Meloxicam: influence on arachidonic acid metabolism. Part II. In vivo findings

In vivo effects of tepoxalin, an inhibitor of cyclooxygenase and lipoxygenase, on prostanoid and leukotriene production in dogs with chronic osteoarthritis

OBJECTIVE

To evaluate in vivo effects of tepoxalin, an inhibitor of cyclooxygenase (COX) and lipoxygenase (LOX), on prostaglandin (PG) and leukotriene production in osteoarthritic dogs.

ANIMALS

7 mixed-breed adult dogs with chronic unilateral arthritis of a stifle joint.

PROCEDURE

Dogs were treated in accordance with a randomized 3-way crossover design. Each dog received an inert substance, meloxicam, or tepoxalin for 10 days. On day 0 (baseline), 3, and 10, dogs were anesthetized and samples of blood, stifle joint synovial fluid, and gastric mucosa were collected. Concentrations of PGE2 were measured in synovial fluid and after lipopolysaccharide stimulation of whole blood; PGE1 and PGE2 synthesis was measured in gastric mucosa. Thromboxane B2 (TxB2) concentration was measured in whole blood. Leukotriene B4 (LTB4) concentration was determined in gastric mucosa and in whole blood after ex vivo stimulation with a calcium ionophore.

RESULTS

Tepoxalin significantly decreased LTB4 concentrations in the blood and gastric mucosa at day 10 and TxB2 concentrations in the blood and PGE2 in the gastric mucosa and synovial fluid at days 3 and 10, compared with baseline values. Meloxicam significantly decreased PGE2 concentrations in the blood at days 3 and 10 and synovial fluid at day 3. Meloxicam also decreased PGE1 and PGE2 synthesis in the gastric mucosa at day 3. Meloxicam did not affect LTB4 synthesis in the blood or LTB4 concentrations in the gastric mucosa.

CONCLUSIONS AND CLINICAL RELEVANCE

Tepoxalin has in vivo inhibitory activity against COX-1, COX-2, and 5-LOX in dogs at the current approved recommended dosage.

Inhibition of COX activity by NSAIDs or ascorbate increases cAMP levels and enhances differentiation in 1alpha,25-dihydroxyvitamin D3-induced HL-60 cells

Arachidonic acid metabolism is modulated during differentiation induced by 1alpha,25(OH)(2)D(3) in HL-60 cells. Antioxidants that affect arachidonic acid metabolism enhance this differentiation program. Ascorbate also enhances differentiation in 1alpha,25(OH)(2)D(3)-induced cells depending on the induction of cAMP. The aim of this work was to study if this cAMP rise depends on modulation of arachidonic acid metabolism by ascorbate. Cyclooxygenase inhibitors, indomethacin and aspirin, increased cAMP levels and also enhanced 1alpha,25(OH)(2)D(3)-induced differentiation in HL-60 cells. Ascorbate did not affect the release of arachidonic acid-derived metabolites but decreased the levels of TXB(2) and PGE(2), suggesting the inhibition of cyclooxygenase. On the other hand, free arachidonic acid increased both cAMP levels and differentiation in the absence or presence of 1alpha,25(OH)(2)D(3). Neither cyclooxygenase inhibitors nor ascorbate modified AA effect. Then, inhibition of cyclooxygenase activity by ascorbate could accumulate free arachidonic acid or other metabolites that increase cAMP levels and enhance differentiation in 1alpha,25(OH)(2)D(3)-induced HL-60 cells.

Analgesic Comparison of Meloxicam or Ketoprofen for Orthopedic Surgery in Dogs

OBJECTIVE

To compare the safety and efficacy of 2 analgesic protocols (preoperative meloxicam or intraoperative ketoprofen administration) during the first 24 hours after orthopedic surgery in dogs.

STUDY DESIGN

Double-blind, prospective randomized clinical trial.

ANIMALS

Sixty client-owned dogs.

METHODS

Dogs with surgical orthopedic disorders were randomly separated into 2 groups: 30 dogs were administered 0.2 mg/kg meloxicam intravenously (IV) immediately before induction and 30 dogs were administered 2 mg/kg ketoprofen IV, 30 minutes before the end of surgery. Pain was assessed with a visual analog scale (VAS) and a cumulative pain score (CPS) preoperatively and at 30 minutes, 1, 2, 3, 4, 6, 8, and 24 hours after extubation. Selected serum biochemical variables were measured before and 24 hours after surgery and, buccal mucosal bleeding time (BMBT) and whole blood clotting time (WBCT) were measured before and 8 hours after surgery. Dogs were anesthetized with propofol and maintained on halothane in oxygen. Any complications were documented for 7 days after surgery. Results were compared between the 2 groups for significant differences in VAS scores (2-sample t-test) and in CPS (Wilcoxon's 2-sample test). Moreover, results were analyzed for significant differences in area under the curve (AUC) for VAS (2-sample t-test) and CPS (Wilcoxon's 2-sample test) among groups. To assess the effects of treatments on biochemical and coagulation functions, pre- and postoperative mean values of BMBT and WBCT were compared within both treatment groups (paired t-tests) and between both groups (2-sample t-test).

RESULTS

No significant differences in pain response or coagulation were found between meloxicam- and ketoprofen-treated dogs. In both groups, alkaline phosphatase and alanine aminotransferase concentrations were significantly increased compared with baseline. No serious complications occurred.

CONCLUSIONS

Preoperative administration of meloxicam is a safe and effective method of controlling postoperative pain for up to 24 hours in dogs undergoing orthopedic surgery.

CLINICAL RELEVANCE

Analgesia after administration of preoperative meloxicam was comparable with administration of ketoprofen at the end of the surgery.

Mucosal damage induced by preferential COX-1 and COX-2 inhibitors: role of prostaglandins and inflammatory response

Nonsteroidal anti-inflammatory drugs (NSAID) are well known to induce gastric mucosal damage including bleeding, ulceration and perforation in humans and animals too. These effects are related with the inhibition of the enzyme cyclooxygenase, which is the main established mechanism of action for these drugs. Fasted rats were given piroxicam, preferential COX-1 inhibitor (10-20 mg/kg) or meloxicam, preferential COX-2 inhibitor (7.5-15 mg/kg) orally. Six or nine hours (h) later, respectively, the stomach was excised, the severity of the damage assessed and myeloperoxidase (MPO) activity measured, as well as prostaglandin PGE(2) content. Furthermore, in order to assess the effects of these oxicams over previously damaged gastric mucosa, 1 ml of 0.6 N HCl was administered p.o. followed, 1 h after, of the correspondent dose of each NSAID, and the same parameters were determined. Oral administration of both drugs dose-dependently caused acute gastric haemorrhage erosions. Myeloperoxidase activity was significantly increased by piroxicam administration. In addition, PGE(2) content was significantly reduced. The association between the administration of the acid and NSAID caused a worsening of the damage and, while myeloperoxidase activity did not modify by both piroxicam and meloxicam, PGE(2) levels were reduced. These results suggest that the PG derived from both COX-1 and COX-2 pathway plays a beneficial role in the gastroprotection, and thus caution should be exercise in the clinical use of preferential COX-2 inhibitors.

Endoscopic evaluation of the gastroduodenal mucosa to determine the safety of short-term concurrent administration of meloxicam and dexamethasone in healthy dogs

OBJECTIVE

To evaluate the safety, with respect to the development of gastric ulcers and erosions, of concurrent administration of meloxicam and dexamethasone for 3 days to healthy dogs.

ANIMALS

20 conditioned purpose-bred research Beagles.

PROCEDURE

Seven days prior to treatment, dogs were anesthetized for endoscopic evaluation of the upper portion of the gastrointestinal tract (ie, the gastric and duodenal mucosa). Five regions of the gastroduodenal area were scored by 2 investigators. Dogs were randomly assigned to 1 of 4 treatment groups as follows: saline-saline, dexamethasone-saline, saline-meloxicam, and dexamethasone-meloxicam groups. On days 1, 2, and 3, dogs received either dexamethasone or saline (0.9% NaCl) solution injections SC twice daily. On days 2, 3, and 4, dogs received either meloxicam or saline solution injections SC once daily. On day 2, dogs were anesthetized for a sham surgery (ie, electrostimulation). On day 5, the gastroduodenal area of each dog was reevaluated by use of endoscopic evaluation and histologic examination of biopsy specimens.

RESULTS

The total endoscopic score of the dexamethasone-meloxicam group was significantly greater than the scores of the other groups. The dexamethasone-saline group had a mean cumulative score that was significantly greater than the saline-meloxicam or saline-saline groups. Endoscopic scores of the saline-meloxicam group were not significantly different from scores of the saline-saline group. No significant differences in histologic findings were found between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

In healthy dogs, meloxicam appears to be safe with regard to adverse effects on the gastrointestinal tract. Concurrent administration of dexamethasone and meloxicam is more likely to cause gastric erosions than meloxicam administration alone.

Effect of carprofen, etodolac, meloxicam, or butorphanol in dogs with induced acute synovitis

OBJECTIVE

To compare the analgesic and anti-inflammatory effect of single doses of carprofen, etodolac, meloxicam, and butorphanol in dogs with induced acute synovitis (acute pain model) via kinetic gait analysis and orthopedic evaluation and examine measurement of serum C-reactive protein (CRP) concentration as an indicator of treatment efficacy.

ANIMALS

12 Beagles and 6 additional Beagles that were used only in serum CRP analyses.

PROCEDURE

Acute synovitis was induced in right stifle joints of dogs via intra-articular injection of monosodium urate solution. Treatments included butorphanol (0.2 mg/kg, i.v.), carprofen (4 mg/kg, PO), etodolac (17 mg/kg, PO), or meloxicam (0.2 mg/kg, PO); control dogs received no treatment. The procedure was repeated (3-week intervals) until all dogs received all treatments including control treatment. Lameness was assessed on a biomechanical force platform and via orthopedic evaluations of the stifle joints; blood was collected to monitor serum CRP concentration.

RESULTS

Compared with control dogs, treated dogs had significantly different vertical ground reaction forces and weight-bearing scores. Greatest improvement in lameness was observed in carprofen-treated dogs. Etodolac had the fastest onset of action. Compared with butorphanol treatment, only carprofen and etodolac were associated with significantly lower pain scores. An increase in serum CRP concentration was detected after intra-articular injection in all dogs; this change was similar among groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Carprofen, etodolac, and meloxicam had greater efficacy than butorphanol in relief of acute pain. Carprofen was most effective overall. In this acute pain model, serum CRP analysis was not useful to assess drug efficacy.

Therapeutic effect of cyclo-oxygenase inhibitors with different isoform selectivity in lipopolysaccharide-induced preterm birth in mice

OBJECTIVE

Cyclo-oxygenase inhibitors have different selectivity for inhibitory action on the isoforms of the enzyme. Our purpose was to compare the tocolytic and maternal toxic effects of various cyclo-oxygenase inhibitors in the lipopolysaccharide-induced preterm birth in pregnant mice.

STUDY DESIGN

We randomly assigned 50 ICR pregnant mice into five groups of 10 mice each and treated them intraperitoneally with either phosphate-buffered saline solution or lipopolysaccharide (50 microg) on day 15 of pregnancy. Of the four groups that received lipopolysaccharide, three groups also were treated either with nonselective cyclo-oxygenase inhibitors (indomethacin [1 mg/kg/d] or diclofenac [2 mg/kg/d]) or with the cyclo-oxygenase-2 preferential inhibitor, meloxicam (2 mg/kg/d), with a gavage tube on days 15 through 18 of pregnancy or until maternal death. The mice were killed immediately after preterm birth or on day 21 of pregnancy. Preterm birth rates and maternal side effect profiles were evaluated.

RESULTS

Preterm birth occurred in 90% of mice after intraperitoneal lipopolysaccharide injection and in 20% of mice after phosphate-buffered saline solution injection. Indomethacin and meloxicam, but not diclofenac, significantly decreased the incidence of preterm birth that was induced by lipopolysaccharide (33.3% and 33.3%, respectively; P =.028). Although the overall incidence of maternal gastric and/or renal toxicities was not significantly increased in the indomethacin or meloxicam groups, a significant increase was noticed in the diclofenac group compared with the lipopolysaccharide-treated control group (P =.006).

CONCLUSION

Indomethacin and meloxicam, but not diclofenac, inhibit the lipopolysaccharide-induced preterm birth in an animal model. Meloxicam appears to have no advantage over indomethacin with regard to tocolysis and maternal side effects.

Effects of cyclooxygenase inhibitor pretreatment on nitric oxide production, nNOS and iNOS expression in rat cerebellum

1. The therapeutic effect of nonsteroidal anti-inflammatory drugs (NSAIDs) is thought to be due mainly to its inhibition of cyclooxygenase (COX) enzymes, but there is a growing body of research that now demonstrates a variety of NSAIDs effects on cellular signal transduction pathways other than those involving prostaglandins. 2. Nitric oxide (NO) as a free radical and an agent that gives rise to highly toxic oxidants (peroxynitrile, nitric dioxide, nitron ion), becomes a cause of neuronal damage and death in some brain lesions such as Parkinson and Alzheimer disease, and Huntington's chorea. 3. In the present study, the in vivo effect of three NSAIDs (lysine clonixinate (LC), indomethacine (INDO) and meloxicam (MELO)) on NO production and nitric oxide synthase expression in rat cerebellar slices was analysed. Rats were treated with (a) saline, (b) lipopolysaccharide (LPS) (5 mg kg(-1), i.p.), (c) saline in combination with different doses of NSAIDs and (d) LPS in combination with different doses of NSAIDs and then killed 6 h after treatment. 4. NO synthesis, evaluated by Bred and Snyder technique, was increased by LPS. This augmentation was inhibited by coadministration of the three NSAIDs assayed. None of the NSAIDs tested was able to modify control NO synthesis. 5. Expression of iNOS and neural NOS (nNOS) was detected by Western blotting in control and LPS-treated rats. LC and INDO, but not MELO, were able to inhibit the expression of these enzymes. 6. Therefore, reduction of iNOS and nNOS levels in cerebellum may explain, in part, the anti-inflammatory effect of these NSAIDs and may also have importance in the prevention of NO-mediated neuronal injury.

[Role of anti-inflammatory drugs in the treatment of acute coronary syndromes. From athero-inflammation to athero-thrombosis]

Coronary thrombosis is the most important cause of morbidity and mortality and the most severe manifestation of atherosclerosis. Knowledge of the pathophysiology of atheroma formation and the causes of atheroma accidents have allowed the development of new therapeutic measures for reducing thrombotic events after a coronary episode. Treating the thrombosis after plaque rupture is useful, but a late measure once coronary flow is disturbed. Therefore, treatment at an earlier stage, which we call athero-inflammation, a central event in atheroma progression leading to atherothrombosis, seems wise. There is evidence of an inflammatory component in the pathogenesis of atheroma rupture in acute coronary events. Earlier studies of anti-inflammatory medication have not demonstrated a reduction in thrombotic complications after an acute coronary episode. However, there are pathophysiological arguments and clinical findings that suggest that it would be advisable to include anti-inflammatory medications, especially those that inhibit preferentially COX-2, in the therapeutic arsenal for this pathology. We postulated that blocking athero-inflammation could prevent thrombosis. A pilot study was carried out in 120 patients with acute coronary syndrome without ST-segment elevation in which 60 patients were treated with meloxicam, a preferential COX-2 inhibitor. All patients received heparin and aspirin. During the stay in the coronary care unit, as well as after 90 days, meloxicam lowered composite outcomes (myocardial infarction, death and revascularization procedures) compared with the control group. These results and available pathophysiological and clinical evidence support the hypothesis of potential benefits of non-steroidal anti-inflammatory drugs with preferential inhibitory activity on COX-2 in patients with acute coronary syndromes. More trials are needed to confirm their preventive effect.

Meloxicam

Meloxicam (Mobic trade mark, Boehringer Ingelheim) is a relatively new oral non-steroidal anti-inflammatory drug (NSAID) approved for the treatment of osteoarthritis in the US. It has also been evaluated for the treatment of rheumatoid arthritis, ankylosing spondylitis and acute 'rheumatic' pain. Meloxicam has been shown to be COX-2 preferential, particularly at its lowest therapeutic dose, and is anti-inflammatory by inhibiting prostanoid synthesis in inflammatory cells. Since it is COX-2 preferential, it would be expected to have less gastrointestinal toxicity than non-selective NSAIDs. In clinical trials of meloxicam in osteoarthritis, it was found to be as effective as piroxicam, diclofenac and naproxen with less clinical gastrointestinal symptoms and less perforations, obstructions and bleeds by meta-analysis. Adverse events, including peripheral oedema and hypertension, occurred at a similar rate as with traditional NSAIDs.

Efficacy assessment of meloxicam, a preferential cyclooxygenase-2 inhibitor, in acute coronary syndromes without ST-segment elevation: the Nonsteroidal Anti-Inflammatory Drugs in Unstable Angina Treatment-2 (NUT-2) pilot study

BACKGROUND

Despite the use of heparin, aspirin, and other antiplatelet agents, acute coronary syndrome patients without ST-segment elevation remain at risk of cardiovascular thrombotic events. Given the role of inflammation in the pathogenesis of arterial thrombosis, we tested the hypothesis that the combination of meloxicam, a preferential COX-2 inhibitor, and heparin and aspirin would be superior to heparin and aspirin alone.

METHODS AND RESULTS

In an open-label, randomized, prospective, single-blind pilot study, patients with acute coronary syndromes without ST-segment elevation were randomized to aspirin and heparin treatment (n=60) or aspirin, heparin, and meloxicam (n=60) during coronary care unit stay. Patients then received aspirin or aspirin plus meloxicam for 30 days. During the coronary care unit stay, the primary outcomes variable of recurrent angina, myocardial infarction, or death was significantly lower in the patients receiving meloxicam (15.0% versus 38.3%, P=0.007). The second composite variable (coronary revascularization procedures, myocardial infarction, and death) was also significantly lower in meloxicam-treated patients (10.0% versus 26.7%, P=0.034). At 90 days, the primary end point remained significantly lower in the meloxicam group (21.7% versus 48.3%, P=0.004), as did the secondary end point (13.3% versus 33.3%, P=0.015) and the need for revascularization alone (11.7% versus 30.0%, P=0.025). No adverse complications associated with the meloxicam treatment were observed.

CONCLUSIONS

Meloxicam with heparin and aspirin was associated with significant reductions in adverse outcomes in acute coronary syndrome patients without ST-segment elevation. Additional larger trials are required to confirm the findings of this pilot study.

Evidence for the involvement of cyclooxygenase activity in the development of cocaine sensitization

Phospholipase A2 (PLA(2)) activation generates the release of arachidonic acid (AA) and platelet-activating factor (PAF), two compounds which may be involved in neuroplasticity. In previous studies, we found that PLA(2) activation is involved in the development of stimulant sensitization. In the present study, we have examined the roles of AA and PAF in the development of stimulant sensitization using agonists and antagonists selective for PAF receptors or the induction of various AA cascade-mediated eicosanoids. Sprague-Dawley rats were treated for 5 days with cocaine (30 mg/kg) or D-amphetamine (1 mg/kg) preceded 15 min earlier by various antagonists, and then tested following a 10-day withdrawal period for cocaine (15 mg/kg) or D-amphetamine (0.5 mg/kg)-induced locomotion. Consistent with our earlier work, pretreatment with the PLA(2) inhibitor quinacrine (25 mg/kg) blocked the development of cocaine and amphetamine sensitization. The lipoxygenase (LOX) inhibitors nordihydroguaiaretic acid (NDGA) (5-10 mg/kg) and MK-886 (1 mg/kg) had no effect on cocaine sensitization. The PAF receptor antagonist WEB 2086 (5-10 mg/kg) reduced the development of cocaine sensitization. The cyclooxygenase (COX) inhibitors indomethacin (1-2 mg/kg), piroxicam (0.5-1 mg/kg), 6-methoxy-2-napthylacetic acid (6-MNA; 0.5-1 mg/kg), and NS-398 (0.5-1 mg/kg) blocked the development of cocaine sensitization. The COX inhibitors indomethacin (2 mg/kg) and 6-MNA (1 mg/kg) also reduced the development of amphetamine sensitization. Rats were administered bilateral intraventral tegmental area (VTA) injections of D-amphetamine (5 microg/side) or saline coadministered with indomethacin (0.5 microg/side) or vehicle three times over 5 days and were then tested after a 10-day withdrawal for D-amphetamine (0.5 mg/kg ip)-induced locomotion. Intra-VTA amphetamine induced a robust form of amphetamine sensitization, which was blocked by coadministration of indomethacin. Unilateral intra-VTA injections of PAF (1 microg) did not significantly alter cocaine (15 mg/kg ip)-induced locomotion when tested after a 3-day withdrawal. These findings suggest that COX, and possibly PAF, activity is involved in the development of stimulant sensitization. Neuroanatomical studies demonstrate that this may occur at the level of the VTA.

Slow-binding inhibition of human prostaglandin endoperoxide synthase-2 with darbufelone, an isoform-selective antiinflammatory di-tert-butyl phenol

The antiinflammatory agent darbufelone, ((Z)-5-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl] methylene]-2-imino-4-thiazolidinone, methanesulfonate salt), was discovered as a dual inhibitor of cellular prostaglandin and leukotriene production. To study the mechanism of action of this drug, we expressed human prostaglandin endoperoxide synthase-1 (PGHS-1) and PGHS-2 and purified the recombinant enzymes using buffers that contain octylglucoside. In cyclooxygenase assays following a 15-min incubation of enzyme with inhibitor, darbufelone potently inhibits PGHS-2 (IC(50) = 0.19 microM) but is much less potent with PGHS-1 (IC(50) = 20 microM). Interestingly, when the assay buffer contains traces of Tween 20 (0.0001%), darbufelone appears inactive with PGHS-2 due to a detergent interaction that is detectable by absorption spectroscopy. We therefore used octylglucoside, which does not affect darbufelone in this way, in place of Tween 20 in our PGHS buffers. Inhibition of PGHS-2 with darbufelone is time dependent: with no preincubation, darbufelone is a weak inhibitor (IC(50) = 14 microM), but after a 30-min incubation it is 20-fold more potent. Plots of PGHS-2 activity vs preincubation time at various darbufelone concentrations reach a plateau. This finding is inconsistent with irreversible or one-step slow-binding inhibition. A two-step slow-binding inhibition model is proposed in which the E.I complex (K(i) = 6.2 +/- 1.9 to 14 +/- 1 microM) slowly transforms (k(5) = 0.015-0.030 s(-)(1)) to a tightly bound E.I form with K(i) = 0.63 +/- 0.07 microM and k(6) = 0.0034 s(-)(1). In steady-state kinetics inhibition experiments performed with no preincubation, we find that darbufelone is a noncompetitive inhibitor of PGHS-2 (K(i) = 10 +/- 5 microM). Darbufelone quenches the fluorescence of PGHS-2 at 325 nm (lambda(ex) = 280 nm) with K(d) = 0.98 +/- 0.03 microM. The PGHS substrate, arachidonate, and various cyclooxygenase inhibitors do not alter this binding affinity of darbufelone but a structural analogue of darbufelone competes directly for binding to PGHS-2. Di-tert-butyl phenols such as darbufelone may inhibit PGHS-2 by exploiting a previously unrecognized binding site on the enzyme.

Articular diffusion of meloxicam after a single oral dose: relationship to cyclo-oxygenase inhibition in synovial cells

OBJECTIVE

To investigate the distribution of meloxicam in the human knee joint and to compare it with the inhibition of cyclo-oxygenase (COX) activity in synovial cells.

DESIGN

Prospective pharmacokinetic study and in vitro laboratory investigation.

PATIENTS AND PARTICIPANTS

42 male and female patients aged 26 to 85 years hospitalised for rheumatic disease and requiring a diagnostic and/or therapeutic knee puncture.

METHODS

After a single oral dose of meloxicam 15mg, synovial fluid and blood samples were collected once per patient at various intervals after administration. Meloxicam concentrations were determined by a validated high performance liquid chromatography assay, protein binding by equilibrium dialysis, and pharmacokinetic parameters were calculated by noncompartmental analysis from the mean drug concentration-time profiles. The inhibitory effect of meloxicam on COX activity was investigated separately in unstimulated or interleukin-1beta-stimulated human synovial cells from osteoarthritic patients.

RESULTS

Meloxicam was found in synovial fluid at the earliest sampling time (1 hour). Peak concentrations were reached approximately 6 hours postdose in both plasma (842 microg/L) and synovial fluid (320 microg/L). A plateau was observed after the distribution phase (6 hours), corresponding to a constant ratio of drug concentration between synovial fluid and plasma of about 0.47. This ratio was higher in patients with acute inflammation (0.58) than in those with no inflammation (0.38). Meloxicam was extensively bound to protein, mainly to serum albumin. The area under the drug concentration-time curve (AUC) in plasma was more than 2.5 times that in synovial fluid. The AUC for free meloxicam was similar in plasma and synovial fluid. The 50% inhibitory concentrations (IC50) for basal and stimulated COX activity in human synovial cells were 33.7 nmol/L (11.8 microg/L) and 2.0 nmol/L (0.70 microg/L), respectively. The free concentration of meloxicam in synovial fluid was higher than the IC50 for stimulated COX activity from 6 to 36 hours postdose.

CONCLUSION

On the basis of free synovial concentrations and the IC50 for stimulated COX activity, meloxicam is expected to have a long duration of action. Inhibition of COX activity is expected to be more marked in inflamed synovium compared with non-inflamed synovium.

Effects of caffeine and paracetamol alone or in combination with acetylsalicylic acid on prostaglandin E(2) synthesis in rat microglial cells

Paracetamol has mild analgesic and antipyretic properties and is, along with acetylsalicylic acid, one of the most popular "over the counter" analgesic agents. However, the mechanism underlying its clinical effects is unknown. Another drug whose mechanism of action is unknown is caffeine, which is often used in combination with other analgesics, augmenting their effect. We investigated the inhibitory effect of paracetamol and caffeine on lipopolysaccharide (LPS)-induced cyclooxygenase (COX)- and prostaglandin (PG)E(2)-synthesis in primary rat microglial cells and compared it with the effect of acetylsalicylic acid, salicylic acid, and dipyrone. Furthermore, combinations of these drugs were used to investigate a possible synergistic inhibitory effect on PGE(2)-synthesis. Both paracetamol (IC(50)=7.45 microM) and caffeine (IC(50)=42.5 microM) dose-dependently inhibited microglial PGE(2) synthesis. In combination with acetylsalicylic acid (IC(50)=3.12 microM), both substances augmented the inhibitory effect of acetylsalicylic acid on LPS-induced PGE(2)-synthesis. Whereas paracetamol inhibited only COX enzyme activity, caffeine also inhibited COX-2 protein synthesis. These results are compatible with the view that the clinical activity of paracetamol and caffeine is due to inhibition of COX. Furthermore, these results may help explain the clinical experience of an adjuvant analgesic effect of caffeine and paracetamol when combined with acetylsalicylic acid.

Meloxicam

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Selective cyclooxygenase-2 inhibition prevents alveolar bone loss in experimental periodontitis in rats

BACKGROUND

Prostaglandins are implicated in periodontal bone destruction. We investigated the effect of a non-selective cyclooxygenase (COX) inhibitor (indomethacin-IND) or a type 2 COX inhibitor (meloxicam-MLX) in an experimental periodontal disease (EPD) model.

METHODS

Wistar rats were subjected to placement of a nylon thread ligature around the maxillary molars and sacrificed after 7 days. Alveolar bone loss (ABL) was measured in one quadrant as the distance between the cemento-enamel junction and the alveolar bone. The other quadrant was processed for histopathologic analysis. Daily weight and white blood cell count were recorded. Groups were treated subcutaneously for 7 days with either IND (0.5, 1, or 2 mg/kg) or MLX (0.75, 1.5, or 3 mg/kg). Controls received no treatment. Macroscopic analysis of the gastric mucosa was done. The control group did not receive any manipulation, and a non-treated group consisted of rats subjected to periodontitis that received no pharmacological treatment.

RESULTS

In the non-treated (NT) group, there was significant ABL, severe mononuclear influx, and an increase in osteoclast numbers. Significant neutrophilia and lymphomonocytosis occurred at 6 hours and at 7 days, respectively, as compared to controls. Significant weight loss persisted until the seventh day in the NT group. Both IND and MLX reduced ABL and histopathologic changes. Neutrophilia and lymphomonocytosis were also significantly reversed. Both IND and MLX induced earlier weight recovery. The stomachs of the IND (1 and 2 mg/kg) groups presented hemorrhage and ulcers, whereas in the MLX-treated groups, there were mild petechiae just in the 3 mg/kg group.

CONCLUSIONS

COX inhibition prevented ABL in this experimental periodontal disease model. MLX displays similar efficacy and less gastric damage than IND. MLX may provide a better risk/benefit ratio in the treatment of human periodontitis than non-selective COX inhibitors.

Modulation of oxidant status by meloxicam in experimentally induced arthritis

Meloxicam is a new non-steroidal anti-inflammatory drug, that possesses a selective inhibition of the inducible isoform of cyclooxygenase enzyme (COX-2) relative to the constitutive one, COX-1. Oxidative stress has been documented to be involved in the aetiology of many pathological conditions. The present study aims to further explore the relationship between free radical generation and the inflammatory process, and extends more to investigate the effect of meloxicam on the oxidant status in experimentally induced arthritis, namely, Freund's adjuvant-induced arthritis in rats. Results of the present investigation revealed that animals inoculated with Freund's complete adjuvant showed a biphasic response regarding changes in the right hind paw oedema volume. During the chronic phase of the disease, arthritic animals showed an elevated plasma level of lipid peroxides, enhanced blood glutathione peroxidase activity, with depletion of plasma total thiols and albumin; while no significant effects have been observed on erythrocytic superoxide dismutase activity and plasma total proteins content, as compared to normal untreated rats. Long-term administration of meloxicam, at two dose levels, produced significant antioedemetous effect and succeeded in modulating the altered parameters affected during arthritis. The selected dose regimens of meloxicam did not show any apparent lesions in the gastric mucosa. The results of the present investigation lend further support to the reported observations concerning selective COX-2 inhibitors. The modulatory influence of meloxicam on the oxidant status, particularly on lipid peroxidation and thiols might be a relevant effect accounting for its anti-inflammatory properties.

Cyclooxygenase metabolites mediate glomerular monocyte chemoattractant protein-1 formation and monocyte recruitment in experimental glomerulonephritis

BACKGROUND

Monocyte chemoattractant protein-1 (MCP-1) has been shown to play a significant role in the recruitment of monocytes/macrophages in experimental glomerulonephritis. Whereas a number of inflammatory mediators have been characterized that are involved in the expression of MCP-1 in renal disease, little is known about repressors of chemokine formation in vivo. We hypothesized that cyclooxygenase (COX) products influence the formation of MCP-1 and affect inflammatory cell recruitment in glomerulonephritis.

METHODS

The effect of COX inhibitors was evaluated in the antithymocyte antibody model and an anti-glomerular basement membrane model of glomerulonephritis. Rats were treated with the COX-1/COX-2 inhibitor indomethacin and the selective COX-2 inhibitors meloxicam and SC 58125. Animals were studied at 1 hour, 24 hours, and 5 days after induction of the disease.

RESULTS

Indomethacin, to a lesser degree the selective COX-2 inhibitors, enhanced glomerular MCP-1 and RANTES mRNA levels. Indomethacin enhanced glomerular monocyte chemoattractant activity an the infiltration of monocytes/macrophages at 24 hours and 5 days.

CONCLUSIONS

Our studies demonstrate that COX products may serve as endogenous repressors of MCP-1 formation in experimental glomerulonephritis. The data suggest that COX-1 and COX-2 products mediate these effects differently because the selective COX-2 inhibitors had less influence on chemokine expression.

Interleukin-1 induces slow-wave sleep at the prostaglandin D2-sensitive sleep-promoting zone in the rat brain

To determine the site of action of the sleep-promoting effect of interleukin-1 (IL-1), we continuously infused (between 11 P.M. and 5 A.M.) murine recombinant IL-1beta into seven different locations in the ventricular and subarachnoid systems of the brain in freely moving rats. When IL-1 was infused at 10 ng/6 hr into the subarachnoid space underlying the ventral surface of the rostral basal forebrain, which previously was defined as the "prostaglandin (PG) D2-sensitive sleep-promoting zone" (PGD2-SZ), the total amount of slow-wave sleep (SWS) increased by 110.7 min (IL-1 was 208.1 +/- 14.3 min vs control at 97.4 +/- 9.3 min; n = 8; p < 0.01 by paired Student's t test) from the baseline control level obtained under continuous infusion of saline vehicle. The hourly SWS during the infusion period reached the level of daytime SWS, the physiological maximum, whereas paradoxical sleep (PS) was decreased transiently. This site of action for the SWS promotion was dissociated from the site in the third ventricle sensitive to the IL-1-mediated PS suppression, fever, and anorexia. The SWS increase caused by IL-1 infusion into the PGD2-SZ was blocked completely by coadministered diclofenac, a nonselective cyclooxygenase (COX) inhibitor. Pretreatment of rats with NS-398 or piroxicam (3 mg/kg of body weight, i.p.), which are said, respectively, to possess high and relative specificity for the COX-2 enzyme, also blocked the SWS-promoting effect of IL-1. We present a hypothesis that IL-1 induces SWS, at least in part, via COX-2-mediated PG production in the PGD2-SZ.

Endoscopy of the gastroduodenal mucosa after carprofen, meloxicam and ketoprofen administration in dogs

Endoscopy was undertaken to examine the gastroduodenal mucosa of 24 healthy dogs after seven days and again after 28 days of oral non-steroidal anti-inflammatory drug (NSAID) administration. The dogs were divided into four groups. One group received ketoprofen (1 mg/kg every 24 hours), one group carprofen (2 mg/kg every 12 hours for seven days followed by 2 mg/kg every 24 hours), a third group meloxicam suspension (0.2 mg/kg every 24 hours), and the last group gelatin (one capsule every 24 hours). Serum biochemical and complete blood count parameters did not change significantly after NSAID administration. Gastroduodenal lesions were observed in 17 dogs, but in all cases these were mild to moderate. The dogs receiving gelatin or carprofen showed the fewest and the least severe lesions, although there was no statistically significant difference between the three test drugs and the control group (P < or = 0.05). None of the dogs showed any clinical signs related to the gastrointestinal lesions.

Design of selective inhibitors of cyclooxygenase-2 as nonulcerogenic anti-inflammatory agents

The discovery of a second isoform of cyclooxygenase (cyclooxygenase-2) that is expressed in inflammatory cells and the central nervous system, but not in the gastric mucosa, offers the possibility of developing anti-inflammatory and analgesic agents that lack the gastrointestinal side effects of currently available nonsteroidal anti-inflammatory drugs. Lead compounds from several different structural classes have been identified and shown to be slow, tight-binding inhibitors that express their selectivity for cyclooxygenase-2 in the time-dependent step. The determination of structures of enzyme-inhibitor co-crystals along with site-directed mutagenesis experiments reveal the molecular basis for selectivity of some, but not all, inhibitors. Preclinical and clinical studies suggest cyclooxygenase-2 inhibitors are highly promising new agents for the treatment of pain and inflammation, and for the prevention of cancer.

Activation of genes for growth factors and cyclooxygenases in rat gastric mucosa during recovery from stress damage

Growth factors and prostaglandins protect the gastric mucosa against stress-induced lesions but their role in the recovery of the mucosa from these lesions has been little studied. We evaluated gastric mucosa lesions, gastric blood flow, mucosal generation of prostaglandin E2 and mucosal gene expression of epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) as well as constitutive prostaglandin cyclooxygenase-1 and inducible cyclooxygenase-2 and the effect of the inhibition of these enzymes on the recovery of mucosa from the stress-induced lesions. Rats were exposed to 3.5 h of water immersion and restraint stress and killed at 0, 2, 4, 6, 8, 12 and 24 h after stress. The number of gastric lesions was determined and gastric blood flow was measured by H2-gas clearance. Gastric acid secretion was tested in separate gastric fistula rats. Gastric mucosa biopsies were taken for determination of immunoreactive EGF and TGF alpha. Expression of EGF and TGF alpha mRNA and cyclooxygenase-1 and cyclooxygenase-2 mRNA was also determined by reverse-transcriptase polymerase chain reaction. The number of gastric lesions induced by 3.5 h stress averaged approximately 20 per rat and declined significantly at 2, 4, 6, 8 and 12 h, to disappear almost completely after 24 h. This was accompanied by a gradual rise in gastric blood flow, mucosal generation of prostaglandin E2 and mucosal EGF and TGF alpha contents, while the increased gastric acid secretion returned to normal. In the intact mucosa, EGF mRNA was not detected but TGF alpha mRNA was found in measurable amounts. Following exposure to stress, the expression of both these factors was significantly increased. Similarly, the expression of cyclo-oxygenase-1 and cyclooxygenase-2 mRNA was detected in the oxyntic mucosa at all time intervals after exposure to stress. Indomethacin (5 mg/kg i.p.), an inhibitor of cyclooxygenase-1 and cyclooxygenase-2, and meloxicam (1 mg/kg i.p.), an inhibitor of cyclooxygenase-2, both prolonged the healing of stress lesions and reduced the gastric blood flow, while enhancing gastric acid secretion at all times tested. We conclude that healing of stress lesions results in the restoration gastric blood flow and mucosal prostaglandin generation and that these effects are accompanied by overexpression of EGF and TGF alpha as well as cyclooxygenase-1 and cyclooxygenase-2 mRNA and by increased biosynthesis of gastroprotective prostaglandin.

Development of a radiochemical cyclooxygenase-1 and -2 in vitro assay for identification of natural products as inhibitors of prostaglandin biosynthesis

A radiochemical enzyme assay for studying cyclooxygenase (COX)-catalyzed prostaglandin biosynthesis in vitro was optimized with respect to both COX-1 and COX-2 activity. The assay can be used to assess the relative selectivity of plant-derived inhibitors on COX-1 and COX-2 Assay conditions were optimized for both enzymes with respect to concentration of cofactors (l-epinephrine, reduced glutathione, and hematin), activation time (enzyme and cofactors), reaction time, and pH. Moreover, the kinetic parameters, Km and Kcat, of both enzymes were estimated. Five COX inhibitors were used to validate the assay, indomethacin, aspirin, naproxen, ibuprofen, and the arylsulfonamide NS-398, all with different COX selectivity and time dependency. Time-dependent inhibition was determined by comparing the inhibition, with and without preincubation of enzyme and inhibitor. Two flavonoids, (+)-catechin and quercitrin, were examined with respect to inhibition of COX-catalyzed prostaglandin biosynthesis. (+)-Catechin showed equal inhibitory effects on the two enzymes. Quercitrin was found to be inactive toward both COX-1- and COX-2-catalyzed prostaglandin biosynthesis. The optimization procedure resulted in a considerable reduction of the amount of enzyme required for adequate prostglandin biosynthesis and a reliable method suited to evaluate natural products on inhibition of COX-2-catalyzed prostaglandin biosynthesis, as well as on COX-1.

Nonsteroidal anti-inflammatory drugs and corticosteroids for the management of canine osteoarthritis

Anti-inflammatory medications have long been prescribed for relief of the pain and discomfort associated with OA. This occurs despite the recognized side effects associated with use of NSAIDs and corticosteroids. Available evidence suggests that NSAIDs provide this relief through a combination of central and peripheral actions. Recent discovery of two isoforms of cyclooxygenase has increased our understanding of NSAID activity and may result in identification of drugs that potentially will have fewer side effects. A review of NSAIDs used in veterinary medicine indicates that relatively little is known regarding their role in treating OA, although controlled studies involving carprofen and etodolac have increased our knowledge of the efficacy of specific NSAIDs used for this purpose.

Effect of structural modification of enol-carboxamide-type nonsteroidal antiinflammatory drugs on COX-2/COX-1 selectivity

Meloxicam (5), an NSAID in the enol-carboxamide class, was developed on the basis of its antiinflammatory activity and relative safety in animal models. In subsequent screening in microsomal assays using human COX-1 and COX-2, we discovered that it possessed a selectivity profile for COX-2 superior to piroxicam and other marketed NSAIDs. We therefore embarked on a study of enol-carboxamide type compounds to determine if COX-2 selectivity and potency could be dramatically improved by structural modification. Substitution at the 6- and 7-positions of the 4-oxo-1,2-benzothiazine-3-carboxamide, alteration of the N-methyl substituent, and amide modification were all examined. In addition we explored several related systems including the isomeric 3-oxo-1,2-benzothiazine-4-carboxamides, thienothiazines, indolothizines, benzothienothiazines, naphthothiazines, and 1,3- and 1,4-dioxoisoquinolines. While a few examples were found with greater potency in the COX-2 assay, no compound tested had a better COX-2/COX-1 selectivity profile than that of 5.

Efficacy and tolerability of intramuscular and oral meloxicam in patients with acute lumbago: a comparison with intramuscular and oral piroxicam

In this controlled, randomised, parallel-group, multicentre study, the efficacy and tolerability of an intramuscular (i.m.) dose of meloxicam (15 mg) on Day 1 followed by seven days of oral meloxicam (15 mg/day) were compared with those of an i.m. dose of piroxicam (20 mg) on Day 1 followed by seven days of oral piroxicam (20 mg/day) therapy in a total of 169 outpatients with acute lumbago. Time to onset of analgesic action after i.m. injection was determined, and overall efficacy, pain on movement, limitation of daily activities, local tolerability at the injection site and overall tolerability were assessed by investigators and patients on verbal rating scales (VRSs). Adverse events and laboratory assessments were documented. Meloxicam and piroxicam showed a rapid onset of action after i.m. injection (40 and 45 minutes median time, respectively), overall efficacy of both therapies was highly rated, and limitations to daily life were greatly reduced in the majority of patients in both groups. There were no statistically significant differences in efficacy between meloxicam and piroxicam. Local and overall tolerabilities were equally good for the two drugs, but there were fewer gastrointestinal (GI) adverse events among meloxicam patients (1.2% of patients) than piroxicam patients (7.0% of patients). The improved tolerability profile of meloxicam may be explained by its selectivity towards cyclooxygenase-2.

Meloxicam

Meloxicam is a new nonsteroidal anti-inflammatory drug (NSAID) developed for the treatment of rheumatoid arthritis and osteoarthritis. It has greater in vitro and in vivo inhibitory action against the inducible isoform of cyclo-oxygenase (COX-2), which is implicated in the inflammatory response, than against the constitutive form of this enzyme (COX-1), inhibition of which is associated with gastric, renal and other adverse effects. It has anti-inflammatory effects similar to or better than those of other NSAIDs in animal models, and a greater therapeutic ratio (ulcerogenic potential:efficacy in adjuvant arthritis). In healthy volunteers meloxicam 7.5 or 15 mg caused less gastrointestinal mucosal damage on endoscopy than piroxicam 20 mg, with a significant difference between meloxicam 7.5 mg and piroxicam. In comparative clinical trials, meloxicam was at least as effective as piroxicam and naproxen in patients with rheumatoid arthritis, and diclofenac and piroxicam in patients with osteoarthritis. Meloxicam was at least as well tolerated as piroxicam, diclofenac or naproxen overall but had improved gastrointestinal tolerability compared with these agents.