sacrificed at 0, 3, 6 and 24 h. Gastric pH was measured by a precise pH meter; gastric emptying rate (GER) was measured by using a methylcellulose test meal; myeloperoxidase activity (MPO), macrophage migration inhibitory factor (MIF), proliferating cell nuclear antigen (PCNA), and heat shock protein 70 (HSP70) were measured by immunohistochemical staining; and mucosal cell apoptosis was measured by transferase dUTP nick end labeling.

RESULTS: In the cold-restraint stress model, the development of stress ulcers peaked at 3 h and basically regressed after 24 h. Gastric lesions were significantly different in the RP and XP groups at each time point. Interestingly, although this index was much lower in the RP group than in the XP group immediately following stress induction (7.00 ± 1.10 vs 10.00 ± 1.79, P < 0.05. Concerning gastric pH, between the RP and XP groups, we detected a statistically significant difference immediately after stress induction (0 h: 4.56 ± 0.47 vs 3.34 ± 0.28, P < 0.05) but not at any of the subsequent time points. For GER, compared to the RP group, GER was remarkably elevated in the XP group because a statistically significant difference was detected (3 h: 46.84 ± 2.70 vs 61.16 ± 5.12, P < 0.05; 6 h: 60.96 ± 6.71 vs 73.41 ± 6.16, P < 0.05; 24 h: 77.47 ± 3.17 vs 91.31 ± 4.34, P < 0.05). With respect to MPO and MIF, comparisons between the RP and XP groups revealed statistically significant differences at 3 h (MPO: 18.94 ± 1.20 vs 13.51 ± 0.89, P < 0.05; MIF: 150.67 ± 9.85 vs 122.17 ± 5.67, P < 0.05) and 6 h (MPO: 13.22 ± 1.54 vs 8.83 ± 0.65, P < 0.05; MIF: 135.50 ± 9.46 vs 109.83 ± 6.40, P < 0.05). With regard to HSP70, HSP70 expression was significantly increased in the RP and XP groups at 3 and 6 h compared to the MP and CP groups. In addition, comparing the RP and XP groups also showed statistically significant differences at 3 and 6 h. The expression of PCNA was higher in the RP and XP groups 3 h after stress induction. Between these two groups, small but statistically significant differences were observed at all of the time points (3 h: 69.50 ± 21.52 vs 79.33 ± 15.68, P < 0.05; 6 h: 107.83 ± 4.40 vs 121.33 ± 5.71, P < 0.05; 24 h: 125.33 ± 5.65 vs 128.50 ± 14.49, P < 0.05) except 0 h. With regard to apoptosis, the apoptotic activity in the RP and XP groups was significantly different from that in the MP and CP groups. The XP group exhibited a higher inhibition of cell apoptosis than the RP group at 3 h (232.58 ± 24.51 vs 174.46 ± 10.35, P < 0.05) and 6 h (164.74 ± 18.31 vs 117.71 ± 12.08, P < 0.05).

CONCLUSION: The Xiaotan Tongfu granule was demonstrated to be similar to ranitidine in preventing stress ulcers. It exhibited multiple underlying mechanisms and deserves further study.

Smooth Muscle Relaxation Activity of an Aqueous Extract of Dried Immature Fruit of Poncirus Trifoliata (PF-W) on an Isolated Strip of Rat Ileum

We demonstrated that an aqueous extract of dried immature fruit of Poncirus trifoliate (PF-W) produces relaxation of intestinal smooth muscle using the ileac strips of a rat. Furthermore, the underlying mechanism of its relaxant activity was investigated. PF-W was prepared using the standard extraction protocol. A 1.5 – 2 cm long rat ileac strip was placed in an organ bath with Tyrode's solution and smooth muscle contractility was recorded by connecting it to a force transducer. Various compounds were added to the organ baths, and changes in muscular contractility were measured. PF-W concentration-dependently induced relaxation of rat ileac strips that were contracted both spontaneously and via acetylcholine treatment. Various potassium channel blockers did not inhibit the relaxation by PF-W. No difference in the effect of PF-W was observed between ileac strips treated with low (20 mM) and high concentrations (60 mM) of KCl. PF-W inhibited the contraction of rat ileac strips induced by extracellular calcium. PF-W acts as a potent smooth muscle relaxant, implicating its possible action as a rapid acting reliever for abdominal pains and a cure for intestinal convulsion. Considering that PF-W also exhibits prokinetic activity, its use in various gastrointestinal disorders seems promising.

Assessment of the variation associated with repeated measurement of gastrointestinal transit times and assessment of the effect of oral ranitidine on gastrointestinal transit times using a wireless motility capsule system in dogs

This study aimed to evaluate the variation associated with repeated measurement of gastrointestinal (GI) transit times and the effect of oral ranitidine on GI transit times in healthy dogs using a wireless motility capsule (WMC) system. Eight privately owned healthy adult dogs were enrolled, and one developed diarrhea and was removed from the study. For the first 3 repetitions, each dog was fed a standard meal followed by oral administration of a WMC. For the 4th repetition, each dog was given ranitidine hydrochloride (75 mg PO every 12 hours) prior to and during assessment of GI transit times. Mean between-subject coefficients of variation for gastric emptying time (GET), small and large bowel transit time (SLBTT), and total transit time (TTT) were 26.9%, 32.3%, and 19.6%, respectively. Mean within-subject coefficients of variation for GET, SLBTT, and TTT were 9.3%, 19.6%, and 15.9%, respectively. Median GET, SLBTT, and TTT without ranitidine were 719, 1,636, and 2,735 minutes, respectively. Median GET, SLBTT, and TTT with ranitidine were 757, 1,227, and 2,083 minutes, respectively. No significant differences in GI transit times were found between any of the 4 repetitions. Under these experimental conditions, no significant effects of oral ranitidine on GI transit times were observed.

Evaluation of the effect of ranitidine on gastroduodenal contractile activity and gastric emptying in horses

OBJECTIVE

To determine the effect of ranitidine on gastric emptying in horses.

ANIMALS

11 adult horses.

PROCEDURES

In vitro, isolated muscle strips from the pyloric antrum and duodenum of 5 horses were suspended in baths and attached to isometric force transducers. Once stable spontaneous contractions were observed, ranitidine or diluent was added at cumulative increasing concentrations. Isometric stress responses were compared. In vivo, 6 horses were assigned to a group in a prospective randomized crossover study design with a wash-out period of 2 weeks between trials. Ranitidine (2.2 mg/kg) or saline (0.9% NaCl) solution was administered IV, and 15 minutes later, acetaminophen (20 mg/kg), diluted in 400 mL of water, was administered via nasogastric tube to evaluate the liquid phase of gastric emptying. Serum acetaminophen concentration was measured at several time points for 3 hours by use of liquid chromatography tandem mass spectrometry. Frequency of defecation was recorded during the 3 hours of the study.

RESULTS

Ranitidine increased the contractile activity of the pyloric antrum smooth muscle at a concentration of 10(-4) M. No significant effect of ranitidine on plasma kinetics of acetaminophen was identified. Frequency of defecation did not differ between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Ranitidine did increase gastric motility in vitro, but no effect on liquid phase gastric emptying was identified in healthy horses by use of the acetaminophen absorption model. Results do not support the use of ranitidine to promote gastric emptying.

[Clinicopharmacological study of gastrointestinal drugs from the viewpoint of postmarketing development]

Pharmaceutical development starts with the discovery of a new compound. Drugs become commercially available after non-clinical and clinical studies, but processes that take place after marketing are also important for pharmaceutical development. In recent years, use of the phrase "Ikuyaku" meaning postmarketing development has become more common. Sometimes, the proper usage, indications and harmful effects of a drug are discovered only after it becomes commercially available and is administered to many patients. Hence, pharmacists need to actively perform postmarketing studies to reveal the true nature of drugs. In the present clinicopharmacological study, we investigated the effects of histamine H(2) receptor antagonists (H(2)-RAs) on the plasma concentrations of gastrointestinal peptides from the viewpoint of postmarketing development. First we established an enzyme immunoassay for secretin, which is involved in gastrointestinal motility. Then we used this and existing peptide assays to investigate the above-mentioned issues. Ranitidine and nizatidine increased the plasma concentration of motilin. It is believed that the plasma concentration of Ach is elevated by ranitidine and nizatidine, which possesses an anti-AchE activity, and that the increased the plasma concentration of Ach facilitated release of motilin, elevating the plasma concentration of motilin. When compared to the placebo, lafutidine significantly increased the plasma concentration of CGRP (calcitonin gene-related peptide) and substance P. Furthermore, released CGRP stimulated CGRP1 receptors to facilitate secretion of somatostatin. Therefore, lafutidine appears to protect the gastric mucosa and regulate gastrointestinal motility. The same results were obtained with ranitidine and nizatidine. While H(2)-RAs have a common function in suppressing the secretion of gastric acid, they do not exhibit the same effects on factors related to recurrence of peptic ulcer, such as gastrointestinal motility and blood flow in the gastrointestinal mucosa. Hence, measuring the plasma concentration of gastrointestinal peptides can be used to estimate the effects of drugs on gastrointestinal motility. From the viewpoint of postmarketing development, we are in the process of establishing indicators for the proper usage of pharmaceutical drugs. Pharmacists need to closely follow and monitor adverse reactions. In order to further improve monitoring of drug therapy, it will be necessary to assess not only the blood concentrations of drugs, but also biological reactions to the drugs. Since the levels of peptides reflect the clinical efficacy of gastrointestinal drugs, measuring peptide levels appears to be useful for selecting appropriate drugs.

Lafutidine, a newly developed antiulcer drug, elevates postprandial intragastric pH and increases plasma calcitonin gene-related peptide and somatostatin concentrations in humans: comparisons with famotidine

Lafutidine, a newly developed histamine H(2)-receptor antagonist, inhibits daytime (i.e., postprandial) as well as nighttime gastric acid secretion in clinical studies. It also has gastroprotective activity that particularly affects mucosal blood flow in rats. This study focused on the efficacy of lafutidine on plasma concentrations of gastrointestinal peptides in humans. Six healthy male volunteers aged 23-32 years without Helicobacter pylori infection were orally administered either 10 mg lafutidine, 20 mg famotidine, or water only (control) 30 min after a standard meal (650 kcal). Plasma concentrations of lafutidine and famotidine were highest from 90 to 150 min after administration. Intragastric pH was elevated after both lafutidine and famotidine compared with the control. Plasma concentrations of calcitonin gene-related peptide (CGRP) and somatostatin were significantly increased after lafutidine at 60 and 90 min. We concluded that lafutidine increases plasma concentrations of CGRP and somatostatin in humans, which may result in inhibition of postprandial acid secretion and gastroprotective activity.

Lafutidine changes levels of somatostatin, calcitonin gene-related peptide, and secretin in human plasma

We examined the effects of the histamine H2-receptor antagonist, lafutidine, on the levels of gastrointestinal peptides (somatostatin, calcitonin gene-related peptide (CGRP), gastrin, secretin, and motilin) in plasma from healthy subjects. After a single oral administration of lafutidine (10 mg), the plasma lafutidine level (186 +/- 13.4ng/ml) was highest in the 60-min sample after administration and then the plasma level fell. Lafutidine caused significant increase in plasma somatostatin levels at 20 to 120 min and in CGRP levels at 40 to 120 min, compared with a placebo group. The physiological release of plasma secretin was reduced by administration of lafutidine, but the medicine did not alter the level of gastrin or motilin. These results suggest that the pharmacological effects of lafutidine on regulation of gastrointestinal functions closely relate to changes of somatostatin-, CGRP- and secretin-immunoreactive substance levels in human plasma.

Nizatidine and cisapride enhance salivary secretion in humans

BACKGROUND

Salivation plays an important role in the defence of the oesophageal mucosa against gastric acidic reflux and can be evoked by cholinergic stimulation. Both nizatidine and cisapride have been reported to increase acetylcholine concentrations in the cholinergic system.

AIM

To investigate the effect of nizatidine and cisapride on salivary secretion, salivary epidermal growth factor and bicarbonate output.

METHODS

The salivary volume and concentration of salivary epidermal growth factor and bicarbonate were measured after the administration of nizatidine (150 mg), famotidine (20 mg) and cisapride (5 mg) in 30 male healthy volunteers.

RESULTS

Basal and stimulated salivary secretions were found to be increased after the administration of nizatidine and cisapride. In contrast, salivary secretion was not increased by famotidine. Although epidermal growth factor content was not augmented, nizatidine and cisapride administration also increased the bicarbonate output in mastication-stimulated saliva.

CONCLUSIONS

Increased salivary secretion and bicarbonate output induced by nizatidine may be useful for the treatment of patients with gastro-oesophageal reflux disease.

Bicarbonate stimulatory action of nizatidine, a histamine H(2)-receptor antagonist, in rat duodenums

Nizatidine, a histamine H(2)-antagonist, is known to inhibit acetylcholinesterase (AChE) activity and is used clinically as a gastroprokinetic agent as well as the anti-ulcer agent. We examined whether or not nizatidine stimulates duodenal HCO(3)(-) secretion in rats through vagal-cholinergic mechanisms by inhibiting AChE activity. Under pentobarbital anesthesia, a proximal duodenal loop was perfused with saline, and the HCO(3)(-) secretion was measured at pH 7.0 using a pH-stat method and by adding 10 mM HCl. Nizatidine, neostigmine, carbachol, famotidine or ranitidine was administered i.v. as a single injection. Intravenous administration of nizatidine (3-30 mg/kg) dose-dependently increased the HCO(3)(-) secretion, and the effect at 10 mg/kg was equivalent to that obtained by carbachol at 0.01 mg/kg. The HCO(3)(-) stimulatory action of nizatidine was observed at the doses that inhibited the histamine-induced acid secretion and enhanced gastric motility. This effect was mimicked by neostigmine (0.03 mg/kg) and significantly attenuated by bilateral vagotomy and pretreatment with atropine but not indomethacin. The IC(50) of nizatidine for AChE of rat erythrocytes was 1.4 x 10(-6) M, about 12 times higher than that of neostigmine. Ranitidine showed the anti-AchE activity and increased duodenal HCO(3)(-) secretion, similar to nizatidine, whereas famotidine had any influence on neither AChE activity nor the HCO(3)(-) secretion. On the other hand, duodenal damage induced by acid perfusion (100 mM HCl for 4 h) in the presence of indomethacin was significantly prevented by nizatidine and neostigmine, at the doses that increased the HCO(3)(-) secretion. These results suggest that nizatidine increases HCO(3)(-) secretion in the rat duodenum, mediated by vagal-cholinergic mechanism, the action being associated with the anti-AChE activity of this agent.

Stimulation by nizatidine, a histamine H2-receptor antagonist, of duodenal HCO3- secretion in rats: relation to anti-cholinesterase activity

AIM: To examine whether nizatidine stimulates duodenal HCO₃^- secretion in rats by inhibiting AChE activity.

METHODS: Under pentobarbital anesthesia, a proximal duodenal loop was perfused with saline, and the HCO₃^- secretion was measured at pH7.0 using a pH-stat method and by adding 10 mM HCl. Nizatidine, neostigmine, carbachol or famotidine was administered i.v. as a single injection.

RESULTS: Intravenous administration of nizatidine (3-30 mg/kg) dose-dependently increased duodenal HCO₃^- secretion, and the effect at 10 mg/kg was equivalent to that obtained by carbachol at 0.01 mg/kg. This nizatidine action was observed at the same dose range that inhibited acid secretion and enhanced gastric motility, mimicked by i.v. injection of neostigmine (0.03 mg/kg), and significantly attenuated by bilateral vagotomy and prior s.c. administration of atropine but not by indomethacin, a cyclooxygenase inhibitor, or N^G-nitro-L-arginine methyl ester, a NO synthase inhibitor. The HCO₃^- secretory response to acetylcholine (0.001 mg/kg) was significantly potentiated by the concurrent administration of nizatidine (3 mg/kg, i.v.). The IC₅₀ of nizatidine for AChE of rat erythrocytes was 1.4 × 10^-6 M, about 12 times higher than that of neostigmine. Neither famotidine (> 10^-3 M, 30 mg/kg, i.v.) nor cisapride (> 10^-3 M, 3 mg/kg, i.v.) had any influence on AChE activity or duodenal HCO₃^- secretion. Duodenal damage induced by acid perfusion (100 mM HCl for 4 h) in the presence of indomethacin was significantly prevented by nizatidine and neostigmine, at the doses that increased the HCO₃^- secretion.

CONCLUSION: Nizatidine stimulates duodenal HCO₃^- secretion, in both vagal-dependent and atropine-sensitive manners, and the action is associated with the anti-AChE activity of this agent.

Management of gastrointestinal motility disorders. A practical guide to drug selection and appropriate ancillary measures

The focus of management of gastrointestinal motility disorders should be to improve survival and quality of life. Some motor disorders are annoying, but are compatible with virtually normal activity and carry no significant life risk. Conversely, other motor disorders are highly incapacitating and may shorten life expectancy because of complications and nutritional impairment. Management is based first on establishing the correct diagnosis and prognosis; secondly, on adjusting therapy to the severity of illness; and thirdly, on preventing significant complications. Simple recommendations on appropriate changes in lifestyle and reassurance may suffice in mild cases. Pharmacological therapy and, exceptionally, surgical or nutritional measures may be required in other patients. Generally, pharmacological agents should be directed towards correcting specific pathophysiological abnormalities, but this is not always possible. Symptomatic relief may be achieved on an empirical basis. Long term treatment may often require the combination of different therapeutic approaches either sequentially or simultaneously.

Omeprazole causes delay in gastric emptying of digestible meals

We have studied gastric emptying of a solid, realistic meal (800 cal, 15% protein, 45% fat, 40% carbohydrate) in 21 healthy subjects twice, with and without a four-day pretreatment with 40 mg omeprazole. The last dose of the drug was taken 24 hr before the test, to avoid hypothetical nonsecretory side effects of the drug . Gastric emptying was measured by ultrasound of antral diameters. The results show that basal and maximal postprandial antral cross-sectional areas were the same during the two tests. A greater residual distention of the antrum was present throughout the study after the omeprazole treatment, the difference being significant at time 120 and 240. Omeprazole induced a highly significant delay in gastric emptying [control 199.6 (12.6) vs omeprazole 230.9 (12.7) min, mean (1 SEM); P<0.003]. The delay was not due to a prolonged lag phase, but rather to an effect on the slope of the emptying curve. This study shows that in normal subjects omeprazole delays gastric emptying of a digestible solid meal.

First-pass metabolism of alcohol. Absence of diurnal variation and its inhibition by cimetidine after evening meal

To determine whether the first-pass metabolism (FPM) of orally consumed alcohol varies with the time of day, 12 healthy male subjects were tested with both oral and intravenous alcohol (0.3 g/kg), in the morning and evening, always 1 hr after the same standard meal. The results revealed no significant differences in FPM (81.6 +/- 11.6 vs 92.8 +/- 10.6 mg/kg) or in any other index of alcohol absorption and metabolism. Eleven subjects were also tested in the evening after treatment with cimetidine, an H2-antagonist that inhibits gastric alcohol dehydrogenase activity in vitro. Compared to baseline, cimetidine (1 g/day for eight days) significantly decreased FPM (from 100.1 +/- 8.0 to 52.6 +/- 11.4 mg/kg, P < 0.01) and increased the systemic bioavailability of alcohol (from 66 +/- 3 to 82 +/- 4%, P < 0.01), as well as peak blood alcohol concentrations (from 4.3 +/- 0.4 to 5.9 +/- 0.5 mM, P < 0.05) and areas under the curve (from 5.1 +/- 0.5 to 7.0 +/- 0.5 mM/hr, P < 0.01). The results indicate the absence of diurnal variation in FPM and suggest that patients given cimetidine should be warned of its possible interaction with alcohol regardless of the time of day.

Nizatidine accelerates gastric emptying of a solid meal in rats

Nizatidine, a new histamine-2-receptor antagonist, stimulates gastrointestinal motility in dogs and gastric emptying of liquids in rats. Effect of nizatidine on gastric emptying of a solid meal was investigated using a novel gastric emptying model in rats. Male Wistar rats (weighing 200-300 g) were supplied with powdered food containing 30 w/w% barium 14 hr before the beginning of the experiment and x-ray photography of rat stomach was taken under light ether anesthesia. Gastric emptying was assessed by percentage of a decrease in area 30 min after drug was injected intraperitoneally. There was a positive correlation between the area of the gastric outline and the weight of the gastric contents (r = 0.94, P < 0.01). Ether anesthesia itself did not affect gastric emptying. Nizatidine increased gastric emptying dose-dependently (emptied percentage; vehicle: 4.9 +/- 1.5%, 1 mg/kg: 7.2 +/- 0.4%, 3 mg/kg: 10.4 +/- 2.0%, 10 mg/kg: 16.7 +/- 4.9%, 30 mg/kg: 25.7 +/- 7.4%). N-Desmethyl nizatidine (NDM) also stimulated gastric emptying, but nizatidine S-oxide, cimetidine, an famotidine had no significant effects on gastric emptying. Nizatidine and neostigmine, but not NDM, at a subthreshold dose accelerated gastric emptying treated with a low dose of acetylcholine (0.1 mg/kg). Atropine (2 mg/kg, -30 min) did not modulate the gastroprokinetic action of nizatidine, but blocked that of NDM. These findings suggest that this noninvasive method may allow measurement of gastric emptying of solids accurately and that nizatidine and NDM facilitate gastric emptying probably mediated by a direct and/or an indirect (acetylcholinesterase inhibition) cholinergic mechanism.

Synthesis of 2-imidazolidinylidene propanedinitrile derivatives as stimulators of gastrointestinal motility--III

Recently, we reported that a ranitidine derivative 2 (fumarate: KW-5092), which had a 2-imidazolidinylidene propanedinitrile moiety (A), showed potent gastrointestinal motility enhancing activity. We have also found that introduction of substituents such as benzyl or 4-fluorobenzyl (i.e., giving 3 or 4) at the N-3 position of the moiety (A) significantly increased this activity. In this study, novel 2-imidazolidinylidene propanedinitrile derivatives possessing a thioether 5-15 were prepared and evaluated for in vitro assays; acetylcholinesterase (AChE) inhibitory activity and potentiating action on electrically induced contractions of guinea pig ileum. Compound 5, in which a nitrogen atom of compound 2 was replaced by a sulfur atom, was more potent than 2 in these tests. Also, in a series of thioether derivatives, introduction of substituents at the N-3 position of the 2-imidazolidinylidene propanedinitrile moiety markedly influenced both activities. In particular, compounds 12 and 13, which showed an excellent potency during in vitro study (AChE IC50 = 3.6 and 2.7 nM; ES. EC30 = 2.1 and 2.5 nM, respectively), were found to be more active in the enhancement of gastrointestinal motility in anesthetized rabbits than their corresponding parent compounds 3 and 4, respectively. In addition, compounds 12 and 13 showed lower affinity for the histamine H2-receptor than ranitidine. Therefore, these compounds may be potent and selective stimulators of gastrointestinal motility.

Pharmacokinetic considerations in gastrointestinal motor disorders

Although it has been recognised that alterations in gastrointestinal motility, whether induced by physiological or pathological processes, have significant effects on the pharmacokinetics of orally administered drugs, this subject has received inappropriately little attention. Studies relating to this topic have focused on healthy volunteers and animals and have largely been confined to the effects of single drug doses. There is limited information about the effects of disease on pharmacokinetics under steady-state conditions. Changes in gastrointestinal motility may affect the pharmacokinetics of orally administered drugs by altering the rate of delivery, bioavailability or mucosal absorption of the drug. In general the rate of absorption and time taken to achieve maximal plasma concentrations for well absorbed drugs may be modified by changes in gastrointestinal motility, but overall bioavailability is not usually affected. In these cases the therapeutic and clinical effects of the alteration in pharmacokinetics will, therefore, depend on which parameters are important for the action of the drug. For poorly absorbed drugs both the rate of absorption and bioavailability are likely to be altered by changes in gastrointestinal motility. However, the complex effects of food and disease, as well as the properties and formulation of any drug (solubility, ease of dispersion, delayed release formulation) often make the prediction of the magnitude, or even the direction, of any effect difficult to predict. Drugs with direct effects on gastrointestinal motility may influence their own patterns of absorption. In patients with gastrointestinal motility disorders, drugs administered in a controlled release formulation, or those with poor bioavailability, are most likely to have a poorly predictable therapeutic effect. Care should be taken to ensure that the formulation of the drug, its timing of administration in relation to meals and the use of coadministered drugs optimise, or at least ensure consistent absorption.

Synthesis of 2-imidazolidinylidene propanedinitrile derivatives as stimulators of gastrointestinal motility--II

In a previous paper, we reported that a novel ranitidine derivative 2 (fumarate: KW-5092), which had a 2-imidazolidinylidene propanedinitrile moiety (A), showed potent gastrointestinal motility enhancing activity. In order to obtain more potent gastrointestinal motility enhancing agents than compound 2 and to examine the effects of various substituents both at a nitrogen atom (B) in the 2-imidazolidinylidene propanedinitrile moiety and a basic nitrogen atom (C), compounds 5-29 were synthesized and evaluated for acetylcholinesterase (AChE) inhibitory activity and potentiating action on electrically stimulated contractions of guinea pig ileum. Introduction of alkyl, benzyl, aryl or acyl groups to the nitrogen (B) or (C), remarkably influenced both activities. Among these, compounds 14 and 15 showed more potent AChE inhibitory activity (IC50 = 6.7, 6.8 nM, respectively) than compound 2 and were active in potentiating action on the ileal contraction (EC30 = 9.5, 11 nM, respectively) together with a negligible histamine H2-receptor blocking property. Furthermore, these compounds were found to be more effective in the enhancement of gastrointestinal motility in anesthetized rabbits than compound 2.

Sucralfate versus cimetidine in the treatment of reflux esophagitis, with special reference to the esophageal motor function

Sixty patients entered a double-blind clinical trial comparing the effect of 1 g of sucralfate granulate given four times daily and cimetidine, 400 mg twice daily. Twenty-six patients treated with sucralfate and 26 treated with cimetidine were examined with short-term pH monitoring before and after 12 weeks of treatment. Thirty patients, 19 treated with cimetidine and 11 treated with sucralfate, had esophageal motility studied by a radionuclide test before and after 12 weeks of treatment. The efficacy of the treatments was judged by symptoms and endoscopic response after 4, 8, and 12 weeks of treatment. The endpoint healing rate was approximately 60% in both groups and symptoms were relieved in half of the patients in both groups (difference not significant). The effect of the treatments on pH and number of spikes reflected the different pharmacodynamic profiles of the drugs, whereas the mean transit time (MTT) was not changed by the treatments. The residual activity after radionuclide transit in the sitting position was significantly increased after treatment with cimetidine. The data support the hypothesis that primary dysmotility might be involved in the pathogenesis of reflux esophagitis in about 33% of the patients. Possibilities for a combination therapy with sucralfate and cimetidine are stressed.

Sucralfate versus cimetidine in reflux oesophagitis. The effect on oesophageal pH and motility

Sixty patients with endoscopically verified oesophagitis entered a double-blind study comparing the effect of 1 g of sucralfate granulate given four times a day and cimetidine, 400 mg twice a day. Fifty-two patients, 26 treated with cimetidine and 26 with sucralfate, were examined with short-term pH monitoring before and after 12 weeks of treatment. In about half of the patients, 19 treated with cimetidine and 11 treated with sucralfate, the oesophageal motility was studied with a radionuclide test before and after treatment. The sucralfate treatment did not affect either mean pH or the emptying rate but reduced the number of spikes. The cimetidine treatment increased mean pH and reduced the number of spikes but did not affect emptying rates. Both groups had significantly prolonged mean transit time (MTT) compared with healthy volunteers. MTT did not change after either treatment. The residual activity in the sitting position was significantly increased after cimetidine. It is concluded that the pharmacodynamic effect on oesophageal motility is different for the two drugs in question. Primary dysmotility might be involved in the pathogenesis of oesophagitis.

Involvement of different receptors in the central and peripheral effects of histamine on intestinal motility in the rat

The effects of histamine on intestinal motility have been investigated in conscious rats, fed or fasted, using an electromyographic method. Histamine peripherally administered (10 mg kg-1) in 15 h fasted rats induced an inhibition followed by a period of irregular spiking activity disrupting the duodenojejunal migrating myoelectric complexes (MMC) and suppressed the postprandial motor spiking activity when administered 50 min after a meal. The selective agonist of the H1-receptors, 2-pyridylethylamine (2-PEA) induced an irregular spiking activity while dimaprit acting on H2-receptors, inhibited the MMC pattern. Effects of peripherally administered histamine were antagonized by previous administration of chlorpheniramine (0.5 mg kg-1 i.p.) and in a lesser extent by cimetidine (10 mg kg-1 i.p.). Histamine (1-10 micrograms) administered intracerebroventricularly (i.c.v.) in fasted rats increased the motor cycle frequency and immediately restored the MMC pattern when given to fed rats. Among the three agonists of the H1- H2- and H3-receptors (2-PEA, dimaprit and R-alpha-methylhistamine, respectively) only R-alpha-methylhistamine (1-10 micrograms i.c.v.) was able to reproduce this effect. It is concluded that the effects of histamine on intestinal motility were centrally and peripherally mediated involving mainly H1-receptors at the peripheral level and H3-receptors at the CNS level.

Effects of cimetidine on gastric alcohol dehydrogenase activity and blood ethanol levels

Chronic use of cimetidine and alcohol are commonly associated, but studies on their interactions are the subject of controversy. To investigate this question, a small ethanol dose (0.15 g/kg body wt) was randomly administered on 2 consecutive days either orally or intravenously to 6 normal volunteers, before and after 1 wk of oral administration of 400 mg of cimetidine twice daily. Although cimetidine did not change the areas under the curve of blood ethanol concentrations after intravenous administration, those after oral alcohol intake were twice as large with cimetidine than without. Similar effects were reproduced in rats after intravenous administration of cimetidine (50 mg/kg body wt). In vitro, cimetidine was a noncompetitive inhibitor of gastric alcohol dehydrogenase activity at concentrations as low as 0.01 mM, 100-fold lower than those needed to inhibit the hepatic dehydrogenase. These results indicate that gastric alcohol dehydrogenase activity governs, in part, the systemic bioavailability of ethanol. Consequently, systemic effects of alcohol may be exacerbated in patients receiving cimetidine.

Action of the new H2-receptor antagonist oxmetidine on the duodenum of different species

The new H2-receptor antagonist, oxmetidine was studied for its effects on the motility of the duodenum of different species. Oxmetidine did not modify basal motility of the rat and guinea pig duodenum but it reduced or abolished the contractions elicited by different spasmogenic compounds (acetylcholine, BaCl2, KCl, eledoisin). In the rabbit duodenum, oxmetidine reduced in a dose-dependent fashion the basal motility. The effect of this compound appears to be indirect on the smooth muscle and not mediated through specific receptors. Experiments performed in Ca++-free and K+-depolarizing solution suggest that oxmetidine acts through interference with the transport and/or utilization of intracellular Ca++ions.

Effect of cigarette smoking on gastric emptying in patients with an active duodenal ulcer

The effect of cigarette smoking on gastric emptying (GE) of a radiolabelled solid meal was examined in 14 patients with an active duodenal ulcer. The patients underwent GE measurement thrice: under basal conditions and for two smoking sessions, without and after cimetidine pretreatment (2 X 400 mg orally for 2 days and 400 mg orally 1.5 h before the isotropic GE examination) in random order. Cigarette smoking significantly delayed GE (p less than 0.05 for both the gastric half emptying time (H) and the mean transit time (MTT90)). The inhibitory effect of smoking on GE was enhanced after cimetidine pretreatment (p less than 0.02 for H and p less than 0.004 for MTT90, respectively). Potential mechanisms and pathophysiological meaning of the findings are discussed.

A comparative study of the effect of cimetidine and ranitidine on the rate of gastric emptying of liquid and solid test meals in man

Paired studies were carried out on 18 healthy male volunteers (20.9 +/- 1.9 years; mean +/- S.D.) to compare the effect of oral doses of the H2-receptor antagonists, ranitidine and cimetidine, on the rate of gastric emptying of radiolabelled solid and liquid test meals. Oral administration of ranitidine 300 mg accelerated the emptying of a liquid meal from the stomach, but it had no significant effect on the rate of emptying of a solid meal. Oral administration of either 400 or 800 mg cimetidine did not alter the rate of emptying of either the liquid or the solid meals from the stomach.

Antisecretory and antiulcer effect of the H2-receptor antagonist famotidine in the rat: comparison with ranitidine

1 The effects of the new H2-receptor antagonist famotidine, administered orally, on gastric secretion and emptying as well as on experimentally-induced gastric and duodenal ulcers were studied in the rat. Ranitidine was used as a reference compound. 2 Both compounds inhibited acid secretion in a dose-dependent manner. Calculated ED50 values were 0.80 and 6.84 mg kg-1 for famotidine and ranitidine, respectively. However, the duration of the antisecretory action was the same for both drugs. 3 The effect of the two drugs, administered at equiactive antisecretory doses, on gastric emptying was different. Ranitidine significantly accelerated the emptying rate whereas famotidine had no effect. 4 Famotidine reduced, in a dose-dependent manner, ulcer incidence in stomachs of dimaprit-treated rats and in duodena of cysteamine-treated animals with a potency respectively 2 and 7 times higher than that of ranitidine. 5 Famotidine is therefore an effective antisecretory and untiulcer compound. Its potency, but not its efficacy, is higher than that of ranitidine. Moreover, the duration of the antisecretory action is virtually the same for both drugs.

Relaxant effect of the H2-receptor antagonist oxmetidine on guinea-pig and human airways

The effects of three different H2-receptor antagonists (cimetidine, ranitidine and oxmetidine) were tested on isolated preparations of guinea-pig trachea and human bronchus against contractions induced by acetylcholine, histamine and potassium chloride (KCl). In addition, their influence on calcium concentration-response curves in guinea-pig tracheal spirals was examined in a potassium-rich solution (30 mM). Finally, their effects were studied in vivo against acetylcholine and histamine-induced bronchoconstriction in anaesthetized guinea-pigs. In guinea-pig isolated trachea, oxmetidine--in contrast to cimetidine and ranitidine, which were completely inactive--induced a concentration-dependent relaxation regardless of the excitatory stimulus: its--log EC50 values (i.e. the negative log concentration that caused a 50% relaxation) were 3.46 +/- 0.11, 4.61 +/- 0.09 and 4.20 +/- 0.12 against acetylcholine, histamine and KCl, respectively. In Ca2+-free, K+-enriched solution, the compound was able to inhibit Ca2+-induced contractions at concentrations close to those needed to counteract the spasmogenic effect of histamine in normal Krebs solution. Results obtained in the human bronchus preparation were similar to those observed in guinea-pig tracheal spirals. When tested against acetylcholine or histamine-induced bronchoconstriction in vivo, oxmetidine (10 and 30 mg Kg-1 intravenously) significantly reduced the increase in pulmonary airway resistance (Raw) induced by both agents. Once again, cimetidine and ranitidine were completely ineffective. In summary, oxmetidine displayed non-specific antispasmogenic activity on guinea-pig and human airways. This effect, which is independent of H2-receptor blockade, represents a side-effect of the drug which may be connected to its interference with Ca2+ influx and the action or release of intracellular Ca2+.

A further study on the kinetics of the subcellular current events at the mouse end-plate in the presence of cimetidine and ranitidine

The cholinomimetic activity of Cimetidine and Ranitidine has been demonstrated by several authors. In the aim to better understand the phenomenon, we analyse the miniature end-plate current decay time. The prolongation of the decay phase of the synaptic current induced by the "selective" H2-antagonist Ranitidine, and to a lesser extent and at higher concentrations by Cimetidine, resembles that of the cholinesterase inhibitors. These agents usually prolong the quantal conductance change having little or no effect on the channel lifetime. The results of our previous experiments, which data were obtained by analyzing the "voltage" events, either spontaneous or evoked, of a classic frog preparation, showed a marked alteration of the temporal parameters. These effects, obtained at higher drug concentrations than those used in the present work, are now better defined by deriving extracellularly the "current" events. The results are also compared with those obtained by assaying the cholinesterase inhibitor Eserine, under the same experimental conditions.

Inhibitory effect of famotidine on cat gastric secretion

The inhibitory effect of the novel H2 receptor antagonist famotidine was studied in conscious gastric fistula cats against dimaprit-induced hypersecretion, in comparison with ranitidine. On the secretory plateau induced by dimaprit (2 mumol kg-1 h-1) famotidine (0.05-0.2 mumol kg-1 i.v.) exerted a dose-dependent inhibitory effect, being approximately 4.5 times as potent as ranitidine (ID50 values were 0.067 +/- 0.015 and 0.30 +/- 0.025 mumol kg-1 for famotidine and ranitidine, respectively). No significant differences were found between the two drugs, as for the time-course of the inhibitory effect. Famotidine (0.01-0.32 mumol kg-1 h-1) caused a parallel displacement of the dose-response curve to dimaprit to the right, without reducing the maximum response to the stimulant, thus behaving as a competitive antagonist, like ranitidine. pA2 values for famotidine and ranitidine were 7.95 and 6.92, respectively. In the same range of doses famotidine dose-dependently reduced also the secretory response to histamine. From these data it was concluded that famotidine is a potent histamine H2 receptor antagonist in the cat gastric mucosa; moreover, conversely from "in vitro" data, the antagonism was surmountable even at the highest doses tested. In vivo experiment, therefore, did not reveal any particular feature of this compound, apart from the undoubtedly high potency, in comparison with other members of the family.

Cholinergic effects of histamine-H2 receptor antagonists partly through inhibition of acetylcholinesterase

The effects of histamine H2-receptor antagonists on acetylcholinesterase and pseudocholinesterase activity were studied. All H2-antagonists tested inhibited both enzyme activities dose-dependently. The potency of inhibitory activity of H2-antagonists on acetylcholinesterase estimated from median inhibitory dose were in the following order of decreasing activity: ranitidine greater than TZU-0460 greater than cimetidine greater than YM-11170, whereas that on pseudocholinesterase were TZU-0460 greater than ranitidine greater than cimetidine greater than YM-11170. As the effects derived from the inhibition of acetylcholinesterase by H2-antagonists may affect intestinal motility, we studied ileal muscle contractions. Ranitidine had the most potent stimulating effect on contraction, the pattern of which was similar to physostigmine and was blocked by atropine and morphine. YM-11170 had a weak action on muscle contraction and cholinesterase activities.

Effect of sham feeding on gastric emptying of liquids in dogs

The effects of sham feeding and of cimetidine, an inhibitor of gastric acid secretion, used alone or in combination on the gastric emptying of liquids were studied in four dogs fitted with a gastric fistula and a Komarov esophagostomy. Gastric emptying of a 290-ml water meal was slowed by sham feeding but not by cimetidine. Our experiments indicate that, in dogs, sham feeding slows gastric emptying of liquids by a mechanism independent of the acid secretion induced by vagal stimulation.

Ranitidine potentiates ileum contractions caused by GABA and electrical stimulation

GABA-evoked contractions of the guinea pig ileum were significantly potentiated by the histamine H2-receptor antagonist ranitidine in concentrations above 10 microM. To help define the mechanism of this interaction, the present study compared the effects of ranitidine on contractile responses of the guinea pig ileum to GABA, acetylcholine (A Ch) and electrical stimulation of intrinsic cholinergic neurons. Ranitidine, at concentrations that potentiated responses to GABA, also potentiated contractions induced by transmural electrical stimulation. The ability of ranitidine to amplify these latter responses was antagonized by atropine. Contractile responses to exogenous A Ch, however, were unaffected by ranitidine at any concentration. These results suggest that prejunctional, rather than postjunctional mechanisms, are of primary importance in the interaction between ranitidine and GABA.

In vitro histamine H2-antagonist activity of the novel compound HUK 978

Histamine stimulated adenylate cyclase from guinea-pig fundic mucosa and 3H-tiotidine binding in guinea-pig cerebral cortex were used to assess the in-vitro histamine H2-activity of the novel H2-antagonist HUK 978. The results showed that HUK 978 was a more potent H2-antagonist than either cimetidine or ranitidine. HUK 978 was also shown to be devoid of activity at the histamine H1-receptor, the muscarinic receptor and the alpha and beta-adrenergic receptors.

Inhibition of gastric emptying and secretion by pirenzepine and atropine in rats

The effects of pirenzepine and atropine on gastric emptying, gastric secretion and heart rate were studied in rats. Both drugs inhibited gastric emptying and secretion dose dependently and increased pulse rate. In the gastric secretory studies both compounds displayed potencies which were not very dissimilar (ID50 were 8.1 mumol X kg-1 and 1.4 mumol X kg-1 for pirenzepine and atropine respectively, potency ratio 6); pirenzepine was however decidedly less potent than atropine in inhibiting gastric emptying (potency ratio 36 on a molar basis) and in increasing heart rate (potency ratio 125). These data, in accordance with results of clinical trials, indicate that pirenzepine-unlike atropine-can inhibit acid secretion without appreciably affecting gastric motility and cardiac function.

Ranitidine hydrochloride

Ranitidine is a selective, competitive histamine H2-receptor antagonist recently approved by the Food and Drug Administration for use in the short-term treatment of active duodenal ulcers and gastric hypersecretory conditions. Ranitidine is four to ten times more potent than cimetidine on a molar basis in inhibiting stimulated gastric acid secretion. Clinical studies have demonstrated that ranitidine is as effective as cimetidine and is similarly well tolerated. Based on available literature (approximately 700 publications), this article reviews the pharmacology, safety profile, and clinical efficacy of ranitidine in duodenal ulcers and gastric hypersecretory conditions.