Evaluation of 24-hour gastric acidity in patients with hepatic cirrhosis

BACKGROUND/AIMS

Data from previous studies on gastric acid secretion in patients with hepatic cirrhosis are controversial, due, at least in part, to the possible interference of liver failure and altered gastric mucosal microcirculation on the pharmacological action of the substances used to stimulate the parietal cell. For this reason, we wished to investigate the circadian pattern of gastric acidity by means of continuous 24-hour pH monitoring, which permits measurement of pH fluctuations in a nearly physiological manner and does not require any pharmacological stimulus.

METHODS

Forty-nine patients with liver cirrhosis of different aetiology were recruited for this study. They underwent 24-hour gastric pH-metry with an electrode positioned in the gastric corpus, and their pattern of gastric acidity was compared with that of 49 healthy subjects, matched for age and sex. In a subgroup of 31 patients with cirrhosis, antral pH was recorded in addition to body pH in order to assess whether there are regional differences in gastric acidity.

RESULTS

The circadian, daytime and nocturnal gastric acidity in patients with cirrhosis was significantly lower (p < 0.05-0.001) than that of controls. In the 31 patients studied with two electrodes, antral pH was higher (p < 0.05) than body pH only during the night. The prevalence of Helicobacter pylori infection was rather low (42%) in our patients.

CONCLUSIONS

There is a marked hypoacidity over the circadian cycle in patients with cirrhosis compared to controls, and the greatest difference between them is visible during the nocturnal hours. Also, in patients with liver cirrhosis the pH in the antrum is higher than that in the body of the stomach during the night for reasons that need to be elucidated.

Absence of tolerance in duodenal ulcer patients treated for 28 days with a bedtime dose of roxatidine or ranitidine

There is much experimental work on the occurrence of tolerance to the antisecretory effect of H2-receptor antagonists in healthy subjects, while data on its development in patients with duodenal ulcer are poor and conflicting. Moreover, this phenomenon has not been studied previously with 24 h gastric pH-metry in patients with active duodenal ulcer. For these reasons, we carried out a prospective pharmacodynamic investigation in 48 patients with endoscopically proven duodenal ulcer using the well-established once daily dosing schedule of H2 blockers. They were studied by means of 24 h continuous endoluminal pH-metry which was performed before, on d1 and d28 after receiving an oral bedtime dose (2200 hours) of either roxatidine 150 mg or ranitidine 300 mg, given in randomized and single-blind fashion. Eight patients did not complete the study for various reasons and 82% of ulcers healed after 4 weeks of therapy. Gastric pH was higher (P < 0.001) on d1 and d28 than basal values during all time periods, but the evening, with both H2 blockers. There was no significant difference between pH values of d1 and d28 in any time interval with both roxatidine and ranitidine. There was also no difference in pharmacodynamic data between the two active treatments. We conclude that tolerance does not develop after 1 month's treatment with a bedtime dose of H2 antagonist in patients with active duodenal ulcer and therefore data gathered on this phenomenon in healthy subjects are not applicable to ulcer patients.

Are duodenal ulcer seasonal fluctuations paralleled by seasonal changes in 24-hour gastric acidity and Helicobacter pylori infection?

The occurrence of duodenal ulcer is characterized by seasonal variation, for poorly understood reasons. No previous study has assessed whether 24-h intragastric acidity and Helicobacter pylori infection have similar seasonal fluctuations in patients with this disorder. For this reason, we evaluated retrospectively the circadian gastric pH in 319 new patients (226 men and 93 women, mean age 45.2 years) with endoscopically proven duodenal ulcer, who agreed to undergo this examination during the years 1987-1992 in our center. The month-by-month occurrence of the disease over the global 6-year period was assessed, and the mean pH values were calculated for each patient during three time intervals of interest: 24 h, daytime (08:00-19:59 h), and nighttime (20:00-07:59 h). The mean pH values of these three time periods were then calculated month by month throughout the annual cycle. H. pylori infection was sought by histology in 171 patients examined in the period from 1990 to 1992. The percentage of H. pylori-positive duodenal ulcer patients was then calculated for each season. The calendar fluctuation of duodenal ulcer occurrence showed an evident increase (p < 0.001) in fall (October-December) and in winter (January-March) compared with spring (April-June) and summer (July-September). Both 24-h and nighttime gastric acidity showed no significant variation by month, whereas daytime gastric pH varied significantly (p < 0.05) with two evident decreases, meaning higher acidity, in April and August. H. pylori infection was detected in 152 of 171 patients (89%), and the percentage of H. pylori-positive duodenal ulcers did not differ from season to season. We conclude that there was no parallel circannual fluctuation of duodenal ulcer, gastric acidity, and H. pylori infection in the restricted sample of patients we studied. This reduces the apparent relevance of acid in inducing ulcer seasonal fluctuation. Also, the responsibility of H. pylori in this phenomenon can be excluded until a reliable diagnostic method capable of distinguishing recent from old infection is found.

Antisecretory effects of three omeprazole regimens for maintenance treatment in duodenal ulcer

This study was carried out to assess the antisecretory effects and their possible changes over time of three different dose regimens of omeprazole that could be proposed for maintenance treatment in duodenal ulcer. Forty-five patients with endoscopically proven duodenal ulcer were studied by means of 24-hr gastric pH-metry both in basal conditions and on the fifth day of acute treatment with omeprazole 20 mg in the morning. Ulcers healed after four weeks (in three cases after eight weeks) and afterwards, 15 patients were randomized to receive orally at 0800 hr in single-blind fashion omeprazole 10 mg daily (group A), 15 to receive omeprazole 40 mg on Saturday and Sunday followed by a five-day period without medication (group B), and 15 to receive omeprazole 20 mg every other day (group C) for up to three months. On the 20th and 80th days of these maintenance treatments 24-hr gastric pH-metry was repeated to assess the antisecretory effectiveness of each regimen over a two-month period. In patients of group B these tests began at 1700 hr on Friday, the last of five days off treatment, and in those of group C at 1700 hr of the day off medication. All three dose regimens of omeprazole were able to raise pH values significantly (P < 0.01-0.001) compared to basal levels. Omeprazole 20 mg every other day was more effective (P < 0.01) than omeprazole 40 mg weekend, but did not differ significantly from omeprazole 10 mg daily. The durations of acid inhibition (pH > 3.0 units/24 hr) were 12.44, 10.00, and 17.38 hr with groups A, B, and C, respectively. There was no significant difference between the pH profiles of the 20th and 80th days with every dose regimen. It is concluded that all three dose regimens of omeprazole are effective in reducing gastric acidity and their pharmacodynamic action does not change with time. Therefore they are suitable to be assessed in large clinical trials aimed at verifying the prevention of duodenal ulcer recurrence for longer periods.

Bolus infusion of famotidine: effects on gastric pH by repeated 12-hour doses of 20 mg in postoperative patients

This study was carried out to assess the efficacy of intravenous (IV) famotidine in suppressing gastric secretion over a 48-hour period. Twenty postoperative patients requiring a nasogastric tube received famotidine 20 mg IV every 12 hours and gastric pH was measured continuously by means of an indwelling probe. A baseline recording was performed over the first 4 hours and then the drug was infused every 12 hours (q12h) over a 15-minute period for the subsequent 48 hours. The mean pH value achieved during each time segment under active treatment was significantly higher (P < .001) than the mean basal value. Also the density distributions of minutes spent at the various pH units confirm that famotidine is highly effective (P < .001) in raising and maintaining gastric pH above 4.0 units during most of the drug-related period (44 hours). It can be concluded that repeated intravenous boli of famotidine 20 mg every 12 hours allow us to obtain an effective control of intragastric acidity. The antisecretory action is consistent over the total 48-hour period examined and therefore the use of intermittent infusion of famotidine seems to be advisable, as opposed to the recommended continuous IV administration of cimetidine and ranitidine. There is, however, a considerable intersubject variability in the antisecretory response to the drug.

Variability in individual response to various doses of omeprazole. Implications for antiulcer therapy

This study was carried out in order to perform a combined prospective assessment of the individual pharmacodynamic response and of duodenal ulcer healing in patients treated with three different doses of omeprazole. Ninety-nine patients with endoscopically proven duodenal ulcers were subdivided into three parallel groups of 33 cases, who were randomly assigned to receive orally at 0800 hr, in single blind fashion, either 10 mg, 20 mg, or 40 mg of omeprazole. All of them underwent continuous intragastric pH monitoring both in basal conditions and on the fifth day of each dose regimen; ulcer healing was then assessed endoscopically after four weeks of treatment. All three doses of omeprazole caused pH values to increase significantly (P < 0.001) over the whole 24-hr period. In patients treated with omeprazole 10 mg, the individual responses showed the highest variability: the acid inhibition, expressed in terms of time spent above pH 3.0, lasted for more than 16 hr in 42% of cases, for more than 8 hr in 28%, and for less than 6 hr in 30%. In patients treated with omeprazole 20 mg, the pharmacological response was more marked and uniform and lasted for more than 16 hr in 79% of cases; however, it is worth noting it lasted for less than 6 hr in three patients (10%). In patients treated with omeprazole 40 mg, the individual response was excellent (more than 16 hr) in 94% of cases, and it lasted for less than 6 hr in only one patient (3%).(ABSTRACT TRUNCATED AT 250 WORDS)

Circadian acidity pattern in prepyloric ulcers: a comparison with normal subjects and duodenal ulcer patients

We used continuous 24-h pH monitoring to compare the circadian intragastric acidity of 36 patients with prepyloric ulcers (PPU) with that of 101 normal subjects (NS) and that of 206 patients with duodenal ulcer (DU). The ulcer crater was endoscopically ascertained in all cases, and PPU were located within an area up to 2 cm proximal to the pylorus. The pH curve pertaining to DU patients ran below that of NS during most of the circadian period, whereas the pH profile of PPU patients was higher than that of NS, and this was particularly true during the evening and the night. The acidity of PPU patients was significantly lower (p < 0.01) than that of NS during the night only, whereas it was lower (p < 0.05-0.001) than that of DU patients during each time interval analysed (24 h, nighttime, and daytime). Our findings show that the gastric acidity of PPU patients differs greatly from that of DU patients, since it is lower throughout the whole 24-h period, and particularly during the night. Thus these two entities are pathophysiologically different with regard to the acidity pattern and should be considered two distinct subgroups of peptic ulcer disease instead of being incorporated, as usually happens, in the clinical group 'duodenal ulcer disease'.

Antisecretory effect of three premeal doses of cimetidine 400 mg versus a single morning dose of omeprazole 20 mg: pathophysiological implications for duodenal ulcer treatment

The success of omeprazole in the healing of duodenal ulcer has been attributed to its profound and almost around-the-clock inhibition of acid, but the relevance of reducing meal-stimulated acid secretion exclusively has recently been emphasized in several clinical trials. For this reason, we used 24-h continuous intragastric pH monitoring to compare the pharmacodynamic effects of placebo, three fractioned premeal doses of cimetidine 400 mg and omeprazole 20 mg mane. Fifteen patients with duodenal ulcer in clinical remission were randomized to receive the above medications in single-blind fashion on three separate occasions, at least 2 wk apart. Both active regimens produced higher pH values (p < 0.05-0.001) than placebo, but omeprazole was much more effective than cimetidine (p < 0.01-0.001) during the various time intervals analyzed (24 h, evening, nighttime, daytime). The greater effectiveness of omeprazole was confirmed by its longer-lasting antisecretory action, insofar as the drug increased gastric pH above 3.0 units for about 21 h, whereas the daytime cimetidine regimen maintained this threshold for 7.30 h (p < 0.001) over the circadian cycle. As these markedly different pharmacodynamic effects have been proven to produce similar fast rates of duodenal ulcer healing in clinical trials, it is reasonable to assume that a small but well addressed reduction of gastric acidity can ensure the same therapeutic benefit as a strong and continuous acid inhibition. In this light, the acid peaks in response to meals seem to be important pathophysiological events, whose control is sufficient to permit quick ulcer healing.

Twenty-four-hour control of gastric acidity by twice-daily doses of placebo, nizatidine 150 mg, nizatidine 300 mg, and ranitidine 300 mg

This study was carried out to assess the effects on gastric acidity of placebo twice daily (bid), nizatidine 150 mg bid, nizatidine 300 mg bid, and ranitidine 300 mg bid by means of continuous 24-hour intragastric pH monitoring. Twelve patients with duodenal ulcer in remission were randomized to receive in single-blind fashion the above medications on four separate occasions, at least 1 week apart. The three active regimens produced higher pH values (P < .001) and maintained gastric pH above 3.0 units for a longer period (P < .001) than placebo in all time intervals but evening. Nizatidine 150 mg bid caused a lower rise in pH than nizatidine 300 mg bid (P < .01) and ranitidine 300 mg bid (P < .05) during both the daytime and the whole 24 hours. In these time windows also the time spent above 3.0 pH units was significantly shorter for the former regimen than for 300 mg bid of both nizatidine (P < .01) and ranitidine (P < .05). There was no difference between the latter two dosing schedules in terms of both potency and duration of action in all the time intervals considered. It is concluded that twice daily doses of H2 blockers are more effective than placebo in reducing gastric acidity. Three hundred milligrams twice daily of both nizatidine and ranitidine produce a significantly greater and longer-lasting acid suppression than 150 mg bid of nizatidine. Our study also confirms the greater effectiveness of H2 antagonists during nighttime than during day-time.

Mealtime versus nighttime acid inhibition. A clinical pharmacological study with ranitidine

This study was carried out in order to compare the effects of mealtime and bedtime regimens of ranitidine on gastric acidity. Fifteen duodenal ulcer patients in clinical remission were randomized to receive in single-blind fashion either placebo, ranitidine 300 mg at night (2200 hr) or ranitidine 150 mg three times a day given before each of the three daily meals (1800, 0800 and 1200 hr). Over 24 hr, the two active treatments produced a significantly greater acid inhibition than placebo, while the single daily regimen was superior to the three times a day regimen of ranitidine in terms of both rise in pH values (P less than 0.001) and duration of action expressed as time spent above 3.0 pH units (P less than 0.05). The analysis of these two parameters during fractioned periods of the circadian cycle showed that the three divided doses of ranitidine were more effective during the daytime (P less than 0.01) and the evening (P less than 0.001), whereas the bedtime dose of ranitidine was superior during the night (P less than 0.0001). Thus a short-lasting antisecretory action, which is, however, capable of fully controlling the high acidity of postprandial periods, might be the key to understanding the results of several recent clinical trials in which the suppression of daytime gastric acidity has been shown to promote similar or even faster duodenal ulcer healing rates than the suppression of nocturnal acidity.

Duration of acid suppression in H2-antagonist nonresponders

We monitored 24-hour gastric acidity in 16 resistant duodenal ulcer patients treated with ranitidine 300 mg hora somni (9 cases) and famotidine 40 mg hora somni (7 cases) for 3 months. Data obtained in these patients were compared with those of a group of unselected duodenal ulcer patients who responded to a 4-week course of the same H2-antagonist regimens. In the time window 22.00-07.59 h there was a reduced effectiveness of ranitidine in nonresponder patients in terms of both mean pH levels (4.8 +/- 0.9 vs. 5.6 +/- 0.7, p < 0.04) and the mean duration of the antisecretory effect defined as the time spent in minutes above pH 3.0 (403 +/- 73 vs. 490 +/- 59, p < 0.02). Also, the action of famotidine was diminished in nonresponder patients in the same time interval as regards both pH values (4.1 +/- 1.6 vs. 5.7 +/- 0.6, p < 0.03) and the duration in minutes (329 +/- 163 vs. 473 +/- 45, p < 0.05). The analysis of all individual nonresponder patients shows that there was a certain variability in the duration of acid suppression: the majority of them had an adequate nocturnal acid inhibition, while in some cases of both the ranitidine and the famotidine subgroups, acid inhibition lasted only few hours or did not occur at all. At present, it is not possible to distinguish with certainty two different subsets of H2-antagonist nonresponders because of the small size of the population studied.(ABSTRACT TRUNCATED AT 250 WORDS)

[Esophageal pH monitoring: factors influencing the definition of normality]

Prolonged esophageal pH-metry has become an irreplaceable investigative tool in diagnosing gastroesophageal reflux. Given the presence of episodes of acid reflux even under physiological circumstances, it is of primary importance to define the range of normal values in order to correctly identify the condition of disease. This task is complicated by the lack of an absolute and objective marker of normality, to be referred to, and by the number of variables that can influence the measurement of the esophageal pH. Among the most important factors that can influence this test there are age, physical exercise, posture and diet. Even voluptuary habits, such as smoking and alcohol intake, could be detrimental in this respect. Then there are many technical factors that can act as sources of relevant errors in measuring and calculating the parameters chosen to discriminate normality from abnormality, the most important ones being as follows: defective electrodes, electrodes that have not been calibrated accurately, electrodes positioned erroneously, interference with the pH readings by mucus, food, aiming at the walls of the esophagus, inconsistent sampling rates among the recording equipment, differences in the software used to automatically analyze the experimental data, failure to recognize and consequently to eliminate the artifacts present in the pH-metry tracings, inadequate "in situ" repeatability of the esophageal pH measurements on the part of paired electrodes that simultaneously record the pH.

Single morning and nightly doses of ranitidine 300 mg: an appraisal of their antisecretory effects by continuous pH monitoring

Gastric acidity of 12 patients with healed duodenal ulcers was continuously monitored over 24 h in order to assess the antisecretory effects of two different administration times of a single daily dose of ranitidine 300 mg. Each patient orally received either (a) placebo at 08.00 h and 22.00 h; (b) ranitidine 300 mg at 08.00 h and placebo at 22.00 h, or (c) placebo at 08.00 h and ranitidine 300 mg at 22.00 h in randomized and double-blind fashion. Each medication was administered on three separate occasions, with intervals of at least 1 week. Both the morning and the bedtime doses of ranitidine were significantly superior (p less than 0.001) to placebo in controlling 24-hour gastric acidity, while, in the same period, ranitidine nocte was more effective (p less than 0.001) than ranitidine mane. During the night, bedtime ranitidine caused more acid inhibition (p less than 0.001) than morning ranitidine, but the opposite (p less than 0.01) occurred during the daytime. This study shows that the antisecretory effect of morning ranitidine during the daytime is less consistent than that achieved by bedtime ranitidine during the nocturnal period. As similar rates of duodenal ulcer healing have recently been achieved with morning and conventional nighttime administration of H2 antagonists, it becomes clear that antisecretory drugs can also be beneficial with an acid inhibition which is shorter-lasting than that which was previously thought to be necessary or, alternatively, that also daytime acidity is important in ulcerogenesis.