Safety of proton-pump inhibitors: the acid test

Gastric achlorhydria in H/K-ATPase-deficient (Atp4a(-/-)) mice causes severe hyperplasia, mucocystic metaplasia and upregulation of growth factors

BACKGROUND

Gastric neoplasia is common in humans, yet controversy remains over contributions of chronic achlorhydria, gastrinemia and hyperplasia, to cancer risk. To study this, mice lacking the gastric H/K-ATPase (Atp4a(-/-) mice) were used to determine whether chronic loss of acid secretion, with attendant hypergastrinemia, predisposes to cancer phenotype.

METHODS

Atp4a(-/-) and Atp4a(+/+) mice, paired for age and gender, were examined at 3, 8, 12 and 20 months for histopathology, and for expression of the trefoil factor family (TFF)1-3, Reg IIIbeta, gamma and delta, osteopontin, CD44, chromogranin A, Crp-ductin, and galectin, all of which are important in cell growth.

RESULTS

By 8 months, the glandular stomach of the Atp4a(-/-) mice doubled in weight and thickness, and several modulators of growth were increased. Female Atp4a(-/-) mice were more hyperplastic than Atp4a(-/-) males at 12 and 20 months. By 1 year, severe mucocystic hyperplasia, incomplete intestinal metaplasia, ciliated metaplasia, a shift in mucins from neutral to acidic, and inflammation were widespread. Cells in the mucus pit zone developed a pyloric-type appearance, containing large hyaline-like, periodic acid-Schiff (PAS)-negative/alcian blue-negative inclusions. But critical characteristics of gastric neoplasia, such as nuclear atypia, invasion into the muscularis mucosa, and metastases were absent. In Atp4a(-/-) mice, chromogranin A and histidine decarboxylase, RegIIIgamma and delta, TFF3, osteopontin and CD44 were upregulated while Reg IIIbeta, and TFF1 were reduced.

CONCLUSIONS

Chronic achlorhydria and hypergastrinemia in aged Atp4a(-/-) mice produced progressive hyperplasia, mucocystic and incomplete intestinal metaplasia, and the upregulation of growth factors without histological evidence of neoplasia.

The use of proton pump inhibitors in children: a comprehensive review

Proton pump inhibitors (PPIs) belong to a group of chemically related compounds whose primary function is the inhibition of acid production in the final common metabolic pathway of gastric parietal cells. PPIs are highly selective and effective in their action and have few short- or long-term adverse effects. These pharmacologic features have made the development of PPIs the most significant advancement in the management of acid peptic related disorders in the last two decades. There are numerous published adult studies that describe the pharmacology, efficacy and safety of these anti-secretory agents; however, in the pediatric population, there are very few comparable studies, particularly multicenter studies with significant patient enrollment. In preparing this article, our aim was to perform a comprehensive review of the literature on the clinical pharmacology and use of PPIs in the pediatric population, and to briefly review some recent articles. Relevant literature was identified by performing MEDLINE/Pubmed searches from January 1990 to December 2001. Combinations of the following search terms were use to analyze these databases: proton pump inhibitor, children, pediatrics, gastroesophageal reflux disease (GERD), esophagitis, intestinal metaplasia, Helicobacter pylori, omeprazole, lansoprazole, pantoprazole, rabeprazole, esomeprazole, and safety. Abstracts from the 14th annual conference of the North American Society for Pediatric Gastroenterology, Hepatology and Nutrition (NASPGHAN) 2001, and the Disease and Digestive Week 2001, were also included in the review. All pediatric studies reviewed were limited to either omeprazole or lansoprazole. The dosage range used for the management of GERD and related disorders with lansoprazole was 0.73-1.66 mg/kg/day (maximum 30 mg/day). The dosage range for GERD management using omeprazole was 0.3-3.5 mg/kg (maximum 80 mg/day). The dosage range for omeprazole used for H. pylori was 0.5-1.5 mg/kg/day, with a maximum dosage of 40 mg/day, and lansoprazole-containing regimens for H. pylori eradication used dosages ranging from 0.6-1.2 mg/kg/day, with a maximum dosage of 30 mg/day. Few severe adverse events were reported with the use of either drug. Eradication rates for H. pylori were 56-87% for lansoprazole-based triple therapy, and 75-94% for omeprazole-based eradication regimens. To date, there are no published controlled trials of sufficient power comparing the efficacy of the five commercially available PPIs in children, for a variety of acid peptic diseases. Studies suggest that PPIs are highly effective for the management of GERD and related disorders, and are a critically needed component of triple therapy to eradicate H. pylori. PPIs have a very good tolerability profile in adults and children, but long-term tolerability studies are needed, particularly in the pediatric population. Multicenter studies are critically needed to evaluate the second-generation PPIs, to compare PPI efficacy to each other, and to assess the importance of developmental and genetic pharmacology of these drugs in children with acid-peptic disease.

Gastric mucosal morphological consequences of acid suppression: a balanced view

In the chapter, an analysis of the literature on the relationship between Helicobacter pylori, the use of proton pump inhibitors and the development of atrophic gastritis is presented, and the difficulties of classifying gastritis and the new possibilities of quantifying chronic inflammation by morphometric analysis are discussed. The issue surrounding the necessity of eradicating H. pylori in H. pylori-positive patients has still not been solved. Most studies have now accepted that proton pump inhibitors indeed accelerate the onset of atrophic gastritis in H. pylori-positive patients, but evidence against such an association was published in one recent (Scandinavian) study; conclusions from this study have, however, been challenged by several groups. Some data are available on the efficacy of H. pylori eradication with regard to the prevention of atrophy. The limited significance of the development of parietal cell protrusions and fundic gland cysts is better understood, but much less is known of the development and long-term consequence of H. pylori-induced autoimmune gastritis. Finally, recent studies in H. pylori-positive patients indicate that treatment with proton pump inhibitors may promote bacterial N-nitrosation formation. These data taken together suggest that the eradication of H. pylori may be based not only on morphological arguments, but also on bacterial alterations in the gastric milieu.