Pantoprazole. A review of its pharmacological properties and therapeutic use in acid-related disorders

Proton pump inhibitors and acute interstitial nephritis

BACKGROUND & AIMS

Proton pump inhibitors (PPIs) are a widely prescribed class of drugs, and their usage worldwide is increasing. Although well-tolerated, there have been case reports and a recent case series implicating these drugs in acute interstitial nephritis (AIN) and progression to acute renal failure (ARF). The aim of this study was to investigate how widespread this complication is in Australia, to identify which PPIs are implicated, and to establish whether PPI-induced AIN is a class effect.

METHODS

We undertook a retrospective case review of potential cases at 2 teaching hospitals and a review of registry data from the Therapeutic Goods Administration of Australia (TGA). Parameters sought included the drug implicated, concurrent medications, symptoms, signs, serum creatinine, and time of onset after prescription.

RESULTS

We identified 18 cases of biopsy-proven PPI-induced AIN causing ARF in the retrospective case review, which is the largest hospital-based case series to date. The TGA registry data identified an additional 31 cases of "biopsy proven interstitial nephritis." An additional 10 cases of "suspected interstitial nephritis," 20 cases of "unclassified acute renal failure," and 26 cases of "renal impairment" were also identified. All 5 commercially available PPIs were implicated in these cases.

CONCLUSION

With the ever more widespread use of this class of medications, PPI-induced AIN is likely to become more frequent. There is now evidence to incriminate all the commercially available PPIs, suggesting there is a class effect. Failure to recognize this entity might have catastrophic long-term consequences including chronic kidney disease. Increased awareness might facilitate more rapid diagnosis and management of this potentially reversible condition.

Preparation, characterization, and in vivo anti-ulcer evaluation of pantoprazole-loaded microparticles

Pantoprazole is an important drug in the treatment of acid-related disorders. This work concerns the preparation and characterization of gastro-resistant pantoprazole-loaded microparticles prepared using an O/O emulsification/solvent evaporation technique. The in vivo activity of the pantoprazole-loaded Eudragit S100 microparticles was carried out in rats. Furthermore, tablets containing the microparticles were also investigated. Microparticles presented spherical and smooth morphologies (SEM) and they remained intact in the inner surface of tablets. DSC and IR analyses showed that pantoprazole was physically and molecularly dispersed in the polymer. In vivo anti-ulcer evaluation showed that the microparticles were able to protect rat stomachs against ulcer formation, while the drug aqueous solution did not present activity. Drug dissolution profiles from tablets demonstrated slower release than untabletted microparticles. Weibull equation was the best model for describing the drug release profiles from microparticles and tablets. As regards the acid protection, tablets showed a satisfactory drug protection in acid medium (61.05 +/- 8.09% after 30 min).

Hydroxyl radical scavenging reactivity of proton pump inhibitors

In addition to the established control of acid secretion of the class of proton pump inhibitors (PPI) reactivity from the pyridyl methyl sulphinyl benzimidazole type a second independent anti-inflammatory reactivity was observed in vitro. This inhibitory reactivity was clearly noticed using three different assays where the aggressive hydroxyl radicals were successfully trapped in a concentration dependent manner. There is unequivocal evidence that the proton pump inhibitors having the sulphoxide group are able to scavenge hydroxyl radicals which are generated during a Fenton reaction. By way of contrast, the corresponding thioethers were substantially less active. No detectable effect was seen in the superoxide radical scavenging system. In conclusion, pantoprazole as well as the other proton pump inhibitors have a pronounced inhibitory reactivity towards hydroxyl radicals.

Pharmacodynamic comparison of pantoprazole enantiomers: inhibition of acid-related lesions and acid secretion in rats and guinea-pigs

Pantoprazole is an irreversible proton pump inhibitor that is administered as a racemic mixture clinically. The effects of pantoprazole sodium (PAN.Na) enantiomers on acid-related lesions were compared using models of pylorus ligation induced ulcer, histamine induced ulcer and reflux oesophagitis in rats and guinea-pigs. Compared with (+)-PAN.Na and (+/-)-PAN.Na, (-)-PAN.Na showed much stronger inhibitory effects on pylorus ligation induced and histamine induced ulcers, but similar effects on reflux oesophagitis. The doses of (-)-PAN.Na, (+)-PAN.Na and (+/-)-PAN.Na required for 50% inhibition (ID50) of acid-related lesions were 1.28, 5.03 and 3.40 mg kg(-1) against pylorus ligation induced ulcer, 1.20, 4.28 and 3.15 mg kg(-1) against histamine induced ulcer, and 2.92, 3.56 and 3.70 mg kg(-1) against reflux oesophagitis, respectively. The inhibitory effects of PAN.Na enantiomers on basal gastric acid output were compared in rats with acute fistula. In contrast to inhibitory rates of 89.3% and 83.6% on gastric acid output by (-)-PAN.Na and (+/-)-PAN.Na at 1.5 mg kg(-1), (+)-PAN.Na had an inhibitory rate of only 24.7% at the same dose. The above results indicate that (-)-PAN.Na is more potent than (+)-PAN.Na at inhibiting acid-related lesions owing to its stronger inhibition of acid secretion.

Selective induction of apoptosis with proton pump inhibitor in gastric cancer cells

PURPOSE

To survive in an ischemic microenvironment with a lower extracellular pH, ability to up-regulate proton extrusion is critical for cancer cell survival. Gastric H+/K(+)-ATPase exchanges luminal K+ for cytoplasmic H+ and is the enzyme primarily responsible for gastric acidification. On the basis of the fact that blocking the clearance of acidic metabolites are known to induce the cell death, we hypothesized that pantoprazole (PPZ), one of gastric H+/K(+)-ATPase inhibitors used frequently to treat acid-related diseases, could inhibit growth of tumor cells.

EXPERIMENTAL DESIGN

Genomic DNA fragmentation, terminal deoxynucleotidyl transferase (Tdt)-mediated nick end labeling assay, and annexin V staining were performed to detect PPZ-induced apoptosis. Mitogen-activated protein kinase activation and heat shock proteins expression were determined by immunoblot with specific antibodies. The antitumor effect of PPZ was evaluated in vivo by a xenograft model of nude mice.

RESULTS

After PPZ treatment, apoptotic cell death was seen selectively in cancer cells and was accompanied with extracellular signal-regulated kinase deactivation. By contrast, normal gastric mucosal cells showed the resistance to PPZ-induced apoptosis through the overexpression of antiapoptotic regulators including HSP70 and HSP27. In a xenograft model of nude mice, administration of PPZ significantly inhibited tumorigenesis and induced large-scale apoptosis of tumor cells.

CONCLUSIONS

PPZ selectively induced in vivo and in vitro apoptotic cell death in gastric cancer, suggesting that proton pump inhibitors could be used for selective anticancer effects.

Pharmacokinetic Differences between Pantoprazole Enantiomers in Rats

PURPOSE

The purpose of this study was to quantitatively clarify the contribution of the absorption, protein binding, and metabolism of cytochrome P450 enzymes to the enantioselective pharmacokinetics of pantoprazole enantiomers in rats.

METHODS

The enantioselective pharmacokinetics of pantoprazole enantiomers was estimated by an oral administration of racemic pantoprazole to rats. The pharmacokinetic differences between pantoprazole enantiomers were evaluated by the experiments of the in situ perfusion into rat small intestine, the protein binding, and the in vitro metabolism in rat liver microsomes of pantoprazole enantiomers.

RESULTS

The mean area under the curve value of S-pantoprazole was 1.5 times greater than that of R-pantoprazole after administration of racemic pantoprazole to rats (20 mg/kg, p.o.). There were significant differences in k(e) (p < 0.05), t1/2 (p < 0.01), and mean residence time (p < 0.01) values between the two enantiomers. In the in situ absorption study, the absorption rate constants were of no significant differences between the two enantiomers. The mean unbound fraction of R-pantoprazole was slightly greater than that of S-pantoprazole. The intrinsic clearance (CLint) of the formation of the 5'-O-demethyl metabolite from S-pantoprazole was 4-fold lower than that from R-pantoprazole. However, the CLint value for the sulfone and 6-hydroxy metabolites from S-pantoprazole was higher than that from R-pantoprazole. The sum of the CLint of the formation of all three metabolites was 3.06 and 4.82 mL/min/mg protein for S- and R-pantoprazole, respectively.

CONCLUSIONS

This study suggests that the enantioselective pharmacokinetics of pantoprazole enantiomers in rats is probably ascribable to their enantioselective metabolism, which is contributed by all the three metabolic pathways, including sulfoxide oxidation, 4'-O-demethylation, and 6-hydroxylation.

Pharmacokinetics of proton pump inhibitors in children

The use of proton pump inhibitors (PPIs) has become widespread in children and infants for the management of paediatric acid-related disease. Pharmacokinetic profiles of only omeprazole and lansoprazole have been well characterised in children over 2 years of age with acid-related diseases. Few data have been recently published regarding the pharmacokinetics of pantoprazole in children, and none are available for rabeprazole or esomeprazole. The metabolism of PPI enantiomers has never been studied in the paediatric population. A one-compartment model best describes the pharmacokinetic behaviour of omeprazole, lansoprazole and pantoprazole in children, with important interindividual variability for each pharmacokinetic parameter. Like adults, PPIs are rapidly absorbed in children following oral administration; the mean time to reach maximum plasma concentration varies from 1 to 3 hours. Since these agents are acid labile, their oral formulations consist of capsules containing enteric-coated granules. No liquid formulation is available for any of the PPIs. Thus, for those patients unable to swallow capsules, extemporaneous liquid preparations for omeprazole and lansoprazole have been reported; however, neither the absolute nor the relative bioavailabilities of these oral formulations have been studied in children. Intravenous formulations are available for omeprazole (in Europe), lansoprazole and pantoprazole. PPIs are rapidly metabolised in children, with short elimination half-lives of around 1 hour, similar to that reported for adults. All PPIs are extensively metabolised by the liver, primarily by cytochrome P450 (CYP) isoforms CYP2C19 and CYP3A4, to inactive metabolites, with little unchanged drug excreted in the urine. Similar to that seen in adults, the absolute bioavailability of omeprazole increases with repeated dosing in children; this phenomenon is thought to be due to a combination of decreased first-pass elimination and reduced systemic clearance. The apparent clearance (CL/F) of omeprazole, lansoprazole and pantoprazole appears to be faster for children than for adults. A higher metabolic capacity in children as well as differences in the extent of PPI bioavailability are most likely responsible for this finding. This may partly account for the need in children for variable and sometimes considerably greater doses of PPIs, on a per kilogram basis, than for adults to achieve similar plasma concentrations. Furthermore, no studies have been able to demonstrate a statistically significant correlation between age and pharmacokinetic parameters among children. Despite the small number of very young infants studied, there is some evidence for reduced PPI metabolism in newborns. The limited paediatric data regarding the impact of CYP2C19 genetic polymorphism on PPI metabolism are similar to those reported for adults, with poor metabolisers having 6- to 10-fold higher area under the concentration-time curve values compared with extensive metabolisers. Finally, because a pharmacokinetic/pharmacodynamic relationship exists for PPIs, the significant interindividual variability in their disposition may partly explain the wide range of therapeutic doses used in children. Further studies are needed to better define the pharmacokinetics of PPIs in children <2 years of age.

Metabolism of pantoprazole involving conjugation with glutathione in rats

We have investigated the metabolism of pantoprazole and have provided an explanation for the formation mechanism of its metabolites. Metabolites found in the urine of rats after oral administration of pantoprazole sodium (25 mg kg(-1)) were analysed by liquid chromatography/ion trap mass spectrometry (LC/MS(n)). The N -acetylcysteine derivatives of benzimidazole (M1) and pyridine (M2), four pyridine-related metabolites (M3-M6), and three benzimidazole-related metabolites (M7-M9) were found, none of which had been reported previously. Five of the metabolites (M1, M2, M3, M7, and M8) were isolated from the urine of rats after oral administration of pantoprazole sodium by semipreparative HPLC. Structures of these metabolites were identified by a combination analysis of LC/MS(n) and (1)H NMR spectra. Structures of the remaining four metabolites (M4, M5, M6, and M9) were tentatively assigned through LC/MS(n). The metabolites M2, M3, M4, M5 and M6 and the other metabolites (M1, M7, M8, and M9) reflected the fate of the pyridine moiety and the benzimidazole moiety, respectively. The proposed formation route of M3-M6 was via initial reduction to mercaptopyridine followed by S-methylation, O-demethylation, and S-oxidation to the corresponding sulfoxide or sulfone. Meanwhile, M8 and M9 were formed via initial reduction to the 5-difluoromethoxy-1H benzoimidazole-2-thiol (M7) followed by hydroxylation and S-methylation. The metabolism of pantoprazole included an attack by glutathione on the benzimidazole-2-carbon and pyridine-7'-carbon. It is an important metabolic pathway of pantoprazole in rats.

Comparison of efficacy of pantoprazole alone versus pantoprazole plus mosapride in therapy of gastroesophageal reflux disease: a randomized trial

The present study aimed to compare the efficacy for the therapy of GERD of pantoprazole alone with a combination of pantoprazole and mosapride. The study was a prospective, randomized trial involving 68 patients suffering heartburn and/or regurgitation at least twice a week for 6 weeks. Sixty-one patients consented to be randomized to receive either pantoprazole 40 mg b.i.d. (n = 33, group A) or pantoprazole 40 mg b.i.d. plus mosapride 5 mg t.d.s. (n = 28, group B) for 8 weeks. Twenty-four-hour esophageal pH-metry and endoscopy were conducted at recruitment and endoscopy was repeated at 8 weeks in all the patients studied. There were no differences in symptomatic responses to therapy between the groups (69.7% vs 89.2%; P = 0.11). The mean symptom score after 8 weeks was significantly lower in group B (3.78 +/- 3.62 vs 1.67 +/- 2.09; P = 0.009). Nonerosive esophagitis was present in 29 patients. In patients with nonerosive GERD there was no significant difference in symptomatic response to either regimen (17/20 in group A and 7/9 in group B responded; P = 0.63). In erosive esophagitis, symptomatic responses occurred more frequently in group B, 18/19 (94.7%), than in group A, 6/13 (46.2%; P = 0.003). However endoscopic healing of esophagitis occurred equally with either regimen (6/11, 54.5% in group A; 12/17, 70.5% in group B; P = 0.44). In nonerosive GERD, the addition of mosapride offers no benefit over pantoprazole alone. A combination of pantoprazole and mosapride is more effective than pantoprazole alone in providing symptomatic relief to patients with erosive GERD.

Review article: the pharmacodynamics and pharmacokinetics of proton pump inhibitors--overview and clinical implications

During the past two decades, enormous changes occurred in the management of gastric acid-related diseases. First, the histamine2-receptor antagonists were introduced, offering patients the first single-agent therapy that effectively reduced gastric acid secretion. Proton pump inhibitors became widely available in the early 1990s, and they generally appeared to be superior to the histamine2-receptor antagonists in acid-suppressing activity, symptom control and healing. Most physicians now use proton pump inhibitors as first-line treatment for many patients with acid-peptic disorders, including erosive gastro-oesophageal reflux disease (GERD), nonerosive reflux disease (NERD) and duodenal and gastric ulcers. Although proton pump inhibitors are often thought to be interchangeable, some differences have emerged in their pharmacological properties, which may be reflected in some aspects of clinical efficacy. Such differences include potency, speed of onset and duration of pH 'holding times'. Helicobacter pylori has now been recognized as an important factor in the pathogenesis of acid-peptic disorders. It is clear that H. pylori eradication can dramatically reduce the chronicity of gastric and duodenal ulcers, and accepted therapeutic regimens for H. pylori eradication now include proton pump inhibitors and two or more antibiotics. Although all accepted proton pump inhibitor-based 'triple therapies' are roughly equivalent in efficacy, there is now a shortened regimen available that will potentially enhance compliance and decrease cost. This review examines the relative advantages of proton pump inhibitors vs. histamine2-receptor antagonists in the context of acid suppression and in various gastric acid-related diseases. A brief overview presents the pharmacodynamics and pharmacokinetics of the proton pump inhibitors with particular attention paid to rabeprazole, one of the newer drugs in its class.

Progress with novel pharmacological strategies for gastro-oesophageal reflux disease

Gastro-oesophageal reflux disease (GORD) is a chronic disorder characterised by an increased exposure of the oesophagus to intragastric contents. Currently, GORD symptoms are maintained under control with antisecretory agents, mainly gastric proton pump inhibitors (PPIs). Although impaired oesophageal motility may partly underlie the pathophysiology of GORD, the use of prokinetic agents has been found to be unsatisfactory. To date, novel pharmacological approaches for GORD are mainly related to the control of transient lower oesophageal sphincter (LOS) relaxations (TLOSRs). The majority of patients with GORD have reflux episodes during TLOSRs, which are evoked by gastric distension, mainly occurring after ingestion of a meal. Patients with reflux disease with normal peristalsis and without or with mild erosive disease could potentially benefit from anti-TLOSR therapy. This therapy might also be of value to treat some severe forms of esophagitis in combination with PPIs. GABA-B-receptor agonists are the most promising class of agents identified so far for TLOSR control. The GABA-B-receptor agonist, baclofen, is the most effective compound in inhibiting TLOSRs in humans. Since baclofen has several CNS adverse effects, novel orally available GABA-B agonists are needed for effective and well tolerated treatment of GORD. Endogenous or exogenous cholecystokinin (CCK) causes a reduction in LOS pressure, an increase in TLOSR frequency and a reduction in gastric emptying. In healthy volunteers and patients with GORD, loxiglumide, a selective CCK1-receptor antagonist, was found to reduce the rate of TLOSRs, although its effect on postprandial acid reflux may be modest. Orally effective CCK antagonists are not marketed to date. The anticholinergic agent atropine, given to healthy volunteers and patients with GORD, markedly reduced the rate of TLOSRs. Because of severe gastrointestinal (and other) adverse effects of anticholinergics, including worsening of supine acid clearance and constipation, it is unlikely that this class of drugs will have a future as anti-TLOSR agents on a routine basis. In spite of their effectiveness in reducing TLOSR rate, untoward adverse effects, such as addiction and severe constipation, currently limit the use of morphine and other opioid mu-receptor agonists. The same applies to nitric oxide synthase inhibitors, which are associated with marked gastrointestinal, cardiovascular, urinary and respiratory adverse effects. Animal studies provide promising evidence for the use of cannabinoid receptor 1 agonists, by showing potent inhibition of TLOSRs in the dog, thus opening a new route for clinical investigation in humans. A better understanding of TLOSR pathophysiology is a necessary step for the further development of novel drugs effective for anti-reflux therapy.

Pharmacokinetic and pharmacodynamic evaluation of a novel proton pump inhibitor, YH1885, in healthy volunteers

To evaluate the pharmacokinetic and pharmacodynamic characteristics of YH1885, a novel proton pump inhibitor, a single-blind, randomized, placebo-controlled, dose-rising, parallel-group study was conducted in 46 healthy volunteers. The volunteers were randomly allocated to single dose groups of 60 mg, 100 mg, 150 mg, 200 mg, and 300 mg (6 subjects per dose, including 2 placebos) or to multiple-dose groups of 150 mg and 300 mg (once-daily dosing for 7 days; 8 subjects per dose, including 2 placebos). The multiple-dose study was conducted separately after the single-dose study. YH1885 was administered orally after overnight fasting. Serial blood samples, urine samples, and pharmacodynamic measurements were taken. Drug concentrations in plasma and urine were determined by liquid chromatography/mass spectrometry (LC/MS). Pharmacodynamic changes were evaluated by ambulatory intragastric pH monitoring and by serial measurements of serum gastrin concentrations. Assessments of safety and tolerability also were made. Plasma concentrations of YH1885 reached peak levels 1.3 to 2.5 hours after single-dose administration and then declined monoexponentially with a terminal half-life (t(1/2)) of 2.2 to 2.4 hours in dosage groups up to 200 mg in the single-dose study. YH1885 showed linear pharmacokinetic characteristics, and little accumulation occurred after multiple administrations. The parent drug was not detected in urine. Dose-related pharmacological effects were obvious for dose groups of 150 mg and higher in the single-dose study. The mean intragastric pH and the percentage of time at pH>4 were significantly increased. The onset of drug effect was rapid, and maximal effects were observed on the first day of administration during multiple dosing. Serum gastrin levels also showed rapid increases during dosing but with a weak dose-effect relationship. Neither serious nor dose-limiting adverse effects were observed. YH1885 was found to be safe and well tolerated and effectively inhibited acid secretion with dose-dependent increases in intragastric pH. The acid-suppressing efficacy of YH1885 needs to be further evaluated in patients with gastric acid-related diseases.

Acute Interstitial Nephritis Due to Pantoprazole

OBJECTIVE:

To describe what is believed, as of November 4, 2003, to be the first case published in the literature of acute interstitial nephritis (AIN) due to pantoprazole.

CASE SUMMARY:

A 77-year-old white woman presented to the hospital with elevated serum creatinine, oliguria for the past 24 hours, arthralgia, fatigue, fever, and bilateral flank pain. The patient had initiated treatment with oral pantoprazole 40 mg/d for gastroesophageal reflux 2 months prior to admission. After 5 weeks of therapy, she stopped taking pantoprazole due to general malaise. Upon admission, all home medications, including pantoprazole, were reinitiated based on the patient's medication list. Serum creatinine increased to 6.1 mg/dL on day 4 of admission from a baseline of 1.0 mg/dL. Pantoprazole therapy was promptly discontinued, and prednisone 40 mg/d was initiated. Urinalysis revealed eosinophils, and a subsequent renal biopsy confirmed a diagnosis of AIN. The serum creatinine level gradually declined over 2 weeks, and the patient was discharged home with a serum creatinine level of 1.6 mg/dL. The Naranjo probability scale suggests a highly probable relationship between AIN and pantoprazole therapy in this patient.

DISCUSSION:

Drug hypersensitivity reactions are the most common cause of AIN. There have been several reported cases of omeprazole-induced AIN. Although there are very few prospective data on the efficacy of treatment of drug-induced AIN, corticosteroids may have a role in recovery of renal function. Prednisone doses of 1 mg/kg/d have been suggested.

CONCLUSIONS:

Physicians should be aware that drug-induced AIN can be associated with proton-pump inhibitors. Early detection of this rare adverse reaction may prevent acute renal insufficiency.

Pantoprazole based therapies in Helicobacter pylori eradication: a systematic review and meta-analysis

AIM

To perform a systematic review on the efficacy of pantoprazole based therapies in Helicobacter pylori eradication, and to conduct a meta-analysis comparing the efficacy of pantoprazole and other proton pump inhibitors (PPIs) when co-prescribed with antibiotics.

METHODS

Studies evaluating pantoprazole combined with antibiotics were considered. Only randomized clinical trials comparing pantoprazole and other PPIs when co-prescribed with antibiotics, and differing only in the PPI (pantoprazole vs other), were eligible for inclusion in the meta-analysis. Bibliographical searches in several electronic databases, and manual search of abstracts from congresses, were conducted. The percentage (weighted mean) of patients with eradication success was calculated. Meta-analysis was performed combining the odds ratios (ORs) of the individual studies in a global OR.

RESULTS

The mean eradication rate with pantoprazole plus clarithromycin for 14 days was 60%. Cure rates with 7 day pantoprazole based triple regimens were higher: pantoprazole, amoxicillin and clarithromycin (78%); pantoprazole, clarithromycin and nitroimidazole (84%); and pantoprazole, amoxicillin and nitroimidazole (74%). Twelve studies comparing pantoprazole and other PPIs were selected for the meta-analysis, including 534 and 603 patients, respectively. The mean eradication rate for H. pylori using pantoprazole plus antibiotics was 83%, and 81% when other PPIs were used (OR = 1; 95% confidence interval (CI) from 0.61 to 1.64). When sub-analysis was performed, including only studies comparing pantoprazole with omeprazole, or pantoprazole with lansoprazole, differences were also statistically non-significant. The meta-analysis of the six studies prescribing equivalent doses of all PPIs demonstrated similar results with pantoprazole and with other PPIs (OR = 1.07; 95% CI from 0.71 to 1.62), the results being statistically homogeneous.

CONCLUSIONS

Pantoprazole achieves similar cure rates to those of omeprazole and lansoprazole when co-prescribed with antibiotics for the eradication of H. pylori infection.

The effect of intravenous pantoprazole and ranitidine for improving preoperative gastric fluid properties in adults undergoing elective surgery

We studied pantoprazole, a new potent and fast-acting proton pump inhibitor. Its effects on preoperative gastric fluid volume and pH have not yet been determined. In this randomized, controlled trial, we examined the effects of preoperative IV pantoprazole or ranitidine on gastric pH and volume. Ninety patients (ASA status I and II, scheduled for elective surgery) were studied. One hour before surgery, patients in Group I (n = 30) were given IV saline 5 mL, those in Group II (n = 30) were given 40 mg of pantoprazole IV, and those in Group III (n = 30) were given 50 mg of ranitidine IV. A nasogastric tube was inserted immediately after anesthesia induction. Gastric contents were aspirated, and volume and pH were recorded. The pH values determined in Group I were 3.73 +/- 0.82; in Group II, they were 5.30 +/- 1.84; and in Group III, they were 4.80 +/- 1.40. There was no statistical difference between Groups 2 and 3, but there was a significant difference between Group I and Groups 2 and 3 (P < 0.0005). The volume of the gastric contents was 28.67 +/- 10.98 mL in Group I, 15.20 +/- 15.52 mL in Group II, and 7.77 +/- 11.17 mL in Group III. There was no statistical difference between Groups 2 and 3, but there was a statistically significant difference between Group I and Groups 2 and 3 (P < 0.0005). The proportion of patients considered "at risk" of significant lung injury should aspiration occur was 20% of Group I, 10% of Group II, and 3.3% of Group III. When statistically evaluated, there was no difference among groups. We concluded that the administration of IV pantoprazole and ranitidine 1 h before surgery is effective in reducing gastric pH and volume.

IMPLICATIONS

This randomized, controlled trial examined the effects of preoperative IV pantoprazole or ranitidine on gastric pH and volume. We concluded that IV pantoprazole and ranitidine, given 1 h before surgery, are effective in reducing gastric pH and volume.

Square-wave adsorptive cathodic stripping voltammetry of pantoprazole

Adsorption and reduction of pantoprazole were investigated by cyclic and square-wave voltammetry on a hanging mercury drop electrode in Britton-Robinson buffers at pH 2.0-11.0. The reduction process gave rise to a single peak within the entire pH range. Study of the variation of the reduction signal with solution variables such as pH and concentration of pantoprazole and instrumental variables such as accumulation time and potential, frequency, pulse height and pulse amplitude, has resulted in optimization of the reduction signal for analytical purposes. The voltammetric procedure was applied successfully to give a rapid and precise assay of pantoprazole in a tablet dosage form.

Pantoprazole rapidly improves health-related quality of life in patients with heartburn: a prospective, randomized, double blind comparative study with nizatidine

BACKGROUND

Health-related quality of life (HRQoL) is impaired in untreated patients with gastroesophageal reflux disease (GERD). In the absence of an objective marker such as erosions, assessment of treatment efficacy can be based on symptoms and HRQoL.

OBJECTIVE

To evaluate changes in HRQoL during treatment with pantoprazole or nizatidine in patients with GERD.

METHODS

This was a prospective, randomized, double blind Canadian multicenter study. Patients with GERD, characterized by heartburn that had occurred 4 or more times per week for at least 6 months, were treated for 28 days with either pantoprazole 40 mg once daily or nizatidine 150 mg twice daily. HRQoL assessment was performed before endoscopy (baseline) and on days 7 and 28 after treatment. HRQoL was assessed using 4 domains of the SF-36, the SF-12 summary scales and the gastrointestinal system rating scale (GSRS).

RESULTS

A total of 208 patients (n = 106 pantoprazole treatment group, n = 102 nizatidine treatment group) was available for intention-to-treat analysis. Baseline HRQoL scores were comparable between the 2 treatment groups. After 7 days, treatment with pantoprazole led to a statistically significant greater improvement in HRQoL in 2 SF-36 domains: bodily pain (pantoprazole versus nizatidine, P = 0.0088) and vitality (pantoprazole versus nizatidine, P = 0.0137), and in the GSRS reflux score (pantoprazole versus nizatidine, P = 0.0078). After 28 days of treatment, the changes in scores relative to baseline were still greater with pantoprazole than with nizatidine. The improvement in the 4 SF-36 domains and the GSRS reflux score achieved by pantoprazole after 7 days were also significantly greater than those achieved by nizatidine after 28 days.

CONCLUSIONS

HRQoL improves more rapidly and to a greater degree following treatment with pantoprazole than nizatidine. Control of heartburn strongly predicts HRQoL improvement during the acute treatment of GERD. Our data support the approach to use pantoprazole instead of nizatidine as the initial therapy for patients with heartburn in a primary care practice setting.

Intra-oesophageal pH profiles and pharmacokinetics of pantoprazole and esomeprazole: a crossover study in patients with gastro-oesophageal reflux disease

AIM

To compare the effect of pantoprazole and esomeprazole on intra-oesophageal pH and investigate their pharmacokinetics in patients with symptomatic gastro-oesophageal reflux disease (GORD).

METHODS

Double-blind, randomized, two-period crossover study. Caucasian men with symptomatic GORD (n=48) were selected on the basis of clinical records of typical GORD symptoms, confirmed by a pathological reflux time (oesophageal pH<4 for > or =6% of the time). They received oral pantoprazole 40 mg once daily (od) or esomeprazole 40 mg od for seven days. Continuous 24 h oesophageal pH-metry was performed at baseline and day 7. Evaluations included: pre- and post-treatment differences in the percentage of time with pH<4.0 and <3.0 between baseline and day 7; area under the curve (AUC), Cmax, and T(1/2); point estimates and 90% confidence intervals (CI) on days 1 and 7, calculated for ratios of the AUC and Cmax.

RESULTS

Both drugs decreased the mean total number of reflux episodes and reduced the percentage of reflux time within 24 h to <3%. No pathological reflux was detectable after repeated administration of either drug. The 90% CI were within the predefined range at all time points; thus, equivalence of pantoprazole and esomeprazole was concluded. For pantoprazole, Cmax and AUC were unchanged on day 7 vs day 1, confirming its high and constant bioavailability. For esomeprazole, Cmax and AUC were increased on day 7 vs day 1 by 80% and 50%, respectively, indicating low initial bioavailability. No clinically relevant side effects were seen for either drug.

CONCLUSION

Pantoprazole and esomeprazole have equivalent effect on oesophageal pH, since no pathological reflux was detected after treatment with either drug. For esomeprazole, the Cmax and AUC increased after multiple dosing; for pantoprazole the pharmacokinetics were predictable and independent of the number of administered doses.

Treatment of acid-related diseases in the elderly with emphasis on the use of proton pump inhibitors

Proton pump inhibitors (PPIs) have revolutionised the treatment of acid-related disorders, and they have also made it possible to define the spectrum of acid inhibition required for optimal treatment in each disorder. Five PPIs are now available: the older drugs, omeprazole, lansoprazole and pantoprazole, and the two newest, rabeprazole and esomeprazole. These agents have predominantly been developed in the younger adult population, and data for the elderly population are limited. Subtle differences have emerged between the old and the new PPIs in their pharmacokinetic, pharmacodynamic and efficacy profiles. The degree of clinical relevance of these differences in the adult population is in question. However, according to this review, based on the available data for the elderly and by inference from the adult population, the differences are highly relevant in the elderly population. Studies of the pharmacokinetics of older PPIs demonstrated considerable variation in drug clearance that was reflected in a wide range of efficacy related to acid suppression with standard dosages. The newer PPIs offer several advantages over older agents, particularly in terms of rapid, profound and consistent acid inhibition. Consistent acid inhibition is particularly important in the elderly since clinical response is often difficult to judge in this patient group. An individual's cytochrome P450 (CYP) 2C19 genotype predicts the degree of acid suppression and consequently the clinical efficacy of the PPIs. The older PPIs are predominantly metabolised by CYP2C19, with this being of more importance for omeprazole and lansoprazole than pantoprazole. The hepatic metabolism of rabeprazole is predominantly by nonenzymatic reactions and minimally by CYP-mediated reactions, which therefore confers an advantage over older PPIs in that genetic polymorphisms for CYP2C19 do not significantly influence rabeprazole clearance, clinical efficacy or potential for drug interactions. The metabolism of esomeprazole involves CYP2C19 but to a lesser extent than its predecessor omeprazole. Furthermore, esomeprazole has a more rapid onset of action and less variation in clearance rates than omeprazole. Drug clearance decreases with age independently of CYP2C19 status, exaggerating some of the differences between the PPIs and increasing the risk of drug interactions.

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Pantoprazole: an update of its pharmacological properties and therapeutic use in the management of acid-related disorders

Pantoprazole (Protonix) is an irreversible proton pump inhibitor (PPI) that reduces gastric acid secretion. In combination with two antimicrobial agents (most commonly metronidazole, clarithromycin or amoxicillin) for 6-14 days, pantoprazole 40 mg twice daily produced Helicobacter pylori eradication rates of 71-93.8% (intent-to-treat [ITT] or modified ITT analysis) in patients without known antibacterial resistance. Pantoprazole-containing triple therapy was at least as effective as omeprazole- and similar in efficacy to lansoprazole-containing triple therapy in large trials. In the treatment of moderate to severe gastro-oesophageal reflux disease (GORD), oral pantoprazole 40 mg/day was as effective as other PPIs (omeprazole, omeprazole multiple unit pellet system, lansoprazole and esomeprazole) and significantly more effective than histamine H(2)-antagonists. Pantoprazole 20 mg/day provided effective mucosal healing in patients with GORD and mild oesophagitis. Intravenous pantoprazole 40 mg/day can be used in patients who are unable to take oral medication. Oral pantoprazole 20-40 mg/day for up to 24 months prevented relapse in most patients with healed GORD. According to preliminary data, oral pantoprazole 20 or 40 mg/day was effective at healing and preventing non-steroidal anti-inflammatory drug (NSAID)-related ulcers, and intravenous pantoprazole was at least as effective as intravenous ranitidine in preventing ulcer rebleeding after endoscopic haemostasis. Oral or intravenous pantoprazole up to 240 mg/day maintained target acid output levels in most patients with hypersecretory conditions, including Zollinger-Ellison syndrome. Oral and intravenous pantoprazole appear to be well tolerated in patients with acid-related disorders in short- and long-term trials. Tolerability with oral pantoprazole was similar to that with other PPIs or histamine H(2)-antagonists in short-term trials. Formal drug interaction studies have not revealed any clinically significant interactions between pantoprazole and other agents. In conclusion, pantoprazole is an effective agent in the management of acid-related disorders. As a component of triple therapy for H. pylori eradication and as monotherapy for the healing of oesophagitis and maintenance of GORD, pantoprazole has shown similar efficacy to other PPIs and greater efficacy than histamine H(2)-antagonists. Limited data suggest that it is also effective in Zollinger-Ellison syndrome and in preventing ulcer rebleeding. Pantoprazole is well tolerated with minimal potential for drug interactions. The availability of pantoprazole as both oral and intravenous formulations provides flexibility when the oral route of administration is not appropriate. Thus, pantoprazole is a valuable alternative to other PPIs in the treatment of acid-related disorders.

Efficacy and safety of oral pantoprazole 20 mg given once daily for reflux esophagitis in children

OBJECTIVES

To investigate the efficacy and safety of oral pantoprazole, 20 mg (0.5 to 1.0 mg/kg/day) once daily for 28 days, in pediatric patients with reflux esophagitis.

METHODS

Patients in this study (n = 15; 6 to 13 years old, 9 boys) had reflux esophagitis grade Ic or II (Vandenplas classification). The efficacy of pantoprazole to reduce esophageal acid exposure time (pH < 4), reduce the number and duration of reflux episodes, and to increase the percentage of time with gastric pH > 3 was assessed by continuous 24-hour pH monitoring. The intensity of 5 common symptoms of esophagitis was scored before and after treatment on a 4-point scale. Esophagitis was assessed at baseline and after treatment by visual inspection and by the histology of biopsies from the distal third of the esophagus.

RESULTS

Before treatment, the median percentage of time with intra-esophageal pH <4 was 9.3%. After 28 days of therapy with pantoprazole, this value decreased to 2.7% (P = 0.0006). The median percentage of time with intragastric pH > 3 increased from 21% at baseline to 39% on day 28 of therapy (P = 0.005). After 28 days of treatment, all patients experienced at least partial relief from reflux symptoms. Endoscopically confirmed healing of esophagitis was seen in 47% of children (Savary-Miller classification). Histologic evidence of healing was not observed. Median serum gastrin levels were slightly elevated over baseline levels (from 74 pg/ml to 93 pg/ml). In one patient there was a transient elevation of serum GOT and GPT during treatment.

CONCLUSIONS

Oral pantoprazole 20 mg daily provided gastric acid control in 15 pediatric patients with reflux esophagitis with partial clinical improvement of symptoms after 28 days of treatment. Pantoprazole was safe and well tolerated.

Pantoprazole maintenance therapy prevents relapse of erosive oesophagitis

OBJECTIVES

To compare the safety and efficacy of pantoprazole with ranitidine for the maintenance of endoscopically documented healed (grade 0 or 1) erosive oesophagitis.

METHODS

Patients (371) were randomly assigned to receive pantoprazole 10, 20 or 40 mg or ranitidine 150 mg. Endoscopies were performed after 1, 3, 6 and 12 months or when symptoms suggesting relapse (grade = 2) developed. Gastric biopsies were obtained at baseline and on at least one postbaseline visit. Symptom-free days and Gelusil use were assessed.

RESULTS

Pantoprazole was significantly (P < 0.001) more effective in maintaining erosive oesophagitis healing. After 12 months, 33%, 40%, 68% and 82% of patients remained healed for the ranitidine and pantoprazole 10, 20 and 40 mg groups, respectively. Daytime and night-time heartburn were eliminated in > 90% of days for the pantoprazole 40 mg group. Gelusil use was significantly lower with pantoprazole 20 and 40 mg than with ranitidine (P < 0.02) during the first 9 months.

CONCLUSIONS

Twelve months of maintenance therapy with pantoprazole (10-40 mg once daily) was superior to ranitidine (150 mg twice daily) in maintaining erosive oesophagitis healing. Pantoprazole 40 mg provided the most consistent efficacy and was well tolerated.

Optimal Treatment of Zollinger-Ellison Syndrome and Related Conditions in Elderly Patients

Zollinger-Ellison syndrome is characterised by refractory peptic ulcer disease, severe diarrhoea and gastric acid hypersecretion associated with an islet-cell tumour of the pancreas (gastrinoma). The true incidence and prevalence of this rare disease is unknown; in the US, the frequency is one per one million people and the age at presentation varies from 7 to 90 years. Zollinger-Ellison syndrome is sporadic in 62-80% of cases and in 20-38% of cases is associated with multiple endocrine neoplasia type 1 (MEN 1). The diagnosis of Zollinger-Ellison syndrome is certain when the plasma gastrin is >1000 pg/mL and the basal acid output is >15 mEq/h in patients with an intact stomach, >5 mEq/h in gastrectomised patients, or when this hypergastrinemia is associated with a pH <2. The treatment is based on control of gastric acid hypersecretion and of the malignant tumour and its possible metastases. Proton pump inhibitors are the most effective antisecretory drugs and can be administered in the elderly at high dosages without drug-related adverse effects. As an initial therapy, daily dosages of omeprazole 80-100 mg or pantoprazole 40-160 mg are employed. In long-term treatment the doses can be greatly reduced once effective control of the gastric output has been established. Intravenous proton pump inhibitors may be administered when patients cannot take oral therapy, particularly in acute conditions. All sporadic localised gastrinomas should be excised if possible. When liver metastases are also present, their debulking may improve symptoms and survival, and facilitate medical treatment. There is some controversy as to the surgical approach for gastrinomas associated with MEN 1. Somatostatin analogues can be useful in reducing gastric acid hypersecretion, serum gastrin and gastric enterochromaffin-like (ECL) cells and can thus contribute to treating the disease more effectively. Their antiproliferative effect can be used in treating liver metastases. Chemotherapy is not the therapy of choice in patients with gastrinomas and is indicated only in those with malignant progressive disease; interferon alpha, embolisation and chemoembolisation are not advisable for the elderly. The treatment of elderly Zollinger-Ellison syndrome patients, similarly to all elderly oncological patients, should be based on the use of comprehensive geriatric assessment. This will enable the clinician to define the functional status of the elderly person, to decide whether the patient can tolerate surgery and/or the stress of antineoplastic therapy, and finally, to determine whether this patient can tolerate an aggressive treatment for Zollinger-Ellison syndrome or whether the only possible choice is palliative relief of symptoms.

Characteristics of diarrhoea in 10,008 users of lansoprazole in daily practice: which co-factors contribute?

PURPOSE

Diarrhoea is one of the most frequently reported adverse events during proton pump inhibitor use in any setting. Because of the limited available information, this study was set up with the aim of assessing the incidence and characteristics of diarrhoea and to investigate possible associated co-factors in proton pump inhibitor users in daily practice.

METHODS

Data were used from a prospective, observational study in which 10,008 lansprazole users were followed over time (1994-1998). The study was designed according to the SAMM guidelines. A nested case-control design was used to compare proton pump inhibitor users reporting diarrhoea with those reporting no diarrhoea.

RESULTS

The frequency of diarrhoea was 3.7% and the incidence density 10.7 per 1000 patients months of proton pump inhibitor use. The diarrhoea was most commonly loose and occurred on average 4.4 times per day. The analysis of co-factors revealed that patients with concomitant use of oral antibiotics and patients reporting neurological and/or dermatological adverse events, were at risk of developing diarrhoea during proton pomp inhibitor use.

CONCLUSIONS

In conclusion, diarrhoea was as frequently reported in our study as in clinical trials and observational data of lansoprazole users. We found the concomitant use of oral antibiotics and the reporting of certain other adverse events to be associated with the reporting of diarrhoea during lansoprazole use. Although a relationship with the proton pump inhibitor intake seemed very plausible, we recommend that use of concomitant medicines as a cause of diarrhoea must be taken into consideration in lansoprazole users.

Determinants of headache in lansoprazole users in The Netherlands: results from a nested case-control study

OBJECTIVE

During proton pump inhibitor (PPI) use, in clinical trials, headache is one of the most frequently reported adverse events (frequency 1.3 to 8.8%), while results of one observational study indicate that headache is the fifth most frequently reported adverse event (incidence densities 2.5 to 4.6 per 1000 patient-months of exposure). However, there are no observational studies performed regarding the occurrence and features of headache during use of PPIs in daily practice. For this reason this study was set up with the aim to assess the incidence and characteristics of headache and to investigate possible associated co-factors in PPI users in daily practice.

DESIGN

Data were used from a prospective, observational study in which 10 008 lansoprazole users were followed over time. The study was designed according to the Safety Assessment of Marketed Medicines guidelines. A nested case-control design was used to compare PPI users reporting headache or not.

RESULTS

The frequency of headache was 2.5% in users of lansoprazole and the incidence density was 7.2 per 1000 patient-months of PPI lansoprazole use. Two-thirds of patients with headache had tension headache and one-third had migraine. The analysis of co-factors revealed that women, patients with previous use of analgesics and patients reporting several adverse events, were at risk to develop headache during PPI use. Patients with headache also, significantly more often, reported diarrhoea, nausea and dizziness. A discontinuation of PPI therapy resulted in a cessation or reduction of the headache in 80.0% (20 of 25).

CONCLUSIONS

As can be expected, headache was reported less frequently in this study compared with clinical trials with lansoprazole. The incidence density was comparable with other observational data of lansoprazole and omeprazole users. Besides several commonly accepted co-factors such as female gender and a history of analgesic use, we also found the reporting of other adverse events to be associated with the reporting of headache during lansoprazole use. The cessation of headache after a discontinuation of use of the PPI and the observed dose relationship suggested that headache was indeed an adverse effect of lansoprazole use.

Esomeprazole: a review of its use in the management of acid-related disorders

Esomeprazole (S-isomer of omeprazole), the first single optical isomer proton pump inhibitor, generally provides better acid control than current racemic proton pump inhibitors and has a favourable pharmacokinetic profile relative to omeprazole. In a large well designed 8-week trial in patients (n >5000) with erosive oesophagitis, esomeprazole recipients achieved significantly higher rates of endoscopically confirmed healed oesophagitis than those receiving lansoprazole. Respective healed oesophagitis rates with once-daily esomeprazole 40mg or lansoprazole 30mg were 92.6 and 88.8%. Overall, esomeprazole was also better than omeprazole, although these differences were not always statistically significance. Ninety-two to 94% of esomeprazole recipients (40mg once daily) achieved healed oesophagitis versus 84 to 90% of omeprazole recipients (20mg once daily). Esomeprazole was effective across all baseline grades of oesophagitis; notably, relative to lansoprazole, as baseline severity of disease increased, the difference in rates of healed oesophagitis also increased in favour of esomeprazole. Resolution of heartburn was also significantly better with esomeprazole 40mg than with these racemic proton pump inhibitors. Long-term (up to 12 months) therapy with esomeprazole effectively maintained healing in these patients. Once-daily esomeprazole 20 or 40mg for 4 weeks resolved symptoms in patients with symptomatic gastro-oesophageal reflux disease (GORD) without oesophagitis. Symptoms were effectively managed in the long-term with symptom-driven on-demand esomeprazole (20 or 40mg once daily). Eradicating Helicobacter pylori infection is considered pivotal to successfully managing duodenal ulcer disease. Seven days' treatment (twice-daily esomeprazole 20mg plus amoxicillin 1g and clarithromycin 500mg) eradicated H. pylori in >/=86% of patients (intention-to-treat), a rate that was similar to equivalent omeprazole-based regimens. Esomeprazole is generally well tolerated, both as monotherapy and in combination with antimicrobial agents, with a tolerability profile similar to that of other proton pump inhibitors. Few patients discontinued therapy because of treatment-emergent adverse events (<3% of patients), with very few (<1%) drug-related serious adverse events reported.

CONCLUSIONS

Esomeprazole is an effective, well tolerated treatment for managing GORD and for eradicating H. pylori infection in patients with duodenal ulcer disease. In 8-week double-blind trials, esomeprazole healed oesophagitis and resolved symptoms in patients with endoscopically confirmed erosive oesophagitis and overall, provided better efficacy than omeprazole. Notably, in a large (n >5000 patients) double-blind trial, esomeprazole 40mg provided significantly better efficacy than lansoprazole in terms of healing rates and resolution of symptoms. Long-term therapy with esomeprazole maintained healed oesophagitis in these patients. Esomeprazole also proved beneficial in patients with symptomatic GORD without oesophagitis. Thus, esomeprazole has emerged as an option for first-line therapy in the management of acid-related disorders.

Esomeprazole: a review of its use in the management of acid-related disorders in the US

Esomeprazole, the S-isomer of omeprazole, is the first proton pump inhibitor to be developed as a single optical isomer. It provides better acid control than current racemic proton pump inhibitors and has a favourable pharmacokinetic profile relative to omeprazole. In large well designed 8-week trials in patients with erosive oesophagitis, esomeprazole recipients achieved significantly higher rates of endoscopically confirmed healed oesophagitis than those receiving omeprazole or lansoprazole. Esomeprazole was effective across all baseline grades of oesophagitis; notably, relative to lansoprazole, as the baseline severity of disease increased, the difference in rates of healed oesophagitis also increased in favour of esomeprazole. In two trials, 94% of patients receiving esomeprazole 40mg once daily achieved healed oesophagitis versus 84 to 87% of omeprazole recipients (20mg once daily). In a study in >5000 patients, respective healed oesophagitis rates with once-daily esomeprazole 40mg or lansoprazole 30mg were 92.6 and 88.8%. Resolution of heartburn was also significantly better with esomeprazole than with these racemic proton pump inhibitors. Long-term (up to 12 months) therapy with esomeprazole effectively maintained healed oesophagitis in these patients. Esomeprazole 20 or 40mg once daily for 4 weeks proved effective in patients with symptomatic gastro-oesophageal reflux disease (GORD) without oesophagitis. Eradicating Helicobacter pylori infection is considered pivotal to successfully managing duodenal ulcer disease. Ten days' triple therapy (esomeprazole 40mg once daily, plus twice-daily amoxicillin 1g and clarithromycin 500mg) eradicated H. pylori in 77 to 78% of patients (intention-to-treat) with endoscopically confirmed duodenal ulcer disease. Esomeprazole is generally well tolerated, both as monotherapy and in combination with antimicrobial agents. The tolerability profile is similar to that of other proton pump inhibitors. Few patients discontinued therapy because of treatment-emergent adverse events (<3% of patients) and very few (<1%) drug-related serious adverse events were reported.

CONCLUSIONS

Esomeprazole is an effective and well tolerated treatment for managing GORD and for eradicating H. pylori infection in patients with duodenal ulcer disease. In 8-week double-blind trials, esomeprazole effectively healed oesophagitis and resolved symptoms in patients with endoscopically confirmed erosive oesophagitis. Notably, in large (n >1900 patients) double-blind trials, esomeprazole provided significantly better efficacy than omeprazole or lansoprazole in terms of both healing rates and resolution of symptoms. Long-term therapy with esomeprazole effectively maintained healed oesophagitis in these patients. Esomeprazole was also effective in patients with symptomatic GORD. Thus, esomeprazole has emerged as an effective option for first-line therapy in the management of acid-related disorders.

Proton pump activation in stimulated parietal cells is regulated by gastric acid secretory capacity: a human study

Under normal physiological conditions, gastric acid production is controlled by a negative feedback mechanism. Proton pump inhibitors, such as pantoprazole, inhibit gastric acid secretion by irreversibly binding and inactivating luminally active hydrogen potassium ATPase. Recovery of acid production after treatment with a proton pump inhibitor is driven by new pump synthesis, activation of existing cytoplasmic pumps, or reversal of proton pump inhibition. The authors measured the time course of the inhibition and recovery of acid secretion in healthy volunteers following intravenous administration of pantoprazole to determine the rate of proton pump activation under maximally stimulated conditions. Gastric acid production was measured in 27 Helicobacter pylori negative healthy volunteers (mean age = 31 +/- 7 years; 17 men, 10 women) who received single doses of intravenous pantoprazole (20, 40, 80, or 120 mg) in the presence of a continuous intravenous infusion of 1 ug/kg/h of pentagastrin. From the time profile of acid secretion, the authors described the rate of change of acid output using an irreversible pharmacodynamic response model represented by the equation dR/dt = -k x R x Cpanto + Ln2/PPR x (Ro-R) and correlated the parameter values with demographic factors and gastric acid measurements. Mean stimulated acid output secretion was 21.6 +/- 18.4 mEq/h (range: 1.6-90.5) prior to the administration of pantoprazole and remained steady for 25 hours after placebo administration. Intravenous pantoprazole inhibited acid output in a dose-response fashion, with maximal inhibition (99.9%) occurring after an 80 mg dose. Mean proton pump recovery time was 37.1 +/- 21.0 hours (range: 6.7-75), and recovery was independent of the dose of pantoprazole. There was no association noted between proton pump recovery time and gender, age, race, body weight, or pantoprazole dose. However, there was an inverse correlation between acid output during baseline stimulation and recovery of acid secretion. Mean proton pump recovery time in stimulated normal human volunteers was 37.1 +/- 21.0 hours, with a range of 6.7 to 75 hours. The authors hypothesize that there may be a normal homeostatic mechanism that maintains acid secretory capability within a normal range by altering the rate of proton pump activation dependent on the individual's parietal cell mass. Abnormalities of this process may be responsible for the development of acid peptic disease in susceptible individuals.

Dose-dependent control of intragastric pH by pantoprazole, 10, 20 or 40 mg, in healthy volunteers

BACKGROUND

Proton pump inhibitors have emerged as the most effective class of drugs for the treatment of gastro-oesophageal reflux. Pantoprazole is a proton pump inhibitor that has demonstrated high clinical efficacy.

AIM

To evaluate the effect of once-daily doses of pantoprazole, 10, 20 and 40 mg, on gastric acidity in healthy volunteers.

METHODS

Thirty-six subjects received pantoprazole in a three-way crossover design study. Ambulatory 24-h intragastric pH and distal oesophageal pH were monitored at baseline and on the last day of each treatment period. The measured endpoints were the median intragastric and oesophageal pH, the percentage of time the intragastric pH < 4 and oesophageal pH < 4 and the area under the curve for gastric acidity over 24 h. Safety was evaluated by incidence and severity of adverse events.

RESULTS

Pantoprazole demonstrated a linear dose- dependent suppression of gastric acidity over the dose range 10-40 mg. The dose of 40 mg demonstrated a significantly greater response than the lower doses, particularly at night. All pantoprazole doses were well tolerated.

CONCLUSIONS

Pantoprazole demonstrates a dose-related effect in the range 10-40 mg once daily. The once-daily dose of 40 mg provides the highest and most consistent control of gastric pH, especially at night.

Clinical pharmacology and safety profile of esomeprazole, the first enantiomerically pure proton pump inhibitor

Awareness of important differences in the pharmacological profile of individual optical isomers of chiral drugs led to the development of esomeprazole, the S-isomer of omeprazole, a new pharmacological entity designed to improve the clinical outcome of available proton pump inhibitors in the management of acid-related disorders. The superior acid control achieved by esomeprazole is mainly due to an advantageous metabolism compared with racemate omeprazole, leading to improved bioavailability and to enhanced delivery of the drug to the gastric proton pump.

No clinical benefit of adding cisapride to pantoprazole for treatment of gastro-oesophageal reflux disease

OBJECTIVE

Although a proton pump inhibitor (PPI) and a prokinetic drug are often combined for the medical treatment of gastro-oesophageal reflux disease (GORD), there are few well-conducted clinical studies on the efficacy and tolerability of this therapy. This study investigates whether pantoprazole plus cisapride leads to an additional benefit in comparison to pantoprazole alone.

DESIGN AND SETTING

Randomized double-blind prospective multicentre study conducted in patients of 33 hospitals in Ireland, South Africa and the UK.

PARTICIPANTS

A total of 350 intention-to-treat (ITT) patients aged 18 years or older with GORD of grade II and III were included in the study. The per-protocol (PP) population comprised 152 patients in the pantoprazole group and 136 in the pantoprazole plus cisapride group.

INTERVENTIONS

Patients received either pantoprazole 40 mg once daily or pantoprazole 40 mg once daily plus cisapride 20 mg twice daily. Treatment outcome was assessed after 4 and 8 weeks. The primary criterion was endoscopically confirmed healing after 4 weeks. Additionally, relief of leading symptoms was studied.

MAIN OUTCOME MEASURES

The prior null hypothesis was no difference in healing rates between both treatment groups.

RESULTS

After 4 weeks of treatment 81% and 82%, and after 8 weeks 89% and 90%, of PP patients treated with pantoprazole or pantoprazole plus cisapride were healed, respectively. Thus, equivalence of the two treatment strategies could be proven. Additionally, improvement of symptom relief showed no significant difference between the two regimens. In contrast to disease grade at baseline, Helicobacter pylori status did not influence the healing rates in our study. Both study medications were tolerated well.

CONCLUSION

Addition of cisapride to pantoprazole provides no further benefit in the treatment of GORD.

Pharmacological and pharmacodynamic essentials of H(2)-receptor antagonists and proton pump inhibitors for the practising physician

The suppression of gastric acid secretion with anti-secretory agents has been the mainstay of medical treatment for patients with acid-related disorders. Although the majority of Helicobacter pylori -related peptic ulcers can be healed with antibiotics, ulcer healing and symptom control can be significantly improved when antibiotics are given with anti-secretory agents, especially with a proton pump inhibitor. There is a dynamic relationship between the suppression of intragastric acidity and the healing of peptic ulcer and erosive oesophagitis and control of acid-related symptoms. The suppression of gastric acid secretion achieved with H(2)-receptor antagonists has, however, proved to be suboptimal for effectively controlling acid-related disorders, especially for healing erosive oesophagitis and for the relief of reflux symptoms. H(2)-receptor antagonists are also not effective in inhibiting meal-stimulated acid secretion, which is required for managing patients with erosive oesophagitis. Furthermore, the rapid development of tolerance to H(2)-receptor antagonists and the rebound acid hypersecretion after the withdrawal of an H(2)-receptor antagonist further limit their clinical use. Although low-dose H(2)-receptor antagonists are currently available as over-the-counter medications for self-controlling acid-related symptoms, their pharmacology and pharmacodynamics have not been well studied, especially in the self-medicating population. Proton pump inhibitors have been proved to be very effective for suppressing intragastric acidity to all known stimuli, although variations exist in the rapidity of onset of action and the potency of acid inhibition after oral administration at the approved therapeutic doses, which may have important clinical implications for the treatment of gastro-oesophageal reflux disease and perhaps for eradicating H. pylori infection when a proton pump inhibitor is given with antibiotics. Once-daily dosing in the morning is more effective than dosing in the evening for all proton pump inhibitors with respect to the suppression of intragastric acidity and daytime gastric acid secretion in particular, which may result from a better bio-availability being achieved with the morning dose. When higher doses are needed, these drugs must be given twice daily to achieve the optimal suppression of 24 hour intragastric acidity. Preliminary results have shown that esomeprazole, the optical isomer of omeprazole, given at 40 mg, is significantly more effective than omeprazole 40 mg, lansoprazole 30 mg or pantoprazole 40 mg for suppressing gastric acid secretion. However, more studies in different patient populations are needed to compare esomeprazole with the existing proton pump inhibitors with regard to their efficacy, cost-effectiveness and long-term safety for the management of acid-related disorders.

The role of acid suppressants in upper gastrointestinal ulcer bleeding

Re-bleeding and mortality remain significant in peptic ulcer haemorrhage despite the widespread use of endoscopic therapy. The acidic gastric environment interferes with coagulation. In vitro studies show that an intragastric pH of above 6 results in normal blood coagulation and platelet function. Because of induced tachyphylaxis, H(2)-receptor antagonists are not able to maintain a high pH. In addition, in randomized trials using H(2)-receptor antagonists, there was no reduction in re-bleeding and mortality. High-dose intravenous proton pump inhibitors are capable of maintaining a pH above 6. Four randomized trials, using high-dose intravenous proton pump inhibitors, significantly improved the outcome (in terms of a reduction in re-bleeding and surgery) in patients with peptic ulcer haemorrhage. Mortality was, however, not reduced. The additional effect of acid-suppressant agents after successful endoscopic therapy is limited to the reduction of re-bleeding and need for surgery, with no effect on mortality.

Proton pump inhibitors and their drug interactions: an evidence-based approach

The proton pump inhibitors (PPIs) are the most effective antisecretory agents used to treat acid-related disorders. As such, they are frequently prescribed for patients who are concurrently using other medications. PPIs may interact with other drugs through numerous mechanisms. The most important include competitive inhibition of hepatic cytochrome P (CYP) 450 enzymes involved in drug metabolism, and alteration of the absorption of other drugs via changes in gastric pH levels. Poor metabolizers, who lack CYP2C19, may be particularly predisposed to drug interactions. Although the potential for drug interactions is high, few clinically significant interactions have been reported for the PPIs. Nevertheless, caution is indicated when certain drugs are co-prescribed with these agents. The incidence of clinically significant drug interactions increases proportionately with the number of drugs taken and with the age of the patient. The drug interaction with the greatest clinical importance is the reduction in benzodiazepine clearance by omeprazole.

Pharmacodynamic modeling of pantoprazole's irreversible effect on gastric acid secretion in humans and rats

The relationship between the pharmacokinetics of pantoprazole, an irreversible proton pump inhibitor, and its effect on gastric acid secretion was evaluated in humans and rats. Pantoprazole pharmacokinetics were studied in 6 rats (5 mg/kg, i.v.) and 22 healthy volunteers (10 to 80 mg, i.v. and oral). Gastric acid secretion under maximum pentagastrin stimulation was measured after i.v. administration of placebo or pantoprazole in 31 rats (0.12 to 1.15 mg/kg) for 4 hours and in 31 subjects (20 to 120 mg) for 24 hours. Pantoprazole has short half-lives of 0.5 hours in rats and 0.8 hours in humans. After administration of the highest dose, acid secretion was fully inhibited within 1 hour and for the whole observation period in both species. An irreversible pharmacodynamic response model was successfully developed and validated. The apparent reaction rate constants of pantoprazole with the proton pumps were 0.691 L/mg/h in rats and 0.751 L/mg/h in humans, and the apparent recovery rates of the pumps were 0.053 h-1 and 0.031 h-1, respectively. The maximum inhibition and the overall effect of pantoprazole are related to exposure, and the onset is related to initial pantoprazole concentrations. It was concluded that this irreversible response model accurately describes the effect of i.v. and oral pantoprazole on gastric secretion and may be used to predict effects under other dosage regimens.

Management of severe gastroesophageal reflux disease

Gastroesophageal reflux disease (GERD) affects more than one third of the population. It is generally a chronic condition and has the potential to be serious. Some patients with GERD experience persistent daytime or nighttime heartburn and some sustain severe damage, including ulceration, stricture, and Barrett's esophagus, which can predispose to development of adenocarcinoma. Extraesophageal manifestations of GERD can include otolaryngologic, respiratory, and cardiac problems. Severe GERD responds best to agents that suppress gastric acid secretion. Of these, proton pump inhibitors (PPIs) provide the most effective control of gastric acidity and are, therefore, the medical treatment of choice. In fact, nonresponse to a PPI should raise the suspicion that the diagnosis is not GERD. Proton pump inhibitors are quickly becoming the treatment of choice for GERD, especially for severe or refractory cases. For patients whose GERD is refractory even to PPIs or who are unwilling to face years of PPI therapy, antireflux surgery remains an option.

Are the orally administered proton pump inhibitors equivalent? A comparison of lansoprazole, omeprazole, pantoprazole, and rabeprazole

Four proton pump inhibitors (PPIs) are currently marketed in various parts of the world, and all of these (lansoprazole, omeprazole, pantoprazole, and rabeprazole) are available for prescription use in the United States. As a therapeutic group, the PPIs are highly useful for the relief of symptoms and healing of gastroesophageal reflux disease, gastric and duodenal ulcer disease, eradication of Helicobacter pylori infection, prevention and treatment of nonsteroidal anti-inflammatory drug (NSAID)-associated damage, management of hypersecretory states such as Zollinger-Ellison syndrome, and care of patients with non-variceal upper gastrointestinal bleeding, or non-ulcer dyspepsia. The pathophysiologic basis of these management benefits lies in the potent gastric acid inhibitory effects of the PPIs. There are differences between the PPIs in their pharmacokinetics, pharmacodynamics, influence by food and antacids, clinical efficacy, and potential for drug interactions. It is not always clear whether these often subtle variations are necessarily of clinical importance. The physician's choice of one PPI over another must rest with her/his interpretation of the clinical importance of the generally small differences between PPIs, their approval for treatment of specific clinical indications within the physician's practice jurisdiction, and the strength of the evidence based on the quantity and quality of the supporting clinical trials.

Pantoprazole: a new proton pump inhibitor

OBJECTIVE

This paper reviews the pharmacology, clinical efficacy, and tolerability of pantoprazole in comparison with those of other available proton pump inhibitors (PPIs).

METHODS

Relevant English-language research and review articles were identified by database searches of MEDLINE, International Pharmaceutical Abstracts, and UnCover, and by examining the reference lists of the articles so identified. In selecting data for inclusion, the author gave preference to full-length articles published in peer-reviewed journals.

RESULTS

Like other PPIs, pantoprazole exerts its pharmacodynamic actions by binding to the proton pump (H+,K+ -adenosine triphosphatase) in the parietal cells, but, compared with other PPIs, its binding may be more specific for the proton pump. Pantoprazole is well absorbed when administered as an enteric-coated, delayed-release tablet, with an oral bioavailability of approximately 77%. It is hepatically metabolized via cytochrome P2C19 to hydroxypantoprazole, an inactive metabolite that subsequently undergoes sulfate conjugation. The elimination half-life ranges from 0.9 to 1.9 hours and is independent of dose. Pantoprazole has similar efficacy to other PPIs in the healing of gastric and duodenal ulcers, as well as erosive esophagitis, and as part of triple-drug regimens for the eradication of Helicobacter pylori from the gastric mucosa. It is well tolerated, with the most common adverse effects being headache, diarrhea, flatulence, and abdominal pain. In clinical studies, it has been shown to have no interactions with various other agents, including carbamazepine, cisapride, cyclosporine, digoxin, phenytoin, theophylline, and warfarin.

CONCLUSIONS

Pantoprazole appears to be as effective as other PPIs. Its low potential for drug interactions may give it an advantage in patients taking other drugs.

Oral pantoprazole for erosive esophagitis: a placebo-controlled, randomized clinical trial. Pantoprazole US GERD Study Group

OBJECTIVES

The aim of this dose-response study was to compare the effectiveness of 10 mg, 20 mg, and 40 mg of pantoprazole with that of placebo tablets in the healing and symptom relief of gastroesophageal reflux disease associated with erosive esophagitis, and to determine the optimal dose.

METHODS

A total of 603 patients with endoscopically confirmed (Hetzel-Dent scale) erosive esophagitis of grade 2 (64.5%) or grades 3 or 4 (35.3%) were enrolled in a double-blind, multicenter study and randomly assigned to receive pantoprazole (10 mg, 20 mg, or 40 mg) or placebo, administered once daily in the morning, for 4 or 8 wk depending on healing.

RESULTS

The healing rates after 4 wk for placebo and pantoprazole 10 mg, 20 mg, and 40 mg/day were 14%, 42%, 55%, and 72%, respectively (p < 0.001 for all doses of pantoprazole vs placebo). Cumulative healing rates after 8 wk for placebo and pantoprazole 10 mg, 20 mg, and 40 mg/day were 33%, 59%, 78%, and 88%, respectively (p < 0.001 for all doses of pantoprazole vs placebo). The 40-mg pantoprazole dose produced greater rates of healing and earlier healing of esophagitis than either the 10- or 20-mg dose, regardless of severity. Pantoprazole, at any dose, was significantly more effective than placebo in relieving reflux symptoms. Patients on pantoprazole 40 mg experienced relief of symptoms on day 1 of treatment. No serious treatment-related adverse events occurred.

CONCLUSIONS

Pantoprazole was safe and effective for healing erosive esophagitis and provided rapid symptomatic relief. These results indicate that pantoprazole offers a new option for treatment of erosive esophagitis. Among the three doses studied, the 40-mg dose was the most effective.

Clinical experience with pantoprazole in gastroesophageal reflux disease

BACKGROUND

Pantoprazole is a new proton pump inhibitor indicated for the treatment of erosive esophagitis associated with gastroesophageal reflux disease (GERD) and is available in both oral and intravenous (IV) formulations.

OBJECTIVE

This paper reviews the pharmacologic properties of pantoprazole and summarizes the findings from clinical studies of this drug.

METHODS

This review was compiled from the published literature, abstracts from clinical trials, and data on file with the manufacturer of pantoprazole.

RESULTS

Pantoprazole selectively accumulates in the acidic environment of gastric parietal cells and acts at the final step of acid secretion by binding 2 key cysteine residues of the proton pump involved in gastric acid production. The bioavailability of pantoprazole is not altered by concomitant administration of food or antacids or with repeated dosing. Both oral and IV formulations of pantoprazole exhibit linear pharmacokinetics. Several clinical trials have proved pantoprazole superior to histamine-2-receptor antagonists (H2RAs) in reducing acid secretion and elevating gastric pH levels. Pantoprazole has been shown to be more effective than ranitidine (P < 0.05), famotidine (P < 0.001), and nizatidine (P < 0.05), and at least as effective as omeprazole, in healing erosive esophagitis and relieving associated symptoms of GERD, including regurgitation. Pantoprazole is also more effective than the H2RA nizatidine for the treatment of nighttime heartburn (P < 0.05). Studies have shown pantoprazole to be well tolerated; adverse events, including headache, diarrhea, flatulence, abdominal pain, eructation, nausea, and rash, occurred in < or = 6% of patients. The oral and IV formulations of pantoprazole are equally potent in inhibiting gastric acid secretion; thus, switching between formulations requires no dosage adjustments. Special patient populations, including the elderly and patients with renal or mild to moderate hepatic impairment, can take pantoprazole without an adjustment in dosage.

CONCLUSIONS

Because of its unique pharmacokinetic properties, mechanism of action, and reduced potential for producing cytochrome P-450-based drug interactions, pantoprazole in both oral and IV formulations is effective over a full 24 hours and is well tolerated in a variety of patient types.

Overuse of proton pump inhibitors

BACKGROUND

There have been concerns raised about the potential adverse effects of proton pump inhibitors, especially with long-term use. In particular, their potent action can suppress the features and delay the diagnosis of gastric cancer, while prolonged exposure may hasten the development of gastric carcinoids.

AIM

To examine the use of proton pump inhibitors in patients at the major teaching hospital in Tasmania, Australia, principally to determine the appropriateness of the therapy according to published guidelines.

METHODS

A retrospective review of the medical records of all patients prescribed any of the proton pump inhibitors at the hospital over a 7-month period, was performed. An extensive range of demographic and clinical variables was recorded for each patient. The patients were also asked a series of questions during their hospitalization to extract some of the relevant information - in particular, if and when they had undergone endoscopy.

RESULTS

The 200 patients (52% males) had a mean age of 69 +/- 16.4 years. The most common indications for using proton pump inhibitors were acute gastrointestinal bleeding (20.9%), severe refractory ulcerating oesophagitis (17.3%), mild/moderate oesophageal reflux (17.3%) and refractory peptic ulcer (11.7%). A large number of patients were using a proton pump inhibitor for 'other' indications (39.6%). The prescribing of proton pump inhibitors satisfied the approved indications, as outlined in the Australian Schedule of Pharmaceutical Benefits, in only 37.1% of cases. Endoscopy had been performed in 54.1% of patients prior to commencing therapy with a proton pump inhibitor and within the next 7 days in another 12.8% of patients. Only 59% of patients had previously been treated with an H2-receptor antagonist before commencing therapy with a proton pump inhibitor. Even worse, only 58.5% of patients had used an H2-receptor antagonist before a proton pump inhibitor for mild/moderate oesophagitis. The median duration of proton pump inhibitor therapy for patients admitted to the hospital and already receiving one of the drugs was 450 days. Over half of the patients were being concurrently treated with other drugs which are known to cause or exacerbate gastro-oesophageal disease, and 18% were smokers.

CONCLUSION

Whereas the proton pump inhibitors are undoubtedly effective agents, studies of their prescribing in practice consistently suggest over-use prior to endoscopy, use in patients who do not fit the approved criteria, and prescribing for indications in which 'less powerful' agents should have been sufficiently effective for the patient's symptoms. This poses economic and safety concerns, particularly in light of the suggestion that these drugs could delay the diagnosis of gastric cancer.

Proton pump inhibitors in the treatment of gastro-oesophageal reflux disease

Gastro-oesophageal reflux disease (GERD) is the most common peptic acid disease in the western world and is the commonest indication for acid suppression therapy. Major advances have been made over the past 30 years in the understanding of lower oesophageal sphincter function and the mechanism of acid secretion. Developments in surgical and pharmacological therapy have paralleled these advances. Pharmacotherapy for GERD has evolved from antacids to H2-receptor antagonists (H2RAs) to prokinetics to proton pump inhibitors (PPIs). The H2RAs, while modestly effective in symptom relief and healing of GERD, are limited by pharmacological tolerance. The prokinetics (metoclopramide and cisapride) are limited by low efficacy, pharmacological tolerance and toxicity. The PPIs have emerged as the most effective therapy for symptom relief, healing and long-term maintenance. They have also proved to be remarkably safe and cost-effective in long-term therapy. This review evaluates the pharmacology, efficacy, tolerability, safety and cost-effectiveness of the four currently available PPIs, lansoprazole, omeprazole, pantoprazole and rabeprazole, in the treatment of GERD.

Efficacy of a 1-week pantoprazole triple therapy in eradicating Helicobacter pylori in Asian patients

BACKGROUND

The aim of the present paper was to determine the efficacy and tolerability of a 1-week treatment regimen consisting of pantoprazole and two antibiotics: clarithromycin and amoxycillin, in the eradication of Helicobacter pylori.

METHODS

The patients selected had unequivocal evidence of H. pylori infection based on urease test, culture and histology on antral and corpus biopsies obtained at endoscopy. Patients received pantoprazole 40 mg twice a day, clarithromycin 500 mg twice a day and amoxycillin 1 g twice a day for 1 week and were assessed for successful eradication at least 4 weeks after completion of therapy by repeat gastroscopy and gastric biopsies. Eradication was defined as absence of bacteria in both antral and corpus biopsies tested by culture, histology and urease test.

RESULTS

One hundred and six patients were recruited for the study. The mean age was 48.0 years (range: 23-74 years). Four patients defaulted follow up and five patients were not compliant (taking less than 85%) with medications. Eradication rates on per-protocol analysis were: 88/97 (90.7%; 95% CI: 83.1-95.7); and on intention-to-treat analysis they were: 88/106 (83.0%; 95% CI: 75.9-90.2). Side-effects were in general mild and tolerable: 57 of 106 (53.7%) patients complained of a bitter taste; 15 (14.1%) complained of giddiness; 10 (9.4%) complained of increased abdominal pain; 11 (11.5%) complained of lethargy and 16 (15.1%) complained of loose motions. Pre-treatment metronidazole resistance was encountered in 57/74 strains (77.0%). Clarithromycin resistance was not encountered in any of the strains.

CONCLUSIONS

The pantoprazole 1-week triple therapy with amoxycillin and clarithromycin is effective in H. pylori eradication. The treatment was well tolerated by patients. Metronidazole resistance was reported in a high percentage of strains isolated from patients. Clarithromycin resistance was, however, not detected in any of the strains.

Review article: comparison of the pharmacokinetics, acid suppression and efficacy of proton pump inhibitors

Proton pump inhibitors have dramatically influenced the management of acid-peptic disorders in recent years. They all have a broadly similar mechanism of action and are extensively metabolized in the liver via cytochromes P450 2C19 and 3A4. There is some variation in their potential for drug interactions due to differences in enzyme inhibition. Relatively few serious adverse effects have been reported for the proton pump inhibitors. Comparative studies of acid suppression suggest that lansoprazole and pantoprazole have a potency similar to that of omeprazole on a mg for mg basis; however, rabeprazole may have a greater potency than omeprazole. Lansoprazole and rabeprazole display a more rapid onset of maximal acid suppression than the other proton pump inhibitors. Comparative studies using proton pump inhibitors for the treatment of reflux oesophagitis, duodenal ulcer healing and Helicobacter pylori eradication show little overall difference in outcome between the proton pump inhibitors when used in their standard doses. Lansoprazole and rabeprazole provide earlier and better symptom relief than the other proton pump inhibitors in some studies of peptic ulcer treatment. The few studies of gastric ulcer treatment suggest that there is an advantage in using the proton pump inhibitors that have a higher standard daily dose.

Stereoselective chiral inversion of pantoprazole enantiomers after separate doses to rats

(+/-)-Pantoprazole ((+/-)-PAN), (+/-)-5-(difluoromethoxy)-2-[[3.4-dimethoxy-2-pyridinyl)methyl]sul finyl]- 1H-benzimidazole) is a chiral sulfoxide that is used clinically as a racemic mixture. The disposition kinetics of (+)-PAN and (-)-PAN given separately has been studied in rats. Serum levels of (+)- and (-)-PAN and its metabolites, pantoprazole sulfone (PAN-SO2), pantoprazole sulfide (PAN-S), 4'-O-demethyl pantoprazole sulfone (DMPAN-SO2), and 4'-O-demethyl pantoprazole sulfide (DMPAN-S) were measured by HPLC. Following single intravenous or oral administration, both enantiomers were rapidly absorbed and metabolized, resulting in similar serum concentrations, suggesting that the two enantiomers have approximately the same disposition kinetics. The major metabolite of both (+)- and (-)-PAN was PAN-SO2, while DMPAN-SO2 was also detected as a minor metabolite. Serum levels of PAN-S and DMPAN-S could not be quantified after intravenous or oral administration of either enantiomer. Significant chiral inversion occurred after intravenous and oral administration of (+)-PAN. The AUCs of (-)-PAN after intravenous and oral dosing of (+)-PAN were 36.3 and 28.1%, respectively of those of total [(+) + (-)] PAN. In contrast, the serum levels of (+)-PAN were below quantitation limits after intravenous or oral administration of (-)-PAN. Therefore, chiral inversion was observed only after administration of (+)-PAN, supporting the hypothesis that stereoselective inversion from (+)-PAN to (-)-PAN occurs in rats.

Acute gastrointestinal bleeding in the intensive care unit. The gastroenterologist's perspective

Although SRES-associated hemorrhage previously constituted a significant cause of bleeding in the ICU, improvements in ICU management and the institution of prophylactic measures in high-risk patients have significantly reduced SRES-associated hemorrhage since the 1980s. Antacids, H2-receptor antagonists, and sucralfate have been shown to be effective in preventing clinically significant bleeding resulting from SRES, particularly when the intragastric pH is maintained at greater than 4. A selective approach should be adopted in SRES prophylaxis: Patients on mechanical ventilation, with coagulopathy, or with two of the other known risk factors should receive prophylaxis. Although the drug of choice depends to some extent on local preferences, an H2-receptor antagonist by continuous intravenous infusion may represent the best option. No pharmacologic therapy is of proven value once hemorrhage begins, but the current interventional techniques are effective in controlling hemorrhage. Gastrointestinal bleeding from NOMV has become less common with improvements in the hemodynamic monitoring of critically ill patients, but this disease must always be considered when lower gastrointestinal bleeding occurs in the context of relative hypoperfusion. For SRES and NOMV, treatment of the underlying disease or diseases is the optimal route to prevention.