Medical management of gastroesophageal reflux disease

Reconstruction of the Gastro-esophageal Junction Based on Ultramill Imaging for Biomechanical Analysis

The gastro-esophageal junction (GEJ) regulates the entry of food into the stomach and prevents reflux of acidic gastric contents into the lower esophagus. This is achieved through multiple mechanisms and the maintenance of a localized high-pressure zone. Diseases of the GEJ typically involve impairments to its muscular functions and often are accompanied by symptoms of reflux, heartburn, and dysphagia. This study aimed to develop a finite element-based model from a unique human cadaver GEJ data reconstructed from an ultramill imaging setup. A pipeline was developed to generate a mesh from an input stack of images. The anatomy of the model was compared to an existing Visible Human finite element GEJ model. Biomechanical simulations were also performed on both models using loading steps of differing levels of calcium to model different levels of contraction. It was found that the ultramill GEJ model is shorter than the Visible Human model (31 vs 48.3 mm), as well as producing lower pressure (1.35 vs 4.36 kPa). The model will be used to investigate detailed pressure development in the GEJ during swallowing under realistic loading conditions. Clinical Relevance - The modeling of the GEJ would allow further insights into pressure influencing factors and aid in the development and testing of treatments.

Proton pump inhibitors do not impair the effectiveness of metformin in patients with diabetes

AIMS

In order to exert its pharmacodynamic effect, the diabetes drug metformin needs to be taken up into hepatocytes by the organic cation transporter (OCT) system. A recent in vitro study found that proton pump inhibitors (PPIs) inhibit OCT1, OCT2 and OCT3, suggesting that PPIs might reduce metformin's effectiveness. This pharmacoepidemiologic study looked for evidence of a clinical effect of such an interaction.

METHODS

This was an observational cohort study examining changes in glycosylated haemoglobin (HbA1c) with exposure to metformin and to PPIs as single agents and in combination. The aim was to assess evidence of a deleterious drug-drug interaction.

RESULTS

PPIs did not reduce the effectiveness of metformin, and indeed were associated with a minimally better glycaemic response by - 0.06 HbA1c percentage points (95% confidence interval, -0.10, -0.01) in metformin initiators.

CONCLUSIONS

Despite a mechanistic basis for a potential drug-drug interaction, we found no evidence of a deleterious interaction between PPIs and metformin.

Acid peptic diseases: pharmacological approach to treatment

Acid peptic disorders are the result of distinctive, but overlapping pathogenic mechanisms leading to either excessive acid secretion or diminished mucosal defense. They are common entities present in daily clinical practice that, owing to their chronicity, represent a significant cost to healthcare. Key elements in the success of controlling these entities have been the development of potent and safe drugs based on physiological targets. The histamine-2 receptor antagonists revolutionized the treatment of acid peptic disorders owing to their safety and efficacy profile. The proton-pump inhibitors (PPIs) represent a further therapeutic advance due to more potent inhibition of acid secretion. Ample data from clinical trials and observational experience have confirmed the utility of these agents in the treatment of acid peptic diseases, with differential efficacy and safety characteristics between and within drug classes. Paradigms in their speed and duration of action have underscored the need for new chemical entities that, from a single dose, would provide reliable duration of acid control, particularly at night. Moreover, PPIs reduce, but do not eliminate, the risk of ulcers in patients taking NSAIDs, reflecting untargeted physiopathologic pathways and a breach in the ability to sustain an intragastric pH of more than 4. This review provides an assessment of the current understanding of the physiology of acid production, a discussion of medications targeting gastric acid production and a review of efficacy in specific acid peptic diseases, as well as current challenges and future directions in the treatment of acid-mediated diseases.

The effect of lansoprazole, an OCT inhibitor, on metformin pharmacokinetics in healthy subjects

PURPOSE

Gastro-esophageal reflux disease is common in patients with type 2 diabetes. A common treatment is the co-administration of proton-pump inhibitors (PPIs) and metformin. To date, however, the effects of co-administration of PPIs, which inhibit organic cation transporter (OCT) activity, on the action of metformin (a well-known substrate of OCTs) have not been clearly demonstrated.

METHODS

This was a randomized, double-blind, two-way crossover, placebo-controlled trial. Healthy male volunteers (n = 20) received metformin (single dose 1,000 mg on day 1 and single dose 750 mg on day 2, with a 12-h interval) co-administered with placebo or with lansoprazole (30 mg). Plasma concentrations of metformin were measured up to 24 h after the second dose. The glucose-lowering effects of metformin were evaluated by the oral glucose tolerance test before and after each single dose of metformin within the 2-day period.

RESULTS

Lansoprazole increased the mean metformin maximum plasma concentration and area under the plasma concentration-time curve from zero to 24 h after the second dosing by 15 and 17 %, respectively (P < 0.05). Moreover, lansoprazole prolonged the metformin elimination half-life from 3.9 to 4.5 h and decreased its renal clearance by 13 % (P < 0.05). However, lansoprazole had no effect on the maximum glucose level and the area under the serum glucose concentration-time curve of metformin.

CONCLUSIONS

Collectively, we found a modest pharmacokinetic drug interaction between lansoprazole and metformin, which suggests that the concomitant use of these drugs should be appropriately monitored. Further studies are warranted to assess changes in metformin pharmacokinetics in patients with diabetes receiving long-term lansoprazole therapy.

Proton pump inhibitors inhibit metformin uptake by organic cation transporters (OCTs)

Metformin, an oral insulin-sensitizing drug, is actively transported into cells by organic cation transporters (OCT) 1, 2, and 3 (encoded by SLC22A1, SLC22A2, or SLC22A3), which are tissue specifically expressed at significant levels in various organs such as liver, muscle, and kidney. Because metformin does not undergo hepatic metabolism, drug-drug interaction by inhibition of OCT transporters may be important. So far, comprehensive data on the interaction of proton pump inhibitors (PPIs) with OCTs are missing although PPIs are frequently used in metformin-treated patients. Using in silico modeling and computational analyses, we derived pharmacophore models indicating that PPIs (i.e. omeprazole, pantoprazole, lansoprazole, rabeprazole, and tenatoprazole) are potent OCT inhibitors. We then established stably transfected cell lines expressing the human uptake transporters OCT1, OCT2, or OCT3 and tested whether these PPIs inhibit OCT-mediated metformin uptake in vitro. All tested PPIs significantly inhibited metformin uptake by OCT1, OCT2, and OCT3 in a concentration-dependent manner. Half-maximal inhibitory concentration values (IC(50)) were in the low micromolar range (3-36 µM) and thereby in the range of IC(50) values of other potent OCT drug inhibitors. Finally, we tested whether the PPIs are also transported by OCTs, but did not identify PPIs as OCT substrates. In conclusion, PPIs are potent inhibitors of the OCT-mediated metformin transport in vitro. Further studies are needed to elucidate the clinical relevance of this drug-drug interaction with potential consequences on metformin disposition and/or efficacy.

Vitamin/mineral supplements and calcium-based antacids increase maternal calcium intake

OBJECTIVE

The contributions of over-the-counter (OTC) calcium-based antacid medications and calcium-containing vitamin/mineral supplements to total calcium intake during pregnancy, have rarely been assessed. This study estimates the contributions of calcium-based antacids and vitamin/mineral supplements to maternal calcium intake.

METHODS

Over an 8-month period, a cohort of 724 prenatal class attendees (out of a possible 1100 participants) at >28 weeks gestation in Calgary, Alberta, completed an anonymous questionnaire on vitamin/mineral supplement intake and the use of calcium-based antacids. A subset of 264 women completed a self-reported calcium-modified food frequency questionnaire.

RESULTS

The use of prenatal vitamins/minerals increased during pregnancy as did use of the single nutrients calcium and iron. Calcium-based antacids were used by 52% (n = 365) of pregnant women. Median intake of calcium from maternal diet alone was 1619 mg/d (mean intake, 1693 +/- 94), which rose to 2084 mg/d (mean intake, 2228 +/- 116) when diet, vitamin/mineral supplements, and antacids were considered. From diet alone, 18% had less than adequate intake (AI = 1000 mg/d) of calcium and 12% exceeded the tolerable upper intake level (UL = 2500 mg/d). Adding antacids reduced to 5% those below the AI and increased those surpassing the UL to 33%. No adverse events were reported at calcium intakes above the UL.

CONCLUSIONS

Vitamin/mineral supplements and calcium-based antacids increased total maternal calcium intake, resulting in fewer women with intakes < AI but also increasing the number of those with intakes > UL. It is suggested that health care providers discuss all sources of nutrient intake with pregnant clients, as cumulative intakes may unintentionally exceed recommended levels.

Rabeprazole: a review of its use in the management of gastric acid-related diseases in adults

Rabeprazole (Aciphex, Alfence, Pariet) is a proton pump inhibitor (PPI) used for the treatment of adults with conditions requiring a reduction of gastric acid secretion such as erosive or ulcerative gastro-oesophageal reflux disease (GORD), non-erosive reflux disease (NERD), duodenal and gastric ulcers, and pathological hypersecretory conditions including Zollinger-Ellison syndrome (ZES). It is also used as part of combination therapy for the eradication of Helicobacter pylori, a pathogen frequently implicated in the development of gastric and duodenal ulcers. Rabeprazole has a well established efficacy and safety profile in the treatment of gastric acid-related diseases. Rabeprazole is a useful, well tolerated and cost-effective option for the treatment of GORD, NERD, peptic ulcer and other gastric acid-related diseases (including ZES), and provides an appropriate alternative to other currently available PPIs, with the added benefits of having a consistent efficacy profile and low drug interaction potential due to its predominantly nonenzymatic metabolism.

Proton pump inhibitors: an update of their clinical use and pharmacokinetics

BACKGROUND

Proton pump inhibitors (PPIs) represent drugs of first choice for treating peptic ulcer, Helicobacter pylori infection, gastrooesophageal reflux disease, nonsteroidal anti-inflammatory drug (NSAID)-induced gastrointestinal lesions (complications), and Zollinger-Ellison syndrome.

RESULTS

The available agents (omeprazole/esomeprazole, lansoprazole, pantoprazole, and rabeprazole) differ somewhat in their pharmacokinetic properties (e.g., time-/dose-dependent bioavailability, metabolic pattern, interaction potential, genetic variability). For all PPIs, there is a clear relationship between drug exposure (area under the plasma concentration/time curve) and the pharmacodynamic response (inhibition of acid secretion). Furthermore, clinical outcome (e.g., healing and eradication rates) depends on maintaining intragastric pH values above certain threshold levels. Thus, any changes in drug disposition will subsequently be translated directly into clinical efficiency so that extensive metabolizers of CYP2C19 will demonstrate a higher rate of therapeutic nonresponse.

CONCLUSIONS

This update of pharmacokinetic, pharmacodynamic, and clinical data will provide the necessary guide by which to select between the various PPIs that differ-based on pharmacodynamic assessments-in their relative potencies (e.g., higher doses are needed for pantoprazole and lansoprazole compared with rabeprazole). Despite their well-documented clinical efficacy and safety, there is still a certain number of patients who are refractory to treatment with PPIs (nonresponder), which will leave sufficient space for future drug development and clinical research.

Gastroesophageal reflux disease (GERD): is there more to the story?

Gastroesophageal reflux disease (GERD) affects both men and women worldwide, with the most common symptom of GERD being frequent heartburn. If left untreated, more serious diseases including esophagitis and/or esophageal cancer may result. GERD has been commonly held to be the result of gastric acid refluxing into the esophagus. Recent work, however, has shown that there are acid-producing cells in the upper aerodigestive tract. In addition, acid-producing bacteria located within the upper gastrointestinal tract and oral cavity may also be a contributing factor in the onset of GERD. Proton pump inhibitors (PPIs) are commonly prescribed for treating GERD; these drugs are designed to stop the production of gastric acid by shutting down the H(+)/K(+)-ATPase enzyme located in parietal cells. PPI treatment is systemic and therefore significantly different than traditional antacids. Although a popular treatment choice, PPIs exhibit substantial interpatient variability and commonly fail to provide a complete cure to the disease. Recent studies have shown that H(+)/K(+)-ATPases are expressed in tissues outside the stomach, and the effects of PPIs in these nongastric tissues have not been fully explored. Likewise, acid-producing bacteria containing proton pumps are present in both the oral cavity and esophagus, and PPI use may also adversely affect these bacteria. The use of PPI therapy is further complicated by the two philosophical approaches to treating this disease: to treat only symptoms or to treat continuously. The latter approach frequently results in unwanted side effects which may be due to the PPIs acting on nongastric tissues or the microbes which colonize the upper aerodigestive tract.

Systematic review: health-related quality of life (HRQOL) questionnaires in gastro-oesophageal reflux disease

BACKGROUND

Although gastro-oesophageal reflux disease (GERD) has a well-established pathophysiology, the impact of GERD symptoms on the patients' quality of life can be profound. Therefore, health-related quality of life (HRQOL) questionnaires have become standard instruments to evaluate the effect of treatment in clinical trials.

AIM

To evaluate the reliability, validity and responsiveness of available GERD-specific HRQOL.

METHODS

A systematic literature search using the Medical Subject Headings terms: 'Gastro-oesophageal reflux', 'Heartburn' and 'Oesophagitis' with 'quality of life' and 'questionnaires' was preformed to identify the available HRQOL questionnaires. To analyse the psychometric properties of the respective tools, the actual guidelines for the use of patient-reported outcomes in clinical trials were applied.

RESULTS

We identified five GERD-specific HRQOL questionnaires but none of them fulfilled all quality criteria; either they did not meet the actual standards for psychometric properties (HBQOL, GERD-HRQL, Jasani et al.Aust Fam Physician 1999; 28: 515), or were impracticable to use in clinical trials. The generic and hybrid instruments lack specificity and sensitivity and were not designed for treatment evaluation in GERD patients.

CONCLUSION

There is need for a new evaluative tool in the assessment of HRQOL during GERD therapy.

Advances in roles of prokinetic agents in the treatment of gastroesophageal reflux disease

Gastroesophageal reflux disease (GERD) is characterized by the reflux of gastric content into esophagus with or without histological changes. Pathogenesis of GERD is lower esophageal sphincter (LES) dysfunction, abnormal clearing capacity of refluxed materials, delayed gastric emptying and abnormal resistance of esophageal mucosa to gastric acid, but the primary upper gastrointestinal motility dysfunction is regarded as the most important factor in general. Therefore, prokinetic agents which can restore gastric motility with increasing of LES and esophageal motility have been developed and used frequently in the treatment of GERD. There are several prokinetic agents such as metoclopramide, domperidone, cisapride and mosapride that facilitate acetylcholine release from the enteric cholinergic neurons through a selective 5-HT₄ receptor agonistic action. It is considered that prokinetic agents have the same effect as H2 blocker in the treatment of patients with mild GERD. Additionally, it was reported that a combination therapy with prokinetic agents and proton pump inhibitors (PPI) or H2 receptor antagonists (H2RAs) is more effective than monotherapy in patients with severe GERD. This article reviews the recent advances in the role of prokinetic agents in the treatment of gastroesophageal reflux disease.