Current Status of Gastric Proton Pump Inhibitors in the Treatment of Acid-Peptic Disease

Proton pump inhibitors represent an important advance in the treatment of acid-peptic disease. Omeprazole, the prototype of the drug class, produces a profound and sustained degree of gastric acid suppression. Recent studies confirm earlier reports that omeprazole 20 mg/d is generally more effective than standard histamine2 receptor antagonist (H2RA) dosage regimens in treating duodenal ulcer (DU), gastric ulcer (GU), and erosive esophagitis. Omeprazole tends to accelerate DU and GU healing, especially during the first 2 weeks of treatment, and also accelerates mucosal healing in patients with all grades of esophagitis. Omeprazole is the drug of choice for treating patients with large or refractory ulcers, severe or refractory erosive esophagitis, Barrett's esophagus, and Zollinger-Ellison syndrome. Maintenance therapy with omeprazole seems to reduce ulcer recurrence and esophagitis, but optimal treatment regimens must be established. Dual therapy with omeprazole and amoxicillin shows encouraging results in eradicating Helicobacter pylori, reducing duodenal ulcer recurrence rates, and altering the natural history of peptic ulcer disease. Further studies are required to determine the efficacy of omeprazole in preventing nonsteroidal anti-inflammatory drug-induced ulcers and stress-related mucosal bleeding, and in treating upper gastrointestinal bleeding. Omeprazole is well-tolerated in the majority of patients receiving either short-term or long-term treatment. The type and frequency of adverse effects are similar to those reported with the H2RAs. There is no evidence to support genotoxicity or hypergastrinemia-induced enterochromaffin-like cell carcinoid of the stomach in patients receiving omeprazole treatment for more than 5 years. Omeprazole interacts selectively with hepatic P-450 and may potentially interact with phenytoin, warfarin, or diazepam. Pharmacoeconomic studies suggest that treatment with omeprazole provides a significant cost-savings over the H2RAs in patients with moderate to severe erosive esophagitis and possibly in patients with DU. Lansoprazole, a newly developed proton pump inhibitor, seems to offer no clear advantage over omeprazole.

Alcohol: Gastrointestinal and other Toxicities

This article will focus on the two areas of alcohol injury: first, the gastrointestinal system, primarily liver toxicity and cirrhosis, and second, the human toll in injury, examining injury epidemiology information that estimates alcohol's involvement in trauma. Any pharmacist consulting in any capacity, especially related to gastrointestinal disorders, will need to understand the significant sociological, pathological, pharmacological, and psychological impact of alcohol. Pharmacists providing care, including dispensing many different drugs to patients, should be cognizant of the interacting effects of alcohol and the need to warn patients. Finally, the reader will learn of a case in which a pharmacist was sued for not warning about the use of alcohol with a central nervous system depressant, and the resultant litigation after that lawsuit.

Deep Vein Thrombosis and Stress Ulcer Prophylaxis in the Intensive Care Unit

Deep vein thrombosis (DVT) and stress gastric ulcers can be serious complications in patients admitted to the intensive care unit. This review discusses the risk factors associated with the development of DVT and stress-related mucosal disease (SRMD), evaluates the available literature on current options for DVT and stress ulcer prophylaxis, and examines the associated adverse effects and optimal duration of therapy.

Esomeprazole induces upper gastrointestinal tract transmucosal permeability increase

BACKGROUND

Proton pump inhibitors (PPIs) are one of the most widely used drug classes in the US and are now frontline medications for gastro-oesophageal reflux disease (GERD) and dyspepsia. In a previous work, we observed that a transmucosal, upper gastrointestinal (GI) leak exists in Barrett's oesophagus (BO) patients. PPI medications are commonly used by Barrett's patients.

AIM

To examine if the PPI, esomeprazole, affects the barrier function of the upper GI tract.

METHODS

The sucrose permeability test (SPT) was used to assess the possible effect of the PPI, esomeprazole, on upper GI leak in 37 first-time-presenting GERD patients and 25 healthy controls.

RESULTS

Esomeprazole induced a significant transmucosal leak in the upper GI tract of patients taking the drug for the first time. The leak occurred quickly, within days of first taking the drug. The leak was also reversed within days of stopping the medication.

CONCLUSIONS

This is the first patient-based study showing that a PPI compromises upper GI barrier function. There are potential implications for transmucosal leak of other medications that a patient on a PPI may be taking, as well as possible leak of endogenous peptides/proteins. The clinical consequences of this phenomenon are currently unknown, but are potentially important.

Proton pump inhibitor formulary considerations in the acutely ill. Part 2: Clinical efficacy, safety, and economics

OBJECTIVE

To review, using an evidence-based approach, the clinical efficacy, safety, and cost-effectiveness of proton pump inhibitors (PPIs) for treatment of common acid peptic disorders in the acutely ill and provide clinicians with guidance when making hospital formulary decisions with this class of agents.

DATA SOURCES

MEDLINE (1966-May 2005) and the Cochrane Library databases were searched using the key words proton pump inhibitor, acid suppression, peptic ulcer disease, gastrointestinal bleeding, stress ulcer prophylaxis, critical care, safety, and cost-effectiveness. Bibliographies of cited references were reviewed, and a manual search of abstracts from recent gastroenterology, critical care, and surgery scientific meetings was completed.

STUDY SELECTION AND DATA EXTRACTION

All articles identified from the data sources were evaluated, and all information deemed relevant was included for this review.

DATA SYNTHESIS

PPIs have become a mainstay for acute acid suppression in hospitalized patients. Various commercially available PPI products are available either enterally or parenterally for administration to patients unable to swallow a tablet or capsule. The results of studies comparing the clinical efficacy of different PPI dosage forms and routes of administration, safety considerations, and cost-effectiveness analyses are among the factors to consider when making formulary decisions for this class of drugs.

CONCLUSIONS

While the introduction of new PPI products has expanded the therapeutic options for acid suppression in acutely ill patients, a number of unresolved questions remain surrounding the interchangeability of these products, the clinical significance of one PPI formulation over the other, and how oral/enteral therapy should be used as step-down therapy after parenteral therapy.

Overview of pharmacologic agents for acid suppression in critically ill patients

PURPOSE

The physiology of acid secretion, rationale and goals for acid suppression in critically ill patients, and mechanism of action, pharmacokinetics, pharmacodynamics, and safety of histamine H2-receptor antagonists (H2RAs) and proton pump inhibitors (PPIs) are discussed.

SUMMARY

Acid-suppressant therapy may be used in critically ill patients to prevent stress-related mucosal disease or the recurrence of peptic ulcer bleeding. The intragastric pH goal is 3.5-4.5 and 6 or higher, respectively. H2RAs block only one of three pathways in acid secretion and provide less potent acid suppression than PPIs, which block the final common pathway in acid secretion. In addition, tolerance that occurs with H2RAs does not occur with PPIs. All PPIs work in a similar manner, but differences exist in the pharmacokinetic profiles and binding to the proton pump; the clinical relevance of these differences remains debated. The safety profiles of H2RAs and PPIs are similar; however, the H2RA dose, but not the PPI dose, must be adjusted for patients with renal dysfunction. The risk of drug interactions mediated by cytochrome P-450 enzymes is lower with PPIs than with cimetidine, an H2RA. Several new PPI dosage forms have been introduced, facilitating drug administration in the critical care setting.

CONCLUSION

Both H2RAs and PPIs are safe agents to use for providing acid suppression in critically ill patients, but PPIs offer several potential advantages over H2RAs.

Pharmacologic properties of proton pump inhibitors

Since their introduction into clinical practice in the 1980s, proton pump inhibitors (PPIs) have proved to be of enormous value in the management of acid peptic disorders. They have become the treatment of choice for most, if not all, acid-related gastrointestinal disorders, including gastroesophageal reflux disease, peptic ulcer, and Zollinger-Ellison syndrome. With approval of an intravenous formulation, the benefits of PPIs are extended to critically ill patients for whom oral drug administration is often unsuitable. Five PPIs are approved for clinical use in the United States. Although they share a common core structure and mechanism of action, it is important to understand the general pharmacology of these agents and how they differ from histamine2-receptor antagonists in order to optimize PPI therapy.

Pharmacologic features of proton pump inhibitors and their potential relevance to clinical practice

In conclusion, PPIs differ slightly in their PK and PD properties and in their propensity to interact with other medications. Inhibition of acid secretion is a function of proton pump inhibition, and PPIs work in a similar fashion to achieve this goal. PK/PD principles can be used to optimize PPI therapy when considering issues related to administration, such as timing of drug delivery relative to the number of active pumps and the drug's AUC.

Pharmacologic strategies for treating gastroesophageal reflux disease

OBJECTIVE

This paper presents a synopsis of the pathophysiology of gastroesophageal reflux disease (GERD) and the efficacy, safety, and cost of the agents commonly used in its treatment.

BACKGROUND

Symptomatic relief of GERD can be obtained with lifestyle changes (avoidance of factors that may exacerbate symptoms, such as overeating and use of alcohol and tobacco) and use of over-the-counter medications such as antacids or histamine-2 (H2)-receptor antagonists. When these measures are unsuccessful, treatment with prescription-strength medications is required to prevent complications, such as Barrett's esophagus or esophageal adenocarcinoma.

METHODS

Current guidelines for the management of GERD were identified through a MEDLINE search of the English-language literature from January 1995 through December 1999 and a search of the bibliographies of identified articles.

CONCLUSION

Patients who do not respond to initial therapy should be managed with prescription-strength H2-receptor antagonists. Endoscopy should be considered for patients with atypical or refractory symptoms. Patients with a confirmed diagnosis of refractory GERD, severe esophagitis, Barrett's esophagus, or peptic stricture should be treated with and maintained on a proton-pump inhibitor.

Evaluation of omeprazole, lansoprazole, pantoprazole, and rabeprazole in the treatment of acid-related diseases

OBJECTIVE

To review the comparative efficacy and safety of the proton pump inhibitors (PPIs)--omeprazole, lansoprazole, pantoprazole, and rabeprazole--in the management of acid-related diseases.

DATA SOURCES

English-language journal articles retrieved from a MEDLINE search from 1990 to the present using these index terms: proton pump inhibitors, omeprazole, lansoprazole, pantoprazole, rebeprazole, and each of the acid-related diseases.

STUDY SELECTION

Clinical trials and pertinent review articles that discussed the pharmacology, pharmacokinetics, efficacy, and safety of PPIs in the management of acid-related disease.

DATA EXTRACTION

By the authors.

DATA SYNTHESIS

PPIs are substituted benzimidazoles that inhibit gastric acid secretion by covalently binding to the proton pump (H+/K+ ATPase). All undergo extensive hepatic metabolism and conjugation. The four agents differ in their metabolism by and effects on specific hepatic enzymes and thus in their ability to interact with other medications. PPIs are important agents used for eradicating Helicobacter pylori, in treating peptic ulcer disease, gastroesophageal reflux disease, Zollinger-Ellison syndrome, and upper gastrointestinal bleeding, and for preventing acid aspiration. Short-term side effects of the four agents are similar. The long-term safety of pantoprazole and rabeprazole appears similar to that of omeprazole and lansoprazole. Pantoprazole, which is in the final stages of approval for marketing in the United States, will be available in both an oral and injectable formulation.

CONCLUSION

Based on superior efficacy profiles, PPIs are the drugs of choice in managing patients with peptic ulcer disease, gastroesophageal reflux disease, and Zollinger-Ellison syndrome. The decision to select one PPI versus another is most likely to be based on the agents' acquisition costs, formulations, FDA-labeled indications, and overall safety profiles. Intravenous or parenteral pantoprazole may become the preferred antisecretory agent for patients unable to take oral medications (e.g., critically ill patients and those with Zollinger-Ellison syndrome).

Review article: pharmacokinetic concerns in the selection of anti-ulcer therapy

Rabeprazole is a new, highly potent proton pump inhibitor (PPI) being introduced for the treatment of disorders of gastric acid hypersecretion. Rabeprazole joins other drugs in this class, such as omeprazole, pantoprazole, and lansoprazole, which share a common mechanism of action. Each of these drugs is a substituted benzimidazole, which inhibits activity of the H+, K+ -ATPase located on the apical surface of parietal cells, thereby preventing the secretion of gastric acid. As a result of structural and functional similarities, the PPIs share many pharmacokinetic features. They have comparable rates of absorption, maximum plasma concentrations, and total drug absorptions resulting in similar bioavailability after single-dose administration. With multiple dosing, rabeprazole differs from omeprazole in that its pharmacokinetic profile does not change significantly over the course of therapy. All the PPIs are metabolized rapidly, resulting in short half-lives. However, their duration of activity is much longer, due to the way in which they bind to H+, K+ -ATPase. All are metabolized by hepatic cytochrome P450 enzymes, although only omeprazole has demonstrated significant interactions with other drugs metabolized by this pathway. Rabeprazole, which has a low potential for interacting with drugs metabolized by cytochrome P450, does interfere with the absorption of digoxin and ketoconazole because of its antisecretory effects. The pharmacokinetics of rabeprazole are altered slightly in elderly subjects and in patients with renal and moderate hepatic disease. However, the pharmacokinetic findings suggest that no dosage adjustment is required in these special populations.

Review article: drug interactions with agents used to treat acid-related diseases

Patients with acid-related diseases often need to take multiple medications. Treatment of Helicobacter pylori infection often includes either a histamine type 2 (H2)-receptor antagonist or a proton pump (H+,K(+)-ATPase) inhibitor (proton pump inhibitor), administered in conjunction with one or more antimicrobials. Also, treatment for acid-related diseases often requires extended therapy during which many concomitant medications may be administered for concurrent disease states. Polypharmacy may be the result, particularly in elderly patients, who are at increased risk for both acid-related and many other diseases. Thus, it is important to understand the potential for clinically significant drug-drug interactions in this setting. H2-receptor antagonists and proton pump inhibitors can influence the pharmacokinetic profiles of other commonly administered medications by elevating intragastric pH, which can alter drug absorption, and by interacting with the cytochrome P (CYP) 450 enzyme system, which can affect drug metabolism and clearance. Such interactions are particularly important when they affect the pharmacokinetics of drugs with narrow therapeutic ranges (e.g. warfarin, digoxin). In these cases, drug-drug interactions can result in significant toxicity and even death. There are marked differences among H2-receptor antagonists and proton pump inhibitors in their potential for such interactions. The oldest drugs in each class, cimetidine and omeprazole, respectively, have the greatest potential to alter CYP activity and change the pharmacokinetics of other drugs. The most recently developed H2-receptor antagonist, famotidine, and the newer proton pump inhibitors, rabeprazole and pantoprazole, are much less likely to induce or inhibit CYP and thereby change the metabolism of other medications. These differences are important when choosing medications for the safe treatment of patients with acid-related diseases.