Lumiracoxib: pharmacokinetic and pharmacodynamic profile when coadministered with fluconazole in healthy subjects

Clinical use and pharmacological properties of selective COX-2 inhibitors

Selective COX-2 inhibitors (coxibs) are approved for the relief of acute pain and symptoms of chronic inflammatory conditions such as osteoarthritis (OA) and rheumatoid arthritis (RA). They have similar pharmacological properties but a slightly improved gastrointestinal (GI) safety profile if compared to traditional nonsteroidal anti-inflammatory drugs (tNSAIDs). However, long-term use of coxibs can be associated with an increased risk for cardiovascular (CV) adverse events (AEs). For this reason, two coxibs were withdrawn from the market. Currently celecoxib, etoricoxib, and lumiracoxib are used. These three coxibs differ in their chemical structure and selectivity for COX-2, which might explain some of their pharmacological features. Following oral administration, the less lipophilic celecoxib has a lower bioavailability (20-40%) than the other two coxibs (74-100%). All are eliminated by hepatic metabolism involving mainly CYP2C9 (celecoxib, lumiracoxib) and CYP3A4 (etoricoxib). Elimination half-life varies from 5 to 8 h (lumiracoxib), 11 to 16 h (celecoxib) and 19 to 32 h (etoricoxib). In patients with liver disease, plasma levels of celecoxib and etoricoxib are increased about two-fold. Clinical efficacies of the coxibs are comparable to tNSAIDs. There is an ongoing discussion about whether the slightly better GI tolerability (which is lost if acetylsalicylic acid is coadministered) of the coxibs is offset by their elevated risks for CV AEs (also seen with tNSAIDs other than naproxen), which apparently increase with dose and duration of exposure. In addition, the higher costs for coxibs (if compared to tNSAIDs, even when a "gastroprotective" proton pump inhibitor is coadministered) should be taken into consideration, if a coxib will be selected for certain patients with a high risk for GI complications. For such treatment, the lowest effective dose should be used for a limited time. Monitoring of kidney function and blood pressure appears advisable. It is hoped that further controlled studies can better define the therapeutic place of the coxibs.

Lumiracoxib in the management of osteoarthritis and acute pain

Lumiracoxib is a highly selective COX-2 inhibitor with a novel chemical structure and a relatively short plasma half-life. It has been approved in > 40 countries for the symptomatic treatment of osteoarthritis and/or acute pain related to primary dysmenorrhoea and dental or orthopaedic surgery. In these conditions, lumiracoxib has proved to be as effective as standard doses of conventional NSAIDs and other COX-2 selective inhibitors (coxibs). According to the Therapeutic Arthritis Research Gastrointestinal Trial, which enrolled 18,325 patients with osteoarthritis, lumiracoxib 400 mg/day (four times its recommended dosage) was associated with a significant decrease in the risk of ulcer complications compared with naproxen 1000 mg/day and ibuprofen 2400 mg/day, at least in the population not taking low-dose aspirin. The atherothrombotic potential of NSAIDs, especially coxibs, has been much debated. In this respect, available data do not suggest that lumiracoxib may be associated with an increased hazard of cardiovascular events compared with non-selective NSAIDs. Finally, lumiracoxib may be an effective and safe drug provided both physicians and patients will comply with its approved indications and contraindications.

Pharmacogenetics, drug-metabolizing enzymes, and clinical practice

The application of pharmacogenetics holds great promise for individualized therapy. However, it has little clinical reality at present, despite many claims. The main problem is that the evidence base supporting genetic testing before therapy is weak. The pharmacology of the drugs subject to inherited variability in metabolism is often complex. Few have simple or single pathways of elimination. Some have active metabolites or enantiomers with different activities and pathways of elimination. Drug dosing is likely to be influenced only if the aggregate molar activity of all active moieties at the site of action is predictably affected by genotype or phenotype. Variation in drug concentration must be significant enough to provide "signal" over and above normal variation, and there must be a genuine concentration-effect relationship. The therapeutic index of the drug will also influence test utility. After considering all of these factors, the benefits of prospective testing need to be weighed against the costs and against other endpoints of effect. It is not surprising that few drugs satisfy these requirements. Drugs (and enzymes) for which there is a reasonable evidence base supporting genotyping or phenotyping include suxamethonium/mivacurium (butyrylcholinesterase), and azathioprine/6-mercaptopurine (thiopurine methyltransferase). Drugs for which there is a potential case for prospective testing include warfarin (CYP2C9), perhexiline (CYP2D6), and perhaps the proton pump inhibitors (CYP2C19). No other drugs have an evidence base that is sufficient to justify prospective testing at present, although some warrant further evaluation. In this review we summarize the current evidence base for pharmacogenetics in relation to drug-metabolizing enzymes.

Clinical pharmacology of lumiracoxib: a selective cyclo-oxygenase-2 inhibitor

Lumiracoxib (Prexige) is a selective cyclo-oxygenase (COX)-2 inhibitor developed for the treatment of osteoarthritis, rheumatoid arthritis and acute pain. Lumiracoxib possesses a carboxylic acid group that makes it weakly acidic (acid dissociation constant [pKa] 4.7), distinguishing it from other selective COX-2 inhibitors. Lumiracoxib has good oral bioavailability (74%). It is rapidly absorbed, reaching maximum plasma concentrations 2 hours after dosing, and is highly plasma protein bound. Lumiracoxib has a short elimination half-life from plasma (mean 4 hours) and demonstrates dose-proportional plasma pharmacokinetics with no accumulation during multiple dosing. In patients with rheumatoid arthritis, peak lumiracoxib synovial fluid concentrations occur 3-4 hours later than in plasma and exceed plasma concentrations from 5 hours after dosing to the end of the 24-hour dosing interval. These data suggest that lumiracoxib may be associated with reduced systemic exposure, while still reaching sites where COX-2 inhibition is required for pain relief. Lumiracoxib is metabolised extensively prior to excretion, with only a small amount excreted unchanged in urine or faeces. Lumiracoxib and its metabolites are excreted via renal and faecal routes in approximately equal amounts. The major metabolic pathways identified involve oxidation of the 5-methyl group of lumiracoxib and/or hydroxylation of its dihaloaromatic ring. Major metabolites of lumiracoxib in plasma are the 5-carboxy, 4'-hydroxy and 4'-hydroxy-5-carboxy derivatives, of which only the 4'-hydroxy derivative is active and COX-2 selective. In vitro, the major oxidative pathways are catalysed primarily by cytochrome P450 (CYP) 2C9 with very minor contribution from CYP1A2 and CYP2C19. However, in patients genotyped as poor CYP2C9 metabolisers, exposure to lumiracoxib (area under the plasma concentration-time curve) is not significantly increased compared with control subjects, indicating no requirement for adjustment of lumiracoxib dose in these subjects. Lumiracoxib is selective for COX-2 compared with COX-1 in the human whole blood assay with a ratio of 515 : 1 in healthy subjects and in patients with osteoarthritis or rheumatoid arthritis. COX-2 selectivity was confirmed by a lack of inhibition of arachidonic acid and collagen-induced platelet aggregation. COX-2 selectivity of lumiracoxib is associated with a reduced incidence of gastroduodenal erosions compared with naproxen and a lack of effect on both small and large bowel permeability. Lumiracoxib does not exhibit any clinically meaningful interactions with a range of commonly used medications including aspirin (acetylsalicylic acid), fluconazole, an ethinylestradiol- and levonorgestrel-containing oral contraceptive, omeprazole, the antacid Maalox, methotrexate and warfarin (although, as in common practice, routine monitoring of coagulation is recommended when lumiracoxib is co-administered with warfarin). As such, dose adjustments are not required when co-administering these agents with lumiracoxib. In addition, moderate hepatic impairment and mild to moderate renal impairment do not appear to influence lumiracoxib exposure.

Effects of the antifungals voriconazole and fluconazole on the pharmacokinetics of s-(+)- and R-(-)-Ibuprofen

Our objective was to study the effects of the antifungals voriconazole and fluconazole on the pharmacokinetics of S-(+)- and R-(-)-ibuprofen. Twelve healthy male volunteers took a single oral dose of 400 mg racemic ibuprofen in a randomized order either alone, after ingestion of voriconazole at 400 mg twice daily on the first day and 200 mg twice daily on the second day, or after ingestion of fluconazole at 400 mg on the first day and 200 mg on the second day. Ibuprofen was ingested 1 h after administration of the last dose of voriconazole or fluconazole. Plasma concentrations of S-(+)- and R-(-)-ibuprofen were measured for up to 24 h. In the voriconazole phase, the mean area under the plasma concentration-time curve (AUC) of S-(+)-ibuprofen was 205% (P < 0.001) of the respective control value and the mean peak plasma concentration (C(max)) was 122% (P < 0.01) of the respective control value. The mean elimination half-life (t(1/2)) was prolonged from 2.4 to 3.2 h (P < 0.01) by voriconazole. In the fluconazole phase, the mean AUC of S-(+)-ibuprofen was 183% of the control value (P < 0.001) and its mean C(max) was 116% of the control value (P < 0.05). The mean t(1/2) of S-(+)-ibuprofen was prolonged from 2.4 to 3.1 h (P < 0.05) by fluconazole. The geometric mean S-(+)-ibuprofen AUC ratios in the voriconazole and fluconazole phases were 2.01 (90% confidence interval [CI], 1.80 to 2.22) and 1.82 (90% CI, 1.72 to 1.91), respectively, i.e., above the bioequivalence acceptance upper limit of 1.25. Voriconazole and fluconazole had only weak effects on the pharmacokinetics of R-(-)-ibuprofen. In conclusion, voriconazole and fluconazole increased the levels of exposure to S-(+)-ibuprofen 2- and 1.8-fold, respectively. This was likely caused by inhibition of the cytochrome P450 2C9-mediated metabolism of S-(+)-ibuprofen. A reduction of the ibuprofen dosage should be considered when ibuprofen is coadministered with voriconazole or fluconazole, especially when the initial ibuprofen dose is high.

IMPACT OF CYP2C9 GENOTYPE ON PHARMACOKINETICS: ARE ALL CYCLOOXYGENASE INHIBITORS THE SAME?: TABLE 1

The market withdrawals of rofecoxib (Vioxx) and valdecoxib (Bextra) have focused considerable attention on the side effect profiles of cyclooxygenase (COX) inhibitors. As a result, attempts will be made to identify risk factors in the hope that physicians might be able to ensure patient safety. At first glance, CYP2C9 genotype might be considered a risk factor because many COX inhibitors are CYP2C9 substrates in vitro. This observation has led some to hypothesize that a reduction in clearance, in subjects expressing variant forms of the enzyme (e.g., CYP2C9*1/*3 or CYP2C9*3/*3 genotype), will lead to increased exposure and a greater risk of cardiovascular or gastrointestinal side effects. For any drug, however, one has to consider all clearance pathways. Therefore, a number of COX inhibitors were surveyed and it was determined that CYP2C9 plays a relatively minor role in the overall clearance (<or=20% of the dose) of sulindac, naproxen, ketoprofen, diclofenac, rofecoxib, and etoricoxib. CYP2C9 genotype would have no clinically meaningful impact on the pharmacokinetics of these drugs. In contrast, CYP2C9 genotype is expected to impact the clearance of ibuprofen, indomethacin, flurbiprofen, celecoxib, valdecoxib, lornoxicam, tenoxicam, meloxicam, and piroxicam. However, even when CYP2C9 is a major determinant of clearance, it is necessary to consider CYP2C8 genotype (e.g., ibuprofen) and, possibly, CYP3A4 activity (e.g., celecoxib, valdecoxib, and meloxicam) also.

Preclinical pharmacology of lumiracoxib: a novel selective inhibitor of cyclooxygenase-2

1. This manuscript presents the preclinical profile of lumiracoxib, a novel cyclooxygenase-2 (COX-2) selective inhibitor. 2. Lumiracoxib inhibited purified COX-1 and COX-2 with K(i) values of 3 and 0.06 microM, respectively. In cellular assays, lumiracoxib had an IC(50) of 0.14 microM in COX-2-expressing dermal fibroblasts, but caused no inhibition of COX-1 at concentrations up to 30 microM (HEK 293 cells transfected with human COX-1). 3. In a human whole blood assay, IC(50) values for lumiracoxib were 0.13 microM for COX-2 and 67 microM for COX-1 (COX-1/COX-2 selectivity ratio 515). 4. Lumiracoxib was rapidly absorbed following oral administration in rats with peak plasma levels being reached between 0.5 and 1 h. 5. Ex vivo, lumiracoxib inhibited COX-1-derived thromboxane B(2) (TxB(2)) generation with an ID(50) of 33 mg kg(-1), whereas COX-2-derived production of prostaglandin E(2) (PGE(2)) in the lipopolysaccharide-stimulated rat air pouch was inhibited with an ID(50) value of 0.24 mg kg(-1). 6. Efficacy of lumiracoxib in rat models of hyperalgesia, oedema, pyresis and arthritis was dose-dependent and similar to diclofenac. However, consistent with its low COX-1 inhibitory activity, lumiracoxib at a dose of 100 mg kg(-1) orally caused no ulcers and was significantly less ulcerogenic than diclofenac (P<0.05). 7. Lumiracoxib is a highly selective COX-2 inhibitor with anti-inflammatory, analgesic and antipyretic activities comparable with diclofenac, the reference NSAID, but with much improved gastrointestinal safety.

Lumiracoxib

Lumiracoxib is a highly selective and potent cyclo-oxygenase (COX)-2 inhibitor, with a novel structure that conveys weakly acidic properties and a unique pharmacological profile. It is rapidly absorbed, with a relatively short plasma half-life. In well designed clinical trials of 1-52 weeks' duration in patients with osteoarthritis (OA) or rheumatoid arthritis, the efficacy of oral lumiracoxib 100-400 mg/day in decreasing pain intensity and improving functional status was greater than that with placebo and similar to those with nonselective NSAIDs or celecoxib 200mg once daily. In single- and multiple-dose well designed trials in patients with acute pain associated with primary dysmenorrhoea, dental or orthopaedic surgery or tension-type headache, lumiracoxib 100-800 mg once daily was more effective in relieving acute pain than placebo or controlled-release oxycodone 20 mg, and was at least as effective as selective COX-2 inhibitors or nonselective NSAIDs. Lumiracoxib was generally well tolerated in clinical trials, with a similar overall tolerability profile to those of placebo and other COX-2-selective inhibitors. In a large 52-week safety trial in patients with OA, lumiracoxib 400mg once daily had a rate of gastrointestinal ulcer complications that was approximately one-third to one-quarter of that of ibuprofen 800 mg three times daily or naproxen 500 mg twice daily. Lumiracoxib was not associated with an increase in cardiovascular events.