Gastrointestinal toxicity of non-steroidal anti-inflammatory drugs: the effect of nimesulide compared with naproxen on the human gastrointestinal tract.
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This overview includes theories and evaluation of non-steroidal anti-inflammatory drug (NSAID)-induced gastrointestinal toxicity. Factors in damage include microvascular aspects, neutrophil recruitment, mucosal prostaglandins, gastrointestinal secretions and bacteria. We have proposed an extensive simplified framework that includes an important local initiating effect which may involve NSAID accumulation, interaction with surface phospholipids, events that alter cellular ATP, and local/systemic effects of cyclooxygenase (COX) inhibition. COX-2-selective drugs are desirable not only because they spare COX-1 and so avoid gastrointestinal toxicity, but also because COX-2-selective agents are only weakly acidic and therefore avoid substantial accumulation in the gastric mucosa. Short-term endoscopy studies of NSAIDs are important initially to evaluate human gastroduodenal tolerability. They show that injury increases with the amount of NSAIDs even though the lowest therapeutic doses inhibit gastric COX almost completely, and that the more-acidic NSAIDs tend to cause greater gastric damage. Long-term endoscopy studies involve NSAID ingestion for at least 3 months. A main question is the extent to which the ulcers seen cause symptoms, substantial bleeding and/or perforation. Measurement of serious outcomes is thought by many to be the best assessment of gastrointestinal safety, but studies find marked variations even with the same drug. Damage to the small intestine by NSAIDs is even more frequent than to the upper gastrointestinal tract, but is difficult to evaluate. Conventional acidic NSAIDs increase the permeability of human small intestine, probably by a non-prostaglandin mechanism, but nimesulide does not do so, possibly because of its very weak acidity. (+info)
Comparative efficacy and safety of nimesulide and diclofenac in patients with acute shoulder, and a meta-analysis of controlled studies with nimesulide.
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Adverse events, particularly gastrointestinal, partially offset the therapeutic value of NSAIDs. The abilities of nimesulide to inhibit COX-2 preferentially and to exert other novel anti-inflammatory actions are consistent with good efficacy and safety. This is borne out by a double-blind multicentre comparison of nimesulide and diclofenac in 122 patients with acute shoulder, and by a meta-analysis of various nimesulide trials. At the end of the 14 day double-blind study, nimesulide was at least as effective as diclofenac (investigator ratings: good/very good in 79.0% of patients given nimesulide, and 78.0% with diclofenac; patient ratings: good/very good in 82.3 and 78.0% respectively). Four patients (6.5%) dropped out in the nimesulide group (two early recovery, one lack of effect, one adverse event), compared with 13 (21.7%) in the diclofenac group, due mainly to adverse events (P=0.003). Global tolerability was judged by the investigators to be good/very good in 96.8% of the nimesulide group compared with 72.9% of those given diclofenac. Judgements by the patients were 96.8 and 78.0% respectively. Both differences are highly significant statistically. The meta-analysis demonstrates that nimesulide given for 2 weeks is far more efficacious than placebo in treating osteoarthritis, and is at least comparable to other NSAIDs The benefit-risk ratio for nimesulide was better in all individual studies since 100 mg nimesulide twice daily was about equal to placebo in safety and tolerability, especially regarding gastrointestinal adverse events. (+info)
Ex vivo assay to determine the cyclooxygenase selectivity of non-steroidal anti-inflammatory drugs.
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1. In this study we describe experiments to establish ex vivo the selectivity of non-steroidal anti-inflammatory drugs (NSAIDs) given in vivo. 2. Anaesthetised (Inactin, 120 mg kg(-1)) male Wistar rats (220-250 g) received an i.v. dose of one of the following compounds (dose mg kg(-1)): aspirin (20), diclofenac (3), L-745,337 (30), nimesulide (15), salicylate (20), sulindac (10). Blood samples were taken before and up to 6 h after dosing and the plasma obtained from it was tested for its ability to inhibit prostanoid formation in IL-1beta-treated A549 cells (COX-2 system) and human washed platelets (COX-1 system). For control the same compounds were also added directly to the assay systems. 3. All drugs, except sodium salicylate, inhibited COX-1 and COX-2 when added directly to the test systems. Plasma from aspirin-treated rats was without effect on either COX-1 or COX-2, consistent with the rapid in vivo metabolism to salicylate. Conversely, plasma from sulindac-treated rats inhibited COX-1 and COX-2 with potencies according with in vivo metabolism to sulindac sulphide. Diclofenac was COX-1/2 non-selective when tested in vitro, but a slightly preferential inhibitor of COX-2 when tested ex vivo. Nimesulide was confirmed as preferential inhibitor of COX-2 both in vitro and ex vivo. L-745,337 was a selective COX-2 inhibitor when tested in vitro or ex vivo. 4. In conclusion, our experiments show clearly (a) NSAIDs inactivation, (b) activation of prodrugs, and (c) NSAIDs selectivity. Our assay provides useful information about the selectivity of NSAIDs that could be extended by the analysis of plasma samples taken from humans similarly treated with test drugs. (+info)
Nonsteroid drug selectivities for cyclo-oxygenase-1 rather than cyclo-oxygenase-2 are associated with human gastrointestinal toxicity: a full in vitro analysis.
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The beneficial actions of nonsteroid anti-inflammatory drugs (NSAID) can be associated with inhibition of cyclo-oxygenase (COX)-2 whereas their harmful side effects are associated with inhibition of COX-1. Here we report data from two related assay systems, the human whole blood assay and a modified human whole blood assay (using human A549 cells as a source of COX-2). This assay we refer to as the William Harvey Modified Assay. Our aim was to make meaningful comparisons of both classical NSAIDs and newer COX-2-selective compounds. These comparisons of the actions of >40 NSAIDs and novel COX-2-selective agents, including celecoxib, rofecoxib and diisopropyl fluorophosphate, demonstrate a distribution of compound selectivities toward COX-1 that aligns with the risk of serious gastrointestinal complications. In conclusion, this full in vitro analysis of COX-1/2 selectivities in human tissues clearly supports the theory that inhibition of COX-1 underlies the gastrointestinal toxicity of NSAIDs in man. (+info)
Blockade of nitric oxide formation down-regulates cyclooxygenase-2 and decreases PGE2 biosynthesis in macrophages.
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Elevated levels of nitric oxide (NO*) produced by expression of inducible nitric oxide synthase (iNOS/NOS type 2) and high levels of prostaglandins (PGs) generated by expression of inducible cyclooxygenase (COX-2/PGH2 synthase-2) are important mediators of immune and inflammatory responses. Previous studies have shown that endogenous levels of NO* can influence the formation of PGs. We examined the mechanism by which NO* regulates PG biosynthesis in macrophages. Treatment of a murine macrophage cell line (ANA-1) with lipopolysaccharide (LPS, 10 ng/mL) and interferon-gamma (IFN-gamma, 10 U/mL) for 20 h elicited high levels of nitrite (NO2-) and prostaglandin E2 (PGE2) that were inhibited in a dose-dependent fashion by the NOS inhibitor, aminoguanidine (AG), with IC50 values of 15.06 and 0.38 microM for NO2- and PGE2, respectively. Stimulation of cultures with LPS and IFN-gamma for 20 h induced de novo iNOS protein expression that was not altered by the addition of AG (0.1, 10, or 1000 microM). In contrast, treatment of cultures with LPS and IFN-gamma for 20 h promoted COX-2 mRNA and protein expression that were decreased in a dose-dependent fashion by AG (P < 0.05 with 10 and 1000 microM). LPS and IFN-gamma-induced COX-2 protein expression was not decreased in cultures treated with AG for 2 h, illustrating that AG does not inhibit the formation of COX-2 protein. Analysis of partially purified enzyme extracts demonstrated that AG did not directly inhibit the enzymatic activity of COX. Additional experiments revealed that NO* donors (S-nitroso-N-aceytl-D-L-pencillamine, SNAP, at 0.1, 10, and 1000 microM) did not induce de novo COX-2 protein expression or potentiate COX-2 expression in cells treated with LPS and/or IFN-gamma. Our results suggest that, while endogenous NO* is not required for de novo COX-2 mRNA and protein expression, NO* is necessary for maintaining prolonged COX-2 gene expression. (+info)
Dose-dependent inhibition of platelet cyclooxygenase-1 and monocyte cyclooxygenase-2 by meloxicam in healthy subjects.
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We evaluated whether therapeutic blood levels of meloxicam are associated with selective inhibition of monocyte cyclooxygenase (COX)-2 in vitro and ex vivo. Concentration-response curves for the inhibition of monocyte COX-2 and platelet COX-1 were obtained in vitro after the incubation of meloxicam with whole blood samples. Moreover, 11 healthy volunteers received placebo or 7.5 or 15 mg/day meloxicam, each treatment for 7 consecutive days, according to a randomized, double-blind, crossover design. Before dosing and 24 h after the seventh dose of each regimen, heparinized whole blood samples were incubated with lipopolysaccharide (10 microgram/ml) for 24 h at 37 degrees C, and prostaglandin E2 was measured in plasma as an index of monocyte COX-2 activity. The production of thromboxane B2 in whole blood allowed to clot at 37 degrees C for 60 min was assessed as an index of platelet COX-1 activity. The administration of placebo did not significantly affect plasma prostaglandin E2 (21. 3 +/- 7.5 versus 19.1 +/- 4 ng/ml, mean +/- S.D., n = 11) or serum thromboxane B2 (426 +/- 167 versus 425 +/- 150 ng/ml) levels. In contrast, the administration of 7.5 and 15 mg of meloxicam caused dose-dependent reductions in monocyte COX-2 activity by 51% and 70%, respectively, and in platelet COX-1 activity by 25% and 35%, respectively. Although the IC50 value of meloxicam for inhibition of COX-1 was 10-fold higher than the IC50 value of COX-2 in vitro, this biochemical selectivity was inadequate to clearly separate the effects of meloxicam on the two isozymes after oral dosing as a function of the daily dose and interindividual variation in steady-state plasma levels. (+info)
Urinary trypsin inhibitor down-regulates hyaluronic acid fragment-induced prostanoid release in cultured human amnion cells by inhibiting cyclo-oxygenase-2 expression.
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We postulated that urinary trypsin inhibitor (UTI), a Kunitz-type protease inhibitor, may inhibit low molecular weight hyaluronic acid (HA) fragment-induced prostanoid release and de-novo expression of the inducible cyclo-oxygenase-2 (COX-2) isoform in human term amnion cells. Purified amnion cultures were obtained from human fetal membranes and were exposed to a HA fragment (molecular weight 35 kDa) in the presence or absence of UTI (0-5.0 micromol/l). Amnion cells treated with the HA fragment (100 nmol/l) released significantly more prostanoids (PGE2 and PGF2alpha) than controls (PGE2: 2.1 +/- 0.13 pg/10(6) cells/24 h compared with 0.42 +/- 0.01, P < 0.05; PGF2alpha: 1.0 +/- 0.17 pg/10(6) cells/24 h compared with 0.13 +/- 0.01, P < 0.05). UTI inhibited HA fragment-induced prostanoid release in a dose-dependent manner, with 50% inhibitory concentration values of 0.8 micromol/l for PGE2 and 1.9 micromol/l for PGF2alpha. Western blot analyses demonstrated that protein levels of COX-2 were substantially increased in amnion cells treated with HA fragment. HA fragment-mediated COX-2 production was markedly diminished by pretreatment with UTI (1.0 micromol/l). These results are the first to demonstrate that UTI is a potent inhibitor of HA fragment-induced arachidonic acid metabolism. (+info)
Specific inhibition of cyclooxygenase-2 with MK-0966 is associated with less gastroduodenal damage than either aspirin or ibuprofen.
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BACKGROUND: Compared with currently available NSAIDs (which inhibit COX-1 and COX-2 isoforms of cyclooxygenase), MK-0966 (a specific COX-2 inhibitor) is expected to cause less gastrointestinal toxicity. AIM: To compare the effect on the upper gastrointestinal mucosae of a high dose of MK-0966 with that of conventional doses of ibuprofen and aspirin. METHODS: Healthy subjects (n = 170; age range 18-54 years) with endoscopically normal gastric and duodenal mucosa were randomized to either MK-0966 250 mg q.d. (n = 51), ibuprofen 800 mg t.d.s. (n = 51), aspirin 650 mg q.d.s. (n = 17), or placebo (n = 51) in this 7-day, double-blind, parallel-group study. The mucosae were evaluated by endoscopy using a predefined scale; scores could range from 0 to 4. The primary end-point was the percentage of subjects who developed a mucosal score >/= 2 (i.e. the development of one or more erosions). To evaluate COX-1 activity, serum thromboxane B2 levels were determined in a subset of the population. RESULTS: The percentage of subjects who developed a mucosal score >/= 2 in the MK-0966 group (12%) was significantly lower (P < 0.001) than that in the ibuprofen (71%) and aspirin (94%) groups, and was similar to that in the placebo group (8%). Only ibuprofen and aspirin significantly (P < 0.0001) reduced baseline thromboxane B2 levels. All treatments were generally well tolerated. CONCLUSIONS: In this acute short-term endoscopic study, MK-0966 250 mg q.d. (a dose at least 10 times higher than that demonstrated to reduce the signs and symptoms of osteoarthritis) produced significantly less gastrointestinal mucosal damage than either ibuprofen 800 mg t.d.s. or aspirin 650 mg q.d.s. and was comparable to placebo in this regard. (+info)