Radiochromium (chromium-51) evaluation of gastrointestinal blood loss associated with placebo, aspirin, and nabumetone

Time course and pattern of blood loss with ibuprofen treatment in healthy subjects

BACKGROUND & AIMS

Nonselective nonsteroidal anti-inflammatory drug (NSAID) users are at increased risk of gastrointestinal bleeding. We aimed to assess the pattern and extent of fecal blood loss (FBL) with ibuprofen, which is considered to have a favorable gastrointestinal safety profile.

METHODS

We conducted a post hoc analysis of 2 separate randomized, parallel-group, double-blind studies, in which ibuprofen was used as a positive control. FBL was measured by radioactive analysis of chromium-51 labeled red cells in stools during baseline and then followed by 4 weeks of treatment with ibuprofen (800 mg 3 times daily) or placebo in 68 healthy volunteers. FBL was considered significant when blood loss was >2 mL daily.

RESULTS

The baseline period was identical for all subjects, with an average FBL of 0.36 mL (standard deviation, +/-0.075) per day. During the study period, all subjects receiving ibuprofen had a daily mean FBL >2 mL, with a group daily mean loss 3.64-fold greater than in the placebo group (2.55 mL [+/-3.2] vs 0.7 mL [+/-0.37], P < .001). In the ibuprofen group (n = 31), 26 subjects had between 1 and 7 random episodes of microbleeding with FBL >3 mL. Nine had a maximum FBL >10 mL (29.35 +/- 23.32 mL), and in 2 subjects blood loss reached 73 mL and 66 mL, respectively.

CONCLUSIONS

Treatment with a therapeutic dose of ibuprofen, a commonly used nonselective NSAID, in healthy subjects is associated with significant FBL, which occurs randomly with spikes of bleeding, sometimes exceeding 66 mL in a single day. Chronic anemia or gastrointestinal bleeding in patients taking nonselective NSAIDs should be thoroughly investigated.

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.

Complementary studies of the gastrointestinal safety of the cyclo-oxygenase-2-selective inhibitor etoricoxib

BACKGROUND

Cyclo-oxygenase-2-selective non-steroidal anti-inflammatory drugs are intended to preserve cyclo-oxygenase-1-mediated gastroprotection and platelet function, whilst inhibiting cyclo-oxygenase-2-mediated inflammation.

AIM

To assess the gastrointestinal safety of the cyclo-oxygenase-2-selective inhibitor etoricoxib vs. non-selective non-steroidal anti-inflammatory drugs.

METHODS

Two randomized, double-blind, placebo- and active-controlled studies were performed: (i) daily faecal red blood cell loss was measured in 62 subjects receiving etoricoxib (120 mg once daily), ibuprofen (800 mg t.d.s.) or placebo for 28 days; (ii) the incidence of endoscopically detectable gastric/duodenal ulcers was determined in 742 osteoarthritis or rheumatoid arthritis patients receiving etoricoxib (120 mg once daily), naproxen (500 mg b.d.) or placebo over 12 weeks.

RESULTS

In the first study, the between-treatment ratio of faecal blood loss for etoricoxib vs. placebo (1.06) was not significantly different from unity; however, the ratios for ibuprofen vs. placebo (3.26) and etoricoxib (3.08) were significantly greater than unity (P < 0.001). In the second study, the incidence of ulcers of > or = 3 mm with naproxen (25.3%) was significantly higher than that with etoricoxib (7.4%) or placebo (1.4%; P < 0.001); the results were similar for ulcers of > or = 5 mm.

CONCLUSIONS

The reduced toxicity of etoricoxib (less faecal blood loss and fewer endoscopically detectable lesions) suggests that use of this drug will may be associated with a reduced incidence of gastrointestinal perforations, ulcers and bleeds.

A randomized trial measuring fecal blood loss after treatment with rofecoxib, ibuprofen, or placebo in healthy subjects

PURPOSE

Gastrointestinal microbleeding, as assessed by the measurement of (51)chromium-labeled red blood cells, is a marker of the mucosal injury associated with the use of nonsteroidal anti-inflammatory drugs. This study tested the hypotheses that cyclooxygenase-2 specific inhibition with rofecoxib would cause less fecal blood loss than a therapeutic dose of ibuprofen and would be equivalent to placebo.

SUBJECTS AND METHODS

In this randomized, double-blind group study, gastrointestinal blood loss was assessed by measurement of fecal (51)chromium radioactivity during a 1-week placebo baseline period and during 4 weeks of treatment with rofecoxib (25 mg or 50 mg once daily), ibuprofen (800 mg three times daily), or placebo in 67 healthy subjects. Gastrointestinal blood loss during treatment weeks 2 to 4 (versus the baseline period) was expressed as the geometric mean ratio of fecal radioactivity in weeks 2 to 4 compared with baseline.

RESULTS

Ibuprofen caused significantly (P <0.001) greater gastrointestinal blood loss (geometric mean ratio of 5.2, 95% confidence interval [CI]: 4.2 to 6.3) than the 25-mg dose of rofecoxib (2.6, 95% CI: 2.2 to 3.1), the 50-mg dose of rofecoxib (2.6, 95% CI: 2.2 to 3.0), or placebo (2.1, 95% CI: 1.8 to 2.5). In contrast, gastrointestinal blood loss with both doses of rofecoxib were equivalent to placebo by a predetermined clinical similarity bound.

CONCLUSIONS

In healthy subjects, treatment with rofecoxib, at 2 to 4 times the doses that are currently recommended for the treatment of patients with osteoarthritis, produced significantly less fecal blood loss than a therapeutic dose of ibuprofen and was equivalent to placebo.

Uptake of ibuprofen, indomethacin and ketoprofen into isolated rabbit parietal cells

In the United States and other countries, non-steroidal anti-inflammatory drugs (NSAIDs) can be purchased without a prescription. Due to their widespread use, the drugs' most common side effect, gastric toxicity, becomes a more serious concern. Gastric toxicity can occur directly by contact with mucous membranes or indirectly by the inhibition of prostaglandin production in the gastric mucosa. We have studied the uptake of NSAIDs in gastric tissue, specifically parietal cells removed from the rabbit stomach. New Zealand White rabbits were killed and then used to harvest parietal cells. The purified cells were used to study the uptake of ibuprofen, indomethacin and ketoprofen (NSAIDs) over time and under different experimental conditions. The effects of concentration were investigated for all three NSAIDs. In addition, indomethacin and ibuprofen were used to investigate the mechanism of uptake. Studies were determined for the effects of varied extracellular pH from pH 6 to 8, and inhibitory conditions from depressed temperature (5 degrees C), metabolic inhibitors (sodium azide and 2,4-dinitro-phenol), an ionophore (nigericin) and a sodium free support medium. The interaction of NSAIDs with lysed parietal cells was investigated also. Initial rate data indicated that Michaelis-Menten kinetics were apparent; however, poor solubility of all three NSAIDs prevented complete characterization of the inclusion of a passive transport mechanism. Uptake showed a statistically significant increase (P = 0.01 to 0.05) as pH decreased, also suggesting contribution from a passive mechanism. Studies with inhibitors showed minimal effects. However, uptake at equilibrium for the ionophore, nigericin, showed a 10-fold increase over the control for ibuprofen (P = 0.005) and a 1.4-fold increase for indomethacin (P=0.04). Depressed temperature (5 degrees C) increased the initial rate and uptake at equilibrium 2.1- and 2.2-fold, respectively, for ibuprofen (P < 0.01). For indomethacin depressed temperature increased the initial rate and uptake at equilibrium 2.7- and 5.2-fold, respectively (P < 0.01). The increases at 5 degrees C suggests that adsorption may be an important uptake component. Experiments with lysed parietal cells showed a non-specific uptake phenomenon, suggesting an adsorption component was occurring also.

Gastrointestinal safety profile of nabumetone: a meta-analysis

Individual comparative studies suggest that nabumetone has a gastrointestinal (GI) safety profile superior to comparator NSAIDs but lack power to show a statistical difference. The aim of this study was to evaluate systematically the difference in GI adverse events--especially the rate of perforations, ulcers, and bleeds (PUBs)-- between studies, meta-analyses of comparative trials of nabumetone and conventional NSAIDs, and postmarketing, open-label studies of nabumetone meeting predefined inclusion and exclusion criteria. A fully recursive literature search identified 13 studies consisting of 29 treatment arms and 49,501 patients that met the predefined criteria. Tests for heterogeneity found no significant difference between studies of each subgroup. Overall, the dyspeptic symptoms flatulence, constipation, and diarrhea were the most commonly reported adverse events accounting for 98.6% of the total GI adverse events. Significantly more patients treated with a comparator NSAID experienced GI adverse events than did those taking nabumetone (P = 0.007). After adjustment for patient-exposure years, PUBs were 10 to 36 times more likely to develop in patients treated with a comparator NSAID than with nabumetone. This was consistently seen in patients in nonendoscopic (n = 7,468) and endoscopic studies (n = 244). In the analysis of postmarketing or open-label studies of nabumetone, only one PUB was reported per 500 patient-exposure years over 17,502 treatment years (n = 39,389). GI adverse event-related dropouts and hospitalizations were increased by 1.3- and 3.7-fold if patients were treated with a comparator NSAID than with nabumetone. Significantly fewer treatment-related GI adverse events, especially PUBs, are seen in patients treated with nabumetone than with a comparator NSAID. Nabumetone is very safe for the GI tract.

A placebo-controlled study of interaction between nabumetone and acenocoumarol

AIMS

The use of nonsteroidal anti-inflammatory drugs (NSAIDs) in patients treated with oral anticoagulants is generally discouraged due to the risk of interactions that could increase the risk of bleeding complications. Available data suggest the NSAID, nabumetone, does not produce such an interaction. We investigated whether nabumetone would interact with acenocoumarol, an oral anticoagulant widely used in some European countries.

METHODS

A double-blind, randomized, placebo-controlled study was conducted evaluating nabumetone (1-2 g daily for up to 4 weeks) in osteoarthritis patients with thromboembolic risk previously stabilized on acenocoumarol. The primary efficacy end point was the proportion of patients whose International Normalized Ratio (INR) remained within established margins and whose acenocoumarol dose was not changed. Fifty-six patients were randomized to receive nabumetone (n=27) or placebo (n=29).

RESULTS

Eighteen patients in each group (67% for nabumetone and 62% for placebo) completed the study without showing INR or acenocoumarol dose changes, and were considered as study successes. Nine patients (33%) with nabumetone and 11 (38%) with placebo were considered study failures in the intention-to-treat analysis (one patient on nabumetone and four on placebo did not complete the study due to reasons not related to INR and acenocoumarol dose changes). No significant differences were found between groups with regard to study successes. There were two minor bleeding complications, one in each group. Six patients per group presented with eight adverse experiences in each group.

CONCLUSIONS

Treatment with nabumetone did not alter INR levels compared with placebo in patients stabilized on oral acenocoumarol who require NSAID therapy. These results suggest that nabumetone does not produce a clinically relevant interaction with acenocoumarol. In orally anticoagulated patients without other associated risk factors, treatment with nabumetone for up to 4 weeks does not require increased monitoring of INR levels.

Safety profiles of leading nonsteroidal anti-inflammatory drugs

Recently introduced nonsteroidal anti-inflammatory drugs (NSAIDs) have capitalized on new formulations or unique physical and pharmacologic properties in an attempt to provide a greater margin of gastrointestinal (GI) safety. The use of enteric coatings and nonoral or pro-drug formulations have not necessarily provided the expected safety, but other properties have been identified that appear to be more promising. However, as demonstrated by oxaprozin, considered to be one of the least safe NSAIDs but one of the leading drugs on the US market, success may not be dependent on safety. In contrast, the improved tolerability of 2 other new NSAIDs, nabumetone and etodolac, has been established in clinical trials and limited postmarketing surveillance. This improved tolerability is probably associated with several pharmacologic properties that have been suggested to contribute to GI safety: (1) nonacidic pro-drug formulation; (2) lack of enterohepatic recirculation; (3) a short plasma half-life; and (4) preferential inhibition of cyclo-oxygenase-2 (COX-2). Although these factors may not improve efficacy, their incorporation into the design of drugs suggests that safer NSAIDs may be a clinical reality. However, the safety and clinical value of any new drug for the general population will be validated only through extensive postmarketing surveillance.

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.

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.

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.

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.

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.

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.

The use of a 51Cr technique to detect gastrointestinal microbleeding associated with nonsteroidal antiinflammatory drugs

Of techniques used to evaluate gastrointestinal (GI) bleeding, use of radiochromium (51Cr)-tagged erythrocytes is the most quantitative and scientifically acceptable method. The value of this technique as well as systematic errors possible with its use are discussed. The medical literature concerning 51Cr evaluation of GI microbleeding with naproxen therapy is critically reviewed. We suggest that future studies using this technique be parallel, randomized, double-blind, and include a 1-week placebo baseline phase for all subjects. Treatment with nonsteroidal antiinflammatory drugs (NSAIDs) should last 3 to 4 weeks. A parallel group of subjects should receive placebo throughout the study. For valid statistical analyses, randomization must achieve baseline comparability of weight, height, age, and sex in the treatment groups. Data transformations may be necessary to satisfy the assumptions of the statistical model. Following these guidelines will enable investigators to better evaluate GI microbleeding during treatment with naproxen or other NSAIDs, and, hopefully, to establish the safety profiles of these drugs.