Once-daily administration of 300 mg of lamivudine in combination with other antiretroviral agents has been proposed as a possible way to optimize anti-human immunodeficiency virus (HIV) treatment and to facilitate adherence. A single-center, randomized, two-way, crossover study was conducted in 60 healthy subjects to compare the steady-state pharmacokinetics of lamivudine in plasma and its putative active anabolite, lamivudine 5-triphosphate (lamivudine-TP), in peripheral blood mononuclear cells (PBMCs) following 7 days of treatment with lamivudine at 300 mg once daily and 7 days of the standard regimen of 150 mg twice daily. Serial blood samples were collected over 24 h for determination of plasma lamivudine concentrations by liquid chromatography-mass spectrometry and intracellular lamivudine-TP concentrations in peripheral blood mononuclear cells by high-performance liquid chromatography/radioimmunoassay methods. Pharmacokinetic parameters were calculated based on lamivudine and lamivudine-TP concentration-time data. Regimens were considered bioequivalent if 90% confidence intervals (CI) for the ratio (once daily/twice daily) of geometric least-squares (GLS) means for lamivudine and lamivudine-TP pharmacokinetic values fell within the acceptance range of 0.8 to 1.25. Steady-state plasma lamivudine pharmacokinetics following the once-and twicedaily regimens were bioequivalent with respect to the area under the drug concentration-time curve from 0 to 24 h at steady state (AUC 24,ss ) (GLS mean ratio, 0.94; 90% CI, 0.92, 0.97) and average plasma lamivudine concentration over the dosing interval (C ave,ss ) (GLS mean ratio, 0.94; 90% CI, 0.92, 0.97). Steady-state intracellular lamivudine-TP pharmacokinetics after the once-and twice-daily regimens were bioequivalent with respect to AUC 24,ss (GLS mean ratio, 0.99; 90% CI, 0.88, 1.11), C ave,ss (GLS mean ratio, 0.99; 90% CI, 0.88, 1.11), and maximum lamivudine concentration (C max,ss ) (GLS mean ratio, 0.93; 90% CI, 0.81, 1.07). Lamivudine-TP trough concentrations were modestly lower (by 18 to 24%) during the once-daily regimen; the clinical importance of this is unclear, given the large intersubject variability in values that was observed (coefficient of variation, 48 to 124%). Once-daily lamivudine was as well tolerated as the twice-daily regimen. Overall, the results of this study suggest that for key AUC-related parameters, lamivudine at 300 mg once daily is pharmacokinetically equivalent to lamivudine at 150 mg twice daily.Lamivudine is a nucleoside reverse transcriptase inhibitor (NRTI) that is frequently used as a core component of highly active antiretroviral therapy (HAART) regimens in the treatment of human immunodeficiency virus (HIV) infection (13). In clinical trials conducted over 48 weeks, twice-daily regimens combining lamivudine at 150 mg with the NRTIs zidovudine (300 mg) and abacavir (300 mg) have proved equivalent to lamivudine-zidovudine-protease inhibitor combinations in reducing HIV-1 RNA levels and elevating CD4 cell counts (19;

Loperamide (LOP) is a peripherally acting opioid receptor agonist used for the management of chronic diarrhea through the reduction of gut motility. The lack of central opioid effects is partly due to the efflux activity of the multidrug resistance transporter P-glycoprotein (P-gp) at the blood-brain barrier. The protease inhibitors are substrates for P-gp and have the potential to cause increased LOP levels in the brain. Because protease inhibitors, including tipranavir (TPV), are often associated with diarrhea, they are commonly used in combination with LOP. The level of respiratory depression, the level of pupil constriction, the pharmacokinetics, and the safety of LOP alone compared with those of LOP-ritonavir (RTV), LOP-TPV, and LOP-TPV-RTV were evaluated in a randomized, open-label, parallel-group study with 24 healthy human immunodeficiency virus type 1-negative adults. Respiratory depression was assessed by determination of the ventilatory response to carbon dioxide. Tipranavir-containing regimens (LOP-TPV and LOP-TPV-RTV) caused decreases in the area under the concentration-time curve from time zero to infinity for LOP (51% and 63% decreases, respectively) and its metabolite (72% and 77% decreases, respectively), whereas RTV caused increases in the levels of exposure of LOP (121% increase) and its metabolite (44% increase). In vitro and in vivo data suggest that TPV is a substrate for and an inducer of P-gp activity. The respiratory response to LOP in combination with TPV and/or RTV was not different from that to LOP alone. There was no evidence that LOP had opioid effects in the central nervous system, as measured indirectly by CO 2 response curves and pupillary response in the presence of TPV and/or RTV.Loperamide (LOP; Imodium, McNeil-PPC, Inc.) is a peripherally acting opioid receptor agonist that reduces gut motility and that is used for the management of chronic diarrhea (8,25). The principal metabolic fate of loperamide in humans involves oxidative N-dealkylation to N-demethyl-loperamide as the principal metabolite. In human liver microsomes, cytochrome P450 3A4 (CYP3A4) appears to be the major isozyme responsible for loperamide metabolism, with minor contributions from CYP2B6 (9). At the doses used to control diarrhea, LOP has very poor penetration of the blood-brain barrier and produces no central opioid effects, such as respiratory depression, pupillary constrictions, analgesia, or changes in alertness (26). The poor central nervous system (CNS) penetration is attributed both to LOP active cellular efflux via the multidrug resistance transporter P-glycoprotein (P-gp) in the blood-brain barrier and to low systemic oral bioavailability (24). When P-gp is inhibited, LOP and its metabolites may potentially enter the brain and cause opioid-induced central neurological adverse events (AEs) (23, 24).Current treatment for human immunodeficiency virus type 1 (HIV-1) infection consists of a combination of antiretroviral agents of different classes. Tipranavir (TPV) is a potent nonpeptidic HIV-1 and HIV-...

Duloxetine does not affect ventricular repolarization as assessed by both mean changes and outliers in QT corrected by any method.

Telavancin is a rapidly bactericidal antibiotic with multiple mechanisms of action against gram-positive bacteria. Preclinical and early clinical data suggested possible effects on cardiac repolarization requiring the conduct of a definitive evaluation of QT effects in healthy subjects. A total of 160 subjects were randomized into four groups to receive placebo (telavancin vehicle), telavancin at a dose of 7.5 mg/kg or 15 mg/kg, or moxifloxacin 400 mg (positive control). All medications were administered once daily for 3 days as 60-minute IV infusions. Sixteen ECGs were obtained over 24 hours following an infusion of D5W (baseline) and following Day 3 infusions of each medication. ECGs were analyzed digitally in a blinded fashion by a validated core ECG laboratory. The primary endpoint was QT data corrected for heart rate by the Fridericia formula (QTcF). Placebo-corrected mean changes in QTcF values for 7.5 mg/kg telavancin, 15 mg/kg telavancin, and moxifloxacin were 4.1 msec, 4.5 msec, and 9.2 msec, respectively. The mean change from baseline in QTcF for moxifloxacin, which served as the assay-sensitive positive control in the study, helped to establish that telavancin had a minimal effect on QT prolongation. No subject had a QTcF > or = 450 msec, and none experienced clinically significant ECG abnormalities. The telavancin treatment groups were not significantly different from each other. There was no correlation of the magnitude of change in QTc and plasma concentrations of telavancin. Telavancin has a < 5-msec mean effect on cardiac repolarization, with a flat-dose response over a two-fold exposure range.

The authors designed 2 randomized controlled studies to examine the effects of etoricoxib 60 to 120 mg daily on methotrexate pharmacokinetics in 50 rheumatoid arthritis (RA) patients on stable doses of methotrexate (7.5-20 mg). Patients received oral methotrexate at baseline and on days 7 and 14. In study 1, patients received etoricoxib 60 mg (days 1-7) and then 120 mg (days 8-14); in study 2, patients received etoricoxib 90 mg (days 1-7) and then 120 mg (days 8-14). For study 1, the AUC(0-infinity) geometric mean ratio (GMR) (90% confidence interval [CI]) for day 7 versus baseline was 1.01 (0.91, 1.12) for etoricoxib 60 mg; the area under the plasma concentration-time curve from zero to infinity (AUC(0-infinity)) GMR (90% CI) for day 14 was 1.28 (1.15, 1.42) for etoricoxib 120 mg. For study 2, the AUC(0-infinity) GMR (90% CI) for day 7 versus baseline was 1.07 (1.01, 1.13) for etoricoxib 90 mg; the AUC(0-infinity) GMR (90% CI) for day 14 was 1.05 (0.99, 1.11) for etoricoxib 120 mg. In summary, etoricoxib 60 and 90 mg had no effect on methotrexate plasma concentrations. Although no effect on methotrexate pharmacokinetics was observed with etoricoxib 120 mg in study 2, GMR AUC(0-infinity) fell outside the prespecified bounds in study 1. Standard monitoring of methotrexate-related toxicity should be continued when etoricoxib and methotrexate are administered concurrently, especially with doses >90 mg etoricoxib.