Ranitidine bismuth citrate and ranitidine do not affect gastric emptying of a radio-labelled liquid meal

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.

Effects of the H2-receptor antagonist ranitidine on gastric motor function after a liquid meal in healthy humans

OBJECTIVE

Studies on animals have shown that histamine may be involved in the regulation of gastrointestinal smooth muscle tone. However, the role of histamine in the regulation of human gastric motor function is not clear. This study examined the effect of ranitidine, an H(2)-receptor antagonist, on gastric volume and gastric emptying after a liquid meal in healthy humans.

MATERIAL AND METHODS

Twelve healthy volunteers participated in a randomized crossover study with 50 mg ranitidine as a bolus intravenously versus no medication. Gastric volume at baseline was determined with single photon emission computed tomography (SPECT) after intravenous injection of 99(m)Tc-pertechnetate. After ingestion of a 600-mL liquid meal radiolabelled with (111)In-diethylenetriaminepentaacetic acid, dual-isotope technique with SPECT and planar imaging assessed gastric volume as well as gastric emptying.

RESULTS

Ranitidine did not change gastric volume before the meal, nor at 0 h or 1 h after it. Furthermore, ranitidine did not influence gastric retention of meal components after 0.5 h and 1 h.

CONCLUSIONS

Intravenous bolus injection of 50 mg ranitidine does not modify gastric volume or gastric emptying after a 600 mL liquid meal in healthy humans.

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.

Influence of acid suppressants on gastric emptying: cross-over analysis in healthy volunteers

BACKGROUND

Gastric emptying plays an important role in gastroesophageal reflux disease. Acid suppressants such as H2 receptor antagonists and/or proton pump inhibitors are often used in patients with gastroesophageal reflux disease. However, it remains controversial whether H2 receptor antagonists and proton pump inhibitors delay or accelerate gastric emptying. Here, the influence of acid suppressants on gastric emptying was evaluated via a cross-over study using the [13C]-labeled acetate breath test.

METHODS

Twenty normal male subjects without gastroesophageal reflux disease symptoms were enrolled. Gastric emptying was investigated five times in every subject by the [13C]-labeled acetate breath test with oral administration of the vehicle, domperidone, and three acid suppressants: ranitidine, famotidine and rabeprazole. Gastric emptying was estimated by the values of T(max-calc), T(1/2) and %dose/2 h calculated from the 13CO2 breath excretion curve.

RESULTS

Using the T(max-calc) values, rabeprazole, ranitidine and famotidine did not influence gastric emptying time in comparison with vehicle administration. Using the T(1/2) and %dose/2 h values, rabeprazole tended to delay gastric emptying. Domperidone produced a statistically significant acceleration of gastric emptying for all three variables (P < 0.05).

CONCLUSION

Oral dosage of the H2 receptor antagonists, ranitidine and famotidine, has no significant effect on gastric emptying. However, rabeprazole may delay gastric emptying more strongly than H2 receptor antagonists.

Ranitidine and nizatidine stimulate antral smooth muscle contractility via excitatory cholinergic mechanisms

Histamine type 2 receptor antagonists (H2RAs) have been found to alter gastric motility. The aims of this study were to determine if H2RAs affect antral contractility in vitro and the mechanism of this effect. Guinea pig antral muscle strips were pinned in an organ bath after removing the mucosa, and circular muscle tension was measured using an isometric force transducer. Gastric myocytes were isolated from guinea pig stomach using collagenase digestion, and cell lengths were measured using an image analysis system. In muscle strips, ranitidine and nizatidine increased the amplitude of spontaneous phasic antral contractions in a concentration-dependent fashion with threshold concentrations of 5 microM. The order of potency for the H2RAs was ranitidine = nizatidine >> cimetidine > famotidine. The contractile effects of ranitidine and nizatidine were reduced, but not abolished, by tetrodotoxin and omega-conotoxin GVIA and nearly abolished by atropine. In isolated cells, ranitidine and nizatidine, but not famotidine or cimetidine, induced concentration-dependent cell shortening, with maximal shortening at 10 microM. These contractile effects of ranitidine and nizatidine in isolated cells were inhibited by atropine. Ranitidine and nizatidine increase antral contractility; this effect appears to be mediated by an interaction between ranitidine and nizatidine on cholinergic pathways with both direct effects on smooth muscle cholinergic receptors and indirect effects by increasing cholinergic neurotransmission.

Effect of gastric acid suppressants on human gastric motility

BACKGROUND

The effect of histamine H2 receptor antagonists on gastric emptying is controversial.

AIMS

To determine the effects of ranitidine, famotidine, and omeprazole on gastric motility and emptying.

PATIENTS AND METHODS

Fifteen normal subjects underwent simultaneous antroduodenal manometry, electrogastrography (EGG), and gastric emptying with dynamic antral scintigraphy (DAS). After 30 minutes of fasting manometry and EGG recording, subjects received either intravenous saline, ranitidine, or famotidine, followed by another 30 minutes recording and then three hours of postprandial recording after ingestion of a radiolabelled meal. Images were obtained every 10-15 minutes for three hours to measure gastric emptying and assess antral contractility. Similar testing was performed after omeprazole 20 mg daily for one week.

RESULTS

Fasting antral phase III migrating motor complexes (MMCs) were more common after ranitidine (9/15 subjects, 60%), famotidine (12/15, 80%), and omeprazole (8/12, 67%) compared with placebo (4/14, 29%; p < 0.05). Postprandially, ranitidine, famotidine, and omeprazole slowed gastric emptying, increased the amplitude of DAS contractions, increased the EGG power, and increased the antral manometric motility index.

CONCLUSIONS

Suppression of gastric acid secretion with therapeutic doses of gastric acid suppressants is associated with delayed gastric emptying but increased antral motility.

Ranitidine increases the bioavailability of imbibed alcohol by accelerating gastric emptying

To investigate the mechanism of the increase in alcohol bioavailability by ranitidine, we determined by nuclear scan the changes in gastric emptying of a 10% ethanol solution (containing 0.3 g ethanol/kg body weight and 300 microCi of technetium-labeled diethylene triamine pentacetic acid) in 8 normal men, before and after treatment with 300 mg ranitidine orally each evening for 1 week. We compared these changes with those of ethanol bioavailability, calculated by integration of the Michaelis-Menten function over the entire alcohol curves after random i.v. and, on a separate day, oral administration of the same ethanol dose, pre- and post-ranitidine. With ranitidine, we found an acceleration of gastric emptying in 7 of 8 subjects, with 20% shortening of the time to 50% emptying (51.8 +/- 4.1 min vs 64.3 +/- 3.4, without ranitidine; P < .001 by paired t test). Despite the disappearance (from the stomach) of most of the dose by the end of the blood alcohol curves, only 83 +/- 4% reached the systemic blood vs 64 +/- 4% without ranitidine (P < .02), most likely because of a shortened exposure of alcohol dehydrogenase to optimal ethanol concentrations. As a result, after oral but not intravenous alcohol administration, ranitidine increased blood alcohol concentrations (29 +/- 4 mg/dl vs 22 +/- 3, without ranitidine; P < .02), with a corresponding decrease in first pass metabolism of ethanol from 107 +/- 16 mg/kg to 47 +/- 16 (P < .01).