Sucralfate for prevention of naproxen-induced mucosal lesions in the proximal and distal gastrointestinal tract

The pathophysiology of non-steroidal anti-inflammatory drug (NSAID)-induced mucosal injuries in stomach and small intestine

Non-steroidal anti-inflammatory drugs are the most commonly prescribed drugs for arthritis, inflammation, and cardiovascular protection. However, they cause gastrointestinal complications. The pathophysiology of these complications has mostly been ascribed to non-steroidal anti-inflammatory drugs’ action on the cyclooxygenase inhibition and the subsequent prostaglandin deficiency. However, recent clinical demonstrated the prevalence of non-steroidal anti-inflammatory drugs-induced small intestinal mucosal injury is more often than previously expected. In this review, we discuss the defense mechanisms of stomach, and the pathophysiology of non-steroidal anti-inflammatory drugs-induced injury of stomach and small intestine, especially focused on non-steroidal anti-inflammatory drugs’ action on mitochondria.

Assessment and prevention of gastrointestinal toxicity of non-steroidal anti-inflammatory drugs

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used for analgesic, anti-inflammatory and, in the case of aspirin, for anti-thrombotic actions. The serious gastrointestinal side-effects associated with these drugs are of concern and pose a significant obstacle to their use. This review discusses the pathogenic mechanisms by which the conventional acidic NSAIDs induce gastrointestinal toxicity, with particular emphasis on non-prostaglandin effects. Methods of assessment of NSAID-induced enteropathy are reviewed, with particular emphasis on the use of functional measurement of NSAID-induced changes in the gastrointestinal tract. The advances in our knowledge of the pathogenesis of these effects have resulted in the development of a range of novel NSAIDs. Where functional assessment of the effects of NSAIDs has been employed, it appears to be more useful as an indicator of early-stage changes rather than a predictor of the effects of long-term NSAID exposure. Successful pharmaceutical strategies now offer considerable promise for reducing the severity of NSAID damage to the gastrointestinal tract. The utility of intestinal permeability measurements for selection and assessment of these strategies is discussed.

Intestinal permeability in the pathogenesis of NSAID-induced enteropathy

BACKGROUND

The pathogenesis of nonsteroidal antiinflammatory drug (NSAID)-induced small bowel disease suggests that increased intestinal permeability is the central mechanism that translates biochemical damage to tissue damage. The purpose of this review is to summarize studies on the effect of NSAIDs to increase intestinal permeability in humans and methods for limiting this effect.

METHODS

A Medline search was made for papers that described measurements of increased intestinal permeability in humans.

RESULTS

Virtually all studies agree that all conventional NSAIDs increase intestinal permeability in the human within 24 h of ingestion and that this is equally evident when they are taken long term. Various methods have been tried to limit the damage. The most promising agents are coadministration of synthetic prostaglandins, micronutrients, pre-NSAIDs, and COX-2 selective agents. However, their efficacy in preventing the development of NSAID enteropathy in the long term has not been studied in detail, and, in the case of COX-2 selective agents, small bowel damage is comparable to that which is seen with conventional NSAIDs.

CONCLUSIONS

NSAID enteropathy is associated with significant morbidity and occasionally mortality. There are no proven effective ways of preventing this damage. Because increased intestinal permeability appears to be a central mechanism in the pathogenesis of NSAID enteropathy, it becomes a potential therapeutic target for prevention. At present there are a number of ways to limit the increased permeability, but additional studies are required to assess if this approach reduces the prevalence and severity of NSAID enteropathy.

Prophylaxis and treatment of non-steroidal anti-inflammatory drug-induced upper gastrointestinal side-effects

The use of specific agents to heal mucosal lesions or to prevent non-steroidal anti-inflammatory drug toxicity, has focused upon two approaches: replacement of prostaglandin deficiency and inhibition of acid secretion. Acid suppression with traditional ulcer healing doses of H2-blockers is effective in healing gastric and duodenal ulcers upon discontinuation of the offending drug. In the event the non-steroidal anti-inflammatory drug must be continued, the use of H2-blockers is associated with a decrease in the healing rate. In long-term prevention studies, H2-blockers significantly reduce duodenal ulcer rates, but are ineffective in reducing gastric ulceration. More potent acid inhibition with a double-dose of H2-blockers (famotidine 80 mg daily, ranitidine 600 mg daily) may reduce the risk of gastric and duodenal ulcers. Marked acid suppression with proton pump inhibitors (omeprazole 20-40 mg, lansoprazole 30 mg daily) also appears to be very effective in healing gastric and duodenal ulcers in patients continuing the offending drug as well. An analysis of pooled data from comparative studies on omeprazole vs ranitidine, misoprostol and sucralfate shows a therapeutic advantage in favour of the proton pump inhibitor, ranging from 10 to 40%. In long-term prevention studies, omeprazole (20 mg daily) and pantoprazole (40 mg daily) have also been shown to reduce the risk of gastric and duodenal ulcers and non-steroidal anti-inflammatory drug-related dyspepsia. Current data from recent comparative studies of omeprazole (20 mg daily) vs ranitidine (150 mg daily) and misoprostol (200 microg daily) showed that, after 6 months' follow-up, the proton pump inhibitor was significantly superior to control drugs in reducing the risk both of gastric and duodenal ulcer. Misoprostol (at doses ranging from 400 microg to 800 microg/day) is an effective form of therapy for preventing non-steroidal anti-inflammatory drug-induced gastroduodenal lesions. However high-dose misoprostol only, seems adequate for the prevention of ulcer complications, mainly in high-risk non-steroidal anti-inflammatory drug users. Thus, available data are undoubtedly in favour of the proton pump inhibitors as well tolerated and effective drugs in the prophylaxis and treatment of non-steroidal anti-inflammatory drug-related mucosal lesions in the gastrointestinal tract.

Review article: non-steroidal anti-inflammatory drug-induced gastrointestinal permeability

Non-steroidal anti-inflammatory drugs induce damage throughout the entire gastrointestinal tract. Administration of site-specific permeability probes is a non-invasive technique for assessing the functional integrity of the gastrointestinal mucosa. A systematic search tor NSAID-induced permeability studies using MEDLINE and EMBASE, and an analysis of the literature on NSAID-induced gastrointestinal permeability, were carried out. The advantages and disadvantages of the various probes and study protocols are discussed. Identification of the underlying mechanisms of regulatory control of the epithelial tight junction is still needed. A greater appreciation of the pharmacokinetics and distribution of NSAIDs, coupled with gastrointestinal permeability studies, may help delineate the pathogenesis of NSAID-induced gastrointestinal toxicity. Non-invasive tests of gastric, intestinal and colonic permeability have shown promise in both basic research and in clinical practice. While such tests could not replace endoscopy, they may represent clinically useful techniques for identifying patients who would benefit from endoscopy, to assess the response to treatment, and perhaps to predict the clinical course of disease.

Influence of anti-rheumatic drugs on gut permeability and on the gut associated lymphoid tissue

There is great interest in the association between intestinal inflammation and the various arthropathies. However, most studies assessing intestinal function in these diseases are confounded by the fact that non-steroidal anti-inflammatory drugs (NSAIDs) have profound effects on the small intestine. Hence NSAIDs cause quite distinct and severe biochemical damage during drug absorption (uncoupling of mitochondrial oxidative phosphorylation proving to be most important) which results in increased intestinal permeability. All commonly used NSAIDs, apart from aspirin and nabumetone, are associated with increased intestinal permeability in man. Whilst reversible in the short term, it may take months to improve following prolonged NSAID use. Increased intestinal permeability appears to be the central mechanism of converting the biochemical damage to an inflammatory tissue reaction (NSAID enteropathy). The inflammatory enteropathy is not, however, unique to NSAIDs but similar changes are found with other permeability breakers. In intestinal infections and in diseases associated with reduced mucosal defence, suggesting that the small intestinal inflammation represents a common final pathway for a number of intestinal injuries. Spondylarthropathies are associated with a high prevalence of terminal ileitis, but as most patients have been receiving NSAIDs it has been difficult to dissociate the effects of NSAIDs on intestinal function from that of the ileitis itself. Nevertheless, two studies suggest that increased intestinal permeability in spondylarthropathies occur independently of NSAID ingestion. Whilst these findings may have implications for the development of arthritis, the permeability changes in spondylarthropathy do not differ quantitatively or qualitatively from that of NSAIDs or other permeability breakers. NSAID enteropathy can be differentiated from spondylarthropathic enteropathy by differences in location of disease and lack of predilection of certain HLA types. However, as the two may coexist both enteroscopy and ileocolonoscopy may be necessary for this distinction.

Antiinflammatory drug-induced small intestinal permeability: the rat is a suitable model

Excretion of orally administrated 51Cr-EDTA as a marker of small intestinal permeability (a proposed prerequisite for human enteropathy) is increased by corticosteroids and non-steroidal antiinflammatory drugs (NSAIDs). We have investigated the suitability of the rat as an animal model of small intestinal permeability using orally administered 51Cr-EDTA. We dosed Sprague-Dawley rats with NSAIDs and corticosterone followed by 51Cr-EDTA under conditions reported for humans and measured urinary excretion of the marker. In control rats, the urinary excretion of 51Cr-EDTA exhibited a skewed-to-the-left frequency distribution curve with a median of 2.13% of the dose. No sex-related differences were noticed in the baseline permeability. In male rats, single therapeutically equivalent doses of indomethacin, flurbiprofen, ibuprofen, naproxen, diclofenac, sulindac, nambumetone, and corticosterone, increased the intestinal permeability by different extents with indomethacin eliciting the maximum effect, and the last four drugs showing minimal potencies. Therapeutically relevant doses of aspirin did not have any significant effect. The increase in permeability was dependent upon the NSAIDs dose. Administration of glucose/citrate, misoprostol and sulfasalazine significantly reduced the effect of indomethacin. Misoprostol antagonized the effect of naproxen but H2-antagonists and sucralfate did not. All the above observations made in the rat were similar to those previously reported for humans. Thus the rat is a suitable model for studies of small intestinal permeability.

Review article: controversies in NSAID-induced gastroduodenal damage--do they matter?

BACKGROUND

This article reviews various issues surrounding NSAID-induced gastroduodenal ulceration, about which there appear to be conflicting views and data in the literature. These issues include the size, clinical relevance and main site of the problem; when complications occur (early or late?); the relevance of non-ulcer lesions and whether adaptation is a clinically relevant phenomenon.

METHOD

A comprehensive literature search was carried out to identify relevant new data published since 1987.

RESULTS

NSAIDs are causally associated with more gastric than duodenal ulcers but their use may be associated with duodenal ulcers or complications. Erosive lesions may progress to more severe damage. The theories of early or late onset of complications during a course of NSAID therapy may not be mutually exclusive.

CONCLUSIONS

Available data indicate that NSAID ulcers are at least as dangerous as classic peptic ulcers, and result in significant morbidity and mortality which in the patient population does not appear to be significantly reduced by processes such as adaptation.

Side effects of nonsteroidal anti-inflammatory drugs on the small and large intestine in humans

BACKGROUND

It is not widely appreciated that nonsteroidal anti-inflammatory drugs (NSAIDs) may cause damage distal to the duodenum. We reviewed the adverse effects of NSAIDs on the large and small intestine, the clinical implications and pathogenesis.

METHODS

A systematic search was made through Medline and Embase to identify possible adverse effects of NSAIDs on the large and small intestine.

RESULTS

Ingested NSAIDs may cause a nonspecific colitis (in particular, fenemates), and many patients with collagenous colitis are taking NSAIDs. Large intestinal ulcers, bleeding, and perforation are occasionally due to NSAIDs. NSAIDs may cause relapse of classic inflammatory bowel disease and contribute to serious complications of diverticular disease (fistula and perforation). NSAIDs may occasionally cause small intestinal perforation, ulcers, and strictures requiring surgery. NSAIDs, however, frequently cause small intestinal inflammation, and the associated complications of blood loss and protein loss may lead to difficult management problems. The pathogenesis of NSAID enteropathy is a multistage process involving specific biochemical and subcellular organelle damage followed by a relatively nonspecific tissue reaction. The various possible treatments of NSAID-induced enteropathy (sulphasalazine, misoprostol, metronidazole) have yet to undergo rigorous trials.

CONCLUSIONS

The adverse effects of NSAIDs distal to the duodenum represent a range of pathologies that may be asymptomatic, but some are life threatening.

Misoprostol--a logical therapeutic approach to gastroduodenal mucosal injury induced by non-steroidal anti-inflammatory drugs?

Misoprostol is a synthetic analogue of naturally occurring prostaglandin E1. The basis of the damaging actions of non-steroidal anti-inflammatory drugs (NSAIDs) on the gastrointestinal (GI) tract is believed to be a consequence of two events: a direct damaging action on mucosal integrity and depletion of endogenous mucosal prostaglandins (PGs). Due to the latter effect, and because current evidence indicates that PGs play an important role in maintaining the integrity of the GI tract, misoprostol has been developed as a logical therapy to prevent and heal gastric and duodenal damage caused by NSAIDs. The purpose of this review is to consider the need for such a therapy, to describe its pharmaceutical development, to review its pharmacology and to review its efficacy compared with other available agents.

Gastroduodenal lesions induced by naproxen. An endoscopic evaluation of regional differences and natural course

Gastroduodenal endoscopic findings were studied in 65 healthy volunteers receiving 750 mg or 1000 mg naproxen for 1 or 2 weeks. Separate registration of the mid- and distal duodenum showed that mucosal toxicity can be demonstrated even distally to the duodenal bulb. The lesions were closely correlated to the findings in the stomach and duodenal bulb, though generally somewhat less extensive. Whereas a difference between 750 mg and 1000 mg naproxen was demonstrated in an intraindividual comparison (n = 26; median sum of visual analogue scale score in the stomach/duodenal bulb, 129 mm and 183 mm, respectively; p less than 0.05), no difference was seen in two parallel groups (n = 32 and 33). In the stomach and duodenal bulb, a significant aggravation of mucosal lesions was seen from 1 to 2 weeks in 16 subjects. Healing was complete in 10/12 subjects after 3 weeks, independent of the extent of the initial damage.

NSAID-associated gastroduodenal damage: does famotidine protection extend into the mid- and distal duodenum?

Eighteen healthy volunteers were included in a cross-over, double-blind study where 500 mg naproxen b.d. was given for 1 week with 20 mg famotidine b.d., 40 mg nocte or placebo. Endoscopic evaluation of the gastroduodenal mucosa was performed before and after each treatment period, with separate evaluation of the mid- and distal duodenum. 51Cr-EDTA-permeability tests were done to study effects on the mid- and distal gut, and, in addition, symptom registration was performed. The mucosal damage was significant in all treatment periods, and a statistically significant reduction was seen with 20 mg famotidine b.d. for erosive lesions in the stomach/duodenal bulb region as well as for the sum of damage score in the mid- and distal duodenum. The reduction was considerable in a few subjects with extensive duodenal damage. The reduction was considerable in a few subjects with extensive duodenal damage. Intestinal permeation increased significantly in all periods, and was not reduced by famotidine. Symptoms were modest and equal in all periods.