Preclinical overview of nabumetone. Pharmacology, bioavailability, metabolism, and toxicology

Topical nanocarriers for management of Rheumatoid Arthritis: A review

Rheumatoid arthritis (RA) is a systemic autoimmune disease manifested by chronic joint inflammation leading to severe disability and premature mortality. With a global prevalence of about 0.3%-1% RA is 3-5 times more prevalent in women than in men. There is no known cure for RA; the ultimate goal for treatment of RA is to provide symptomatic relief. The treatment regimen for RA involves frequent drug administration and high doses of NSAIDs such as indomethacin, diclofenac, ibuprofen, celecoxib, etorcoxib. These potent drugs often have off target effects which drastically decreases patient compliance. Moreover, conventional non-steroidal anti-inflammatory have many formulation challenges like low solubility and permeability, poor bioavailability, degradation by gastrointestinal enzymes, food interactions and toxicity. To overcome these barriers, researchers have turned to topical route of drug administration, which has superior patience compliance and they also bypass the first past effect experienced with conventional oral administration. Furthermore, to enhance the permeation of drug through the layers of the skin and reach the site of inflammation, nanosized carriers have been designed such as liposomes, nanoemulsions, niosomes, ethosomes, solid lipid nanoparticles and transferosomes. These drug delivery systems are non-toxic and have high drug encapsulation efficiency and they also provide sustained release of drug. This review discusses the effect of formulation composition on the physiochemical properties of these nanocarriers in terms of particle size, surface charge, drug entrapment and also drug release profile thus providing a landscape of topically used nanoformulations for symptomatic treatment of RA.

Determination of the Absolute Configuration of the Nabumetone Metabolite 4-(6-Methoxy-2-naphthyl)butan-2-ol Using the Chiral Derivatizing Agent, 1-Fluoroindan-1-carboxylic Acid

The absolute configuration of (+)-4-(6-methoxy-2-naphthyl)butan-2-ol ((+)-MNBO), a nabumetone metabolite, was determined using 1-fluoroindan-1-carboxylic acid (FICA). Both enantiomers of the FICA methyl esters were derivatized to diastereomeric esters of (+)-MNBO by an ester exchange reaction. The results of ¹H- and ¹⁹F-NMR spectroscopy of the diastereomeric FICA esters of (+)-MNBO confirmed the absolute configuration of (+)-MNBO was (S).

Carbon-carbon bond cleavage in activation of the prodrug nabumetone

Carbon-carbon bond cleavage reactions are catalyzed by, among others, lanosterol 14-demethylase (CYP51), cholesterol side-chain cleavage enzyme (CYP11), sterol 17β-lyase (CYP17), and aromatase (CYP19). Because of the high substrate specificities of these enzymes and the complex nature of their substrates, these reactions have been difficult to characterize. A CYP1A2-catalyzed carbon-carbon bond cleavage reaction is required for conversion of the prodrug nabumetone to its active form, 6-methoxy-2-naphthylacetic acid (6-MNA). Despite worldwide use of nabumetone as an anti-inflammatory agent, the mechanism of its carbon-carbon bond cleavage reaction remains obscure. With the help of authentic synthetic standards, we report here that the reaction involves 3-hydroxylation, carbon-carbon cleavage to the aldehyde, and oxidation of the aldehyde to the acid, all catalyzed by CYP1A2 or, less effectively, by other P450 enzymes. The data indicate that the carbon-carbon bond cleavage is mediated by the ferric peroxo anion rather than the ferryl species in the P450 catalytic cycle. CYP1A2 also catalyzes O-demethylation and alcohol to ketone transformations of nabumetone and its analogs.

Role of carbonyl reducing enzymes in the phase I biotransformation of the non-steroidal anti-inflammatory drug nabumetone in vitro

1. Nabumetone is a clinically used non-steroidal anti-inflammatory drug, its biotransformation includes major active metabolite 6-methoxy-2-naphtylacetic acid and another three phase I as well as corresponding phase II metabolites which are regarded as inactive. One important biotransformation pathway is carbonyl reduction, which leads to the phase I metabolite, reduced nabumetone. 2. The aim of this study is the determination of the role of a particular human liver subcellular fraction in the nabumetone reduction and the identification of participating carbonyl reducing enzymes along with their stereospecificities. 3. Both subcellular fractions take part in the carbonyl reduction of nabumetone and the reduction is at least in vitro the main biotransformation pathway. The activities of eight cytosolic carbonyl reducing enzymes--CBR1, CBR3, AKR1B1, AKR1B10, AKR1C1-4--toward nabumetone were tested. Except for CBR3, all tested reductases transform nabumetone to its reduced metabolite. AKR1C4 and AKR1C3 have the highest intrinsic clearances. 4. The stereospecificity of the majority of the tested enzymes is shifted to the production of an (+)-enantiomer of reduced nabumetone; only AKR1C1 and AKR1C4 produce predominantly an (-)-enantiomer. This project provides for the first time evidence that seven specific carbonyl reducing enzymes participate in nabumetone metabolism.

Nabumetone: therapeutic use and safety profile in the management of osteoarthritis and rheumatoid arthritis

Nabumetone is a nonsteroidal anti-inflammatory prodrug, which exerts its pharmacological effects via the metabolite 6-methoxy-2-naphthylacetic acid (6-MNA). Nabumetone itself is non-acidic and, following absorption, it undergoes extensive first-pass metabolism to form the main circulating active metabolite (6-MNA) which is a much more potent inhibitor of preferentially cyclo-oxygenase (COX)-2. The three major metabolic pathways of nabumetone are O-demethylation, reduction of the ketone to an alcohol, and an oxidative cleavage of the side-chain occurs to yield acetic acid derivatives. Essentially no unchanged nabumetone and < 1% of the major 6-MNA metabolite are excreted unchanged in the urine from which 80% of the dose can be recovered and another 10% in faeces. Nabumetone is clinically used mainly for the management of patients with osteoarthritis (OA) or rheumatoid arthritis (RA) to reduce pain and inflammation. The clinical efficacy of nabumetone has also been evaluated in patients with ankylosing spondylitis, soft tissue injuries and juvenile RA. The optimum oral dosage of nabumetone for OA patients is 1 g once daily, which is well tolerated. The therapeutic response is superior to placebo and similar to nonselective COX inhibitors. In RA patients, nabumetone 1 g at bedtime is optimal, but an additional 0.5-1 g can be administered in the morning for patients with persistent symptoms. In RA, nabumetone has shown a comparable clinical efficacy to aspirin (acetylsalicylic acid), diclofenac, piroxicam, ibuprofen and naproxen. Clinical trials and a decade of worldwide safety data and long-term postmarketing surveillance studies show that nabumetone is generally well tolerated. The most frequent adverse effects are those commonly seen with COX inhibitors, which include diarrhoea, dyspepsia, headache, abdominal pain and nausea. In common with other COX inhibitors, nabumetone may increase the risk of GI perforations, ulcerations and bleedings (PUBs). However, several studies show a low incidence of PUBs, and on a par with the numbers reported from studies with COX-2 selective inhibitors and considerably lower than for nonselective COX inhibitors. This has been attributed mainly to the non-acidic chemical properties of nabumetone but also to its COX-1/COX-2 inhibitor profile. Through its metabolite 6-MNA, nabumetone has a dose-related effect on platelet aggregation, but no effect on bleeding time in clinical studies. Furthermore, several short-term studies have shown little to no effect on renal function. Compared with COX-2 selective inhibitors, nabumetone exhibits similar anti-inflammatory and analgesic properties in patients with arthritis and there is no evidence of excess GI or other forms of complications to date.

Comparative biotransformation and disposition studies of nabumetone in humans and minipigs using high-performance liquid chromatography with ultraviolet, fluorescence and mass spectrometric detection

The disposition of the non-steroidal anti-inflammatory drug (NSAID) nabumetone after a single oral dose administration of nabumetone tablets to humans and minipigs was investigated. Nabumetone is a prodrug, which is metabolized in the organism to the principal pharmacodynamically active metabolite -- 6-methoxy-2-naphthylacetic acid (6-MNA), and some other minor metabolites (carbonyl group reduction products, O-desmethylation products and their conjugates with glucuronic and sulphuric acids). Standards of the above-mentioned metabolites were prepared using simple synthetic procedures and their structures were confirmed by NMR and mass spectrometry. A simple HPLC method for the simultaneous determination of nabumetone, 6-MNA and the other metabolites was developed, validated and used for xenobiochemical and pharmacokinetic studies in humans and minipigs and for distribution studies in minipigs. Naproxen was chosen as the internal standard (I.S.), both UV (for higher concentrations) and fluorescence detection (for very low concentrations) were used. The identity of the nabumetone metabolites in biological samples was confirmed using HPLC-MS experiments. Pharmacokinetics of nabumetone, 6-MNA and 6-HNA (6-hydroxy-2-naphthylacetic acid) in human and minipig plasma was evaluated and compared. The concentration levels of nabumetone metabolites in urine, bile and synovial fluid were also evaluated.

A double-blind study of the effect on hemostasis of nabumetone (Relafen) compared to placebo

A double-blind, placebo-controlled clinical trial comparing the effect on hemostasis of nabumetone (Relafen) to placebo in patients who were about to undergo forefoot surgery was performed. Aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) are reported to inhibit platelet cyclooxygenase activity, resulting in altered platelet function and thus potentially enhanced bleeding. Nabumetone has been reported to have no effect on platelet aggregation and bleeding time in normal volunteers and in patients who have undergone knee arthroscopy. After fulfilling the inclusion criteria and after a 1-week washout period (acetaminophen controlled), 15 patients were enrolled in the nabumetone group and 15 patients were randomized in the placebo group. Hemostatic parameters [prothrombin time (PT), partial thromboplastin time (PTT), and Ivy bleeding time (IBT)] were assessed at baseline, visit 2, visit 3, and final visit. No meaningful differences were observed between treatment groups in any of the measured hemostatic parameters. No significant adverse events were reported. There was no significant change from baseline for PT, PTT, and IBT in the nabumetone group (PT, p < .06; PTT, p < .64; IBT, p < .17) versus the placebo group (PT, p < .61; PTT, p < .63; IBT, p < .25). The lack of bleeding diathesis and significant prolongation of PT, PTT, or IBT in this study suggests that nabumetone in dosages up to 1000 mg/day can be administered safely in the immediate preoperative period to patients undergoing forefoot surgery.

Profile and mechanisms of gastrointestinal and other side effects of nonsteroidal anti-inflammatory drugs (NSAIDs)

The popular view that all nonsteroidal anti-inflammatory drugs (NSAIDs) act by inhibiting the production of prostaglandins has been challenged by the discovery that they also affect a wide variety of cellular processes that are important for their therapeutic actions and side effects. Although recognition of the differential activities of new and established NSAIDs on the activities of the cyclooxygenases (COXs) affecting production of inflammatory prostaglandins (from COX-2) and those that are physiologically important (from COX-1) may have significance for the prostaglandin components of the underlying inflammatory and physiologic processes, there are important features of their chemical structures that determine the various cellular and biochemical actions of these agents. Several established NSAIDs have low propensity to cause gastrointestinal (GI) ulceration and bleeding that may relate to these drugs having unique pharmacokinetic characteristics (pro-drugs, protein binding, etc). They also have weak effects on the production of GI mucosal prostaglandins and have specific physicochemical characteristics such that they cause minimal damage to mucosal membranes or effects on nonprostaglandin-related cellular mechanisms important in mucosal defenses. Some of the new COX-2-selective drugs with methyl or amino-sulfonyl moieties have relatively high pKa values and other properties that are similar to established NSAIDs with low GI ulcerogenicity. These physicochemical properties may contribute to the low irritancy of the new COX-2-selective drugs quite apart from their sparing of COX-1 in the GI mucosa. With concerns that some established NSAIDs may accelerate cartilage destruction in osteoarthritis (OA), interest is now focusing on whether the COX-2-selective drugs may have a lower potential for this adverse effect by avoiding the inhibitory effects on cartilage proteoglycan metabolism seen with such drugs as indomethacin and the salicylates. Meloxicam appears to be without inhibitory effects on proteoglycan metabolism, but it remains to be seen if this translates into any beneficial actions on the progression of joint changes in OA observed radiologically or from magnetic resonance imaging.

Comparative toxicity of nonsteroidal anti-inflammatory drugs

To compare the gastrointestinal (GI) toxicities of various nonsteroidal anti-inflammatory drugs (NSAIDs), it is first necessary to dismantle the imprecise entity "NSAID gastropathy" into its component conditions, and understand their pathogenesis. In this article, toxicities are reviewed only in so far as they affect the upper GI tract, the site of approximately 80% of GI injuries caused by NSAIDs. The phenomena discussed are platelet dysfunction, causing hemorrhage from various lesions, including but not confined to ulcers; various mucosal injuries, ranging from small erosions to large ulcers; and "complications," such as bleeding or perforations, causing admission to hospital, that may arise from ulcers but may also arise from other lesions. Ulcers, when complicated, may either be those caused by an NSAID or "peptic" ulcers that preceded NSAID therapy (having a high prevalence in the population) and gave rise to complications resulting from NSAID effects on platelets, tissues, or biologic processes, for example, healing, necrosis/apoptosis, leukocyte adherence, vasoconstriction, or generation of free radicals. NSAIDs have been compared in various ways, including fecal blood loss, endoscopic lesion development, prospective preclinical cohort studies measuring perforations, ulcers, and bleeds, post-marketing surveillance studies, and studies of the incidence of serious adverse events in populations followed in large databases linked to each individual patient record with regard to drug consumption and outcome. All methods show considerable differences between NSAIDs. Modern studies on the relative toxicities of NSAIDs are summarized and reviewed, and a number of marketed and emerging drugs that appear less toxic than classic NSAIDs are identified.

Non-steroidal anti-inflammatory drugs inhibit Helicobacter pylori-induced human neutrophil reactive oxygen metabolite production in vitro

BACKGROUND

Helicobacter pylori infection is associated with increased production of gastric mucosal reactive oxygen metabolites which have been implicated in mucosal damage and carcinogenesis. In vitro, neutrophils produce reactive oxygen metabolites following activation by H. pylori. Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit neutrophil activation by several factors, e.g. N-formyl-methionyl-leucyl-phenyalanine (f-MLP).

AIM

To examine the effect of NSAIDs on H. pylori-induced reactive oxygen metabolite production by human peripheral blood neutrophils.

METHODS

Neutrophils were stimulated by H. pylori (NCTC 11637) water extract or f-MLP in the presence or absence of NSAIDs. Reactive oxygen metabolite activity was measured by luminol-enhanced chemiluminescence.

RESULTS

H. pylori water extract stimulated a sevenfold increase in chemiluminescence which was inhibited dose-dependently by diclofenac. All six NSAIDs studied (at 10-4 M) significantly inhibited H. pylori-and f-MLP-stimulated neutrophil reactive oxygen metabolite production. Meclofenamic acid and diclofenac had the greatest inhibitory effects on both H. pylori and f-MLP-stimulated neutrophil reactive oxygen metabolite production. The inhibitory effects of other NSAIDs varied with the activation stimulus. NSAIDs did not quench reactive oxygen metabolites generated in a cell-free xanthine:xanthine oxidase assay.

CONCLUSION

Several NSAIDs attenuate H. pylori-induced neutrophil reactive oxygen metabolites production in vitro. This may be relevant to a potential chemopreventative role in gastric cancer and to a possible lack of synergy between H. pylori and NSAID use regarding peptic ulceration.

Health-related quality-of-life effects of oxaprozin and nabumetone in patients with osteoarthritis of the knee

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly prescribed for the treatment of signs and symptoms of osteoarthritis (OA). Nabumetone and oxaprozin are 2 of the newer NSAIDs and have been shown to have similar safety and efficacy profiles. Nabumetone 1000 mg to 1500 mg once a day (QD) and oxaprozin 1200 mg QD are commonly recommended doses. This study compared the health-related quality of life (HRQOL) of patients receiving oxaprozin 1200 mg QD with that of patients receiving nabumetone 1000 mg QD or nabumetone 1500 mg QD for the treatment of signs and symptoms of OA of the knee. Two similarly designed, independent, randomized, double-masked, placebo-controlled clinical trials were conducted. In trial 1, patients were randomized to receive oxaprozin 1200 mg QD (n = 109), nabumetone 1000 mg QD (n = 110), or placebo (n = 109); in trial 2, patients received oxaprozin 1200 mg QD (n = 116), nabumetone 1500 mg QD (n = 115), or placebo (n = 116). HRQOL was measured by the Medical Outcomes Study Short-Form-36 Health Survey (1-week recall period) at baseline and weeks 2 and 6. Data from the 2 trials were combined to assess differences across the 4 groups in 8 domains and 2 summary scores at baseline, and changes in HRQOL scores at weeks 2 and 6. At week 2, the oxaprozin group showed significantly greater improvement than the placebo group in role physical, vitality, and mental component summary (MCS) scores (P < 0.05), and in physical functioning, bodily pain, social functioning, and physical component summary (PCS) scores (P < 0.01). The nabumetone 1500-mg group showed significantly greater improvement than the placebo group in bodily pain and social functioning (P < 0.05), and in vitality and MCS score (P < 0.01). No significant differences were observed between the nabumetone 1000-mg and placebo groups. At week 2, the oxaprozin group showed a greater change than the nabumetone 1000-mg group in PCS score (P < 0.05). At week 6, oxaprozin treatment resulted in significantly greater improvement than placebo in physical functioning, role physical, and bodily pain (P < 0.05); social functioning, role emotional, and mental health (P < 0.01); and vitality and MCS score (P < 0.001). The nabumetone 1500-mg group showed significantly greater responses than the placebo group in vitality (P < 0.05), mental health (P < 0.01), and MCS score (P < 0.001). The oxaprozin group had significantly better scores than the nabumetone 1500-mg group in the PCS (P < 0.05), and it showed significantly greater improvement than the nabumetone 1000 mg group in role physical and PCS score (P < 0.01) and in role emotional (P < 0.05). No statistically significant differences were found between placebo and nabumetone 1000 mg at week 6. Results of this study suggest that oxaprozin 1200 mg QD has a significant positive impact on the HRQOL of patients with OA of the knee compared with nabumetone 1000 mg QD and placebo.

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.

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.

Population pharmacokinetics of the active metabolite of nabumetone in renal dysfunction

We determined the pharmacokinetics of 6-methoxy-2-naphythylacetic acid (6-MNA), the active metabolite of nabumetone, in normal subjects and in subjects with impaired renal function, including subjects requiring hemodialysis. Subjects received a 1000 mg oral dose of nabumetone either as a single dose or daily for 15 days. We used a noncompartmental pharmacokinetic analysis and compared those results to a population pharmacokinetic analysis performed with nonlinear mixed-effects modeling (NONMEM). The results of the two different analyses were similar. The elimination half-life increased with decreased renal function and ranged from 22 to 44 hours. The area under the curve decreased significantly at steady state, regardless of renal function. The apparent clearance determined by NONMEM analysis increased from 0.68 L/hr after a single dose to 1.13 L/hr at steady state. The apparent volume of distribution was directly proportional to the nonalbumin protein concentration and ranged from 23 to 60 L. We conclude that the pharmacokinetics of 6-MNA in this population are complicated by possible protein binding changes. However, the increased half-life in patients with renal failure is offset by changes in the apparent volume of distribution that prevent the accumulation of 6-MNA in the serum of patients with impaired renal function. Therefore dosage adjustments may not be necessary in patients with decreased renal function.

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.

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.

Influence of the xanthine derivative denbufylline and the anti-inflammatory agent nabumetone on microsomal free radical production and lipid peroxidation in rat liver

The influence of denbufylline, nabumetone and its main metabolite BRL 10,720 on iron stimulated lipid peroxidation (LPO), cytochrome P 450 dependent H2O2 and chemiluminescence (CL) production was investigated in rat liver microsomes in vitro (10(-5)-10(-3) M) and in vivo after treatment of rats (5-300 mg/kg b.m. orally on three consecutive days). In rat liver slices the release of thiobarbituric acid reactants (TBAR) was measured after 1 hour of incubation with the drugs. Denbufylline, nabumetone and BRL 10,720 exerted a significant inhibition of iron stimulated LPO in vitro. Nabumetone showed the strongest antioxidative activity, which was also seen in liver slices. These antioxidative effects were not found after in vivo treatment of rats. Denbufylline (10(-3) M) additionally inhibited H2O2 formation and the luminol and lucigenin amplified CL in vitro. Unexpectedly, nabumetone increased H2O2 formation both in vitro and in vivo, but in vitro only lucigenin amplified CL. BRL 10,720 increased microsomal H2O2 production in vivo. Moreover, BRL 10,720 enhanced CL in vitro and in vivo significantly, which is interpreted as an increase of the production of superoxide anion radicals and other reactive oxygen species such as H2O2, but lipid peroxidation in liver microsomes was not enhanced. These results suggest that denbufylline, nabumetone and BRL 10,720 in contrast to the in vitro effects did not exert antioxidative activities after treatment of rats. On the contrary, BRL 10,720 was found to support the formation of reactive oxygen species in liver microsomes.

Comparative effects of nabumetone, sulindac, and indomethacin on urinary prostaglandin excretion and platelet function in volunteers

Nonsteroidal antiinflammatory drugs differ with respect to their effects on prostaglandin metabolism in various tissues, a property that may be partly responsible for some of the differences in the pharmacologic activities and side-effect profiles that are associated with their use. The effects of nabumetone on urinary prostaglandin excretion have not been reported. Fourteen healthy females, age 21-43 years, were treated with nabumetone (NAB) 1000 mg daily, sulindac (SUL) 200 mg every 12 hours, and indomethacin (IND) 50 mg every 12 hours for 7 days in a randomized period-balanced crossover study. The effects of drug treatment on urinary prostaglandin excretion (PGE2, 6-keto-PGF1 alpha, PGF2 alpha, thromboxane [TX] B2) and platelet function (collagen-induced whole blood platelet aggregation [CIPA] and template bleeding time) were determined on day 1 and day 7. For each treatment regimen, mean baseline urinary PG excretion values were comparable for each prostanoid, but the pattern of excretion differed in response to each drug. Treatment with NAB significantly increased the urinary excretion rates of PGE2 and PGF2 alpha, but 6-keto-PGF1 alpha and TXB2 excretion were unchanged. IND treatment did not result in a significant change in PGE2 excretion but did significantly reduce urinary 6-keto-PGF1 alpha and TXB2 excretion rates. Reduced excretion of PGF2 alpha was observed on both study days during treatment with IND and SUL. SUL treatment also resulted in increased urinary PGE2 excretion while significantly reducing 6-keto-PGF1 alpha excretion on day 7. Significant differences were observed between the NAB and SUL regimens with respect to PGF2 alpha excretion and between the NAB and SUL regimens for PGE2, PGF2 alpha, 6-keto-PGF alpha 1 (on day 1 only) and TXB2 (on day 1 only). Neither NAB nor SUL caused inhibition of CIPA or bleeding time although platelet aggregation was inhibited during IND treatment. That NAB treatment was neither associated with alterations in platelet function nor decreases in the urinary excretion of the vasodilatory prostaglandins, PGE2 and 6-keto-PGF1 alpha, suggests that NAB possesses renal sparing properties.

Nabumetone: a clinical appraisal

Nonsteroidal antiinflammatory drugs (NSAIDs) have long been used as therapy for arthritis patients. However, in some patients these drugs can cause gastrointestinal hemorrhage, perforation, or ulcer through direct topical effects, enterohepatic recirculation, and systemic effects. In an effort to address this problem, new NSAIDs have been developed. Nabumetone, which belongs to a new class of NSAID, is a nonacidic agent that has been associated with a low incidence of peptic ulcer. This article examines available clinical data on nabumetone, including studies on gastrointestinal safety and effectiveness in osteoarthritis and rheumatoid arthritis patients, and data that may provide an explanation for nabumetone's low incidence of ulceration.

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.

Dissociation between the antinociceptive and anti-inflammatory effects of the nonsteroidal anti-inflammatory drugs. A survey of their analgesic efficacy

The authors challenge the general view that the analgesic effect of the nonsteroidal anti-inflammatory drugs (NSAIDs) can be universally attributed to their inhibitory effects on the synthesis of peripherally formed prostaglandins. Analgesic activity by some of these compounds in the reduction of physiological pain elicited by a single noxious stimulus, or the treatment of acute pain which results from sudden trauma to otherwise healthy tissue, is better described as an antinociceptive effect. Single-dose studies in the dental pain model that have been conducted in double-blind conditions and included a placebo control group have been reviewed; those NSAIDs which are significantly superior to the reference compound aspirin 650mg and those which could represent real alternatives to the use of narcotics in certain situations for the management of acute pain have been identified. Azapropazone, diflunisal, naproxen, oxaprozin and tolmetin are all weak inhibitors of prostaglandin synthesis, yet they have been shown to be more effective than aspirin. In a model of joint pain, azapropazone 600mg has been shown to be as effective as pethidine (meperidine) 100mg despite being the weakest inhibitor of prostaglandin synthesis. Whether the antinociceptive effect of azapropazone acts at a peripheral or a central level, or both, is not clear; evidence for the effects of NSAIDs on the central nervous system (CNS) is discussed. Historically, the antinociceptive character of some NSAIDs is apparent in several studies in both animals and humans. More recently, experimental algesimetry models designed to distinguish the antinociceptive effects of NSAIDs include the use in humans of photoplethysmography and computer-supported infrared thermographic imaging.

Importance of local versus systemic effects of non-steroidal anti-inflammatory drugs in increasing small intestinal permeability in man

Increased small intestinal permeability caused by non-steroidal anti-inflammatory drugs (NSAIDs) is probably a prerequisite for NSAID enteropathy, a source of morbidity in patients with rheumatoid arthritis. This increased small intestinal permeability may be a summation of a local effect during drug absorption, a systemic effect after absorption, and a local effect of the drug excreted in bile, but the relative contribution made by these factors is unknown. We assessed the effect of indomethacin and nabumetone on intestinal permeability. The principal active metabolite of nabumetone, 6-methoxy-2-naphthylacetic acid, is not subject to appreciable enterohepatic recirculation. Twelve volunteers were studied before and after one week's ingestion of indomethacin (150 mg/day) and nabumetone (1 g/day) with a combined absorption/permeability test. Neither drug had a significant effect on the permeation of 3-0-methyl-D-glucose, D-xylose, and L-rhamnose. Indomethacin increased the permeation of radioactive 51chromium ethylenediaminetetra-acetic acid (51Cr EDTA) significantly from baseline (mean (SEM) 0.63 (0.09)% v 1.20 (0.14)%, p less than 0.01) but nabumetone did not (0.70 (0.10)% p greater than 0.1). These results were supported by the 51Cr EDTA/L-rhamnose urine excretion ratios, which reflect changes in intestinal permeability. They suggest that NSAIDs increase intestinal permeability during absorption or after biliary excretion and that the systemic effect is of minor importance.

Effect of the antiinflammatory prodrug, nabumetone and its principal active metabolite on rat gastric mucosal, aortic and platelet eicosanoid synthesis, in vitro and ex vivo

Nabumetone is a novel non-steroidal antiinflammatory drug which although a weak cyclooxygenase inhibitor is converted by the liver to metabolites that are more potent inhibitors of cyclooxygenase. Nabumetone may thus avoid the occurrence of prostanoid-mediated gastropathy while maintaining its efficacy as an antiinflammatory agent. We compared the effect of nabumetone and 6-methoxy-2-naphthylacetic acid (6-MNA; the principal active metabolite of nabumetone) with that of naproxen and indomethacin on the synthesis of rat gastric prostaglandins I2 and E2, in vitro and ex vivo. Ex vivo platelet TXA2 and aortic PGI2 synthesis was also investigated in order to assess peripheral activity of nabumetone metabolites. In vitro, nabumetone was completely without effect on gastric mucosal prostanoid synthesis, whereas indomethacin, naproxen and 6-MNA (in this order of potency) inhibited prostanoid synthesis. Ex vivo, low dose naproxen and indomethacin (less than 5mg.kg-1) markedly inhibited gastric mucosal prostanoid synthesis at 30 min and 2 h post gavage, whereas nabumetone was without significant effect. Nabumetone administration also resulted in the inhibition of platelet TXA2 synthesis, whereas aortic PGI2 synthesis was unaltered. These data indicate that the administration of nabumetone may avoid NSAID gastropathy by leaving gastric mucosal prostanoid synthesis intact and also that the active metabolite(s) of nabumetone are effective inhibitors of cyclooxygenase in an NSAID-target tissue (platelet). The lack of effect of nabumetone administration on vascular PGI2 synthesis may confer an additional advantage over other NSAIDs, since the inhibition of peripheral PGI2 has been implicated in hypertensive and nephrotoxic side effects of NSAIDs.

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).

A pharmacokinetic study of the active metabolite of nabumetone in young healthy subjects and older arthritis patients

We have performed a detailed pharmacokinetic study of the plasma concentrations of the major active metabolite of nabumetone, 6-methoxy-2-naphthylacetic acid (6 MNA), attained after a single dose and during chronic administration comparing the results of a group of young healthy volunteers with those of a group of elderly arthritic patients. The latter had higher peak plasma concentrations of 6 MNA and slower rates of elimination but there is no tendency for the drug to accumulate unpredictably in the old. Disease activity also influences plasma concentration, those with more active disease, and lower serum albumin concentrations had lower AUC values.

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.