Once and twice daily doses of H2 antagonists revisited, using continuous intragastric pH monitoring

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.

A comparative study of once-a-day morning and once-a-day bedtime administration of 40 mg famotidine in treating duodenal ulcers

A randomized controlled study comparing once-a-day morning and once-a-day bedtime administration of 40 mg famotidine in treating duodenal ulcers was carried out in 99 Japanese patients. Endoscopic examinations were performed at the baseline and repeated at 3-week intervals until healing was confirmed. Eighty-two patients fulfilled the evaluation criteria (38 in the morning group and 44 in the bedtime group). In 13 of these patients the antisecretory effects of these regimens were also assessed by 24 h intragastric pH monitoring. The healing rates were 66% after 3 weeks and 95% after 6 weeks in the morning group, and 57% after 3 weeks and 80% after 6 weeks in the bedtime group. The differences were insignificant between the two groups, but there was a higher healing rate tendency after 6 weeks in the morning group (0.05 less than P less than 0.10). Regarding pain subsidence, there were no significant differences between the two groups. Both treatments were significantly superior to the control group in increasing 24 h intragastric pH. The morning regimen was significantly superior to the bedtime regimen in suppression of daytime acidity. On the contrary, the bedtime regimen was significantly superior to the morning regimen in suppression of nocturnal acidity. These findings suggest that suppression of nocturnal acidity is important but not essential to promote duodenal ulcer healing and suppression of daytime acidity is equally important. Thus, once-a-day morning administration of 40 mg famotidine seems to be at least as effective as once-a-day bedtime administration of 40 mg famotidine in treating duodenal ulcers.

Day-night and individual differences in response to constant-rate ranitidine infusion

Twelve ulcer patients with inactive disease received constant-rate infusions of ranitidine, in doses of 6.25 and 10.0 mg/hr, during separate 24-h spans. Gastric pH and serum ranitidine concentrations were monitored. Serum ranitidine concentrations did not vary significantly after attainment of steady-state. For the group, gastric acidity was controlled above pH 4 during the day; however, at night, when gastric acid secretion was greatest under placebo conditions, ranitidine less effectively controlled gastric pH. There was individual variation in response to ranitidine. Patients (8/12) evidencing control of gastric acidity (pH greater than or equal to 4) for at least 16 h when infused with ranitidine (6.25 mg/h) were considered responders. Those (4/12) not so well controlled were designated poor responders. With parenteral infusion of 6.25, as well as 10.0 mg/h ranitidine, responders evidenced a relatively high 24-h mean pH and only minor day-night variation in gastric acidity. In contrast, poor responders were characterized by a low 24-h mean pH and high-amplitude circadian variation in gastric acidity. Poor responders evidenced statistically significant (p less than 0.05) lower gastric pH responses to parenteral infusions than did responders. A similar, significant difference between the two groups was observed when the percentage of time that gastric pH was maintained below 4 was considered. Differences between responders and poor responders to ranitidine infusion are unknown. Since Zollinger-Ellison syndrome patients were not included in the study, observed differences in drug response cannot be ascribed to hypersecretion of gastric acid.

Inaccuracy of hourly sampled pH measurements in describing the effect of antisecretory drugs on circadian gastric acidity

This study was carried out in order to verify whether gastric pH measurements obtained with continuous monitoring are more accurate in assessing the pharmacodynamic properties of antisecretory drugs than those obtained with the traditional hourly nasogastric aspiration method. Accordingly, we compared the most commonly used acidity indexes (median of pHs and mean of [H+]s) and the total circadian time spent above 4.0 pH units, all of which were calculated from both raw data sampled at rates of a few seconds with modern apparatus and data obtained from the same profiles scanned punctually at a 60 minute rate. The analysis referred to 231 continuous gastric pH-metries which were performed over the circadian period to evaluate the acid inhibitory effects of different doses and dosage regimens of various H2-antagonists. In the population as a whole, the numbers and percentages of subjects, whose 60-minute sampled medians of pHs and means of [H+]s differed by less than +/- 10% from those obtained from raw fast-acquired data, were 107 (46%) and 34 (15%), respectively. There was even less agreement in the case of the circadian time above 4.0 pH units (26 cases = 11%). No statistical difference (P = .7) between the concordance rates of each variable in the three groups was observed. Considered simultaneously, there was concordance of the above three indexes in only seven out of the 231 cases. These results show that the hourly sampling rate fails to represent adequately gastric acidity changes induced by antisecretory drugs, due to the scarcity of experimental points. The acidity indexes calculated from these slowly sampled data are inaccurate, especially when the means of [H+]s are considered, and the duration of action of the drug often is defined randomly.

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

Famotidine is a highly selective histamine H2-receptor antagonist. In healthy volunteers and patients with acid hypersecretory disease it is approximately 20 to 50 times more potent at inhibiting gastric acid secretion than cimetidine and 8 times more potent than ranitidine on a weight basis. As shown in placebo-controlled trials, famotidine is effective in healing both duodenal and gastric ulcers. Famotidine 20mg twice daily or 40mg at bedtime achieves healing rates and symptom relief similar or superior to those achieved by cimetidine 800mg daily or ranitidine 300mg daily in patients with peptic ulcer disease. Results of 1 placebo-controlled study suggest that famotidine prevents recurrence of duodenal ulcer, but comparative trials are needed to establish its relative efficacy in maintenance therapy. The few non-comparative trials conducted to date also suggest that famotidine 10 to 20mg twice daily may be effective in the treatment of gastritis and reflux gastro-oesophagitis. In comparative trials, famotidine was similar in efficacy to cimetidine in the treatment of upper gastrointestinal bleeding and to ranitidine in the prevention of pulmonary aspiration of acid. In patients with Zollinger-Ellison syndrome, the potency and long duration of action of famotidine may confer an advantage over other H2-receptor antagonists--in individualised doses (mean 0.33 g/day) famotidine successfully controlled acid secretion for up to 72 months in 1 study of such patients. Accumulated clinical evidence confirms that famotidine is very well tolerated and is free of the antiandrogenic effects infrequently reported with cimetidine. Moreover, famotidine is not associated with altered hepatic metabolism of drugs. Thus, famotidine is an effective, well-tolerated alternative to cimetidine and ranitidine. Famotidine is also promising as maintenance therapy for preventing recurrence of duodenal ulcer and as initial or maintenance treatment of gastric hypersecretory disorders, but further clinical experience, particularly in the long term, is needed to define the relative efficacy and tolerability of famotidine in these indications.

Clinical relevance of sampling rate in the characterization and analysis of 24-hour gastric acidity. A report on 413 cases

Four hundred and thirteen continuous, high-frequency-sampled gastric pH-metries were subdivided into six groups (normal subjects and patients with duodenal ulcer, gastric ulcer, chronic gastritis, prior cholecystectomy, or antisecretory treatment). The frequency distribution of those pH fluctuations that were greater than the quantitation error of instruments did not differ significantly (p greater than 0.30) between groups. Five per cent of these real pH fluctuations lasted less than 3 min. As the sampling rate increased from 1 to 60 min, the percentage of subjects whose 24-h median of pHs differed by no more than +/- 10% from that calculated on the raw high-frequency-acquired data progressively decreased (99.8%-42%). This error propagation was more marked in the case of [H+] integrals (99%-10%). A sampling rate equal to or faster than 1 min is necessary to provide a proper representation of the circadian pH pattern and to calculate accurate acidity indexes, regardless of the physiologic or pharmacologic nature of the profile.

Low bedtime doses of H2-receptor antagonists for acute treatment of duodenal ulcer

Twenty-four-hour intragastric acidity was measured continuously over five separate occasions in 15 patients with healed duodenal ulcers. They were randomized to receive either placebo, cimetidine 800 mg, ranitidine 150 mg, famotidine 20 mg, or nizatidine 150 mg, given at 2200 hr in double-blind fashion. All H2-receptor blockers were more effective than placebo in suppressing both circadian (P less than 0.05-P less than 0.01) and nocturnal (P less than 0.002) gastric acidity, while there was no significant differences between the effects of the four active drugs in the same time periods. The percentage of nocturnal acid inhibition (2300-0800 hr) over placebo in terms of H+ values was virtually 100% with all active treatments. The effect on daytime (0800-1700 hr) and evening (1700-2300 hr) acidity of both placebo and the four H2-receptor antagonists was similar. Therefore, in the above doses H2-receptor blockers guarantee overnight anacidity to a similar degree and cause the physiological buffering of daily meals on gastric acidity to be fully exploited. Furthermore, the reducing effect of daily meals on drug action can be prevented. Since strong acid suppression strictly confined to the nocturnal period has been shown to be closely correlated with the highest ulcer healing rates, it is suggested that single low bedtime doses of H2-receptor antagonist should be evaluated in the acute treatment of duodenal ulcer.

Gastric aspiration versus antimony and glass pH electrodes. A simultaneous comparative in vivo study

To carry out a simultaneous comparison of the 24-h in vivo performance of antimony and glass electrodes and the findings of intermittent gastric aspiration, a triple-probe system with closely adjacent tips was positioned in the gastric corpus of 10 subjects representing different clinical and pharmacologic conditions. We showed that pH values measured with the antimony and the glass units were well correlated to those assessed in gastric aspirates (rs = 0.87; b = 1.079; a = -0.33; and rs = 0.85; b = 1.121; a = -0.38, respectively). A proportional correlation (rs = 0.86; b = 0.97; a = 0.02) was also found between the two intraluminal pH measurements. With regard to the error frequency distributions obtained by comparing the three measuring systems two at a time, the pH pairs differed by no more than 1 pH unit in most cases (greater than 90%). It can be concluded that antimony and glass pH electrodes can be used interchangeably in 24-h intragastric acidity studies in man.