Gastrointestinal safety of AZD3582, a cyclooxygenase inhibiting nitric oxide donator: proof of concept study in humans

Exploring Nitric Oxide (NO)-Releasing Celecoxib Derivatives as Modulators of Radioresponse in Pheochromocytoma Cells

COX-2 can be considered as a clinically relevant molecular target for adjuvant, in particular radiosensitizing treatments. In this regard, using selective COX-2 inhibitors, e.g., in combination with radiotherapy or endoradiotherapy, represents an interesting treatment option. Based on our own findings that nitric oxide (NO)-releasing and celecoxib-derived COX-2 inhibitors (COXIBs) showed promising radiosensitizing effects in vitro, we herein present the development of a series of eight novel NO-COXIBs differing in the peripheral substitution pattern and their chemical and in vitro characterization. COX-1 and COX-2 inhibition potency was found to be comparable to the lead NO-COXIBs, and NO-releasing properties were demonstrated to be mainly influenced by the substituent in 4-position of the pyrazole (Cl vs. H). Introduction of the N-propionamide at the sulfamoyl residue as a potential prodrug strategy lowered lipophilicity markedly and abolished COX inhibition while NO-releasing properties were not markedly influenced. NO-COXIBs were tested in vitro for a combination with single-dose external X-ray irradiation as well as [¹⁷⁷Lu]LuCl₃ treatment in HIF2α-positive mouse pheochromocytoma (MPC-HIF2a) tumor spheroids. When applied directly before X-ray irradiation or ¹⁷⁷Lu treatment, NO-COXIBs showed radioprotective effects, as did celecoxib, which was used as a control. Radiosensitizing effects were observed when applied shortly after X-ray irradiation. Overall, the NO-COXIBs were found to be more radioprotective compared with celecoxib, which does not warrant further preclinical studies with the NO-COXIBs for the treatment of pheochromocytoma. However, evaluation as radioprotective agents for healthy tissues could be considered for the NO-COXIBs developed here, especially when used directly before irradiation.

Potential Strategies in the Prevention of Nonsteroidal Anti-inflammatory Drugs-Associated Adverse Effects in the Lower Gastrointestinal Tract

With the increasing use of nonsteroidal anti-inflammatory drugs (NSAIDs), the incidence of lower gastrointestinal (GI) complications is expected to increase. However, unlike upper GI complications, the burden, pathogenesis, prevention and treatment of NSAID-associated lower GI complications remain unclear. To date, no cost-effective and safe protective agent has been developed that can completely prevent or treat NSAID-related lower GI injuries. Selective COX-2 inhibitors, misoprostol, intestinal microbiota modulation, and some mucoprotective agents have been reported to show protective effects on NSAID-induced lower GI injuries. This review aims to provide an overview of the current evidence on the prevention of NSAID-related lower GI injuries.

Nitric oxide in the gastrointestinal tract: opportunities for drug development

Nitric oxide (NO) plays important roles in gastrointestinal mucosal defence, as well as in the pathogenesis of several gastrointestinal diseases (e.g. irritable bowel syndrome and inflammatory bowel disease). The potent cytoprotective effects of NO have been demonstrated in a range of animal models. However, in some disease states, inhibition of NO synthesis is beneficial. Several attempts have been made to develop drugs for ulcerative and/or inflammatory disorders of the gastrointestinal tract, with varying degrees of success. Covalently linking a NO-releasing group to non-steroidal anti-inflammatory drugs or to drugs used in the treatment of inflammatory bowel disease and irritable bowel syndrome has shown some benefit, although no drug of this type has yet been fully developed. LINKED ARTICLES: This article is part of a themed section on Nitric Oxide 20 Years from the 1998 Nobel Prize. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.2/issuetoc.

Mechanisms of Damage to the Gastrointestinal Tract From Nonsteroidal Anti-Inflammatory Drugs

Nonsteroidal anti-inflammatory drugs (NSAIDs) can damage the gastrointestinal tract, causing widespread morbidity and mortality. Although mechanisms of damage involve the activities of prostaglandin-endoperoxide synthase 1 (PTGS1 or cyclooxygenase [COX] 1) and PTGS1 (COX2), other factors are involved. We review the mechanisms of gastrointestinal damage induction by NSAIDs via COX-mediated and COX-independent processes. NSAIDs interact with phospholipids and uncouple mitochondrial oxidative phosphorylation, which initiates biochemical changes that impair function of the gastrointestinal barrier. The resulting increase in intestinal permeability leads to low-grade inflammation. NSAID inhibition of COX enzymes, along with luminal aggressors, results in erosions and ulcers, with potential complications of bleeding, protein loss, stricture formation, and perforation. We propose a model for NSAID-induced damage to the gastrointestinal tract that includes these complex, interacting, and inter-dependent factors. This model highlights the obstacles for the development of safer NSAIDs.

Non-steroidal anti-inflammatory drug-induced enteropathy

Non-steroidal anti-inflammatory drugs (NSAIDs) are well known to be associated with serious upper gastrointestinal complications, such as peptic ulcer, bleeding, perforation, and obstruction. Recently, attention has been mainly focused on the small bowel injuries caused by NSAIDs, and new endoscopic techniques such as capsule endoscopy and double balloon endoscopy can help in detecting such injuries. This article reviewed the epidemiology, pathogenesis, clinical manifestations, diagnosis, and treatment of small bowel injuries caused by NSAIDs. Small bowel injures by NSAIDs might occur with a similar frequency and extent as those observed in the upper gastrointestinal tract. The pathogenesis of NSAID-induced enteropathy is complex and not clearly understood. The various lesions observed in the small bowel, including petechiae, reddened folds, loss of villi, erosions, and ulcers can be detected by capsule endoscopy. A drug that could prevent or treat NSAID-induced enteropathy has not yet been developed. Therefore, further investigations should be performed to elucidate the pathogenesis of such enteropathy and develop suitable preventive and treatment strategies.

Review article: a practical approach to the clinical management of NSAID enteropathy

Co-prescription of acid suppressive therapy, together with advances in small bowel imaging techniques, have shifted the burden of NSAID-related toxicity from gastro-duodenal to more distal small bowel injury. Due to predominantly subclinical disease, NSAID enteropathy remains under-recognised, with an incidence of 53-80% amongst healthy short-term users, and a prevalence of 50-71% following long-term (>3 months) use. Despite their distinct pathogenesis, those at risk of NSAID-related gastro-duodenal and small bowel complications share several risk factors. Clinical complications of NSAID enteropathy such as protein-losing enteropathy, small bowel strictures and diaphragm disease, confer significant morbidity, and are often irreversible. Small bowel prophylaxis has proven of modest efficacy after short-term, high-dose NSAID use in asymptomatic patients. While selective COX-2 inhibitors are associated with fewer gastro-duodenal complications relative to non-selective NSAIDs, their comparative benefit in protecting against small bowel enteropathy remains unclear. Prophylaxis should be considered in those at high risk of small bowel complications, as treatment options for established disease remain limited; however, the optimal agent remains unclear. We propose a clinical algorithm that may help prevent, monitor, investigate, and manage the sequelae of NSAID-induced small bowel toxicity.

Nonsteroidal Anti-Inflammatory Therapy: A Journey Toward Safety

The efficacy of nonsteroidal anti-inflammatory drugs (NSAIDs) against inflammation, pain, and fever has been supporting their worldwide use in the treatment of painful conditions and chronic inflammatory diseases until today. However, the long-term therapy with NSAIDs was soon associated with high incidences of adverse events in the gastrointestinal tract. Therefore, the search for novel drugs with improved safety has begun with COX-2 selective inhibitors (coxibs) being straightaway developed and commercialized. Nevertheless, the excitement has fast turned to disappointment when diverse coxibs were withdrawn from the market due to cardiovascular toxicity. Such events have once again triggered the emergence of different strategies to overcome NSAIDs toxicity. Here, an integrative review is provided to address the breakthroughs of two main approaches: (i) the association of NSAIDs with protective mediators and (ii) the design of novel compounds to target downstream and/or multiple enzymes of the arachidonic acid cascade. To date, just one phosphatidylcholine-associated NSAID has already been approved for commercialization. Nevertheless, the preclinical and clinical data obtained so far indicate that both strategies may improve the safety of nonsteroidal anti-inflammatory therapy.

Nonsteroidal anti-inflammatory drugs, proton pump inhibitors, and gastrointestinal injury: contrasting interactions in the stomach and small intestine

Nonsteroidal anti-inflammatory drugs (NSAIDs) and proton pump inhibitors (PPIs) are among the most frequently prescribed groups of drugs worldwide. The use of NSAIDs is associated with a high number of significant adverse effects. Recently, the safety of PPIs has also been challenged. Capsule endoscopy studies reveal that even low-dose NSAIDs are responsible for gut mucosal injury and numerous clinical adverse effects, for example, bleeding and anemia, that might be difficult to diagnose. The frequent use of PPIs can exacerbate NSAID-induced small intestinal injury by altering intestinal microbiota. Thus, the use of PPI is considered to be an independent risk factor associated with NSAID-associated enteropathy. In this review, we discuss this important clinical problem and review relevant aspects of epidemiology, pathophysiology, and management. We also present the hypothesis that even minor and subclinical injury to the intestinal mucosa can result in significant, though delayed, metabolic consequences, which may seriously affect the health of an individual. PubMed was searched using the following key words (each key word alone and in combination): gut microbiota, microbiome, non-steroidal anti inflammatory drugs, proton pump inhibitors, enteropathy, probiotic, antibiotic, mucosal injury, enteroscopy, and capsule endoscopy. Google engine search was also carried out to identify additional relevant articles. Both original and review articles published in English were reviewed.

An overview of history, pathogenesis and treatment of perforated peptic ulcer disease with evaluation of prognostic scoring in adults

Peptic ulcer disease including both gastric and duodenal ulcer form a substantial part of patients seeking surgical opinion world-wide. The concept of acid in peptic ulcer disease, which was the basis of treatment of peptic ulcer was revolutionized by the discovery of H₂-receptor antagonists, that led to the principle of acid suppression therapy for duodenal ulcer which followed decades of preference for surgical interventions in the form of gastric resections, vagotomy etc., After the discovery of Helicobacter pylori organism as the causative factor a triple drug regime was identified to treat peptic disease which was further modified to sequential therapy to avoid antibiotic resistance. This recognition has not concluded the chapter on peptic ulcers. The management of ulcer disease and its complications remain a surgical challenge. All the materials for this review have been accessed from various internet search engines. The references have been narrowed down to 34 by excluding cross references, duplicated citations, pediatric studies, case reports, iatrogenic and malignant perforations and including microbiological, immunohistochemistry references and studies with more than a sample size of ten. Case control, cohort studies, prospective/retrospective, metaanalytical studies were preferred in that order. This article attempts to take an overview of all aspects of the management of peptic ulcer.

Mechanisms, prevention and clinical implications of nonsteroidal anti-inflammatory drug-enteropathy

This article reviews the latest developments in understanding the pathogenesis, detection and treatment of small intestinal damage and bleeding caused by nonsteroidal anti-inflammatory drugs (NSAIDs). With improvements in the detection of NSAID-induced damage in the small intestine, it is now clear that this injury and the associated bleeding occurs more frequently than that occurring in the stomach and duodenum, and can also be regarded as more dangerous. However, there are no proven-effective therapies for NSAID-enteropathy, and detection remains a challenge, particularly because of the poor correlation between tissue injury and symptoms. Moreover, recent studies suggest that commonly used drugs for protecting the upper gastrointestinal tract (i.e., proton pump inhibitors) can significantly worsen NSAID-induced damage in the small intestine. The pathogenesis of NSAID-enteropathy is complex, but studies in animal models are shedding light on the key factors that contribute to ulceration and bleeding, and are providing clues to the development of effective therapies and prevention strategies. Novel NSAIDs that do not cause small intestinal damage in animal models offer hope for a solution to this serious adverse effect of one of the most widely used classes of drugs.

Managing the adverse effects of nonsteroidal anti-inflammatory drugs

Conventional medical treatment for rheumatoid arthritis and osteoarthritis includes the use of NSAIDs (traditional and selective inhibitors of cyclooxygenase [COX]-2), because they provide unmistakable and significant health benefits in the treatment of pain and inflammation. However, they are associated with an increased risk of serious gastrointestinal (GI) and cardiovascular (CV) adverse events. Both beneficial and adverse effects are due to the same mechanism of action, which is inhibition of COX-dependent prostanoids. Since CV and GI risk are related to drug exposure, a reduction in the administered dose is recommended. However, this strategy will not eliminate the hazard owing to a possible contribution of individual genetic background. Further studies will be necessary to develop genetic and/or biochemical markers predictive of the CV and GI risk of NSAIDs.

NSAID gastropathy and enteropathy: distinct pathogenesis likely necessitates distinct prevention strategies

The mechanisms underlying the ability of nonsteroidal anti-inflammatory drugs (NSAIDs) to cause ulceration in the stomach and proximal duodenum are well understood, and this injury can largely be prevented through suppression of gastric acid secretion (mainly with proton pump inhibitors). In contrast, the pathogenesis of small intestinal injury induced by NSAIDs is less well understood, involving more complex mechanisms than those in the stomach and proximal duodenum. There is clear evidence for important contributions to NSAID enteropathy of enteric bacteria, bile and enterohepatic recirculation of the NSAID. There is no evidence that suppression of gastric acid secretion will reduce the incidence or severity of NSAID enteropathy. Indeed, clinical data suggest little, if any, benefit. Animal studies suggest a significant exacerbation of NSAID enteropathy when proton pump inhibitors are co-administered with the NSAID. This worsening of damage appears to be linked to changes in the number and types of bacteria in the small intestine during proton pump inhibitor therapy. The distinct mechanisms of NSAID-induced injury in the stomach/proximal duodenum versus the more distal small intestine likely dictate distinct strategies for prevention.

Endoscopic evaluation of the gastro-duodenal tolerance of short-term analgesic treatment with 25 mg diclofenac-K liquid capsules

BACKGROUND

Diclofenac-potassium (diclofenac--K) 25 mg liquid capsule is absorbed more quickly than the tablet formulation. It offers potential for rapid pain relief, but may alter gastro-duodenal tolerability.

AIM

To evaluate the gastro-duodenal tolerance of diclofenac-K 25 mg liquid capsules vs. diclofenac-K 12.5 mg tablets, acetylsalicylic acid (ASA) 500 mg tablets and ibuprofen 200 mg liquid capsules.

METHODS

In an endoscopist-blinded, randomised, parallel-group study, volunteers received 15 doses of diclofenac-K 25 mg liquid capsules (n = 36), diclofenac-K 2 × 12.5 mg tablets (n = 36), ibuprofen 2 × 200 mg liquid capsules (n = 24) or ASA 2 × 500 mg tablets (n = 36) over 5 days. The primary outcome was the incidence of erosive gastro-duodenal lesions at Day 6. Secondary outcomes included modified Lanza score and change in gastric mucosal prostaglandin synthesis.

RESULTS

The lowest incidence of erosive gastro-duodenal lesions was with diclofenac-K liquid capsules (53%), compared to 61% with diclofenac-K tablets (P = 0.52), 75% with ibuprofen (P = 0.08) and 94% with ASA (P = 0.001). Results were similar for the Lanza scores, although diclofenac-K liquid capsules were significantly superior to ibuprofen liquid capsules (P = 0.04). Diclofenac-K liquid capsules inhibited prostaglandin synthesis by 52% compared to 64% for diclofenac-K tablets (P = 0.10), 50% for ibuprofen (P = 0.85) and 79% for ASA (P = 0.002). With respect to safety, adverse events were most frequent in the ASA group, predominantly gastrointestinal events.

CONCLUSIONS

Mucosal injury with diclofenac-K liquid 25 mg liquid capsules was similar to diclofenac-K 25 mg tablets, significantly lower than ASA 1 g tablets and showed some superiority over ibuprofen 400 mg liquid capsules (EudraCT Number 2009-011278-14).

NSAIDs: take with food or after fasting?

OBJECTIVE

Published and regulatory advice is to take NSAIDs with fluids and/or food irrespective whether NSAIDs are taken over the counter or long-term. The basis for this recommendation is not clear and we sought to establish the reasons for it through a search of published literature and personal files.

RESULTS

Results from experimental animals show that fasting increases the gastric side effects of NSAIDs while food increases small bowel damage, but this has not been tested in humans. The possible effects of food in modifying the gastric damage caused by NSAIDs are complex, as food quantity and composition modify the responses substantially. Food usually delays peak levels of NSAIDs (and hence onset of action) without affecting total bioavailability. This may not be important when a steady state is achieved, but rapid onset of action is highly relevant for over-the-counter use of NSAIDs. The safety of over-the-counter use of ibuprofen and naproxen appears to be excellent and comparable with paracetamol.

CONCLUSION

The rapid onset of action of NSAIDs is most important during over-the-counter use, in which case it may be more appropriate to take the drugs on a fasting stomach.

Heme oxygenase-1 is protective against nonsteroidal anti-inflammatory drug-induced gastric ulcers

OBJECTIVES

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used for the treatment of pain, fever, and inflammation. Long-term use of these drugs is associated with significant gastric injury. Activated neutrophils and oxidative stress seem to play a significant role in NSAID-induced gastric mucosal damage. The objective of our study is to examine the protective effects of an antioxidant and anti-inflammatory enzyme, heme oxygenase-1 (HO-1), in NSAID-induced gastric injury.

METHODS

Mice were intraperitoneally injected with indomethacin (10 mg/kg) or sham. A specific inducer of HO-1, cobalt protoporphyrin (5 mg/kg), was given 24 hours before indomethacin to allow for the expression of HO-1. Controls received sham treatment. Twenty-four hours after indomethacin injection, gastric tissue damage was examined with histology. HO-1 expression was measured with immunoblot; cytokine levels were measured with enzyme-linked immunosorbent assay. Neutrophil infiltration was quantified with myeloperoxidase assay. Using electron paramagnetic resonance and desferrioxamine, we measured the labile iron pool in the mouse stomach as a marker of oxidative stress.

RESULTS

Indomethacin caused gastric inflammation and ulcers, neutrophil activation, and increased tissue expression of interleukin-6 and tumor necrosis factor-alpha in mice. Inducing HO-1 with cobalt protoporphyrin reduced gastric inflammation, number of stomach ulcers, tissue neutrophil activation, and proinflammatory cytokine expression caused by indomethacin.

CONCLUSIONS

These findings suggest that the induction of an anti-inflammatory and cytoprotective enzyme HO-1 may be a strategy to overcome the gastrointestinal adverse effects limiting the use of NSAIDs.

Prevention and management of non-steroidal anti-inflammatory drugs-induced small intestinal injury

Non-steroidal anti-inflammatory drug (NSAID)-induced small bowel injury is a topic that deserves attention since the advent of capsule endoscopy and balloon enteroscopy. NSAID enteropathy is common and is mostly asymptomatic. However, massive bleeding, stricture, or perforation may occur. The pathogenesis of small intestine injury by NSAIDs is complex and different from that of the upper gastrointestinal tract. No drug has yet been developed that can completely prevent or treat NSAID enteropathy. Therefore, a long-term randomized study in chronic NSAID users is needed.

Nitro-aspirin is a potential therapy for non alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver injury; however its therapeutic strategy has not been established yet. Nitro-aspirin (NO-aspirin) is a new molecule in which aspirin and a NO-donating group are covalently linked. This study investigated the potential protective effect of NO-aspirin on NAFLD. Experimental rats were assigned into 4 groups. Group 1 was fed with normal diet and served as normal control group. Group 2 was fed with 2% cholesterol diet and received vehicle as positive control NAFLD group. Group 3 was fed with 2% cholesterol diet plus NO-aspirin (100 mg/kg/day). Group 4 was fed with 2% cholesterol diet plus aspirin (55 mg/kg/day). Rats were treated for 8 weeks. The results showed that NO-aspirin (but not aspirin) prevented the development of NAFLD as evidenced by significant reduction in liver weight/body weight ratio (liver index) and histopathologic changes. The protective effect of NO-aspirin is accompanied with significant decrease in triglycerides, malondialdehyde (MDA), and nitric oxide (NO) in hepatic tissue. Semi-quantitative immunohistochemical studies showed significant decrease in expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in hepatic tissue. In conclusion, NO-aspirin inhibited multiple pathways involved in the pathogenesis of NAFLD indicating that it might serve as a new therapeutic strategy.

Treatment strategies for osteoarthritis patients with pain and hypertension

Out of 100 patients with osteoarthritis (OA), almost 40 have a concomitant diagnosis of hypertension. Nonsteroidal anti-inflammatory drugs (NSAIDs) and cyclooxygenase-2 (COX-2) inhibitors may trigger a rise in blood pressure (BP), which is more marked in patients with established hypertension. NSAIDs and COX-2 inhibitors attenuate the antihypertensive effect of several antihypertensive agents. Frequent BP controls are needed in treated hypertensive patients who are concomitantly receiving NSAIDs or COX-2 inhibitors because even a small increase in BP may be associated with an important rise in the risk of major cardiovascular complications. In meta-analyses, an increase in systolic BP of 5mmHg was associated with a 25% higher risk of cardiovascular events. These data have been confirmed in randomized studies with rofecoxib and celecoxib, where a modest increase in BP was associated with a significantly higher risk of cardiovascular disease. There is emerging evidence that the COX-inhibiting nitric oxide donator (CINOD) class is promising in the treatment of patients with OA. Naproxcinod, the first CINOD investigated in clinical trials, is composed of the traditional NSAID naproxen covalently bound to the nitric oxide (NO)-donating moiety butanediol mono-nitrate (BDMN). The molecule has the potential to provide a sustained release of NO. In clinical studies, naproxcinod prevented the BP rise in normotensive and hypertensive patients observed with naproxen. The BP benefit of naproxcinod over naproxen was greater in patients concomitantly receiving angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. These investigational data suggest that naproxcinod is a valuable alternative to NSAIDs and COX-2 inhibitors for treatment of OA patients.

Efficacy and safety of naproxcinod in the treatment of patients with osteoarthritis of the knee: a 13-week prospective, randomized, multicenter study

OBJECTIVE

To evaluate the efficacy and safety of the cyclooxygenase-inhibiting nitric-oxide donator, naproxcinod, compared with naproxen and placebo in patients with osteoarthritis (OA) of the knee.

METHOD

918 eligible patients were randomly assigned to double-blind treatment with either naproxcinod 375 mg, naproxcinod 750 mg, naproxen 500 mg or placebo, twice daily for 13 weeks. The primary objective was to show superiority of naproxcinod compared to placebo. Main efficacy criteria were assessment of pain and physical function using the Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC) and patients' overall rating of disease status (Likert scale). The main secondary objectives were to show that naproxcinod was non-inferior to naproxen 500 mg and to evaluate overall safety.

RESULTS

Both doses of naproxcinod were statistically and clinically superior to placebo in relieving signs and symptoms of OA of the knee after 13 weeks of treatment, as demonstrated by all three co-primary endpoints (P< or =0.0003). The evaluation of the other secondary efficacy measures was consistent with the primary endpoint results. Naproxcinod 750 mg was non-inferior to equimolar doses of naproxen 500 mg in the Intent-to-Treat (ITT) population. 24.5% of patients discontinued prematurely, with a higher incidence in the placebo group (18.6%) than the active groups (4.3-7.1%) discontinuing due to lack of efficacy. Both doses of naproxcinod were well-tolerated, with most adverse events being mild or moderate. Compared to placebo, naproxcinod 750 mg and 375 mg showed a similar blood pressure (BP) profile in contrast to naproxen which increased BP.

CONCLUSIONS

These results demonstrated the clinical efficacy and safety of naproxcinod in the management of the signs and symptoms of OA. Naproxcinod was well-tolerated, with BP effects similar to placebo and different from naproxen. Clinical Trials.gov identifier: NCT00542555.

Treatment of osteoarthritis in hypertensive patients

IMPORTANCE OF THE FIELD

Osteoarthritis and hypertension commonly co-exist. Treatment of osteoarthritis in hypertensive patients is a therapeutic challenge due to the adverse effects of some analgesics, especially non-steroidal anti-inflammatory drugs (NSAIDs), on blood pressure. Even small drug-induced rises in blood pressure due to therapy may significantly increase cardiovascular risk in these patients if sustained over the long term. Patients treated with certain classes of antihypertensive agent may be at particular risk of deterioration in blood pressure control with NSAID therapy. NSAIDs may also increase cardiovascular risk due to mechanisms other than by raising blood pressure.

AREAS COVERED IN THIS REVIEW

We discuss the management of osteoarthritis in the hypertensive patient, review the evidence for the effects of paracetamol and NSAIDs on blood pressure and discuss novel therapeutic strategies for osteoarthritis that might diminish this problem. A literature search was undertaken in PubMed including the years 1980 - 2009.

WHAT THE READER WILL GAIN

Insight will be gained into the complexity of treating patients with co-existent osteoarthritis and hypertension and into possible new approaches to treating osteoarthritis symptoms effectively in these patients while minimising any adverse impact on blood pressure control.

TAKE HOME MESSAGE

There are ways to minimise the adverse impact of treatment of osteoarthritis on blood pressure control in hypertensive patients.

Adverse effects of non-steroidal anti-inflammatory drugs (NSAIDs, aspirin and coxibs) on upper gastrointestinal tract

Non-steroidal anti-inflammatory drugs (NSAIDs) are one of the most widely prescribed medication in the world. Their main benefit derives from their anti-inflammatory and analgesic effect, but the use of these agents is not innocuous since they mainly increase the risk of gastrointestinal (GI) and cardiovascular complications compared with non-NSAID users. NSAIDs injures the upper and lower gut by depleting COX-1 derived prostaglandins and causing topical injury to the mucosa. The risk of upper GI complications varies, depending on the presence of one or more risk factors. Among them, the three main risk factors are prior history of peptic ulcer, the single most important risk factor, age, the most common, and concomitant aspirin use, due to their GI and cardiovascular implications. Those individuals at-risk should be considered for alternatives to NSAID therapy and modifications of risk factors. If NSAID therapy is required, patients at risk will need prevention strategies including co-therapy of NSAID with gastroprotectants (PPI or misoprostol) or the prescription of COX-2 selective inhibitors. The probable introduction of NO-NSAIDs in the market in the near future may open a new therapeutic option for patients with hypertension who need NSAIDs.

Clinical pharmacokinetics of the cyclooxygenase inhibiting nitric oxide donator (CINOD) AZD3582

The clinical pharmacokinetics of the COX-inhibiting nitric oxide donator (CINOD) AZD3582 and its metabolites, including naproxen, nitric oxide and nitrate, are summarized. AZD3582 has low aqueous solubility, moderate and passive intestinal permeability and is degraded by intestinal esterases. Its oral bioavailability (F) appears to be maximally a few per cent, and increases by several-fold after food intake. Ninety-four per cent or more of an AZD3582 dose is absorbed, of which at least 9–20% appears to be taken up as intact substance. AZD3582 has a predicted plasma protein binding degree of ∼ 0.1%, a half-life (t½) of 3 to 10 h and does not accumulate after repeated once- and twice-daily dosing. In patients AZD3582 does not provide a significantly better gastrointestinal (GI) side-effect profile than the highly permeable and locally irritating naproxen. Possible reasons for this include considerable GI uptake as naproxen, limited duration and extent of nitric oxide donation in the GI mucosa and the circulation, tolerance development (involving auto-inhibition of nitric oxide catalysing enzymes) and mucosal damage caused by nitric oxide. Blood pressure data suggest that nitric oxide is mainly donated within 3h. The uptake of naproxen is slightly slower and lower (≥ 94% relative GI uptake and 80–85% relative F) after AZD3582 administration compared with naproxen dosing. The naproxen t½ and trough steady-state concentrations after AZD3582 and naproxen dosing are similar. The average systemic nitrate exposure is approximately doubled after dosing of 375 to 750 mg AZD3582 twice daily.

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.

Naproxcinod, a new cyclooxygenase-inhibiting nitric oxide donator (CINOD)

BACKGROUND

COX-inhibiting nitric oxide donators (CINODs) are a new class of drugs that combine the actions of the parent COX inhibitor with nitric oxide (NO), with the aim of reducing potential toxicity of the parent drug, while maintaining its analgesic and anti-inflammatory effects. AZD3582 (Naproxcinod) is the first in the class of CINODs.

OBJECTIVE/METHODS

To review the effects of NO donation, CINODS in general and naproxen in osteoarthritis (OA), based on literature in PubMed.

RESULTS

In preclinical and human studies, this drug produced similar analgesic and anti-inflammatory effects to its parent naproxen, with improved gastrointestinal safety in OA patients. The results of recent clinical trials, which were designed to study effects on blood pressure, are expected shortly, after peer-review.

CONCLUSIONS

As naproxen is considered the safest COX inhibitor choice from a cardiovascular perspective, AZD3582 has the potential to become a new drug treatment in patients with OA, in whom pain and function are not controlled by the use of analgesics.

Meta-analysis: incidence of endoscopic gastric and duodenal ulcers in placebo arms of randomized placebo-controlled NSAID trials

BACKGROUND

The safety of NSAIDs is often evaluated by comparison with placebo in clinical trials.

AIM

To investigate the incidence of gastric and duodenal ulcers (GDU) in placebo arms in NSAID trials over the last three decades.

METHODS

Randomized placebo-controlled trials of oral NSAIDs from 1975 to 2006 were systematically reviewed. The pooled incidence of GDU in placebo arms was calculated and compared. Meta-regression was used to identify risk factors related to the incidence of the placebo ulcer at the study level.

RESULTS

Thirty-six studies met inclusion criteria (duration of 6.5 days to 24 weeks). In total, 3.29% GDUs were reported in 36 placebo arms. The incidence of GDU in placebo arms was 0, 4.20% and 3.03% in the studies from 1975-1989, 1990-1999 and 2000-2006 respectively (P > 0.05). Eligible subjects with previous GI events and eligible subjects on co-therapy with low-lose aspirin/corticosteroids were associated with the increase in placebo ulcer incidence after adjusting for other factors.

CONCLUSIONS

The incidence of GDU in placebo arms has not changed significantly over the last three decades, although has decreased in the past 10 years. Studies show that previous GI events and co-therapy with low-dose aspirin/corticosteroids were associated with increasing GDU in placebo arms.

Nonsteroidal anti-inflammatory drugs and lower gastrointestinal complications

In addition to the upper GI tract, NSAIDs can damage the small bowel and the colon. NSAID enteropathy is frequent and may be present in more than 60% of patients taking these drugs long term. In most cases, damage is subclinical, including increased mucosal permeability, inflammation, erosions, ulceration, but other more serious clinical outcomes such as anemia, and overall bleeding, perforation, obstruction, diverticulitis and deaths have also been described. The magnitude of these serious outcomes from the lower GI tract is not well defined, but recent data suggest that they may be as frequent and severe as upper GI complications. Contrary to what happens in the upper GI tract, treatment and prevention of NSAID enteropathy is difficult, since the pathogenic mechanisms are different and not well understood. Among other options, misoprostol, antibiotics, and sulphasalazine have been proved to be effective in animal models, but they have not been properly tested in humans. Selective COX-2 inhibition is emerging as a potential alternative to tNSAIDs in the prevention of damage in the lower GI tract in rheumatologic patients. Preliminary studies in healthy volunteers have shown that these drugs are associated with no or less small bowel damage than tNSAIDs plus PPI, although their long-term effects in patients need to be properly tested. Post hoc analysis of previous outcome studies focused on complications of upper GI tract or cardiovascular events have shown contradictory results. Data from one ongoing trial comparing celecoxib versus diclofenac plus PPI and examining serious outcomes from the whole GI tract will probably provide new insights in this area.

Prevention of nonsteroidal anti-inflammatory drug-induced ulcer: looking to the future

The great challenge for those attempting to develop safer NSAIDs is shifting from a focus on GI toxicity to the increasingly more appreciated cardiovascular toxicity. At present, coxib shows an unmatched GI safety and appears to be a rational choice for patients at a low cardiovascular risk who have had serious GI events. In these patients, however, a cost-effective alternative is the use of tNSAIDs associated with comedication with a low-cost PPI or PN400. Because it seems prudent to avoid coxibs in patients who have cardiovascular disease or who are at risk for it, naproxcinod will be an appealing alternative to coxibs and tNSAIDs. However, because naproxcinod carries a significant risk of GI bleeding, a comedication therapy with a PPI inhibitor will be required if these patients also present risk factors for GI events. Although the development of H2S-releasing anti-inflammatory drugs is in its infancy, the preclinical data available thus far provide cause for optimism. The quest for the development of NSAIDs devoid of cardiovascular toxicity and that spare the gastric mucosa to the same extent as that of a coxib, however, is still open.

Efficacy, safety, and tolerability of the cyclooxygenase-inhibiting nitric oxide donator naproxcinod in treating osteoarthritis of the hip or knee

OBJECTIVE

Naproxcinod, a cyclooxygenase-inhibiting nitric oxide donator antiinflammatory drug, was evaluated in this phase 2, double-blind, randomized, parallel group study to determine its optimal dose in patients with osteoarthritis (OA).

METHODS

In total 543 patients with OA of the hip or knee were randomized to receive naproxcinod 750 mg once daily (qd), 750 mg twice daily (bid), 1125 mg bid, rofecoxib 25 mg qd, or placebo for 6 weeks. The primary efficacy variable was the within-patient change from baseline to the average of Weeks 4 and 6 in WOMAC pain subscale score. Treatment-group differences were compared using ANCOVA with factors for treatment and country, and baseline pain subscale score as a covariate. Safety endpoints included vital signs and adverse events. Treatment-group differences in mean change from baseline to Week 6 in systolic blood pressure (SBP) were compared using an ANCOVA with treatment and country as fixed factors and baseline SBP as covariate.

RESULTS

All active treatments showed statistically significant reductions in WOMAC pain score compared to placebo (p<or=0.02). Naproxcinod was well tolerated. The 750 mg bid dose appeared to have the best balance of benefit versus safety. All 3 naproxcinod doses showed a reduction in SBP, while an increase was shown for rofecoxib. The changes for the naproxcinod groups were statistically significantly better compared to rofecoxib (p<or=0.02).

CONCLUSION

This dose-finding study identified naproxcinod 750 mg bid as the upper dose for further therapeutic confirmatory clinical trials. Naproxcinod at all doses decreased mean SBP compared to an increase with rofecoxib.

Cardiovascular risk associated with nonsteroidal anti-inflammatory drugs

Since the introduction of selective cyclooxygenase-2 inhibitors (coxibs), there has been an ongoing discussion about the cardiovascular (CV) safety of coxibs and the traditional nonsteroidal anti-inflammatory drugs (NSAIDs). Available data about the CV safety of NSAIDs come mostly from meta-analyses and a few clinical trials. Current evidence suggests that NSAIDs may increase the risk of CV events. Naproxen might be associated with lower risk, but available data are not conclusive. Recent recommendations on the treatment of patients with NSAIDs favor the use of naproxen in patients with increased CV risk. Therefore, this review focuses on data about naproxen and examines CV risk with ibuprofen and non-naproxen NSAIDs. In addition, data about CV safety of paracetamol (acetaminophen) are presented.

Novel dithiolethione-modified nonsteroidal anti-inflammatory drugs in human hepatoma HepG2 and colon LS180 cells

PURPOSE

Nonsteroidal anti-inflammatory drugs (NSAID) are promising chemopreventive agents against colon and other cancers. However, the molecular basis mediated by NSAIDs for chemoprevention has not been fully elucidated. Environmental carcinogens induce DNA mutation and cellular transformation; therefore, we examined the effect of NSAIDs on carcinogenesis mediated by the aryl hydrocarbon receptor signaling pathway. In this study, we investigated the activities of a new class of NSAIDs containing dithiolethione moieties (S-NSAID) on both arms of carcinogenesis.

EXPERIMENTAL DESIGN

We investigated the effects of the S-NSAIDs, S-diclofenac and S-sulindac, on carcinogen activation and detoxification mechanisms in human hepatoma HepG2 and human colonic adenocarcinoma LS180 cells.

RESULTS

We found that S-diclofenac and S-sulindac inhibited the activity and expression of the carcinogen activating enzymes, cytochromes P-450 (CYP) CYP1A1, CYP1B1, and CYP1A2. Inhibition was mediated by transcriptional regulation of the aryl hydrocarbon receptor (AhR) pathway. The S-NSAIDs down-regulated carcinogen-induced expression of CYP1A1 heterogeneous nuclear RNA, a measure of transcription rate. Both compounds blocked carcinogen-activated AhR from binding to the xenobiotic responsive element as shown by chromatin immunoprecipitation. S-diclofenac and S-sulindac inhibited carcinogen-induced CYP enzyme activity through direct inhibition as well as through decreased transcriptional activation of the AhR. S-sulindac induced expression of several carcinogen detoxification enzymes of the glutathione cycle including glutathione S-transferase A2, glutamate cysteine ligase catalytic subunit, glutamate cysteine ligase modifier subunit, and glutathione reductase.

CONCLUSIONS

These results indicate that S-diclofenac and S-sulindac may serve as effective chemoprevention agents by favorably balancing the equation of carcinogen activation and detoxification mechanisms.

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.

NO-sulindac inhibits the hypoxia response of PC-3 prostate cancer cells via the Akt signalling pathway

Nitric oxide-donating non-steroidal anti-inflammatory drugs are safer than traditional NSAIDs and inhibit the growth of prostate cancer cells with greater potency than NSAIDs. In vivo, prostate cancer deposits are found in a hypoxic environment which induces resistance to chemotherapy. The aim of this study was to assess the effects and mechanism of action of a NO-NSAID called NO-sulindac on the PC-3 prostate cancer cell line under hypoxic conditions. NO-sulindac was found to have pro-apoptotic, cytotoxic, and anti-invasive effect on PC-3 cells under normoxia and hypoxia. NO-sulindac was significantly more cytotoxic than sulindac at all oxygen levels. The sulindac/linker and NO-releasing subunits both contributed to the cytotoxic effects of NO-sulindac. Resistance of PC-3 cells to NO-sulindac was induced as the oxygen concentration declined. Hypoxia-induced chemoresistance was reversed by knocking-down hypoxia-inducible factor-1alpha (HIF-1alpha) mRNA using RNAi. Nuclear HIF-1alpha levels were upregulated at 0.2% oxygen but reduced by treatment with NO-sulindac, as was Akt phosphorylation. NO-sulindac treatment of hypoxic PC-3 cells transfected with a reporter construct, downregulated activation of the hypoxia response element (HRE) promoter. Co-transfection of PC-3 cells with the HRE promoter reporter construct and myr-Akt (constitutively active Akt) plasmids reversed the NO-sulindac induced reduction in HRE activation. Real-time polymerase chain reaction analysis of hypoxic, NO-sulindac treated PC-3 cells showed downregulation of lysyl oxidase and carbonic anhydrase IX mRNA expression. Collectively, these novel findings demonstrate that NO-sulindac directly inhibits the hypoxia response of PC-3 prostate cancer cells by inhibiting HIF-1alpha translation via the Akt signalling pathway. The ability of NO-sulindac to inhibit tumour adaption to hypoxia has considerable relevance to the future management of prostate cancer with the same cellular properties as PC-3.

Role of coxibs in the strategies for gastrointestinal protection in patients requiring chronic non-steroidal anti-inflammatory therapy

Non-steroidal anti-inflammatory drugs (NSAIDs) are among the most commonly prescribed drugs due to their high efficacy in the treatment of pain, fever, inflammation and rheumatic disorders. However, their use is associated with the occurrence of adverse effects at the level of digestive tract, ranging from dyspeptic symptoms, gastrointestinal erosions and peptic ulcers to more serious complications, such as overt bleeding or perforation. To overcome problems related to NSAID-induced digestive toxicity, different therapeutic strategies can presently be considered, including the co-administration of drugs endowed with protective activity on the upper gastrointestinal tract, such as the proton pump inhibitors, or the prescription of coxibs, which have been clinically developed as anti-inflammatory/analgesic drugs characterized by reduced damaging activity on gastrointestinal mucosa. The availability of different treatment options, to reduce the risk of NSAID-induced adverse digestive effects, has fostered intensive preclinical and clinical research aimed at addressing a number of unresolved issues and to establish rational criteria for an appropriate use of coxibs in the medical practice. Particular attention is being paid to the management of patients with high degrees of digestive risk, resulting by concomitant treatment with low-dose aspirin for anti-thrombotic prophylaxis or ongoing symptomatic gastroduodenal ulcers. The present review discusses the most relevant lines of evidence concerning the position of coxibs in the therapeutic strategies for gastrointestinal protection in patients who require NSAID therapy and hold different levels of risk of developing adverse effects at the level of digestive tract.

Prostaglandins, NSAIDs, and gastric mucosal protection: why doesn't the stomach digest itself?

Except in rare cases, the stomach can withstand exposure to highly concentrated hydrochloric acid, refluxed bile salts, alcohol, and foodstuffs with a wide range of temperatures and osmolarity. This is attributed to a number of physiological responses by the mucosal lining to potentially harmful luminal agents, and to an ability to rapidly repair damage when it does occur. Since the discovery in 1971 that prostaglandin synthesis could be blocked by aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs), there has been great interest in the contribution of prostaglandins to gastric mucosal defense. Prostaglandins modulate virtually every aspect of mucosal defense, and the importance of this contribution is evident by the increased susceptibility of the stomach to injury following ingestion of an NSAID. With chronic ingestion of these drugs, the development of ulcers in the stomach is a significant clinical concern. Research over the past two decades has helped to identify some of the key events triggered by NSAIDs that contribute to ulcer formation and/or impair ulcer healing. Recent research has also highlighted the fact that the protective functions of prostaglandins in the stomach can be carried out by other mediators, in particular the gaseous mediators nitric oxide and hydrogen sulfide. Better understanding of the mechanisms through which the stomach is able to resist injury in the presence of luminal irritants is helping to drive the development of safer anti-inflammatory drugs, and therapies to accelerate and improve the quality of ulcer healing.

Role of nitric oxide in the gastrointestinal tract

Worldwide osteoarthritis (OA) affects more than 9.6% of men and 18% of women older that 60 years. Treatment for OA often requires chronic use of selective or nonselective nonsteroidal anti-inflammatory drugs (NSAIDs), which have been associated with gastrointestinal and cardiovascular complications. An increased risk for upper gastrointestinal bleeding with NSAIDs alone and when combined with low-dose aspirin has been described in numerous studies. Although cyclo-oxygenase-2 inhibitors have been shown to carry a lower risk for gastrointestinal injury than nonselective NSAIDs, research continues to identify new treatments that not only are effective but also provide an improved benefit/risk profile, including better gastrointestinal tolerability. Nitric oxide (NO) is known to have a protective effect on the gastrointestinal tract. In preclinical studies NO was shown to help maintain gastric mucosal integrity, to inhibit leukocyte adherence to the endothelium, and to repair NSAID-induced damage. In addition, epidemiologic studies have shown that the use of NO-donating agents with NSAIDs or aspirin resulted in reduced risk for gastrointestinal bleeding. Recent studies have shown that cyclo-oxygenase inhibiting NO-donating drugs (CINODs), in which a NO molecule is chemically linked to an NSAID, are effective anti-inflammatory agents and may result in less gastrointestinal damage than is associated with NSAID use. Therefore, these agents provide a potential therapeutic option for patients with arthritis who require long-term NSAID therapy.

NSAIDs, coxibs, CINOD and H2S-releasing NSAIDs: what lies beyond the horizon

Nonsteroidal anti-inflammatory drugs are widely prescribed for treatment of pain and inflammation, despite their association with gastrointestinal complications, including bleeding and perforation. Inhibition of cyclo-oxygenases, is the main mechanism of action of aspirin and nonsteroidal anti-inflammatory drugs. Non-selective nonsteroidal anti-inflammatory drugs inhibit cyclo-oxygenase-1 and cyclo-oxygenase-2. Inhibition of cyclo-oxygenase-1 derived prostanoids in the stomach represent the underlying mechanism involved in development of gastric and duodenal ulcers in patients taking nonsteroidal anti-inflammatory drugs. Selective cyclo-oxygenases-2 inhibitor (coxibs) spare cyclo-oxygenase-1 show enhanced safety profile in the gastrointestinal tract, but increase the risk of heart attack and stroke. Spurred by these findings, two coxibs, rofecoxib and valdecoxib, were withdrawn from the market. In addition to prostanoids, two gaseous mediators, nitric oxide (NO) and hydrogen sulfide (H(2)S) exert protective effects in gastric mucosa. The inhibitory effects of NO on nonsteroidal anti-inflammatory drugs-induced leukocyte adherence have been exploited in the development of NO-releasing nonsteroidal anti-inflammatory drugs, also indicated as cyclo-oxygenase-inhibiting NO-donating drugs. Despite its non-selective profile versus cyclo-oxygenase isoenzymes, naprocyclo-oxygenase-inhibiting NO-donating drugs, the prototype of this class of anti-inflammatory agents, reduces systemic blood pressure and might have enhanced cardiovascular safety than coxibs, while causing less gastrointestinal damage than its parent drug, the naproxen. H(2)S-releasing nonsteroidal anti-inflammatory drugs derivatives have been recently developed, based on the observed ability of this gaseous mediator to cause vasodilation and to prevent leukocyte adherence. In pre-clinical settings, H(2)S-releasing nonsteroidal anti-inflammatory drugs produce less gastric damage as compared to the parent drugs. Cyclo-oxygenases-inhibiting NO-donating drugs and H(2)S-releasing nonsteroidal anti-inflammatory drugs represent examples of new anti-inflammatory drugs created through the exploitation of the beneficial effects of endogenous gaseous mediators in the gastrointestinal and cardiovascular systems.

Structure-based design, synthesis, and biological evaluation of indomethacin derivatives as cyclooxygenase-2 inhibiting nitric oxide donors

Indomethacin, a nonselective cyclooxygenase (COX) inhibitor, was modified in three distinct regions in an attempt both to increase cyclooxygenase-2 (COX-2) selectivity and to enhance drug safety by covalent attachment of an organic nitrate moiety as a nitric oxide donor. A human whole-blood COX assay shows the modifications on the 3-acetic acid part of the indomethacin yielding an amide-nitrate derivative 32 and a sulfonamide-nitrate derivative 61 conferred COX-2 selectivity. Along with their respective des-nitrate analogs, for example, 31 and 62, the nitrates 32 and 61 were effective antiinflammatory agents in the rat air-pouch model. After oral dosing, though, only 32 increased nitrate and nitrite levels in rat plasma, indicating that its nitrate tether served as a nitric oxide donor in vivo. In a rat gastric injury model, examples 31 and 32 both show a 98% reduction in gastric lesion score compared to that of indomethacin. In addition, the nitrated derivative 32 inducing 85% fewer gastric lesions when coadministered with aspirin as compared to the combination of aspirin and valdecoxib.

Frontiers in nephrology: targeting inflammation using novel nitric oxide donors

Chimeric molecules are single-chemical entities that possess at least two separate functions. In the design of new chimeric medicines, the two biologic actions are often designed to be synergistic and, thereby, complement each other in activating a specific target, such as a gene, a receptor, or an enzyme. In most chimeric molecules, one functionality is designed to provide a high affinity to a designated site, thereby permitting the targeting of the second functionality, which is usually nonspecific. This review focuses on the development of two classes of chimeric medicines, anti-inflammatory and diuretic chimeric agents, both of which incorporate a nitric oxide moiety into the parent pharmacophore.

Building a better aspirin: gaseous solutions to a century-old problem

The gastrointestinal adverse effects of nonsteroidal anti-inflammatory drugs (NSAIDs) have been recognized since shortly after the introduction of aspirin to the marketplace over a century ago. However, the underlying pathogenesis of NSAID-induced gastropathy remains incompletely understood. Advances in understanding some of the factors that contribute to the mucosal injury have provided clues for the development of safer NSAIDs. The inhibitory effects of nitric oxide (NO) on NSAID-induced leukocyte adherence were exploited in the development of NO-releasing NSAIDs. As well as eliciting less gastrointestinal damage than conventional NSAIDs, these drugs do not elevate blood pressure and show anti-inflammatory effects, additional to those of the parent drugs. Modification of other drugs in a similar manner (i.e., NO-releasing derivatives) has similarly resulted in more effective drugs. More recently, hydrogen sulphide-releasing derivatives of NSAIDs and of other drugs, have been developed, based on the observed ability of H(2)S to reduce inflammation and pain in experimental models. H(2)S-releasing NSAIDs produce negligible gastric damage and exhibit enhanced anti-inflammatory potency as compared to the parent drugs. The NO-NSAIDs and H(2)S-releasing NSAIDs represent examples of new anti-inflammatory drugs with greatly reduced toxicity and improved therapeutic activity, both created through the concept of exploiting the beneficial effects of endogenous gaseous mediators.

NMI-1182, a gastro-protective cyclo-oxygenase-inhibiting nitric oxide donor

Non-steroidal anti-inflammatory drugs (NSAIDs) are widely used to treat inflammation and to provide pain relief but suffer from a major liability concerning their propensity to cause gastric damage. As nitric oxide (NO) is known to be gastro-protective we have synthesized a NO-donating prodrug of naproxen named NMI-1182. We evaluated two cyclo-oxygenase (COX)-inhibiting nitric oxide donors (CINODs), NMI-1182 and AZD3582, for their ability to be gastro-protective compared to naproxen and for their anti-inflammatory activity. NMI-1182 and AZD3582 were found to produce similar inhibition of COX activity to that produced by naproxen. Both NMI-1182 and AZD3582 produced significantly less gastric lesions after oral administration than naproxen. All three compounds effectively inhibited paw swelling in the rat carrageenan paw edema model. In the carrageenan air pouch model all three compounds significantly reduced PGE2 levels in the pouch exudate but only NMI-1182 and naproxen inhibited leukocyte influx. These data demonstrate that NMI-1182 has comparable anti-inflammatory activity to naproxen but with a much reduced likelihood to cause gastric damage.

Nonsteroidal antiinflammatory drugs and the small intestine

PURPOSE OF REVIEW

The small intestine may be a more common site for nonsteroidal antiinflammatory drug toxicity than the gastroduodenal mucosa. Two-thirds of regular nonsteroidal antiinflammatory drug users develop subclinical small bowel enteropathy. This review highlights this emerging issue in patients requiring antiinflammatory drugs.

RECENT FINDINGS

Nonsteroidal antiinflammatory drug enteropathy is a stepwise process involving direct mucosal toxicity, mitochondrial damage, breakdown of intercellular integrity, enterohepatic recirculation and neutrophil activation by luminal contents including bacteria. Unlike upper gastrointestinal toxicity, cyclooxygenase-mediated mechanisms are probably less important. Newer imaging modalities such as capsule endoscopy studies demonstrate nonsteroidal antiinflammatory drug-induced small bowel erosions, but the clinical implications are unclear.

SUMMARY

Nonsteroidal antiinflammatory drug toxicity to the small intestine is common. Useful research tools have been developed to indirectly measure intestinal inflammation and permeability, but these are not generally available to the clinician, although enteroscopy and capsule endoscopy can be illuminating. Anaemia or hypoalbuminaemia are useful indications of nonsteroidal antiinflammatory drug enteropathy. Cessation of the drug would be the preferred option, alternatively there are experimental data to support the use of sulphasalazine and metronidazole. Animal models are unravelling new mechanisms for mucosal toxicity beyond the cyclooxygenase model, including mucosal oxidative injury and nitric oxide mediated pathways.

Gastrointestinal safety and anti-inflammatory effects of a hydrogen sulfide-releasing diclofenac derivative in the rat

BACKGROUND & AIMS

Gastrointestinal damage caused by nonsteroidal anti-inflammatory drugs (NSAIDs) remains a significant clinical problem. Hydrogen makes an important contribution to mucosal defense, and NSAIDs can suppress its synthesis. In this study, we evaluated the gastrointestinal safety and anti-inflammatory effects of a novel "HS-NSAID" (ATB-337) that consists of diclofenac linked to a hydrogen sulfide-releasing moiety.

METHODS

The gastrointestinal injury-inducing effects of single or repeated administration of diclofenac versus ATB-337 were compared in rats, as were their effects on prostaglandin synthesis and cyclooxygenase-1 and -2 activities. The ability of these drugs to reduce carrageenan-induced paw edema and to elicit leukocyte adherence to the vascular endothelium (intravital microscopy) were also examined in rats.

RESULTS

Diclofenac (10-50 micromol/kg) dose-dependently damaged the stomach, while ATB-337 did not. Repeated administration of diclofenac caused extensive small intestinal damage and reduced hematocrit by 50%. ATB-337 induced >90% less intestinal damage and had no effect on hematocrit. Diclofenac, but not ATB-337, elevated gastric granulocyte infiltration and expression of tumor necrosis factor alpha, lymphocyte function-associated antigen 1, and intercellular adhesion molecule 1. ATB-337 inhibited cycloxygenase-1 and cyclooxygenase-2 activity as effectively as diclofenac. ATB-337 did not induce leukocyte adherence, whereas diclofenac did, and was more potent at reducing paw edema.

CONCLUSIONS

An HS-NSAID spares the gastric mucosa of injury despite markedly suppressing prostaglandin synthesis. This effect may be related to hydrogen sulfide-mediated inhibition of tumor necrosis factor-alpha expression and of the leukocyte adherence to vascular endothelium normally induced by cyclooxygenase inhibitors.

NSAIDs, coxibs, and the intestine

Nonsteroidal anti-inflammatory drugs (NSAIDs) are capable of damaging the whole gastrointestinal tract. Small and large intestinal injuries manifest as acute changes in permeability with endoscopic erosions, chronic erosions and ulcers, diaphragms in the small bowel, and an increase in small and large bowel complications including perforation and diverticular bleeding. It is quite likely, though not proven, that such lesions contribute to anemia in patients taking them. A growing body of data shows that selective inhibitors of the cyclooxygenase-2 enzyme have much reduced toxicity in this respect. In addition, NSAID use has also been associated with development or relapse of ulcerative colitis. Whether the same is true of Crohn's disease, particularly of the small bowel, is less clear. An important point is that there are data that suggest that paracetamol may also not be devoid of toxicity. This makes use of selective cyclooxygenase-2 inhibitors attractive. There have been a number of reports of their use in inflammatory bowel disease. However, many of these have principally involved Crohn's disease and there have not been enough to be clear whether they affect the influence of relapse of ulcerative colitis.