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

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 Histamine-2 Receptor Antagonists and Proton Pump Inhibitors on the Rate of Gastric Emptying: A Crossover Study Using a Continuous Real-Time C Breath Test (BreathID System)

BACKGROUND/AIMS

The effects of Histamine-2 receptor antagonists and proton pump inhibitors on the gastrointestinal motility have not yet been sufficiently investigated. The aim of this study was to determine the effects of intravenous bolus administration of famotidine and omeprazole on the rate of gastric emptying using the continuous (13)C breath test (BreathID system, Exalenz Bioscience Ltd, Israel).

METHODS

Twelve healthy male volunteers participated in this randomized, 3-way crossover study. After fasting overnight, the subjects were randomly assigned to receive 20 mg of famotidine, 20 mg of omeprazole or 20 mL of saline alone by intravenous bolus injection before a test meal (200 kcal per 200 mL, containing 100 mg of (13)C-acetate). Gastric emptying was monitored for 4 hours after the ingestion of test meal by the (13)C-acetic acid breath test performed using the BreathID system.

RESULTS

No significant differences in the calculated parameters, namely, the T(1/2), T(lag), GEC, β and κ, were observed among the 3 test conditions.

CONCLUSIONS

The study revealed that intravenous administration of gastric acid suppressant drugs had no significant influence on the rate of gastric emptying in comparison with that of saline alone as a placebo. Our results indicating the absence of any effect of either famotidine or omeprazole on accelerating the rate of gastric emptying suggest that both medications can be administered safely to patients suffering from hemorrhagic peptic ulcers who need to be kept nil by mouth from the viewpoint of possible acceleration of gastrointestinal motility in the clinical setting.

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.

Nizatidine and gastric emptying in functional dyspepsia

In clinical practice, H2-receptor antagonists, including nizatidine, in addition to their use in the treatment of peptic ulcer and gastroesophageal reflux, are also useful in alleviating dyspeptic symptoms. Patients with functional dyspepsia show a tendency to delayed gastric emptying. Results of preliminary studies have demonstrated that nizatidine has a prokinetic effect due to its cholinergic properties. The aim of this study was to evaluate the effect of nizatidine on gastric emptying in patients with functional dyspepsia. Sixteen patients with dyspeptic symptoms referred for gastroscopy by primary care physicians were enrolled in this randomized, placebo-controlled, double-blind cross-over study. They received nizatidine 150 mg twice daily or placebo for 2 months. After a 1-month washout period, the 2-month treatment was repeated, with these patients acting as their own controls. Gastric emptying was measured by scintigraphy, and dyspeptic symptoms and quality of life were evaluated at the end of both treatment periods. Gastric emptying of solids during nizatidine therapy was prolonged (T1/2 110.1 +/- 76.7 vs. 65.6 +/- 23.2 min, P = 0.03), but nizatidine had no effect on gastric emptying of liquids. Nizatidine improved the symptom scores and seven of eight aspects of quality of life - but not significantly. In conclusion, nizatidine decreases the gastric emptying rate of solids without having a significant effect on symptoms or quality of life in functional dyspepsia.

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.

Is there an interaction between H2-antagonists and alcohol?

H2-antagonists are commonly prescribed drugs and alcohol use is widespread in the community. Any possible interaction may be important because of the frequent co-administration of both drugs and the potential for unexpected impairment of pyschomotor function, in particular, driving skills. Hepatic ADH is the major site of alcohol metabolism. ADH is also found in the stomach, but it is uncertain whether gastric ADH is able to metabolise a significant amount of alcohol in vivo. Significant first-pass metabolism can be demonstrated at lower doses of alcohol, and if alcohol is given after meals. Varying degrees of extraction of alcohol from the portal circulation probably explains the data regarding first pass metabolism rather than gastric metabolism by gastric ADH. H2-receptor antagonists inhibit gastric ADH activity to a variable extent. If gastric metabolism of alcohol is negligible then this inhibition has no relevance. Given the uncertainty regarding a mechanism of interaction, only carefully conducted studies in controlled environments will answer the question. The large inter-subject variability of alcohol absorption means that any study which seeks to determine the effect of an H2-receptor antagonist on ethanol metabolism must have sufficient numbers. A cross-over design, with each subject acting as his own control, is preferable to avoid ascribing an effect to treatment rather than to chance. The alcohol dosing studies are reviewed and the results summarised according to dose of alcohol given. At a dose of 0.15 g/kg of alcohol, four commonly used H2-antagonists may cause a small increase in blood alcohol concentrations in certain conditions. This absolute increase is very small. The magnitude of effect is far less than the effect of taking a meal before alcohol. At doses of 0.3 g/kg and above the majority of evidence favours no interaction between H2-antagonists and alcohol. There is no interaction at doses that would be expected to impair psychomotor skills (above 25 mg/dl). There remains a question regarding the cumulative effect of repeated small doses of alcohol and further studies are required. The relationship between ethanol absorption and gastric emptying raises the possibility that the effects of H2-receptor antagonists observed at very low doses of alcohol may be due to the acceleration of gastric emptying by these drugs. This is an attractive hypothesis that explains many aspects of the debate, but studies of the effect of H2-antagonists on gastric emptying have been conflicting.

Pharmacokinetic interactions between alcohol and other drugs

The frequent use of alcohol (ethanol) together with prescription drugs gives any described pharmacokinetic interaction significant clinical implications. The issue is both the effect of alcohol on the pharmacokinetics of various drugs and also the effect of those drugs on the pharmacokinetics of alcohol. This review discusses these pharmacokinetic interactions but also briefly describes some other effects of alcohol that are clinically relevant to drug prescribing. The use of several different study designs may be required before we can confidently state the presence or absence of any alcohol-drug interaction. Short term administration of alcohol in volunteers is the most common study design but studies of social drinking and prolonged moderate alcohol intake can be important in some situations. Community-based studies may illustrate the clinical relevance of any interaction. Alcohol can affect the pharmacokinetics of drugs by altering gastric emptying or liver metabolism (by inducing cytochrome P450 2E1). Drugs may affect the pharmacokinetics of alcohol by altering gastric emptying and inhibiting gastric alcohol dehydrogenase. The role of gastric alcohol dehydrogenase in the first-pass metabolism of alcohol is reviewed in this article and the arguments for and against any potential interaction between alcohol and H2 receptor antagonists are also discussed. The inhibition of the metabolism of acetaldehyde may cause disulfiram-like reactions. Pharmacodynamic interactions between alcohol and prescription drugs are common, particularly the additive sedative effects with benzodiazepines and also with some of the antihistamine drugs; other interactions may occur with tricyclic antidepressants. Alcohol intake may be a contributing factor to the disease state which is being treated and may complicate treatment because of various pathophysiological effects (e.g. impairment of gluconeogenesis and the risk of hypoglycaemia with oral hypoglycaemic agents). The combination of nonsteroidal anti-inflammatory drugs and alcohol intake increases the risk of gastrointestinal haemorrhage.

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.

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).

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

Ranitidine bismuth citrate, a new chemical entity which is a salt complex of ranitidine and bismuth citrate, is being developed for the treatment of relapse of benign gastric and duodenal ulcer and eradication of Helicobacter pylori. The aim of the present study was to establish whether ranitidine bismuth citrate (800 mg) or ranitidine hydrochloride (300 mg) have any effect on gastric emptying of a liquid meal using gamma scintigraphy. On three separate occasions, each of twelve subjects received a single oral tablet of 800 mg ranitidine bismuth citrate, 300 mg ranitidine hydrochloride or placebo in random order. Thirty minutes after dosing each subject was given 375 ml of 99mTc-DTPA (diethylene triaminepentaacetic acid) labelled Clinifeed-ISO. The primary endpoint was the time to 50% gastric emptying (t50%). The proportion of the meal remaining was summarised by weighted mean proportion of the meal remaining in the stomach over 0-60 min and 0-180 min, separately. No differences were observed for t50%, weighted mean 0-60 min, and weighted mean 0-180 min between any two treatments. In man, we have detected no significant effect of single oral doses of ranitidine bismuth citrate 800 mg or ranitidine hydrochloride 300 mg on the rate of gastric emptying of a liquid meal when compared with placebo.

Famotidine increases plasma alcohol concentration in healthy subjects

The effect of famotidine on plasma alcohol concentration was studied in 24 healthy male subjects who demonstrated high apparent ethanol first-pass metabolism after oral (p.o.) and intravenous (i.v.) ethanol administration (i.e. AUC(po) < or = 40% of AUC(i.v.), where AUC is area under the plasma ethanol concentration-time curve). Six of the original 30 subjects screened (20%) did not demonstrate high first-pass metabolism and were excluded. In a randomized open crossover study, oral ethanol pharmacokinetics were assessed after breakfast in the morning following a 3-day regimen of famotidine, 40 mg/day, and following a no-drug control period. Famotidine increased the area under the plasma ethanol concentration-time curve (AUC0-t) by 29% (7.1 vs 5.5 mg.h/dL, P = 0.006) and maximal plasma concentration (Cmax) by 23% (9.2 vs 7.5 mg/dL, P = 0.013). The changes in ethanol AUC0-t and Cmax may have been associated with changes in gastric emptying, as they were inversely correlated with changes in the time at which maximal plasma concentration was attained. There was considerable intra-individual variation in ethanol AUC and Cmax. As a result, regression to the mean is a potentially confounding problem in ethanol pharmacokinetic studies when subjects are selected on the basis of having low AUC(po), and properly controlled randomized studies of substantial size are required to detect modest drug effects. Small effects on ethanol pharmacokinetics have now been demonstrated with all four of the major H2-receptor antagonists, but these effects are seen only under specific experimental conditions and appear to be unimportant clinically.

Effect of concomitantly administered cimetidine or ranitidine on the pharmacokinetics of the 5-HT2-receptor antagonist ritanserin

The effects of concurrent administration of either cimetidine 800 mg once daily or ranitidine 300 mg once daily on the single-dose pharmacokinetics of ritanserin 10 mg were investigated in an open, randomized three-way cross-over, controlled investigation in 9 healthy volunteers. Concurrent administration of cimetidine had no significant effect on the area under the plasma concentration-time curve of ritanserin compared with control experiments. The maximum plasma concentration of ritanserin was decreased significantly (105.0 +/- 9.2 versus 125.0 +/- 13.8 ng/mL; P = .0039), whereas time to reach maximal concentration (tmax) of ritanserin was only slightly but not significantly increased, if the subjects were pretreated with cimetidine. After concurrent ingestion of ranitidine, only a trend to a decrease in the maximum plasma concentration of ritanserin was observed. Time to achieve the maximum plasma concentration, terminal half-life of elimination, and the total area under the plasma concentration-time curve of ritanserin were not altered in comparison with control experiments. The results of the study show that concurrent treatment with cimetidine 800 mg once daily or ranitidine 300 mg once daily has no apparent effect on the systemically available amount of ritanserin after a single oral dose of 10 mg. Both H2-antagonists cause a significant (cimetidine) or borderline significant (ranitidine) decrease of the maximum plasma concentration of ritanserin and a slight but not significant increase in tmax (cimetidine). These effects are of minor clinical importance and seem most likely be due to a decrease of the rate of absorption of ritanserin during concurrent administration of cimetidine/ranitidine.

Applied potential tomography. Noninvasive method for measuring gastric emptying of a solid test meal

Applied potential tomography (APT) is a new noninvasive, nonradioactive method of measuring gastric emptying, which generates profiles of emptying of liquids that are similar to those obtained simultaneously by scintigraphy and dye dilution. This study validates the ability of APT to measure emptying of a solid beefburger test meal from the stomach by comparing the results obtained with those obtained simultaneously by scintigraphy. When acid secretion was inhibited, there was a significant correlation between the two methods for the time taken for half the meal to empty from the stomach and the amount of meal emptied at different time intervals. Furthermore, the profiles of gastric emptying obtained by APT resembled those obtained by scintigraphy in most studies. If acid secretion was not inhibited, there was no correlation between values obtained by the two methods.

Influence of acid-pepsin secretion on gastric emptying of solids in humans: studies with cimetidine

The commonly accepted model for gastric emptying suggests that the 'antral mill' is responsible for the triturition and subsequent emptying of solid food from the stomach. Little is known about the contribution to solid emptying made by other digestive mechanisms such as acid-pepsin secretion. We have investigated the effect of inhibiting gastic secretion on the rate at which a solid test meal emptied from the stomach. Using a radiolabelled beefburger, we performed paired gammacamera studies on consecutive days in 10 fasted, healthy volunteers to compare gastric emptying of the test meal with and without oral cimetidine (400 mg 1 hour before the test, 800 mg at the start of the meal). Inhibition of acid-pepsin secretion by cimetidine was associated with an appreciable delay in the rate of emptying of the burger from the stomach (T50 cimetidine 187 (16) min (mean (SEM); T50 no cimetidine 146 (15) min; p less than 0.01, paired t test). This delay was related to a change in the slope of the emptying profile and was not associated with a prolonged lag phase. These results may be explained by the relative achlorhydria and reduced pepsin activity induced by cimetidine impairing the breakdown of solid food into particles small enough to leave the stomach.

Gastric emptying in non-responders to H2-receptor antagonists

H2-receptor antagonists are known to fail to increase the intragastric pH in some patients (so-called non-responders), and we have recently found a higher frequency of non-responders among cirrhotics. Since intragastric pH is also affected by gastric emptying, in the present study we determined the gastric emptying of 300 ml orange juice labelled with [99mTc]-Solco Nanocoll using a gamma camera. Measurements were made over a period of 60 min in cirrhotic patients and controls without liver disease who either responded to 300 mg ranitidine or showed no response. The mean (+/- SD) liquid half-emptying time (T1/2) was 26.3 +/- 17.5 min (range, 9-75 min) in responders (n = 10), 20.9 +/- 8.6 min (range, 7-34 min) in non-responders (n = 10), 19.4 +/- 19.2 min (range, 7-75 min) in cirrhotics (n = 11), and 27 +/- 4.6 min (range, 17-33 min) in controls (n = 9). In 19 of the 20 subjects gastric emptying was normal (T1/2, less than 40 min). Since gastric emptying was not delayed in any of the non-responders, it would appear very unlikely that gastric motility plays a major role in the non-response to H2-receptor antagonists.

Ranitidine. An updated review of its pharmacodynamic and pharmacokinetic properties and therapeutic use in peptic ulcer disease and other allied diseases

Ranitidine, a histamine H2-receptor antagonist, is now well established as a potent inhibitor of gastric acid secretion effective in the treatment and prophylaxis of gastrointestinal lesions aggravated by gastric acid secretion. Therapeutic trials involving several thousands of patients with peptic ulcer disease confirm that ranitidine 300mg daily administered orally in single or divided doses is at least as effective as cimetidine 800 to 1000mg daily in increasing the rate of healing of duodenal and gastric ulcers. Similar dosages of ranitidine have been shown to relieve the symptoms of reflux oesophagitis and heal or prevent gastrointestinal damage caused by ulcerogenic drugs. Ranitidine 150mg orally at night maintains ulcer healing in the long term. Ranitidine has also demonstrated good results in the treatment of Zollinger-Ellison syndrome and in the prevention of aspiration pneumonitis when given prior to surgery and to pregnant women at full term. It may also have a place in the management of acute upper gastrointestinal bleeding and in the prevention of stress ulcers in the intensive care setting, although these areas require further investigation. Ranitidine has been used safely in obstetric patients during labour, in children, the elderly, and in patients with renal impairment when given in appropriate dosages. The drug is very well tolerated and is only infrequently associated with serious adverse reactions or clinically significant drug interactions. Even at high dosages, ranitidine appears devoid of antiandrogenic effects. Ranitidine is clearly comparable or superior to most other antiulcer agents in the treatment and prevention of a variety of gastrointestinal disorders associated with gastric acid secretion. With its favourable efficacy and tolerability profiles, ranitidine must be considered a first-line agent when suppression of gastric acid secretion is indicated.

Ranitidine versus cimetidine. A comparison of their potential to cause clinically important drug interactions

The literature on H2-antagonist drug interactions is now extensive. The whole subject is so complicated as to make things difficult for the potential prescriber. However, it is possible to reduce most of the information contained in the literature to a few simple messages. Firstly, H2-antagonists bind to cytochrome P450 and may inhibit the metabolism of drugs eliminated by the mixed function oxygenase system. In this respect, cimetidine has a marked effect which, in most studies, has reached statistical significance. Ranitidine, on the other hand, has a much weaker effect which, even if demonstrable, is statistically non-significant. The potential benefit of ranitidine, however, has to be weighed against the relative costs of the 2 drugs. Secondly, H2-antagonists inhibit gastric acid production and may alter the rate of gastric emptying, and hence the rate of drug absorption. They may also have some effect on portal vein and hepatic artery flow. However, these effects are small and probably not clinically relevant. Thirdly, pharmacodynamic effects of H2-antagonist-drug interactions are difficult to demonstrate in planned studies, and although they are reported from time to time, adverse reactions of consequence are relatively uncommon. Fourthly, the prescriber needs to be aware that cimetidine may produce higher plasma concentrations of some drugs which have a fairly narrow therapeutic range, and this may be clinically important. Examples of drugs for which it may be undesirable to inadvertently increase plasma concentrations include warfarin, theophylline and phenytoin. Finally, for most drugs metabolised by the liver, the risk of an important interaction is small. However, if such an interaction is noted it may be helpful to refer to the other reported cases, and a number of references are included here.

Treatment of reflux oesophagitis with H2-receptor antagonists

The important therapeutic value of H2-receptor antagonists for the treatment of patients with reflux oesophagitis has been demonstrated beyond doubt. A large number of patients have been treated with cimetidine or ranitidine in controlled as well as open short-term studies. Mild to moderately severe reflux oesophagitis heals effectively when H2-receptor antagonists are prescribed for a sufficient time period, preferentially 12 weeks. The more severe forms of oesophagitis, however, need more profound acid suppression, with potent H2-receptor antagonists, addition of prokinetic agents, or treatment with H+/K+ATP-ase antagonists. Omerpazole has proven to be of high efficacy, particularly in the management of severe reflux oesophagitis. Data on long-term treatment with H2-receptor antagonists, to prevent recurrences after healing, are not reassuring: long-term low-dose H2-receptor antagonist therapy is not effective, and trials should be undertaken with higher doses of H2-receptor antagonists, more potent antagonists, or with combinations of antagonists and prokinetics. In these studies, 24-h intraoesophageal and intragastric pH measurements should be incorporated, to detect more accurately time periods of nonsuppressed acid secretion. Such studies will undoubtedly better define the therapeutic place of the presently available and forthcoming H2-receptor antagonists.