QT and QTc interval with standard and supratherapeutic doses of darifenacin, a muscarinic M3 selective receptor antagonist for the treatment of overactive bladder.

Prolongation of QT interval on an electrocardiogram is a valuable predictor of a drug's ability to cause potentially fatal ventricular tachyarrhythmia (torsades de pointes). Darifenacin is a muscarinic M3 selective receptor antagonist developed for the treatment of overactive bladder, a debilitating condition that is particularly prevalent in the older population. This 7-day, randomized, parallel-group study (n=188) measured QT/QTc interval in healthy volunteers receiving once-daily darifenacin at steady-state therapeutic (15 mg) and supratherapeutic (75 mg) doses, alongside controls receiving placebo or moxifloxacin (positive control, 400 mg) once daily. There was no significant increase in QTcF interval with darifenacin treatment compared with placebo. Mean changes from baseline at pharmacokinetic Tmax versus placebo were -0.4 and -2.2 milliseconds in the darifenacin 15 mg and 75 mg groups, respectively, compared with +11.6 milliseconds in the moxifloxacin group (P<.01). This study demonstrates that darifenacin does not prolong QT/QTc interval.

Lumiracoxib does not affect methotrexate pharmacokinetics in rheumatoid arthritis patients.

BACKGROUND: Methotrexate and nonsteroidal antiinflammatory drugs are frequently coadministered in the treatment of rheumatoid arthritis (RA). OBJECTIVE: To evaluate the effect of lumiracoxib, a novel cyclooxygenase-2 selective inhibitor, on methotrexate pharmacokinetics and short-term safety in patients with RA. METHODS: This multicenter, randomized, double-blind, placebo-controlled crossover study enrolled 18 patients (mean age 49.1 y) with stable RA. Patients were randomized to receive methotrexate 7.5-15 mg orally once weekly plus either lumiracoxib 400 mg/day or placebo for 7 days. Patients then received the other treatment combination for an additional 7 days. Serial blood and urine were collected for 24 hours after the methotrexate dose on day 1 (methotrexate alone) and days 8 and 15 (combination treatment). RESULTS: Plasma methotrexate pharmacokinetics (AUC(0-t), maximum concentration [C(max)], time to C(max)) and methotrexate protein binding were similar for methotrexate alone (108.0 ng.h/mL, 26.7 ng/mL, 1.5 h, and 57.1%, respectively), methotrexate/lumiracoxib (110.2 ng.h/mL, 27.5 ng/mL, 1.0 h, and 53.7%, respectively), and methotrexate/placebo (101.8 ng.h/mL, 22.6 ng/mL, 1.0 h, and 57.0%, respectively). Similarly, no clinically significant difference was found in the urinary excretion of methotrexate. Mean exposure to the 7-OH metabolite was lower when methotrexate was given with lumiracoxib compared with placebo, shown by a reduction in AUC and C(max), although similar amounts of the metabolite were recovered in urine following both lumiracoxib and placebo. Coadministration of methotrexate and lumiracoxib was well tolerated. CONCLUSIONS: Lumiracoxib had no significant effect on the pharmacokinetics, protein binding, or urinary excretion of coadministered methotrexate in patients with RA.

Pharmacokinetics of lumiracoxib in plasma and synovial fluid.

BACKGROUND: Lumiracoxib is a new cyclo-oxygenase-2 (COX-2) selective inhibitor in development for the treatment of rheumatoid arthritis, osteoarthritis and acute pain. OBJECTIVE: To investigate the pharmacokinetics of lumiracoxib in plasma and knee joint synovial fluid from patients with rheumatoid arthritis. DESIGN: Open-label multiple-dose study evaluating the steady-state pharmacokinetics of lumiracoxib in plasma and synovial fluid after 7 days of treatment with lumiracoxib 400 mg once daily. PATIENT POPULATION: Males and females aged 18-75 years with rheumatoid arthritis, having moderate to significant synovial fluid effusion of the knee. OUTCOME MEASURES: Following a 7-day washout period for previous nonsteroidal anti-inflammatory drugs, 22 patients (17 female, 5 male) received lumiracoxib 400 mg once daily for seven consecutive days. On day 7, following an overnight fast, a final dose of lumiracoxib was administered and serial blood and synovial fluid samples were collected for up to 28 hours. Lumiracoxib and its metabolites (4'-hydroxy-lumiracoxib and 5-carboxy-4'-hydroxy-lumiracoxib) were measured by validated high performance liquid chromatography-mass spectrometry methods. The steady-state pharmacokinetics of lumiracoxib were evaluated in plasma and synovial fluid by both a population pharmacokinetic model and noncompartmental analysis. RESULTS: Lumiracoxib was rapidly absorbed (peak plasma concentration at 2 hours) and the terminal elimination half-life in plasma was short (6 hours). Lumiracoxib concentrations were initially higher in plasma than in synovial fluid; however, from 5 hours after administration until the end of the 28-hour assessment period, concentrations of lumiracoxib were higher in synovial fluid than in plasma. Peak drug concentration in synovial fluid occurred 3-4 hours later than the peak plasma concentration. The mean steady-state trough concentration of lumiracoxib in synovial fluid (454 microg/L) was approximately three times higher than the mean value in plasma (155 microg/L), and the area under the concentration-time curve from 12 to 24 hours after administration was 2.6-fold higher for synovial fluid than for plasma. Median lumiracoxib protein binding was similar in plasma and synovial fluid (range 97.9-98.3%). Concentrations of 4'-hydroxy-lumiracoxib, the active COX-2 selective metabolite, remained low in comparison with parent drug in both plasma and synovial fluid. The concentration of lumiracoxib in synovial fluid at 24 hours after administration would be expected to result in substantial inhibition of prostaglandin E(2) formation. CONCLUSION: The kinetics of distribution of lumiracoxib in synovial fluid are likely to extend the therapeutic action of the drug beyond that expected from plasma pharmacokinetics. These data support the use of lumiracoxib in a once-daily regimen for the treatment of rheumatoid arthritis.

Concomitant administration of lumiracoxib and a triphasic oral contraceptive does not affect contraceptive activity or pharmacokinetic profile.

This study evaluated the effect of lumiracoxib on the pharmacokinetics and pharmacodynamics of ethinyl estradiol (EE) and levonorgestrel (LN) in Triphasil-28 (a triphasic oral contraceptive). Females stabilized on Triphasil-28 continued on Triphasil-28 alone for another month (Treatment Period 1), then also received lumiracoxib (400 mg daily) or placebo for 28 days each (Periods 2 and 3) in a double-blind crossover design. Plasma pharmacokinetic profiles were assessed on Day 21 of Periods 2 and 3. Progesterone and plasma sex hormone binding globulin (SHBG) concentrations were measured before and 2 hours after Triphasil-28 administration on Day 21 of all three treatment periods. Lumiracoxib had no significant effect on EE or LN pharmacokinetics or on progesterone or SHBG concentrations, indicating that anovulation and Triphasil-28 effectiveness was maintained. Adverse events were similar for lumiracoxib and placebo. Therefore, no clinically important consequences are anticipated if lumiracoxib is coadministered with oral contraceptives containing EE or LN.

Assessment of lumiracoxib bioavailability from targeted sites in the human intestine using remotely activated capsules and gamma scintigraphy.

PURPOSE: To determine the bioavailability and pharmacokinetic profile of lumiracoxib from different sites in the gastrointestinal tract. METHODS: Subjects (11 healthy adult males) were randomized to receive a 100 mg lumiracoxib dose, via a site-specific radiolabeled delivery capsule, to the stomach (internal reference), proximal small bowel, distal small bowel, or ascending colon. Gamma scintigraphy was used for real-time visualization of capsule location, and a radiofrequency signal was used to activate capsules at target site. RESULTS: Ten subjects completed the study. The mean capsule activation times for the stomach, proximal small bowel, distal small bowel, and ascending colon were 0.22, 1.52, 3.43, and 11.46 h post dose, respectively. Lumiracoxib was well absorbed from the proximal and distal small bowel, with AUC(0-infinity) ratios 104% (86, 127)% and 110% (89, 136)%, respectively. The highest Cmax (2413 ng/ml) and AUC(0-infinity) for lumiracoxib were in the distal small bowel (6842 ng x h/ml). Effective absorption was observed from the ascending colon, with an AUC(0-infinity) ratio of 85% (69, 104)% vs. the reference. CONCLUSIONS: Lumiracoxib is rapidly and efficiently absorbed throughout the gastrointestinal tract.

Lack of effect of omeprazole or of an aluminium hydroxide/magnesium hydroxide antacid on the pharmacokinetics of lumiracoxib.

OBJECTIVE: To evaluate the effects of multiple doses of omeprazole and of a single dose of an aluminium hydroxide/magnesium hydroxide (Al/Mg) antacid on the single-dose plasma pharmacokinetics of lumiracoxib. STUDY DESIGN: Open-label, randomised, three-period, crossover study. POPULATION STUDIED: Healthy subjects aged 18-65 years. METHODS: Fourteen subjects who met eligibility criteria were each administered three treatments in random order: (A) lumiracoxib 400 mg as a single oral dose; (B) oral omeprazole 20 mg once daily for 4 consecutive days, then lumiracoxib 400 mg as a single oral dose just prior to oral omeprazole 20 mg on day 5; and (C) lumiracoxib 400 mg as a single oral dose immediately prior to a 20 mL dose of Al/Mg antacid (magnesium hydroxide 800 mg and aluminium hydroxide 900 mg). The interval between each lumiracoxib dose was 7 days. Analysis of variance was performed to determine whether lumiracoxib alone differed from lumiracoxib plus omeprazole or from lumiracoxib plus Al/Mg antacid for overall exposure (area under the concentration-time curve from zero to infinity [AUC( infinity )]) and peak concentration (C(max)), with treatment sequence, subject, period and treatment as factors. Ratios of geometric means between lumiracoxib plus omeprazole and lumiracoxib plus Al/Mg antacid to lumiracoxib alone (reference) were calculated for AUC( infinity ) and C(max). If the mean ratios, with 90% CIs, fell within the interval 0.80-1.25, the treatments were considered equivalent. RESULTS: Arithmetic mean plasma lumiracoxib concentration-time profiles were similar for all treatments, with a rapid rise in concentration after administration, reaching C(max) values (mean +/- SD) of 9.24 +/- 1.96, 8.81 +/- 2.30, and 10.43 +/- 3.24 mg/L within 2-3 hours for treatments A, B and C, respectively. AUC( infinity ) was similar for the three treatments (36.75 +/- 7.73, 34.88 +/- 8.40 and 35.50 +/- 5.72 mg. h/L). All ratios of geometric means with 90% CIs fell within the interval used for establishing bioequivalence, except for the C(max) comparison between lumiracoxib plus Al/Mg antacid and lumiracoxib alone, which was 1.11 (0.95, 1.31). CONCLUSIONS: Coadministration of lumiracoxib with omeprazole or with an Al/Mg antacid had no clinically significant effect on lumiracoxib single-dose plasma pharmacokinetics. Lumiracoxib can, therefore, be administered concurrently with either of these agents without need for lumiracoxib dosage alteration.

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

This two-way crossover study evaluated the effect of fluconazole on the pharmacokinetics and selective COX-2 inhibition of lumiracoxib. Thirteen healthy subjects were randomized to fluconazole (day 1: 400 mg; days 2-4: 200 mg) or no drug. On day 4, all subjects received a single dose of lumiracoxib (400 mg). Lumiracoxib pharmacokinetics were assessed during the following 48 hours. Thromboxane B(2) (TxB(2)) inhibition was measured prior to lumiracoxib dosing and 2 hours afterwards. Fluconazole caused a small (18%) but not clinically relevant increase in lumiracoxib mean AUC(0- infinity ) but had no effect on lumiracoxib mean C(max). The geometric mean ratio (lumiracoxib plus fluconazole/lumiracoxib alone) for AUC(0- infinity ) was 1.19 (90% confidence interval [CI] = 1.12, 1.27) and for C(max) was 1.11 (90% CI = 0.98, 1.27). The decrease in TxB(2) from predose was not significantly different for lumiracoxib (11.8%) or lumiracoxib plus fluconazole (7.1%); no correlation between lumiracoxib concentration and TxB(2) decrease was seen. As fluconazole is a strong inhibitor of cytochrome P450 (CYP) 2C9, other CYP2C9 inhibitors are unlikely to affect lumiracoxib pharmacokinetics with clinical relevance, making dosage adjustment unnecessary.

Pharmacokinetic drug interactions in children taking oxcarbazepine.

OBJECTIVE: Our objective was to evaluate the drug-drug interactions of oxcarbazepine with coadministered antiepileptic drugs in children. METHODS: In a clinical trial, pediatric patients receiving an oxcarbazepine dose titrated to 30 to 46 mg. kg(-1). d(-1) given twice daily had 1 to 4 blood samples collected per patient for population pharmacokinetic analysis of oxcarbazepine's major bioactive 10-monohydroxy metabolite. With the use of NONMEM, 7 concomitant antiepileptic drugs and 12 additional covariates were examined for their effects on the pharmacokinetics of 10-monohydroxy metabolite. In addition, for each concomitant antiepileptic drug, the ratio of its mean concentration with coadministration of oxcarbazepine to that without coadministration at baseline was calculated to evaluate the effect of oxcarbazepine on the coadministered antiepileptic drugs. RESULTS: The population pharmacokinetic data for 10-monohydroxy metabolite consisted of a total of 376 observations from 109 patients, aged 3 to 17 years. Body surface area and 3 antiepileptic drugs (carbamazepine, phenobarbital, and phenytoin) were significant predictors of the apparent clearance of 10-monohydroxy metabolite, whereas height was a significant predictor of apparent volume. Weight-normalized clearance of 10-monohydroxy metabolite was higher in young children than in older children and adults. Carbamazepine, phenobarbital, or phenytoin administered with oxcarbazepine increased the apparent clearance of 10-monohydroxy metabolite by 31% to 35%, whereas carbamazepine levels decreased by 15% and phenobarbital levels increased by 14%. CONCLUSIONS: Oxcarbazepine has a low propensity to inhibit or induce oxidative enzymes. Young children could be given higher milligrams-per-kilogram oxcarbazepine doses than older children and adults to achieve the same mean steady-state concentration of 10-monohydroxy metabolite. The adjustment is based simply on body size.