Concomitant Administration of Lumiracoxib and a Triphasic Oral Contraceptive Does Not Affect Contraceptive Activity or Pharmacokinetic Profile

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.

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.

Clinical pharmacology of lumiracoxib, a second-generation cyclooxygenase 2 selective inhibitor

Although highly selective cyclooxygenase (COX)-2 inhibitors have been shown to be less toxic to the gastrointestinal tract than conventional non-steroidal anti-inflammatory drugs (NSAIDs), their overall safety profile is questioned. Since different selective COX-2 inhibitors were found to be associated with increased cardiovascular thrombotic events, the thrombotic hazard may be a class effect. Furthermore, warnings have been issued regarding serious skin and hypersensitivity reactions associated with valdecoxib. Lumiracoxib is a novel COX-2 selective inhibitor (coxib) with improved biochemical selectivity over that of currently available coxibs. It is structurally distinct from other drugs in the class and has weakly acidic properties. Clinical studies support a once-daily dosing regimen, despite its relatively short plasma elimination half-life (3 - 6 h). In randomised, controlled clinical trials, lumiracoxib 100 - 200 mg/day has been shown to be superior to placebo in patients with symptomatic osteoarthritis, with clinical efficacy similar to diclofenac 150 mg/day, celecoxib 200 mg/day or rofecoxib 25 mg/day. Furthermore, lumiracoxib 200 - 400 mg/day appeared to be effective in patients with rheumatoid arthritis. In patients with acute pain related to primary dysmenorrhoea, dental or orthopaedic surgery, lumiracoxib 400 mg/day was found to be at least as effective as standard doses of traditional NSAIDs and other coxibs. Endoscopic studies have indicated that lumiracoxib is associated with a rate of gastroduodenal ulcer formation that is significantly lower than with ibuprofen and does not differ from celecoxib. In the Therapeutic Arthritis Research and Gastrointestinal Trial, which enrolled 18,325 patients with osteoarthritis, the cumulative 1-year incidence of ulcer complications (primary end point) was significantly reduced by approximately threefold on lumiracoxib 400 mg/day compared with naproxen 1000 mg/day or ibuprofen 2400 mg/day (0.32 versus 0.91%). Reduction in ulcer complications was more pronounced in the population not taking low-dose aspirin (0.2 versus 0.92%, respectively). Conversely, the gastrointestinal advantage of lumiracoxib was abrogated in patients receiving low-dose aspirin (0.69 versus 0.88%, respectively, p = 0.49). Regarding cardiovascular events contributing to the trialists' composite end point (myocardial infarction, stroke or cardiovascular death), there was no significant difference between lumiracoxib (0.65%) versus combined comparator NSAIDs (0.55%). Similarly, no significant difference was recorded in rates of myocardial infarction (clinical and silent) between the lumiracoxib (0.25%) and the combined NSAID (0.19%) treatment groups. Liver function test abnormalities were more frequent with lumiracoxib (2.57%) than with the comparator NSAIDs (0.63%). Whether or not this would result in an increased risk of clinical hepatitis in the real world setting is unforeseeable.

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.