Nabumetone therapy of osteoarthritis. A six-week, placebo-controlled study

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.

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.

Penetration of the active metabolite of nabumetone into synovial fluid and adherent tissue of patients undergoing knee joint surgery

The concentration of 6-methoxy-2-naphthylacetic acid (6-MNA) in plasma, synovial fluid, synovial tissue and fibrous capsule tissue was determined in an open study with 20 patients scheduled for knee joint surgery after oral treatment with nabumetone under steady-state conditions. 6-MNA is the principle metabolite of the prodrug nabumetone arising from an extensive first-pass metabolism in the liver. Patients suffering from rheumatoid arthritis (n = 12) or osteoarthritis stage III or IV (n = 8) received a daily dose of nabumetone 1 g in the evening starting 4 days prior to surgery. On day 1 an additional loading dose of nabumetone 1 g was given in the morning. At the time of surgery (day 5), blood, synovial tissue and fibrous capsule tissue were taken simultaneously. The samples were analysed by high performance liquid chromatography. After 4 days of treatment mean 6-MNA concentration in plasma was 40.76 mg/L, in synovial fluid 34.79 mg/L, in synovial tissue 19.33 mg/g and in fibrous capsule tissue 11.43 mg/g. Under steady-state conditions mean synovial fluid levels of 6-MNA were higher than after administration of a single dose and, in common with levels in synovial tissue, persist in a range sufficient for in vitro cyclo-oxygenase inhibition.

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.