Proton pump inhibitors (PPIs) have been increasingly used over the last decades and there are concerns about overuse and the numerous reported side-effects. It is uncertain whether associations between PPI use and potential side effects are causal. However, important evidence from experimental and mechanistic studies that could support a causal relationship may have been underestimated by epidemiologists and meta-analysists. In the current manuscript we review the combined epidemiological and mechanistic evidence of the adverse effects of PPI use.

Gastric juice is a unique combination of hydrochloric acid (HCl), lipase, and pepsin. Acidic gastric juice is found in all vertebrates, and its main function is to inactivate microorganisms. The phylogenetic preservation of this energy-consuming and, at times, hazardous function (acid-related diseases) reflects its biological importance. Proton pump inhibitors (PPIs) are one of the most widely used drugs in the world. Due to the reduced prevalence of Helicobacter pylori infection as well as the increased use of inhibitors of gastric acid secretion, the latter has become the most important cause of gastric hypoacidity. In the present manuscript, we review the microbiological consequences of removing gastric acidity. The resulting susceptibility to infections has not been studied extensively, and focus has mainly been restricted to bacterial and parasitic agents only. The strongest evidence concerning the relationship between hypochlorhydria and predisposition to infections relates to bacterial infections affecting the gastrointestinal tract. However, several other clinical settings with increased susceptibility to infections due to inhibited gastric acidity are discussed. We also discuss the impact of hypochlorhydria on the gut microbiome.

TNFalpha-antibodies have been used increasingly in treatment of inflammatory bowel disease (IBD) during the last years. This article provides an overview of indications, contraindications, efficacy, and side effects of this so-called biological treatment of IBD. Based on the clinical experience of the authors, literature was selected through a non-systematic search in PubMed. TNFalpha-antibodies have a documented initial effect in 60-70 % of patients with moderate to severe luminal and/or fistulising IBD. Approximately 30 % of patients achieve remission after a relatively short treatment period. However, the effect seems to decrease during long-term treatment. It is still unsettled whether these drugs prevent colectomy in ulcerative colitis. The treatment seems to increase the risk of serious infections and there are also some indications of an increased risk of malignancy. Combination therapy with azathioprin is common and probably increases both the effect and the risk of side effects. TNFalpha-antibodies have become an important part of the treatment for moderate to severe IBD, but the effect decreases during long-term treatment and has to be evaluated in light of potential side effects. Further long-term studies are necessary.