Endoscopic studies of nabumetone in patients with rheumatoid arthritis. A comparative endoscopic and histologic evaluation

Potentiation of oral anticoagulation and hemarthrosis associated with nabumetone

Concomitant therapy with warfarin and nonsteroidal antiinflammatory drugs (NSAIDs) is of concern due to the potential for increased bleeding. Nonsteroidal antiinflammatory drugs may alter patient response to warfarin by pharmacodynamic or pharmacokinetic interactions. A man receiving long-term, stable warfarin therapy experienced a significant increase in international normalized ratio 1 week after nabumetone was added to his regimen. Despite prompt reduction of the warfarin dosage, he experienced hemarthrosis of his right knee. Previous reports suggested lack of interaction between nabumetone and warfarin. Caution and close monitoring are advisable when the two agents are administered concomitantly.

The in vitro effects of 6-methoxy-2-naphthylacetic acid, the active metabolite of nabumetone, on rat gastric mucosal eicosanoid synthesis and metabolism

Nabumetone is a neutral non-steroidal anti-inflammatory drug with a low propensity to cause gastrointestinal (GI) damage. Previous studies, in vivo, have shown that the drug has weak effects on gastric mucosal cyclooxygenase activity, which may help to explain its favourable GI profile. The present study set out to determine whether the observed effects of nabumetone on cyclooxygenase, in vivo, parallel those of its active metabolite, 6-methoxy-2-naphthylacetic acid (6MNA), in vitro. We have also studied nabumetone and 6MNA on two other systems, namely 15-prostaglandin dehydrogenase (15-PGDH) and 5-lipoxy-genase (5-LO), which when inhibited may confer mucosal protection. The results showed that 6MNA had variable effects on cyclooxygenase activity, depending on the concentration and was less potent and less effective than indomethacin. Cyclooxygenase activity was not inhibited by the reversible inhibitor, aminopyrine, but at low concentrations stimulation was observed. Sulphasalazine inhibited 15-PGDH in a concentration-dependent manner whereas 6MNA inhibited it only at high concentrations. Nabumetone was devoid of activity. Basal 5-LO activity was attenuated by phenidone and unaltered by 6MNA but increased by nabumetone at the highest concentration. In the presence of arachidonic acid, to raise 5-LO activity, nabumetone, 6MNA, BW755C and phenidone apparently inhibited this activity. However, it was possible that both nabumetone and 6MNA inhibited a prostanoid-mediated stimulatory effect on 5-LO rather than effecting enzyme inhibition per se. Nabumetone's favourable GI profile may, therefore, relate to 6MNA having weak effects on mucosal cyclooxygenase and is unlikely to involve inhibition of prostanoid metabolism or 5-LO.

Health-related quality of life assessments in osteoarthritis during NSAID treatment

There is some evidence that nabumetone (1000 mg once daily) in comparison with piroxicam (20 mg once daily) in patients with OA in general practice is associated with a lower incidence and less severe occurrence of stomach pain but with more withdrawals due to lack of efficacy. The aim of this analysis was to investigate whether these differences are reflected in health-related quality of life assessments. Patients (n = 198) included in this study were selected in general practice according to a protocol. The patients were randomized and treated for a period of six weeks. Clinical assessments were performed by the general practitioner (CP) during treatment. The Sickness Impact Profile (SIP), the Activities of Daily Living (ADL), and a pain questionnaire were filled out by the patients before and after treatment. As measured with the SIP, the ADL and the pain questionnaire, there were no significant differences between nabumetone and piroxicam. The correlations between (changes in) patient assessments and (changes in) clinical assessments were low. The differences between the two drugs regarding withdrawals and adverse events were not reflected by patient health-related quality of life assessments. There was a low correlation between patient health-related quality of life assessment and clinical assessments. To get a complete picture of the efficacy and safety of a drug, patient health-related quality of life assessments should be a part of a clinical trial.

Effect of 6-Methoxy-2-Naphthylacetic Acid (6MNA), the Active Metabolite of Nabumetone, on the Glycosaminoglycan Synthesis of Canine Articular Cartilage In Vitro : Comparison with Other Nonsteroidal Anti-Inflammatory Drugs

6-methoxy-2-naphthylacetic acid (6MNA), the active metabolite of nabumetone, a novel nonacidic NSAID, has been studied in an in vitro culture system to determine its effects on glycosaminoglycan synthesis of normal and osteoarthritic canine articular cartilage. The effects were contrasted with those of several other NSAIDs. Dexamethasone potently inhibited synthesis and was used as a positive control in these studies. To reduce the influence of protein binding with these drugs, experiments were performed both in the presence and in the absence of serum in the culture medium. At and above concentrations achieved in the plasma of nabumetone-treated patients, 6MNA did not inhibit glycosaminoglycan synthesis of normal or osteoarthritic cartilage. In contrast, some other NSAIDs had the propensity to significantly suppress chondrocyte synthetic activity.

Comparison of the efficacy and safety of oxaprozin and nabumetone in the treatment of patients with osteoarthritis of the knee

This multicenter, 6-week, double-blind, placebo-controlled, parallel-group study compared the efficacy and safety of oxaprozin 1200 mg once daily with that of nabumetone 1000 mg once daily in patients with moderate-to-severe osteoarthritis (OA) of the knee. To be eligible, patients had to experience a flare of OA within 2 weeks of discontinuing their usual OA medication (nonsteroidal anti-inflammatory drug or analgesic). Eligible patients were assessed at baseline and then randomized to receive oxaprozin (n = 109), nabumetone (n = 110), or placebo (n = 109). Efficacy assessments were performed at weeks 1, 2, 4, and 6. Primary efficacy variables included knee pain on weight bearing, knee pain on motion, and patient's and physician's global assessments of OA. Secondary efficacy variables included pain intensity, time to walk 50 feet, and duration of morning stiffness. Safety was evaluated by use of routine laboratory analyses; physical examination at screening, baseline, and week 6 (or study termination); assessment of symptoms at baseline and at each visit; and testing stools for occult blood at screening and between week 4 and the final visit. Adverse events were monitored throughout the study. Between-group differences in efficacy variables were evident by week 1. The mean change in improvement from baseline with oxaprozin compared with placebo was statistically significant in favor of oxaprozin at weeks 1, 2, 4, and 6 for all primary efficacy variables. The mean change in improvement from baseline with nabumetone compared with placebo, however, was statistically significant only at week 1 for knee pain on motion, patient's global assessment, and physician's global assessment. The mean change in improvement from baseline was statistically significant (P < or = 0.035) in favor of oxaprozin versus nabumetone at weeks 2 and 6 for all four primary efficacy variables and also at week 4 for knee pain on motion. The incidence of adverse clinical events between treatment groups was not statistically significant. However, nine oxaprozin-treated patients had asymptomatic liver enzyme elevations reported as adverse events. Four of these patients had reversible elevations of aspartate aminotransferase and alanine aminotransferase greater than three times the upper limit of normal range (P < 0.05); two of these patients were taking other medications known to induce liver enzyme abnormalities. The study showed that oxaprozin 1200 mg once daily was statistically significantly more efficacious than nabumetone 1000 mg once daily for the treatment of patients with moderate-to-severe OA of the knee. Both drugs were clinically well tolerated.

Comparative effects of nabumetone, naproxen, piroxicam, and diclofenac on rat gastric irritancy following acute exposure to OTC non-steroidal anti-inflammatory agents and other gastric irritants

This study examined the relative effects of equally-effective anti-inflammatory doses of nabumetone, naproxen, piroxicam and diclofenac on gastric irritancy induced by over-the-counter (OTC) non-steroidal anti-inflammatory drugs (NSAIDs) aspirin and ibuprofen and a variety of necrotizing agents (0.6 N HCl, 0.2 N NaOH and 25% NaCl). Within one hour, aspirin 100 and 200 mg/kg and ibuprofen up to 15 mg/kg produced significant gastric mucosal injury. Aspirin 50 mg/kg produced only minimal damage that was enhanced by 5 x ID25 piroxicam and naproxen, but not by nabumetone or diclofenac. 5 x ID25 naproxen, piroxicam, and diclofenac significantly enhanced mucosal damage produced by ibuprofen 2.5 mg/kg. An equivalent anti-inflammatory dose of nabumetone failed to enhance the gastric irritancy produced by ibuprofen 2.5 mg/kg. Similarly, naproxen, piroxicam, and diclofenac enhanced the susceptibility of the gastric mucosa to the necrotizing actions of 0.6 N HCl, 0.2 N NaOH or 25% NaCl. Naproxen, piroxicam, or diclofenac are more likely than nabumetone to enhance gastric mucosal injury produced by OTC NSAIDs (aspirin and ibuprofen) or other gastric irritants.

Gastrointestinal irritancy, antiinflammatory activity, and prostanoid inhibition in the rat. Differentiation of effects between nabumetone and etodolac

Many nonsteroidal antiinflammatory drugs have the ability to cause gastrointestinal damage in both animals and man. The aim of the present study was to compare nabumetone, a nonacidic drug, with etodolac on rat gastric mucosal damage and prostanoid synthesis, while concurrently measuring prostanoid production during edema formation in a carrageenan model of paw inflammation. The results showed that both drugs inhibited paw exudate prostaglandin E2 and edema significantly, but they did not inhibit gastric prostanoid production 4 hr after dosing. Gastric damage, however, was observed with etodolac. Additional time-course studies showed that over a 4-hr period, etodolac, unlike nabumetone, markedly inhibited gastric mucosal prostaglandin E2 production, which was associated with gastric erosion formation. Further studies demonstrated that nabumetone did not induce gastrointestinal damage or blood loss when administered to rats in a high antiinflammatory oral dose. In contrast, etodolac produced marked gastrointestinal damage and bleeding, which was evident for up to 48 hr after the dose. It is suggested that nabumetone's favorable gastrointestinal irritancy profile may relate, in part, to its nonacidic nature and to its differential effects on prostanoid production.

Safety experience with nabumetone versus diclofenac, naproxen, ibuprofen, and piroxicam in osteoarthritis and rheumatoid arthritis

The comparative safety of nabumetone (1,000-2,000 mg/day) versus diclofenac (100-200 mg/day), naproxen (500-1,500 mg/day), piroxicam (10-20 mg/day), and ibuprofen (1,200-3,200 mg/day) was evaluated in a 12-week, randomized, open-label, multicenter study. Patients with osteoarthritis (OA) or rheumatoid arthritis (RA) were enrolled in a 3:1 ratio (nabumetone:one of the four comparator NSAIDs). The incidence of > or = 1 adverse event considered by the investigator to be related or probably related to therapy was similar in all groups. However, significantly (p < 0.02) more diclofenac-treated patients experienced abdominal pain and/or gastritis than nabumetone-treated patients. Naproxen-treated patients experienced significantly (p < 0.002) more dyspepsia as compared with patients treated with nabumetone or ibuprofen and significantly (p < or = 0.001) more nabumetone-treated patients experienced diarrhea than patients treated with naproxen, ibuprofen, or piroxicam. Ulcers occurred in one (0.03%) nabumetone-treated patient versus six (0.5%) patients treated with one of the comparator NSAIDs (p = 0.001). A decrease in hemoglobin > or = 1.5 g/dL occurred in fewer nabumetone-treated patients than in patients treated with diclofenac (p < 0.04), ibuprofen (p < or = 0.04), or piroxicam (p = 0.055). Finally, a similar percentage of patients in all treatment groups withdrew from the study because of adverse events related or probably related to treatment. More (p < 0.001) diclofenac-treated patients withdrew because of elevated hepatic transaminases than patients treated with the other agents. Withdrawal because of gastritis was also noted for more diclofenac-treated patients than nabumetone-treated patients (p < 0.04). In conclusion, nabumetone was demonstrated to be at least as safe as diclofenac, piroxicam, ibuprofen, and naproxen as related to subjective complaints, such as dyspepsia or gastritis. However, more serious events, such as ulcers or meaningful decreases in hemoglobin, seem to occur less often with nabumetone.

Gastrointestinal damage demonstrated with nabumetone or etodolac in preclinical studies

Nabumetone, a nonacidic, nonsteroidal antiinflammatory drug (NSAID), and etodolac, an acidic NSAID, were compared to assess the gastrointestinal (GI) tolerability of these agents and their effects on gastric prostaglandins in rats. In a single-dose study, etodolac caused a significant increase in both gastric and intestinal damage 6, 24, 48, and 144 hours after dosing. In contrast, no significant GI damage was noted with nabumetone. Chronic, 28-day studies comparing five times the ID25 (the dose that reduces carrageenan-induced inflammation by 25% in 50% of animals) of nabumetone with twice the ID25 of etodolac demonstrated a significant increase in both gastric and intestinal damage with etodolac, but no GI damage with nabumetone, despite the higher dose employed. In single-dose studies comparing gastric damage and prostaglandin synthesis 4 hours after dosing, both nabumetone and etodolac did not significantly reduce gastric prostaglandin I2 production. However, there was a significant increase in gastric damage with etodolac, but not with nabumetone. It was hypothesized, and confirmed in a second study, that there is a transient inhibition of gastric prostaglandin synthesis with etodolac that is responsible, in part, for the gastric damage noted. In conclusion, acute and chronic dosing of nabumetone at doses up to five times the ID25 did not cause GI damage in rats. In contrast, etodolac did result in GI damage, which is thought to be, in part, the result of a transient inhibition of gastric prostaglandin synthesis, observed at minimally effective antiinflammatory doses.

Nonsteroidal antiinflammatory drug use in patients receiving warfarin: emphasis on nabumetone

Phenylbutazone has been clearly demonstrated to interact pharmacokinetically and clinically with warfarin, although several other nonsteroidal antiinflammatory drugs (NSAIDs) also have the potential to interact with warfarin to cause alterations in prothrombin time. Aspirin is known to inhibit platelet aggregation irreversibly, whereas nonaspirin NSAIDs are thought to inhibit platelet aggregation reversibly. In contrast, nabumetone was not shown to cause significant inhibition of platelet aggregation, which may be related to the fact that nabumetone preferentially inhibits the prostaglandin synthase-2 isozyme instead of the prostaglandin synthase-1 isozyme. Furthermore, in studies in patients and normal volunteers stabilized on warfarin, nabumetone did not cause alterations in the prothrombin time or international normalized ratio. Based on data evaluating the concomitant use of nabumetone and warfarin, the relative lack of platelet inhibition, and the relatively lower risk of nabumetone-induced gastrointestinal mucosal damage as assessed by radiolabeled chromium-51 fecal blood loss studies and endoscopic evaluations, nabumetone may be preferred if concomitant therapy with warfarin is indicated.

Randomized double-blind study of nabumetone and piroxicam in the treatment of osteoarthritis in Dutch general practice: efficacy and tolerability

To study nabumetone (1,000 mg once daily) by comparison with piroxicam (20 mg once daily) in patients with osteoarthritis, a randomized, double-blind trial was set up in 40 general practices. Evaluation was based on clinical outcome in 198 patients. There was some evidence that nabumetone is associated with a lower and less severe occurrence of gastric pain, and with more withdrawals due to lack of efficacy. Although the differences between nabumetone and piroxicam were small in this study, these were clinically relevant. The general practitioner should balance the respective benefits of greater safety and tolerance against greater efficacy in meeting the requirements of an individual patient with osteoarthritis.

Nabumetone: a "nonacidic" nonsteroidal antiinflammatory drug

OBJECTIVE

To review the pharmacology, pharmacokinetic disposition, dosage recommendations, adverse effects, drug interactions, and efficacy of nabumetone in patients with selected rheumatic disorders and soft-tissue injuries.

DATA SOURCES

Data from scientific literature were extracted, evaluated, and summarized for presentation. A MEDLINE search was conducted using the following indexing terms: antiinflammatory agents, nonsteroidal, nabumetone, rheumatoid arthritis (RA), and osteoarthritis (OA). Studies evaluating nabumetone reported in articles, abstracts, or proceedings involving human subjects were considered for inclusion.

STUDY SELECTION

Special consideration was given to clinical studies using double-blind, randomized, parallel, controlled designs. Studies comparing the effectiveness and safety of nabumetone with placebo and other nonsteroidal antiinflammatory drugs (NSAIDs) were included.

DATA EXTRACTION

Data from human studies published in the English language were evaluated. Trials were assessed according to study design, sample size, and description of outcomes.

DATA SYNTHESIS

Nabumetone is a nonacidic prodrug that is metabolized to an active nonsteroidal antiinflammatory moiety, 6-methoxy-2-naphthylacetic acid (6-MNA). 6-MNA is a structural analog of naproxen. Like naproxen and other NSAIDs, 6-MNA possesses analgesic, antipyretic, and antiinflammatory activity, 6-MNA has a prolonged elimination half-life, ranging from 17 to 74 hours, which allows for once-daily dosing. The efficacy of nabumetone for treating symptoms of RA and OA has been established in controlled clinical trials. Nabumetone also has been studied in ankylosing spondylitis and soft-tissue injuries. Adverse effects associated with nabumetone are similar to those associated with other NSAIDs. Gastrointestinal reactions occur most frequently in the form of abdominal pain or indigestion, nausea, or vomiting. Central nervous system adverse effects occur less frequently, and are followed in order of occurrence by rashes.

CONCLUSIONS

Nabumetone is a prodrug metabolized to an active metabolite structurally related to naproxen. Studies have demonstrated the efficacy of nabumetone, but no advantages over the many other NSAIDs now available.

Antiinflammatory and gastrointestinal effects of nabumetone or its active metabolite, 6-methoxy-2-naphthylacetic acid (6MNA). Comparative studies with indomethacin

6MNA, the active metabolite of the nonacidic antiinflammatory drug nabumetone, was investigated using intravenous administration for effects on (1) carrageenan paw edema and gastric irritancy compared with either oral nabumetone or both oral and intravenous indomethacin when given acutely and (2) gastrointestinal irritancy when given in repeat dosing studies. Oral doses of nabumetone or intravenous 6MNA produced effective antiinflammatory activity together with significant inhibition of paw exudate PGE2. Antiinflammatory oral doses of nabumetone or intravenous 6MNA produced minimal effects on gastric 6-keto PGF1 alpha production with an absence of gastric damage, in contrast with indomethacin. In repeat dose studies, 6MNA failed to induce gastrointestinal damage even at doses where general toxicity was evident. These results show that in the rat, 6MNA is an effective antiinflammatory drug but even in very high intravenous doses does not have the propensity to induce gastrointestinal damage.

Lornoxicam, indomethacin and placebo: comparison of effects on faecal blood loss and upper gastrointestinal endoscopic appearances in healthy men

Forty-five healthy men aged 21-34 years took part in a double-blind, parallel-group, placebo-controlled study of the effects of 28 days' treatment with lornoxicam 4 mg twice daily or indomethacin 50 mg twice daily on faecal blood loss and the endoscopic appearances of gastric and duodenal mucosa. After an initial endoscopic examination, subjects received, intravenously, on day 0, autologous erythrocytes labelled with 51Cr. Complete daily faecal collections were then made from days 6-12, 20-26 and 34-40. The drug treatments or placebo were given from days 13-41. Faecal blood loss was calculated from 51Cr-specific activity of blood and faeces. Endoscopy was repeated 4-8 hours after the last dose of medication; mucosal appearance was graded on a 5-point scale. Lornoxicam caused no more adverse events than placebo; indomethacin caused more indigestion and central nervous system effects, and one subject in this group was withdrawn from the study. Median total blood losses during the pre-treatment and the second and fourth weeks of treatment were respectively 3.33, 3.95 and 5.71 ml for lornoxicam, 2.87, 7.04 and 7.75 ml for indomethacin, and 4.55, 3.64 and 4.13 ml for placebo. Differences between treatments were not statistically significant (P = 0.081 for second week of treatment, P = 0.383 for fourth week of treatment; Kruskal-Wallis test). The effect of chlortenoxicam on faecal blood loss in this study was thus intermediate between placebo and indomethacin, but within- and between-subject variability was such that the differences were not statistically significant. Endoscopic findings were normal in most subjects before and after all treatments, but indomethacin was associated with a slightly greater deterioration in endoscopic score and was the only treatment associated with Grade 3 appearance (in a single patient) in post-treatment endoscopy.

Naproxen. A reappraisal of its pharmacology, and therapeutic use in rheumatic diseases and pain states

Naproxen is a nonsteroidal anti-inflammatory drug (NSAID) advocated for use in painful and inflammatory rheumatic and certain nonrheumatic conditions. It may be administered orally or rectally using a convenient once or twice daily regimen. Dosage adjustments are not usually required in the elderly or those with mild renal or hepatic impairment although it is probably prudent to start treatment at a low dosage and titrate upwards in such groups of patients. Numerous clinical trials have confirmed that the analgesic and anti-inflammatory efficacy of naproxen is equivalent to that of the many newer and established NSAIDs with which it has been compared. The drug is effective in many rheumatic diseases such as rheumatoid arthritis, osteoarthritis, ankylosing spondylitis and nonarticular rheumatism, in acute traumatic injury, and in the treatment of and prophylaxis against acute pain such as migraine, tension headache, postoperative pain, postpartum pain and pain associated with a variety of gynaecological procedures. Naproxen is also effective in treating the pain and associated symptoms of primary or secondary dysmenorrhoea, and decreases excessive blood loss in patients with menorrhagia. The adverse effect profile of naproxen is well established, particularly compared with that of many newer NSAIDs, and the drug is well tolerated. Thus, the efficacy and tolerability of naproxen have been clearly established over many years of clinical use, and it can therefore be considered as a first-line treatment for rheumatic diseases and various pain states.

Comparative gastrointestinal blood loss associated with placebo, aspirin, and nabumetone as assessed by radiochromium (51Cr)

Nabumetone differs from most other nonsteroidal anti-inflammatory drugs. It is presented to the gut as a nonacidic prodrug, and is metabolized to its active form after absorption. Studies in animals and humans suggest it is less irritating to the gastrointestinal mucosa. This study compared the gastrointestinal microbleeding induced by nabumetone to aspirin (acetylsalicylic acid, ASA), and placebo in a double blind parallel study using chromium 51Cr labelled red cells to quantitate fecal blood loss (FBL) in healthy volunteers. Thirty subjects were randomized to treatment with nabumetone (2000 mg), ASA (3.6 g) or placebo for 21 days following a 7 day placebo period. Six subjects served as untreated controls. FBL in nabumetone treated subjects was not significantly different to placebo or untreated subjects. In contrast, ASA-treated subjects exhibited significantly increased FBL than the other 3 groups (P less than .0001).

Nabumetone. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy in rheumatic diseases

Nabumetone is a new non-steroidal anti-inflammatory drug advocated for use in the symptomatic treatment of rheumatic and inflammatory conditions. Unlike most other drugs of its class it is non-acidic and a prodrug, which after absorption forms an active metabolite. Published data suggest that nabumetone 1 to 2g daily is comparable with therapeutic dosages of aspirin, diclofenac, ibuprofen, indomethacin, naproxen and sulindac for the treatment of pain and inflammation associated with rheumatoid arthritis, osteoarthritis and acute soft tissue injuries. While nabumetone produced fewer side effects than aspirin, results have generally shown tolerability to be similar to that of other nonsteroidal anti-inflammatory drugs. If further definition of its efficacy and tolerability relative to other non-steroidal anti-inflammatory drugs confirms these initially favourable results, then nabumetone would appear to offer a useful alternative in the treatment of painful rheumatic and inflammatory conditions.