Antiinflammatory drugs and gastric mucosal damage

Characterization of cimetidine-piroxicam coprecipitate interaction using experimental studies and molecular dynamic simulations

The crystalline states of cimetidine and piroxicam, when coprecipitated from solvents containing 1:1 mole ratio, were transformed to amorphous states as observed using powder X-ray diffraction (PXRD). Amorphous forms of drugs generally exhibit higher water solubility than crystalline forms. It is therefore interesting to investigate the interactions that cause the transformation of both the crystalline drugs. Intermolecular interactions between the drugs were determined using Fourier-transform infrared spectroscopy (FTIR) and solid-state (13)C CP/MAS NMR. Molecular dynamic (MD) simulation was performed for the first time for this type of study to indicate the specific groups involved in the interactions based on radial distribution function (RDF) analyses. RDF is a useful tool to describe the average density of atoms at a distance from a specified atom. FTIR spectra revealed a shift of the C identical withN stretching band of cimetidine. The (13)C CP/MAS NMR spectra indicated downfield shifts of C(11), C(15) and C(7) of piroxicam. RDF analyses indicated that intermolecular interactions occurred between the amide oxygen atom as well as the pyridyl nitrogen of piroxicam and H-N(3) of cimetidine. The hydrogen atom (O-H) at C(7) interacts with the N(1) of cimetidine. Since the MD simulation results are consistent with, and complementary to the experimental analyses, such simulations could provide a novel strategy for investigating specific interacting groups of drugs in coprecipitates, or in amorphous mixtures.

Crystal structure transformations and dissolution studies of cimetidine-piroxicam coprecipitates and physical mixtures

We have recently demonstrated that coprecipitation of cimetidine (C) and piroxicam (P) at a mole ratio of 1:1 results in the transformation of the crystalline forms of both drugs to an amorphous state. In this study, coprecipitates and physical mixtures of cimetidine and piroxicam were further investigated at C/P mole ratios of 1:10, 1:5, 1:4, 1:2, 10:1, 20:1, 30:1, 40:1, and 52.5:1, the latter being the composition of a clinically used dosage. The physicochemical properties of these samples were examined using X-ray diffraction and Fourier transform infrared spectroscopy. Additionally, dissolution of piroxicam in the samples at C/P mole ratios of 10:1, 20:1, 30:1, 40:1, and 52.5:1 was investigated at pH 1.2 and pH 4. In coprecipitates with C/P mole ratios of 10:1, 20:1, 30:1, and 40:1, crystalline forms of both drugs were transformed to amorphous states. A mixture of an amorphous state and cimetidine crystalline form A was observed for the coprecipitate with a C/P mole ratio of 52.5:1. For the coprecipitates with C/P mole ratios of 1:2, 1:4, 1:5, and 1:10, cimetidine form A was transformed to form C, whereas piroxicam form II was modified to form I. It is interesting that small molecules, instead of polymers or solvents, can cause such crystal structure transformations. The dissolution of piroxicam at pH 4 is lower than that at pH 1.2. Additionally, the coprecipitates and physical mixtures with C/P mole ratios of 10:1, 20:1, 30:1, 40:1, and 52.5:1 demonstrate substantially higher dissolution of piroxicam compared to that of drug alone.

Treatment of NSAID-induced gastrointestinal lesions with cimetidine: an international multicentre collaborative study

The efficacy of cimetidine 800 mg nocte in the treatment of erosions or ulcers induced by non-steroidal anti-inflammatory drugs (NSAIDs) was evaluated in an uncontrolled multicentre study of 187 patients requiring continuation of their NSAID therapy. After 4 weeks of treatment, endoscopic healing was achieved in 62% of patients. After 8 weeks of therapy, 88% of patients were lesion-free. Patients with ulcer had a healing rate of 49% at week 4, which increased to 81% at the completion of 8 weeks. The majority of patients (82%) with erosions healed in 4 weeks. By week 8, erosions were healed in 97% of patients. Following endoscopically verified lesion healing, 113 patients entered a maintenance phase of the study, which assessed the efficacy of cimetidine 400 mg nocte in preventing recurrence of erosions or ulcers while continuing NSAID therapy. During a 6-month observation period, the cumulative probability of endoscopically observed recurrence of lesions was 12% (with a mean time to recurrence of 116 days), which is similar to the incidence of relapse achieved with cimetidine 400 mg nocte in patients with uncomplicated peptic ulcer. The results of this study suggest that cimetidine 800 mg nocte is effective in healing NSAID-induced lesions despite continued NSAID use, and that maintenance treatment with cimetidine 400 mg nocte can prevent lesions and reduce lesion recurrence during chronic NSAID administration.

Diagnosis of gastrointestinal lesions during treatment with non-steroidal anti-inflammatory drugs

Probably all non-steroidal anti-inflammatory drugs (NSAIDs) increase the risk of gastrointestinal (GI) mucosal injury. The most frequent lesions are gastric erosions in the pre-pyloric region. Non-steroidal anti-inflammatory drugs also increase the incidence of peptic ulcers, although it is not yet clear whether more gastric ulcers or more duodenal ulcers are produced. Gastrointestinal symptoms are prevalent during NSAID treatment, but there is no correlation between symptoms and lesions. Clinical presentation may therefore vary considerably: many symptomatic patients will have no lesions, whereas others will present with complications but no symptoms. Blood loss is the most frequent complication of NSAID-induced GI lesions. Bleeding is usually 'silent' and occult. Overt haemorrhage, though rare, is more frequent in patients taking NSAIDs. Other complications, such as penetration and perforation, may also occur. Endoscopy is the diagnostic method of choice, as this method can detect even superficial mucosal lesions. However, because of the lack of correlation between symptoms and lesions, it is difficult to ascertain which patients are at risk and thus to avoid unnecessary diagnostic procedures. Future efforts should therefore be directed towards the prevention of NSAID-induced GI lesions.

Treatment of endoscopy-negative NSAID-induced upper gastrointestinal symptoms with cimetidine: an international multicentre collaborative study

In this double-blind multicentre trial, 127 patients on non-steroidal anti-inflammatory drugs (NSAIDs) who experienced gastrointestinal symptoms significant enough to warrant endoscopic evaluation, but without endoscopic evidence of mucosal damage, were randomized to receive cimetidine 400 mg b.d. or placebo for 4 weeks. Non-steroidal anti-inflammatory drug therapy was maintained at pre-trial doses for the duration of the study. After 4 weeks, 72% of cimetidine-treated patients experienced complete symptom resolution, as defined by a global symptom score of zero, compared with 49% on placebo. Complete disappearance of upper abdominal pain was achieved in 72% of the cimetidine-treated patients as opposed to 47% on placebo. Relief of heartburn was experienced by 87% of patients on cimetidine compared with 60% on placebo. Throughout treatment, the proportion of cimetidine-treated patients with nausea was consistently lower than in patients on placebo, while the two groups were similar with respect to disappearance of vomiting. At the completion of acute treatment, 27% of placebo-treated patients but only 12% of those on cimetidine were ineligible to continue maintenance due to persisting gastrointestinal symptoms. Patients who were symptom-free and required continuation of NSAID therapy were followed for 6 months during which they were re-randomized to receive cimetidine 400 mg nocte or placebo. Of the 105 patients included in this maintenance treatment phase of the study, 11% of the cimetidine-treated patients and 10% of those on placebo experienced relapse of symptoms. However, the mean time to relapse was 120 days with cimetidine compared with 35 days with placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Experimental and Computational Studies of Epithelial Transport of Mefenamic Acid Ester Prodrugs

PURPOSE

A series of ester derivatives of mefenamic acid were synthesized with the aim of suppressing local gastrointestinal toxicity of mefenamic acid. A computational method was used to assist the design of the prodrug and to gain insights into the structure relationship of these compounds as P-glycoprotein (P-gp) substrates. The prodrugs were studied for their enzymatic stability, bidirectional permeability across Caco-2 monolayer, and their potential as transporter modulators

METHODS

Bidirectional transport studies were performed using Caco-2 cells. Compounds exhibiting an efflux ratio of > or =2 were further examined for their potential interaction with P-gp and multidrug resistance-associated protein (MRP) using verapamil and indomethacin. Calcein efflux inhibition studies were conducted to investigate the efflux mechanism of these compounds. Geometry optimization of the esters was performed, and the spatial separation of two electron donor groups of each prodrug was measured.

RESULTS

Morpholinoethyl ester (3) and pyrrolidinoethyl ester (4) of mefenamic acid showed evidence of efflux mechanism. Inhibition by verapamil had a pronounced effect on the transport of 3 and 4. Indomethacin, however, completely inhibited the apical efflux of 3 but enhanced the efflux ratio of 4. Both compounds increased the ratio of cellular calcein accumulation by 3- to 5-fold over control. Consistent with the experimental data, the computational results suggest the involvement of P-gp or its interaction in 3 and 4 transport.

CONCLUSIONS

Apical efflux of 3 is associated with P-gp and MRP, but the efflux of 4 involves P-gp and/or MRP. The computational approach used in this study provided the basis for P-gp substrates of compounds 3 and 4 from their electron donor subunits spatial separation.

Characterization of mefenamic acid-guaiacol ester: stability and transport across Caco-2 cell monolayers

PURPOSE

Prodrug of non-steroidal anti-inflammatory drugs (NSAIDs) or NSAIDs linked with guaiacol have been reported to suppress gastrointestinal (GI) toxicity or induce GI protective effect. In this study. mefenamic-guaiacol ester was synthesized and its physicochemical properties. stability, and transport across Caco-2 monolayers were investigated.

METHODS

Synthesis of the ester was carried out using mefenamic acid, guaiacol. N. N'-dimethylaminopyridine, and N,N'dicyclohexylcarbodiimide. The hydrolysis of the ester was investigated in aqueous buffer solutions pH 1-12 as well as in Caco-2 homogenate, human plasma, and porcine liver esterase. Caco-2 cell monolayers were utilized for transport studies. Due to the high lipophilicity of the ester with a calculated logP of 6.15, bovine serum albumin (BSA, 4%) was included in the receiver compartment to obtain a good in vitro-in vivo correlation. Permeation of the ester was assessed with or without the exposure of cells to PMSF, an inhibitor of esterase.

RESULTS

The ester was stable at a wide pH range from 1-10. However, it was hydrolyzed by enzymes from porcine liver esterase and Caco-2 homogenate. With the PMSF exposure on the apical (AP) side and in the presence of 4% BSA on the basolateral (BL) side, the transported amount of the ester from AP-to-BL direction was 14.63% after 3 hr with a lag time of 23 min. The Papp for the ester was 4.72 x 10(-6) cm s(-1).

CONCLUSION

The results from hydrolysis studies indicate that this ester is a prodrug. The Papp value suggests the moderate absorption characteristic of the compound. The accumulation of this highly lipophilic ester in Caco-2 cells is reduced in the presence of BSA.

Prevention and treatment of gastrointestinal symptoms and complications due to NSAIDs

The mechanisms by which aspirin(ASA) and non-steroidal anti-inflammatory drugs (NSAIDs) cause gastrointestinal symptoms are poorly understood. They probably arise from several causes, including direct and indirect mucosal injury, exacerbation of underlying peptic ulcer disease or non-ulcer dyspepsia, exacerbation of Helicobacter pylori gastritis, and possibly motility disorders. No single form of therapy has been generally successful. Because, in most cases, symptoms abate fairly rapidly with continued treatment, there is little evidence that benefit associated with any symptom-directed drug therapy is superior to placebo beyond 4 weeks. Exceptions may be the subsets of patients with pre-existing ulcer disease or heartburn, exacerbated by the NSAID therapy, who usually benefit from acid-suppressive drug treatment. Different NSAIDs vary in the frequency with which their use leads to gastrointestinal(GI) complications such as haemorrhage, perforation, obstruction, or the symptomatic ulcers from which about 40% of the complications arise. Most gastroduodenal ulcers heal over time, albeit more slowly, with conventional doses of any of the available anti-ulcer drugs. Maintenance therapy may be needed in many patients who continue NSAID therapy. Anti-ulcer drugs have not, thus far, been shown to be more effective than placebo in preventing ulcer complications or their recurrence. The use of COX-2-selective inhibitors appears, in outcome studies, to reduce gastrointestinal bleeding, including bleeding from ulcers, but it is not established that the ulcers protected were caused by NSAIDs, as distinct from ulcers exacerbating or recurring from antecedent peptic ulcer disease. To-date, perforation or obstruction have not been shown to be affected by selective COX-2 inhibitor drugs. If the major problem giving rise to severe NSAID complications is pre-existing peptic ulcer disease, it may yet emerge that the most effective approach will be the use of proton pump inhibitor drugs, for the duration of NSAID therapy, in a small subset of high-risk patients. Most other low-risk patients may not need any special care. Co-morbid conditions have a major impact on outcome of NSAID therapy. Morbidity or even death attributable solely to NSAIDs is probably small in normal patients, and requires little in the way of prophylaxis.

The mechanism of action of amtolmetin guacyl, a new gastroprotective nonsteroidal anti-inflammatory drug

Amtolmetin guacyl (2-methoxyphenyl-1-methyl-5-p-methylbenzoyl-pyrrol-2-acetamido acetate) (MED15) is a new nonsteroidal anti-inflammatory drug (NSAID) with anti-inflammatory, analgesic and antipyretic properties similar to the traditional drugs, but with unexpected gastroprotective effects. In an in vivo rat model, amtolmetin guacyl administered orally demonstrates inhibition of gastric acid secretion following stimulation by various agonists, and up-regulation of gastric bicarbonate production. Pretreatment with MED15 also shows a significant reduction of indomethacin-induced gastric damage in the rat. The reason behind this behaviour appears to be bound to the presence in the MED15 molecule of a vanillic moiety known to stimulate capsaicin receptors. In fact, the antisecretive effect of MED15 is blocked by capsazepine (a specific capsaicin receptor antagonist). This effect is confirmed by the interference found with anti-histamine H(1) drugs. Owing to the connection between capsaicin and calcitonin gene-related peptide (CGRP), a possible effect of MED15 on CGRP receptors was hypothesized, considering the leading role played on gastric mucosa by the predominant sensory neuropeptide of the stomach wall, CGRP. In fact, the anti-secretive and gastroprotective effect of MED15 is abolished by CGRP-(8-37) (the specific CGRP receptor antagonist). The unmodified MED15 molecule is found throughout the gastroenteric tract for long periods of time following oral administration, as further confirmation of the mechanism of action being based on the presence of the vanillic moiety at receptor level.

Rheumatoid arthritis: new approaches for its evaluation and management

Rheumatoid arthritis is a chronic, progressive disease with a long-term outcome characterized by significant morbidity, loss of functional capacity, and increased mortality. The cornerstone of therapy includes the appropriate melding of pharmacological, rehabilitative, and surgical treatments. New developments in the care of patients with rheumatoid arthritis have focused on aggressive pharmacological therapy early in the course of the illness, ongoing assessment of disease activity and patient function, and a better understanding of the role of rehabilitative techniques such as therapeutic exercise and behavioral approaches to education. This article synthesizes information from studies on recent advances in the management of rheumatoid arthritis outlining diagnosis and assessment, disability issues, outcome studies, current status of traditional and experimental pharmacological therapies, and new strategies of nonpharmacological treatments aimed at the clinician challenged by this fascinating disorder.

A comparison of severe gastric damage as a result of pirprofen and naproxen treatment in rheumatoid arthritis: a controlled endoscopic study

OBJECTIVE

The aim of this controlled endoscopic study was to compare the therapeutic efficacy and the gastric tolerance of two nonsteroidal anti-inflammatory drugs, pirprofen versus naproxen.

DESIGN

A randomized endoscopic double-blind double-dummy study.

SETTING

The gastrointestinal unit of a teaching hospital.

SUBJECTS

Forty patients suffering from rheumatoid arthritis were enrolled. After an initial upper gastrointestinal endoscopy to rule out the presence of gastric mucosal lesions, the patients were randomly allocated in a double-blind, double-dummy manner, to receive either pirprofen (400 mg t.i.d.) or naproxen (500 mg b.i.d.) for 4 weeks; endoscopic control followed this treatment period, or was anticipated in the event of painful dyspepsia.

INTERVENTIONS

Endoscopy at the beginning of the study and at 4 weeks, or anticipated in the event of painful dyspepsia.

MAIN OUTCOME MEASURES

Primary outcome measure of the study was the possibility that pirprofen was less toxic to the gastric mucosa than naproxen, and at least as effective.

RESULTS

Both drugs proved effective in relieving clinical symptoms, without a statistically significant difference. Gastric mucosa lesions were observed in 90% of pirprofen-treated patients and in 60% of those on naproxen (P = 0.03). The most severe lesions (grades 3 and 4) were found in 65% of subjects treated with pirprofen, as opposed to 15% of those treated with naproxen (P = 0.001).

CONCLUSIONS

This study shows that pirprofen is at least as active as naproxen in relieving rheumatic symptoms, but its administration results in a significantly severe degree of gastric damage.

Comparative toxicity of non-steroidal anti-inflammatory agents

Comparative toxicity of non-steroidal anti-inflammatory drugs was assessed using the Stanford Toxicity Index consisting of weighted symptoms, laboratory abnormalities and hospitalizations in 2976 consecutively enrolled rheumatoid arthritis patients from eight data bank centers with 27,936 patient-years of observation. Scores ranged from 1.77 (SE 0.20) for aspirin to 5.94 (SE 0.92) for meclofenamate, with many differences between drugs being 2- to 3-fold and highly statistically significant. Results are consistent with our prior data, persist when assessed by several different scoring algorithms, are consistent across data bank centers and are consistent with data of others. There are major and reproducible differences in the overall toxicity of different non-steroidal anti-inflammatory drugs.

Non-steroidal anti-inflammatory drug-induced gastropathy: a comparative endoscopic and histopathological evaluation of the effects of tenoxicam and diclofenac

A 4-week double-blind study compared the potential for 20 mg/day tenoxicam or 100 mg/day diclofenac sodium to induce gastropathy in 36 patients with joint disease and assessed the influence of gastric colonization by Helicobacter pylori. Endoscopic assessment at the end of 4 weeks indicated that the mucosa was normal in 79% of tenoxicam-treated patients and 59% of diclofenac-treated patients. Only 5% of patients in the tenoxicam group developed severe gastroduodenitis (> 11 haemorrhages or erosions) compared with 18% in the diclofenac group. Histological evaluation indicated that 58% and 47%, respectively, of tenoxicam-treated and diclofenac-treated patients retained normal mucosa after treatment. Diclofenac treatment was discontinued in two patients, due to a duodenal ulcer or severe erosive gastritis. Overall, 5/14 patients with moderate to severe colonization with Helicobacter pylori developed severe chronic active gastritis or ulceration, compared with the 1/22 patients in whom colonization was either absent or mild (P = 0.02). Tenoxicam and diclofenac did not show major differences in terms of gastrointestinal safety, although the trends favoured tenoxicam. The presence of severe colonization of the gastric mucosa with Helicobacter pylori appears to be an important factor for development of severe gastritis or ulceration.

Nonsteroidal anti-inflammatory drugs--the clinical dilemmas

Physicians using nonsteroidal anti-inflammatory drugs (NSAIDs) are concerned that effective anti-inflammatory doses cause few gastrointestinal side effects. Among the causes of discontinuing therapy, upper gastrointestinal symptoms and the development of 'ulcer' complications are major concerns; endoscopic findings in asymptomatic users are not. Initial symptoms, poorly correlated with endoscopic findings, are relieved by anti-ulcer drugs and ameliorate with time of NSAID use in most patients. Symptoms accompanied by epigastric tenderness, or unrelieved by H2 antagonists, or resulting in cessation of NSAID therapy are more predictive of underlying ulcers. Complications probably arise in several ways, including as hemorrhages due to interference with platelet function, and as complications due to exacerbations of underlying ulcer disease or of ulcers caused by the NSAIDs. Pathogenesis and effective prophylaxis (yet to be established) may therefore vary in different patients, a clinical dilemma.

The problems and pitfalls of NSAID therapy in the elderly (Part II)

The elderly are most susceptible to pharmacokinetic drug interactions between various NSAIDs and anticoagulants, sulphonylurea hypoglycaemic agents, certain anticonvulsants, methotrexate, digoxin, aminoglycosides and lithium. Pharmacodynamic interactions between some NSAIDs and antihypertensive drugs, anticoagulants, sulphonylurea agents and other NSAIDs are also potentially significant in the elderly. Despite the finding that mean therapeutic responses of large groups of patients have been generally equivalent for the wide range of NSAIDs studied thus far, it is also apparent that marked variability exists in the response of individual patients to different NSAIDs. Subsequent dosage increments may predispose 'nonresponders' and some less sensitive 'responders' to toxicity from NSAIDs. This interindividual variability in response to NSAIDs may be contributed to by the differing physicochemical properties of NSAIDs, physician prescribing habits and patient expectations, variations in NSAID pharmacokinetics, and the differing effects of NSAIDs other than their common ability to inhibit prostaglandin synthesis. The principles for drug prescribing in the elderly are no different from those that should be applied to the prescribing of medication in any patient. The clinician should strive to make a diagnosis and should avoid treating symptoms in isolation. Critical assessment of the indication for prescribing NSAID therapy must include consideration of the available effective and safe alternatives. If an NSAID is commenced the lowest effective dose should be the desired goal, but after an appropriate trial it is acceptable clinical practice to employ an alternative NSAID. There is no justification for combination NSAID therapy. The progress of each patient must be carefully monitored, particularly during the first few months of treatment, while periodic review of the ongoing need for the NSAID is essential.

Nonsteroidal anti-inflammatory gastropathy: from theory to practice

The success of nonsteroidal anti-inflammatory drugs in managing joint inflammation and pain has come at the cost of impressive side effects, particularly in the gastrointestinal tract. This manuscript reviews the magnitude of the problem, the risk factors, and presentation of nonsteroidal gastropathy. It also presents some points in the prevention and management of the disorder.

Cod liver oil inhibits indomethacin induced gastropathy without affecting its bioavailability and pharmacological activity

The upper gastrointestinal toxicity is one of the most common side effects associated with the use of nonsteroidal anti-inflammatory drugs (NSAIDs). Many attempts to prepare potent NSAIDs free from gastrotoxicity have failed. Hence, development of formulations to mask the gastropathy of NSAIDs are warranted. The present study was undertaken to investigate the effect of concomitant use of cod liver oil (CLO) on pharmacological activity and gastropathy of indomethacin in rats. The animals were treated with CLO (5 and 10 ml/kg body weight) along with indomethacin (30 mg/kg, body weight). Blood samples were collected for analysis of indomethacin at 0.25, 0.5, 1.0, 1.5, 2.0, 4.0, 6.0 and 24 hours. The anti-inflammatory activity of indomethacin alone and in combination with CLO was studied using carrageenan-induced paw oedema. Our studies related to the effect of these drugs on gastrointestinal tract showed that concurrent use of CLO protects gastric mucosa against indomethacin induced depletion of gastric wall mucus, non protein sulfhydryl (NP-SH) levels and gastric lesions. The result of this study also showed that the concurrent use of the CLO does not affect the bioavailability and anti-inflammatory activity of indomethacin while it inhibits the ulcerogenic effect of indomethacin in a dose dependent manner. These findings suggest that NSAIDs formulations containing CLO may reduce gastrotoxicity without affecting their therapeutic efficacy.

Nonsteroidal anti-inflammatory drug toxicity: increased risk in the elderly

Nonsteroidal anti-inflammatory drugs (NSAIDs) are widely used in the therapy of rheumatic diseases, especially in older patients. The toxicity profile of NSAIDs includes gastrointestinal (GI) toxicity, renal dysfunction and hepatic disease. Altered drug pharmacology in older patients may be a factor in their increased risk for drug toxicity. Elderly patients appear to be at greatest risk for symptomatic GI toxicity, including ulceration and even major GI bleeding. Central nervous system toxicity, characterized by dizziness, headaches, mood alteration and confusion, and renal dysfunction have also been reported to occur more commonly among elderly patients. Hepatic dysfunction is a rare NSAID-induced toxicity, but older patients are often at greatest risk for serious hepatic disease. Understanding the patient's underlying physiologic condition, concomitant drug therapy and the kinetics of the NSAID being used is critical to the safe administration of these agents to elderly individuals.

Mechanisms of NSAID-induced gastroenteropathy

Nonsteroidal anti-inflammatory drugs (NSAIDs) are one of the most commonly used and therapeutically effective groups of drugs in the Western world. However, gastrointestinal problems constitute all too frequently reported unwanted effects of NSAIDs; their effects on the gastric (and intestinal) mucosa are, therefore, well documented. A review of the evidence suggests that NSAID-induced gastric damage occurs as a result of a dual insult, by NSAID-mediated direct (and indirect) acidic damage followed almost simultaneously by the deleterious (systemic) effect of prostaglandin inhibition. A number of strategies have been used in the management of NSAID-induced gastric damage; however, not all have been entirely successful. Nonetheless, a number of approaches have met with a considerable amount of success, including direct gastroprotection, enhancement of mucosal defence mechanisms and, perhaps most encouragingly, the development of newer NSAIDs which display not only considerable clinical efficacy but a reduced gastrointestinal adverse event profile.

Inhibition of chloride/bicarbonate antiports in monkey kidney cells (Vero) by non-steroidal anti-inflammatory drugs

Two chloride/bicarbonate antiport mechanisms are involved in the regulation of cytosolic pH (pHi) in Vero cells, namely Na+-dependent chloride/bicarbonate antiport to normalize pHi after acidification of the cytosol, and Na+-independent Cl-/HCO3- exchange to regulate pHi back to normal after alkalinization of the cytosol. We have tested the effects of the non-steroidal anti-inflammatory drugs acetylsalicylic acid (aspirin), salicylic acid, indomethacin and piroxicam on chloride/bicarbonate exchange and on chloride self exchange in Vero cells. All these drugs were found to inhibit both the Na+-independent and the Na+-linked chloride/bicarbonate antiport in a dose dependent manner. The Na+-independent chloride/bicarbonate antiport was inhibited by lower doses of the drugs than the Na+-linked antiport. The ability of the drugs to inhibit chloride self exchange did not vary much with varying external pH, indicating that the inhibitory effect is due to the anionic form of the drugs. Inhibition occurred immediately upon addition of the drugs, and it was rapidly reversible, indicating that the inhibitory effect is due to direct interaction of the drugs with chloride/bicarbonate antiport, and not to inhibition of prostaglandin synthesis. The relevance of our findings to the clinical effects of the drugs is discussed.

Mechanisms of nonsteroidal anti-inflammatory drug-induced gastric damage

The effects of nonsteroidal anti-inflammatory drugs (NSAIDs) on the gastric mucosa are well documented. The complex mechanisms of gastric damage, however, are not fully understood. This review examines current knowledge about the normal function of the gastric mucosal barrier; the role of prostaglandins in cytoprotection and repair; the mechanisms by which aspirin and other weak organic acids are absorbed by the stomach; and the subsequent cascade of events--including ion trapping and back diffusion of hydrogen ions--that leads to gastric erosion and bleeding. A hypothesis describing NSAIDs' dual insult on the stomach is advanced.

Non-steroidal anti-inflammatory drugs in patients with peptic ulcer disease: to be considered in certain circumstances

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