Slow oxidation of acetoxime and methylethyl ketoxime to the corresponding nitronates and hydroxy nitronates by liver microsomes from rats, mice, and humans.
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Acetoxime and methylethyl ketoxime (MEKO) are tumorigenic in rodents, inducing liver tumors in male animals. The mechanisms of tumorigenicity for these compounds are not well defined. Oxidation of the oximes to nitronates of secondary-nitroalkanes, which are mutagenic and tumorigenic in rodents, has been postulated to play a role in the bioactivation of ketoximes. In these experiments, we have compared the oxidation of acetoxime and methylethyl ketoxime to corresponding nitronates in liver microsomes from different species. The oximes were incubated with liver microsomes from mice, rats, and several human liver samples. After tautomeric equilibration and extraction with n-hexane, 2-nitropropane and 2-nitrobutane were quantitated by GC/MS-NCI (limit of detection of 250 fmol/injection volume). In liver microsomes, nitronate formation from MEKO and acetoxime was dependent on time, enzymatically active proteins, and the presence of NADPH. Nitronate formation was increased in liver microsomes of rats pretreated with inducers of cytochrome P450 and reduced in the presence of inhibitors (n-octylamine and diethyldithiocarbamate). Rates of oxidation of MEKO (Vmax) were 1.1 nmol/min/mg (mice), 0.5 nmol/min/mg (humans), and 0.1 nmol/min/mg (rats). In addition to nitronates, several minor metabolites were also enzymatically formed (two diastereoisomers of 3-nitro-2-butanol, 2-hydroxy-3-butanone oxime and 2-nitro-1-butanol). Acetoxime was also metabolized to the corresponding nitronate at rates approximately 50% of those observed with MEKO oxidation in the three species examined. 2-Nitro-1-propanol was identified as a minor product formed from acetoxime. No sex differences in the capacity to oxidize acetoxime and MEKO were observed in the species examined. The observed results show that formation of sec-nitronates from ketoximes occurs slowly, but is not the only pathway involved in the oxidative biotransformation of these compounds. Due to the lack of sex-specific oxidative metabolism, other metabolic pathways or mechanisms of tumorigenicity not involving bioactivation may be involved in the sex-specific tumorigenicity of ketoximes in rodents. (+info)
A placebo-controlled study of interaction between nabumetone and acenocoumarol.
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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. (+info)
Urinary volatile constituents of the lion, Panthera leo.
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The volatile components of urine from lions were investigated using GC-MS headspace techniques. Fifty-five compounds were found in the urine samples. Seven potential species-identifying compounds were found. Male lion scent marks overlapped significantly more in compound composition with other males than they did with female marks. A similar relationship was not found for the females. Males had a significantly higher absolute content of 2-butanone in their urine than females, and females had a significantly higher relative content of acetone than males. Samples from 13/16 individual lions overlapped more within the individual than they did with samples from the other individuals, but only seven significantly so. (+info)
A functional arginine residue in rabbit-muscle aldolase.
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Rabbit muscle aldolase is irreversibly modified by the arginine-selective alpha-dicarbonyl, phenylglyoxal, loss of activity correlating with the unique modifications of one arginine residue per subunit, as determined by amino acid analysis, and (7-14C)phenylglyoxal incorporation. The affinity of the modified enzyme for dihydroxyacetone phosphate is significantly reduced while substantial protection against inactivation is afforded by fructose 1,6-disphosphate, dihydroxyacetone phosphate or phosphate ion. The nature of the substrate C-1 phosphate binding site in this enzyme is discussed in the light of these and other results. (+info)
Effects of nabumetone compared with naproxen on platelet aggregation in patients with rheumatoid arthritis.
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OBJECTIVE: To test the hypothesis that nabumetone (a partially selective cyclooxygenase-(COX)-2 inhibitor) has less effect on platelet aggregation than naproxen (a non-selective COX-inhibitor) in patients with rheumatoid arthritis (RA). METHODS: A crossover study in 10 RA patients was performed, using either nabumetone or naproxen for two weeks, and, after a washout period of two weeks, the other drug during another two weeks. Platelet aggregation studies were performed and bleeding time was assessed before and after each treatment period. RESULTS: Maximum platelet aggregation induced by epinephrine and by collagen was significantly more reduced after the use of naproxen than of nabumetone; secondary aggregation induced by ADP and epinephrine disappeared more often by naproxen than by nabumetone. Bleeding times were not influenced. CONCLUSION: COX dependent platelet aggregation in RA patients seems to be more inhibited by naproxen than by nabumetone. This may be relevant for patients requiring non-steroidal anti-inflammatory drug treatment but who have an increased risk of bleeding as well. (+info)
Reductive metabolism In vivo of trans-4-phenyl-3-buten-2-one in rats and dogs.
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The reductive metabolism in vivo of a flavoring additive, trans-4-phenyl-3-buten-2-one (PBO; trans-methyl styryl ketone) was investigated in rats and dogs. In both species, the double bond-reduced product, 4-phenyl-2-butanone (PBA), was detected by HPLC as the predominant species in blood after i.v. administration of PBO. PBA detected in rat blood was identified by comparison to the authentic sample. In contrast, the carbonyl-reduced product, trans-4-phenyl-3-buten-2-ol (PBOL) was also detected as a minor metabolite of PBO in both species. The area under the curve of PBOL in rat blood was only 3% of that of PBA. PBO was mutagenic in the Ames test using Salmonella typhimurium TA 100 when S-9 mix was added, but PBA and PBOL were not. It appears that PBO is mainly metabolized to PBA in vivo in rats and dogs as a detoxification pathway. (+info)
Non-steroidal anti-inflammatory drugs and renal response to exercise: a comparison of indomethacin and nabumetone.
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Nabumetone, a newer non-steroidal anti-inflammatory drug (NSAID) which preferentially blocks cyclo-oxygenase-2 activity, may be less nephrotoxic than indomethacin. This study tested whether nabumetone has effects different from those of indomethacin on exercise-induced changes in renal function and the renin-aldosterone system. In a randomized fashion, ten subjects were studied after indomethacin (100 mg), nabumetone (1 g) or no medication (control) administered orally at 22.00 hours on the day before each study day, and again at 8.00 hours upon arrival at the laboratory. Renal function was studied at baseline, during graded 20-min exercise sessions at 25%, 50% and 75% of the maximal oxygen uptake rate, and subsequently during two 1-h recovery periods. Heart rate, arterial blood pressure, cardiac output and plasma catecholamines at rest and during exercise were not altered by indomethacin or nabumetone. Indomethacin decreased urinary rates of excretion of 6-oxo-prostaglandin F(1alpha) (6-oxo-PGF(1alpha)) and thromboxane B(2) in all study periods. Nabumetone decreased 6-oxo-PGF(1alpha) excretion during and after exercise. Excretion rates for PGE(2) did not change. Neither indomethacin nor nabumetone changed baseline values or exercise-induced decreases in renal plasma flow or glomerular filtration rate. Indomethacin, but not nabumetone, decreased sodium excretion, urine flow rate and free water clearance. The renal response to exercise, however, remained unchanged. In contrast with nabumatone, indomethacin decreased the plasma renin concentration. Thus, during exercise, nabumetone may decrease the excretion of 6-oxo-PGF(1alpha) by inhibition of cyclo-oxygenase-1 or by inhibition of specific exercise-induced activation of cyclo-oxygenase-2, or both. None of the drugs changed the renal response to exercise. Inhibition by indomethacin of angiotensin II and thromboxane A(2) synthesis may, during exercise, counterbalance renal vasoconstriction caused by blockade of vasodilatory prostaglandins. (+info)
Safety and efficacy of nabumetone in osteoarthritis: emphasis on gastrointestinal safety.
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AIM: To compare the efficacy and gastrointestinal (GI) safety of nabumetone with two comparator non-steroidal anti-inflammatory drugs (NSAIDs), diclofenac SR and piroxicam. METHODS: Two randomized, double-blind, multicentre, parallel group trials were carried out in patients with moderate to severe osteoarthritis of the hip or knee. During the 6 month treatment phase, the safety and efficacy of nabumetone (1500-2000 mg/day) was compared to diclofenac SR (100 mg/day) or piroxicam (20-30 mg/day). GI safety was evaluated by reviewing all adverse events reported during the trials and presenting all cases of ulcers (complicated and uncomplicated), as well as other bleeding events that may have been associated with NSAID administration. RESULTS: Most of the efficacy parameters showed no significant differences between the NSAIDs, although diclofenac SR was significantly better than nabumetone in one of 18 efficacy parameters. Nabumetone-treated patients experienced significantly fewer ulcer and bleeding events compared to patients treated with the comparator NSAIDs [1.1% (4/348) vs. 4.3% (15/346), P = 0.01]. Bleeding events, including outright upper or lower GI bleeding or a significant decline in haemoglobin, occurred in significantly fewer patients treated with nabumetone than with the comparator NSAIDs [1.1% (4/348) vs. 3.5% (12/346), P < 0.05]. More importantly, complications associated with either ulcers (perforation) or bleeding (leading to hospitalization or withdrawal) occurred in significantly fewer patients receiving nabumetone [0% (0/348)] than with comparator NSAIDs [1.4% (5/346), (P < 0.05)]. CONCLUSION: The results suggest that nabumetone was similar in efficacy by most criteria to diclofenac SR and piroxicam in relieving the symptoms of osteoarthritis; however, nabumetone's GI safety profile was generally superior to that of both comparator NSAIDs. In the pooled analysis, nabumetone was associated with a significantly lower total incidence of ulcers and bleeding events, and a significantly lower incidence of complications associated with these events. (+info)