The effect of once daily omeprazole and succinic acid (VECAM) vs once daily omeprazole on 24-h intragastric pH.

BACKGROUND: Parietal cell H(+)/K(+) ATPase activation is essential for optimal proton pump inhibitor (PPI) activity. Succinic acid (SA) was shown to induce gastric acid secretion. VECAM is a combination of omeprazole (OMP) and SA. To compare the effect of once daily bedtime dosing of VECAM 40 and VECAM 20 without food vs OMP 20 mg administered before breakfast on gastric acidity. METHODS: Open label, randomized, crossover study enrolling 36 healthy subjects comparing the study treatments at steady state for 24 h intragastric pH monitoring. KEY RESULTS: The median percent time intragastric pH > 4 demonstrated that VECAM 40 was superior to VECAM 20 (65.7%vs 49.1%P < 0.0001) and OMP 20 mg (65.7%vs 47.6%P = 0.005) during 24 h. VECAM 40 was superior to VECAM 20 (52.8%vs 38.8%P = 0.0079) and OMP 20 mg (52.8%vs 27.2%P < 0.0001), and VECAM 20 was superior to OMP 20 mg (38.8 vs 27.2 P = 0.0069) during the nighttime. VECAM 20 and OMP 20 mg were comparable during 24 h. CONCLUSIONS & INFERENCES: VECAM 40 and VECAM 20 were significantly better in maintaining intragastric pH > 4 during the nighttime than OMP 20 mg. Succinic acid eliminates the need for a subsequent meal for intragastric pH control by VECAM.

Oral pantoprazole in the form of granules or tablets are pharmacodynamically equivalent in suppressing acid output in patients with gastro-oesophageal reflux disease and a history of erosive oesophagitis.

AIM: To demonstrate the pharmacodynamic comparability between oral 40 mg pantoprazole delayed-release granules and tablets. METHODS: This was a multicentre, randomized, open-label, 2-period, 2-sequence, 9-week crossover study in patients aged 18-65 years with gastro-oesophageal reflux disease and documented erosive oesophagitis. The primary endpoint was a comparison of the inhibition of pentagastrin-stimulated maximum acid output (MAO) at steady state after once daily dosing for 1 week and 23 h after the last dose of pantoprazole granules and tablets. Basal acid output was measured prior to MAO. Standard safety evaluations were performed. The one-sided t-test was used to test the null hypothesis that granules - 1.2 x tablet >/= 0 against the alternative hypothesis that this difference was <0 for both MAO and basal acid output values. RESULTS: Sixty patients completed the study. The mean MAO values were 7.11 +/- 4.98 and 7.29 +/- 4.77 mmol/h, while the mean basal acid output values were 0.74 +/- 0.91 and 0.58 +/- 0.63 mmol/h for the granules and tablets, respectively. The two formulations were shown statistically to be pharmacodynamically equivalent in suppressing MAO (P = 0.006), safe and well tolerated. CONCLUSION: Patients with gastro-oesophageal reflux disease who are unable to swallow the tablet may safely be prescribed the pantoprazole sodium granules.

Comparison of the effects of immediate-release omeprazole oral suspension, delayed-release lansoprazole capsules and delayed-release esomeprazole capsules on nocturnal gastric acidity after bedtime dosing in patients with night-time GERD symptoms.

BACKGROUND: Gastro-oesophageal reflux disease (GERD) patients on proton pump inhibitors before breakfast or dinner have acid recovery at night. Bedtime immediate-release omeprazole (IR-OME) demonstrated better control of nocturnal pH than pantoprazole before dinner. AIM: To compare repeated once daily bedtime dosing of IR-OME, lansoprazole and esomeprazole on nocturnal gastric acidity. METHODS: Open-label, randomized, crossover study enrolling 54 patients with nocturnal GERD symptoms comparing IR-OME, lansoprazole and esomeprazole at steady state for nocturnal acid breakthrough (NAB), percentage of time with gastric pH > 4 and median gastric pH. RESULTS: Onset of nocturnal acid control with IR-OME was rapid. During the first half of the night, percentage of time with gastric pH > 4 and median gastric pH were significantly higher after IR-OME compared to esomeprazole or lansoprazole (P < 0.001, both comparisons). Over the 8-h night-time period, acid control with IR-OME was significantly better than lansoprazole (P < 0.001), and comparable to esomeprazole. IR-OME reduced NAB compared with esomeprazole and lansoprazole (61% vs. 92% and 92%; P < 0.001, both comparisons). CONCLUSIONS: Bedtime IR-OME provided more rapid control of night-time gastric pH and decreased NAB compared with esomeprazole and lansoprazole. Nocturnal acid control with IR-OME was superior to lansoprazole and comparable to esomeprazole. Bedtime dosing with IR-OME may be effective for patients with night-time heartburn.

A role for guanylate cyclase C in acid-stimulated duodenal mucosal bicarbonate secretion.

Luminal acidification provides the strongest physiological stimulus for duodenal HCO3- secretion. Various neurohumoral mechanisms are believed to play a role in acid-stimulated HCO3- secretion. Previous studies in the rat and human duodenum have shown that guanylin and Escherichia coli heat-stable toxin, both ligands of the transmembrane guanylyl cyclase receptor [guanylate cyclase C (GC-C)], are potent stimulators for duodenal HCO3- secretion. We postulated that the GC-C receptor plays an important role in acid-stimulated HCO3- secretion. In vivo perfusion studies performed in wild-type (WT) and GC-C knockout (KO) mice indicated that acid-stimulated duodenal HCO3- secretion was significantly decreased in the GC-C KO animals compared with the WT counterparts. Pretreatment with PD-98059, an MEK inhibitor, resulted in attenuation of duodenal HCO3- secretion in response to acid stimulation in the WT mice with no further effect in the KO mice. In vitro cGMP generation studies demonstrated a significant and comparable increase in cGMP levels on acid exposure in the duodenum of both WT and KO mice. In addition, a rapid, time-dependent phosphorylation of ERK was observed with acid exposure in the duodenum of WT mice, whereas a marked attenuation in ERK phosphorylation was observed in the KO animals despite equivalent levels of ERK in both groups of animals. On the basis of these studies, we conclude that transmembrane GC-C is a key mediator of acid-stimulated duodenal HCO3- secretion. Furthermore, ERK phosphorylation may be an important intracellular mediator of duodenal HCO3- secretion.

Synthesis or rupture: duration of acid inhibition by proton pump inhibitors.

Insight has been gained into the relationship between the structure of proton pump inhibitors (PPIs), their binding, and their suppression of acid secretion. PPIs accumulate in the acidic space of the secreting parietal cell, where then their active forms create disulfide bonds with key cysteines of the H(+), K(+)-ATPase. Studies in humans on the half-lives of recovery of acid secretion have found that while lansoprazole showed a half-life of less than 15 h, and both omeprazole and rabeprazole showed one of less than 30 h, for pantoprazole the half-life was approximately 46 h. This difference in duration of inhibition with PPIs may be related to variations in proton pump inhibitor dwell time. A study in rats suggests that the recovery of gastric pump activity after treatment with omeprazole, esomeprazole, lansoprazole and rabeprazole is likely due to both reversal of binding by disulfide-reducing agents and to pump synthesis. However, for pantoprazole, reversal of acid inhibition is probably due mainly to de novo pump synthesis and not loss of binding. This profile is likely related to the unique binding of pantoprazole to cysteine 822, a binding site which is buried deep within the membrane domain of the pump and may therefore be inaccessible to reducing agents. Although clinical data supporting these findings are limited, prolonged binding of pantoprazole may confer a longer duration of action in comparison with other PPIs.

Human duodenal mucosal brush border Na(+)/H(+) exchangers NHE2 and NHE3 alter net bicarbonate movement.

The proximal duodenal mucosa secretes HCO that serves to protect the epithelium from injury. In isolated human duodenal enterocytes in vitro, multiple luminal membrane proteins are involved in acid/base transport. We postulated that one or more isoforms of the Na(+)/H(+) exchanger (NHE) family is located on the apical surface of human duodenal mucosal epithelial cells and thereby contributes to duodenal mucosal HCO transport. Duodenal biopsies were obtained from human volunteers, and the presence of NHE2 and NHE3 was determined by using previously characterized polyclonal antibodies (Ab 597 for NHE2 and Ab 1381 for NHE3). In addition, proximal duodenal mucosal HCO(3)(-) transport was measured in humans in vivo in response to luminal perfusion of graded doses of amiloride; 10(-5)--10(-4) M amiloride was used to inhibit NHE2 and 10(-3) M amiloride to inhibit NHE3. Both NHE2 and NHE3 were localized principally to the brush border of duodenal villus cells. Sequential doses of amiloride resulted in significant, step-wise increases in net duodenal HCO(3)(-) output. Inhibition of NHE2 with 10(-5) M and 10(-4) M amiloride significantly increased net HCO(3)(-) output. Moreover, there was an additional, equivalent increase (P < 0.05) in duodenal HCO(3)(-) output with 10(-3) M amiloride, which inhibited NHE3. We conclude that 1) NHE2 and NHE3 are localized principally to the brush border of human duodenal villus epithelial cells; 2) sequential inhibition of NHE2 and NHE3 isoforms resulted in step-wise increases in net HCO(3)(-) output; 3) NHE2 and NHE3 participate in human duodenal villus cell HCO(3)(-) transport; and 4) the contribution of NHE-related transport events should be considered when studying duodenal HCO(3)(-) transport processes.

Identification of transport abnormalities in duodenal mucosa and duodenal enterocytes from patients with cystic fibrosis.

BACKGROUND & AIMS: The duodenum is a cystic fibrosis transmembrane conductance regulator (CFTR)-expressing epithelium with high bicarbonate secretory capacity. We aimed to define the role of CFTR in human duodenal epithelial bicarbonate secretion in normal (NL) subjects and patients with cystic fibrosis (CF). METHODS: Endoscopic biopsy specimens of the duodenal bulb were obtained from 9 CF patients and 16 volunteers. Tissues were mounted in modified Ussing chambers. Bicarbonate secretion and short-circuit current (Isc) were quantitated under basal conditions and in response to dibutyryl adenosine 3',5'-cyclic monophosphate (db-cAMP), carbachol, and the heat-stable toxin of Escherichia coli (STa). Duodenocytes were also isolated and loaded with the pH-sensitive fluoroprobe BCECF/AM, and intracellular pH (pH(i)) was measured at rest and after intracellular acidification and alkalinization. RESULTS: Basal HCO(3)(-) secretion and Isc were significantly lower in the CF vs. NL duodenal mucosa. In contrast to NL, db-cAMP failed to alter either HCO(3)(-) or Isc in CF tissues. However, in CF, carbachol resulted in an electroneutral HCO(3)(-) secretion, whereas STa induced electrogenic HCO(3)(-) secretion that was similar to NL. In CF and NL duodenocytes, basal pH(i) and recovery from an acid load were comparable, but pH(i) recovery after an alkaline load in CF duodenocytes was Cl(-) dependent, whereas in NL duodenocytes it was Cl(-) independent. CONCLUSIONS: These findings implicate CFTR in NL duodenal alkaline transport and its absence in CF. Although duodenal bicarbonate secretion is impaired in CF tissues, alternate pathway(s) likely exist that can be activated by carbachol and STa.

Oral and intravenous dosage forms of pantoprazole are equivalent in their ability to suppress gastric acid secretion in patients with gastroesophageal reflux disease.

OBJECTIVE: The aim of this study was to assess the ability of pantoprazole to maintain gastric acid suppression in patients with gastroesophageal reflux disease who are switched from an oral (p.o.) to an intravenous (i.v.) dosage form. METHODS: A total of 65 patients with gastroesophageal reflux disease were administered either 40 or 20 mg of p.o. pantoprazole daily for 10 days, then were switched to either a matching dose of i.v. pantoprazole or to placebo for 7 days. Acid output (basal and maximal) was measured at the end of the p.o. treatment period and on the first and last days of i.v. therapy. In the primary efficacy analysis, the acid output values at the end of the p.o. pantoprazole treatment were compared with those at the end of the i.v. treatment. Safety was monitored by periodic vital sign measurements, clinical laboratory evaluations, ophthalmic examinations, electrocardiograms, and reports of adverse events. The data were tested by an analysis of covariance and by Wilcoxon signed rank and t tests. RESULTS: Maximal acid output (mean +/- SD) in the 40 mg and 20 mg pantoprazole group after p.o. treatment was 6.5 +/- 5.6 mEq/h and 14.5 +/- 15.5 mEq/h, respectively; whereas, at the end of the i.v. treatment period, the values were 6.6 +/- 6.3 mEq/h and 11.1 +/- 10.2 mEq/h, respectively. In patients given i.v. placebo, acid output was significantly (p < 0.05) increased to 29.2 +/- 13.0 mEq/h by day 7. Both p.o. and i.v. pantoprazole dosage forms had similar favorable safety and tolerability profiles. CONCLUSIONS: The p.o. and i.v. formulations of pantoprazole (40 and 20 mg) are equivalent in their ability to suppress gastric acid output. The i.v. form of pantoprazole offers an alternative for gastroesophageal reflux disease patients who are unable to take the p.o. formulation.

Utility of endoscopic biopsy samples to quantitate human duodenal ion transport.

Duodenal mucosal bicarbonate secretion (DMBS) prevents acid-peptic damage and facilitates nutrient absorption. DMBS is diminished in patients with duodenal ulcers and is normalized after Helicobacter pylori eradication. The measurement of DMBS in human patients in vivo requires intubation with a multi-lumen balloon tube and permits limited testing with putative agonists and antagonists. Our purpose was to develop a means to investigate transport events in human duodenal biopsy samples in vitro. After validation studies in a modified mini-Ussing chamber were performed, duodenal transport events were examined in proximal endoscopic biopsy samples from normal volunteers (n = 17). Tissues were mounted in modified mini-Ussing chambers (volume 2.5 ml, surface area 3.8 mm2). Short circuit current (Isc), potential difference (PD), and bicarbonate secretion were determined under basal conditions and after stimulation with graded doses of prostaglandin E2 (PGE2)(10(-8) to 10(-4) mol/L) and dibutyryl cAMP (db-cAMP)(10(-4) to 10(-2) mol/L). Duodenal tissues remained viable for at least 2 hours and exhibited stable basal HCO3(-) secretion and electrical parameters. Stimulation with PGE2 and db-cAMP resulted in dose-related increases in both Isc and HCO3(-) secretion (P < .05) that were abolished by ouabain and anoxia. It is concluded (1) that human duodenal bulb biopsy samples maintain their inherent transport function in mini-Ussing chambers and (2) that by using this novel method it will be possible to define the transport events that modulate human duodenal secretion, in particular bicarbonate secretion, in both health and disease.

Human proximal duodenal alkaline secretion is mediated by Cl-/HCO3- exchange and HCO3- conductance.

The proximal duodenal epithelium secretes bicarbonate into an adherent mucus layer, thereby protecting the mucosa from injury by gastric acid and pepsin. While bicarbonate secretion is stimulated and inhibited by a number of agonists and antagonists, the apical anion transport pathways have not been addressed fully. The objective was to assess if apical Cl-/HCO3- exchange and Cl-:HCO3- conductance are involved in duodenal mucosal bicarbonate secretion (DMBS). In healthy volunteers, the proximal 4 cm of duodenum was isolated, perfused with either saline or 4,4'-diisothiocyano-2,2'-disulfonic acid (DIDS), and bicarbonate secretion and transepithelial potential difference (PD) were stimulated by either PGE2 or the phosphodiesterase inhibitor theophylline to increase cyclic AMP. Luminal DIDS abolished PGE2-stimulated DMBS, yet had no effect on the increase in PD and failed to significantly alter theophylline-induced DMBS and PD. Therefore, in human proximal duodenum, it appears that PGE2 and cAMP activate distinct HCO3- transport pathways likely involving a DIDS-sensitive Cl-/HCO3- exchanger and DIDS-insensitive HCO3- conductance.

Metabolic profiles of montelukast sodium (Singulair), a potent cysteinyl leukotriene1 receptor antagonist, in human plasma and bile.

Montelukast sodium [1-([(1(R)-(3-(2-(7-chloro-2-quinolinyl)-(E)- ethenyl)phenyl)-3-(2-(1-hydroxy-1-methylethyl)phenyl)propyl)thio]methyl)cyclopropylacetic acid sodium salt] (MK-476, Singulair) is a potent and selective antagonist of the cysteinyl leukotriene (Cys-LT1) receptor and is under investigation for the treatment of bronchial asthma. To assess the metabolism and excretion of montelukast, six healthy subjects received single oral doses of 102 mg of [14C]montelukast, and the urine and feces were collected. Most of the radioactivity was recovered in feces, with