High-performance liquid chromatographic determination of a new anti-inflammatory agent, nabumetone, and its major metabolite in plasma using fluorimetric detection

Simplex optimization of the variables affecting the micelle-stabilized room temperature phosphorescence of 6-methoxy-2-naphthylacetic acid and its kinetic determination in human urine

This article reports the kinetic determination of 6-methoxy-2-naphthylacetic acid (6-MNA), the major metabolite of nabumetone, from micelle-stabilized room temperature phosphorescence (MS-RTP) measurements made by using the stopped-flow mixing technique. This methodology allows one to determine analytes in complex matrices without the need for a tedious separation process. It also shortens analysis times substantially. The proposed method uses simplex methodology to optimize the chemical and instrumental variables affecting the phosphorescence. It was applied to the determination of 6-MNA in human urine. The maximum phosphorescence signal is obtained within only 10 s after the sample is prepared. The maximum slope of the kinetic curve, which corresponds to the maximum rate of the phosphorescence development, is measured at lambda(ex)=273 nm and lambda(em)=516 nm. Least-squares regression was used to fit experimental data, and the detection limit, repeatability, and standard deviation for replicate samples were determined.

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.

Analysis of nabumetone in human plasma by HPLC. Application to single dose pharmacokinetic studies

A simple and sensitive high performance liquid chromatography method for the determination of nabumetone in human plasma is described. The procedure involves liquid-liquid extraction with ethyl acetate and reversed-phase chromatography with fluorimetric detection (excitation 230 nm, emission 356 nm). The chromatographic conditions and the extraction procedure gave a clean chromatogram for the compound. The limit of quantitation was established as 0.313 ng/ml and the calibration curve was linear up to 20 ng/ml. The within-day and between-day relative standard deviations were less than 10% and the accuracy of the assay was in the range of 99-104%. The suitability of the method is shown for pharmacokinetic studies.

Simultaneous analysis of naproxen, nabumetone and its major metabolite 6-methoxy-2-naphthylacetic acid in pharmaceuticals and human urine by high-performance liquid chromatography

A high-performance liquid chromatographic (HPLC) method for simultaneous determination of naproxen (NAP), nabumetone (NAB) and its major metabolite, 6-methoxy-2-naphthylacetic acid (6-MNA), was developed for the application to pharmaceuticals and human urine. Isocratic reversed-phase HPLC was employed for quantitative analysis using triethylamine and 1-heptanesulfonic acid sodium salt (HSA) as ion-pair reagents. Urine samples were purified by solid-phase extraction using Bond-Elut Certify II cartridges containing reversed-phase and anion exchange functionalities. The HPLC assay was carried out using a Wakosil ODS 5C18 column (5 microm, 150 x 4.6 mm, i.d.). The mobile phase consisted of 0.5 g of HSA dissolved in 1,000 ml of a mixture of acetonitrile, water and triethylamine (500:500:1, v/v) adjusted with phosphoric acid to pH 3. The calibration curves of NAP and NAB showed good linearity in the concentration range 32-160 microg/ml with UV detection (270 nm) for pharmaceuticals. In the low concentration ranges (8-96 ng of NAP per ml, 24-288 ng of NAB per ml and 5.6-67.2 ng of 6-MNA per ml), the calibration curves were also obtained with fluorimetric detection (excitation 280 nm, emission 350 nm) for biological fluids. The correlation coefficients were better than 0.999 in all cases. The lower limits of detection (defined as a signal-to-noise ratio of about 3) were approximately 0.3 ng for NAP, 1.5 ng for NAB and 0.2 ng for 6-MNA. The procedure described here is rapid, simple, selective, and is suitable for routine analysis of pharmaceuticals and pharmacokinetic studies in human urine samples.

Extractionless determination of 6-methoxy-2-naphthylacetic acid, a major metabolite of nabumetone, in human plasma by high-performance liquid chromatography

Following oral administration of the prodrug nabumetone, the major metabolite 6-methoxy-2-naphthylacetic acid (6-MNA) was determined in human plasma. Minimal sample preparation was followed by reversed-phase liquid chromatography and UV detection, affording high sample throughput. The lower limit of quantification (LLOQ) was 70 ng/ml, at a signal-to-noise ratio of 8:1. The assay method displayed good correlation (r=0.997), and can be readily employed in pharmacokinetic and bioequivalence studies.

Clinical pharmacokinetics of nabumetone. The dawn of selective cyclo-oxygenase-2 inhibition?

Nabumetone is a nonsteroidal anti-inflammatory drug (NSAID) of the 2,6-disubstituted naphthyl-alkanone class. Nabumetone is metabolised to an active metabolite 6-methoxy-2-napthylacetic acid (6-MNA) which is a relatively selective cyclo-oxygenase-2 inhibitor that has anti-inflammatory and analgesic properties. Nabumetone and its metabolites bind extensively to plasma albumin. Nabumetone is eliminated following biotransformation to 6-MNA, which does not undergo enterohepatic circulation and the respective glucoroconjugated metabolites are excreted in urine. Substantial concentrations of 6-MNA are attained in synovial fluid, which is he proposed site of action in chronic inflammatory arthropathies. A smaller area under the plasma concentration-time curve (AUC) is evident at steady state as compared with a single dose; this is possibly due to an increase in the volume of distribution and saturation of protein binding. Relationships between 6-MNA concentrations and the therapeutic and toxicological effects have yet to be elucidated for this NSAID. Renal failure significantly reduces 6-MNA elimination but steady-state concentrations of 6-MNA are not increased, possibly because of nonlinear protein binding. Elderly patients with osteoarthritis demonstrate decreased elimination and increased plasma concentrations of nabumetone as compared with young healthy volunteers. Rheumatic disease activity also influences 6-MNA plasma concentrations, as patients with more active disease and lower serum albumin concentrations demonstrate a lower area under the plasma concentration versus time curve. A reduced bioavailability of 6-MNA in patients with severe hepatic impairment is also evident. Dosage adjustment may be required in the elderly, patients with active rheumatic disease and those with hepatic impairment, but not in patients with mild-to-moderate renal failure.

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 "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.

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.