Pharmacokinetics of JNJ-73763989 and JNJ-56136379 (Bersacapavir) in Participants With Moderate Hepatic Impairment.

JNJ-73763989 is comprised of 2 short interfering RNAs (siRNAs), JNJ-73763976 and JNJ-73763924, that target hepatitis B virus (HBV) mRNAs for degradation, thereby inhibiting HBV replication. JNJ-56136379 is a capsid assembly modulator that inhibits HBV replication by inducing the formation of empty capsids (CAM-E). In 2 phase 1, open-label, non-randomized, single-center studies, the single-dose pharmacokinetics, safety, and tolerability of JNJ-73763989 or JNJ-56136379 were assessed in participants with moderate hepatic impairment (Child-Pugh Class B) versus participants with normal liver function. Participants in both studies received a single subcutaneous dose of JNJ-73763989 200 mg or oral JNJ-56136379 250 mg, followed by an evaluation of plasma pharmacokinetic parameters and safety assessments. Plasma exposure to JNJ-73763976, JNJ-73763924, and JNJ-56136379 was 1.3- to 1.4-, 1.8- to 2.2-, and 1.1- to 1.3-fold higher in participants with moderate hepatic impairment versus participants with normal liver function; however, these increases were not considered clinically relevant. Both drugs were well tolerated and safe, with 7 (21.9%) participants experiencing 1 or more treatment-emergent adverse events, 3 of which were related to JNJ-56136379. Overall, the plasma exposures of JNJ-73763989 and JNJ-56136379 were higher in participants with moderate hepatic impairment, but both were well tolerated. Further studies are needed to evaluate the effect of hepatic impairment under multiple-dose administration.

Drug-Drug Interactions With the Hepatitis B Virus Capsid Assembly Modulator JNJ-56136379 (Bersacapavir).

The capsid assembly modulator JNJ-56136379 (bersacapavir) disrupts hepatitis B virus replication. It is metabolized via cytochrome P450 (CYP) 3A, but little is known about the drug-drug interactions of JNJ-56136379 when combined with drugs that inhibit or are metabolized by CYP3A. In a phase 1, open-label trial (NCT03945539), healthy adults received 1 dose of JNJ-56136379 with and without 21 days of prior exposure to itraconazole 200 mg (CYP3A inhibitor). In a second phase 1, open-label trial (NCT03111511), healthy women received 1 dose of drospirenone/ethinyl estradiol and midazolam before and after 15 days of JNJ-56136379. Itraconazole increased the area under the plasma concentration-time curve (AUC) of JNJ-56136379 by 38%. JNJ-56136379 reduced the maximum observed concentration and AUC of midazolam (CYP3A substrate) by 42%-54%, increased AUC of ethinyl estradiol by 1.6-fold, but had no effect on drospirenone pharmacokinetics. Overall, these results demonstrated that a strong CYP3A inhibitor (itraconazole) modestly increased JNJ-56136379 exposure. Furthermore, JNJ-56136379 was a weak inducer of CYP3A (midazolam) and increased ethinyl estradiol exposure; coadministration of high-dose estrogen-based contraceptives and JNJ-56136379 is not recommended.

JNJ-73763989 pharmacokinetics and safety: Liver-targeted siRNAs against hepatitis B virus, in Japanese and non-Japanese healthy adults, and combined with JNJ-56136379 and a nucleos(t)ide analogue in patients with chronic hepatitis B.

BACKGROUND: JNJ-73763989 comprises two hepatitis B virus (HBV)-specific, liver-targeted N-galactosamine-conjugated short interfering RNA triggers, JNJ-73763976 and JNJ-73763924. JNJ-73763989 pharmacokinetics, safety and tolerability were assessed in two phase 1 studies: Japanese (NCT04002752), and non-Japanese healthy participants and chronic hepatitis B (CHB) patients also receiving the HBV capsid assembly modulator JNJ-56136379 and a nucleos(t)ide analogue (NA) (NCT03365947). METHODS: Healthy participant cohorts were double-blind and randomized to receive a single subcutaneous JNJ-73763989 dose (non-Japanese participants, 35, 100, 200, 300 or 400 mg; Japanese participants, 25, 100 or 200 mg) or placebo. JNJ-73763976 and JNJ-73763924 plasma concentrations were assessed over 48 h. CHB patients received JNJ-73763989 200 mg every 4 weeks plus daily oral JNJ-56136379 250 mg and NA in an open-label fashion. Safety and tolerability were assessed through Day 28 (healthy participants) or Day 112 (patients). RESULTS: Thirty non-Japanese (n = 4/dose; placebo, n = 10) and 24 Japanese healthy participants (n = 6/dose; placebo, n = 6) were randomized. JNJ-73763976 and JNJ-73763924 exposure generally increased in a dose-proportional manner. Mean plasma half-life was 4-9 h. No differences between pharmacokinetic parameters were apparent between non-Japanese and Japanese healthy participants. In the 12 CHB patients, mean JNJ-73763976, JNJ-73763924 and JNJ-56136379 plasma concentrations 2 h post-dose on Day 29 were 663, 269 and 14,718 ng/mL, respectively. In both studies, all adverse events were mild/moderate. CONCLUSION: JNJ-73763976 and JNJ-73763924 had short plasma half-lives and exposure generally increased in a dose-proportional manner; there were no pharmacokinetic differences between Japanese and non-Japanese healthy adults. JNJ-73763989 with or without JNJ-56136379 and NA was generally safe and well tolerated.

Capillary microsampling in clinical studies: opportunities and challenges in two case studies.

Aim: Capillary microsampling of 15 µl whole blood from fingersticks or heelsticks was used to collect pharmacokinetic (PK) samples from pediatric subjects in two projects. Results: In a mebendazole multisite study in Ethiopia and Rwanda in subjects between 1 and 16 years old, complete PK profiles (7 timepoints) could be obtained, although some of the fingerstick samples were contaminated by the dosing formulation. In a multisite study with a respiratory syncytial virus drug in children between 1 and 24 months old, sparse PK sampling was done (2 samples). All samples were successfully analyzed even though some capillaries were not properly filled. Conclusion: CMS shows potential for PK sampling in pediatrics but may need further optimization.

Population pharmacokinetics of trabectedin in adolescent patients with cancer.

PURPOSE: To characterize the trabectedin population pharmacokinetics in children and adolescent patients with cancer and compare it with the trabectedin pharmacokinetics in adults. METHODS: Plasma concentrations from ten adolescent and three children with cancer (age range 4.0-17.0 years) treated with trabectedin at doses ranging from 1.1 to 1.7 mg/m2, administered as a 24-h continuous intravenous infusion every 3 weeks, were available for the analysis. An external model evaluation was performed to verify whether a previously developed adult population pharmacokinetic model was predictive of the pediatric plasma concentrations of trabectedin. The maximum a posteriori estimation of the individual pharmacokinetic parameters for pediatric patients was conducted, after successful completion of the external evaluation step. The relationships between pharmacokinetic parameters and body size were evaluated. RESULTS: External evaluation methods showed no major differences between the adult population and children and adolescent patients of this study. The mean ± standard deviation (SD) of the individual estimated clearance and central volume of distribution in these children/adolescent patients was 36.4 ± 16.1 L/h and 13.2 ± 6.54 L, respectively. These values were similar to the typical values reported for adult patients-37.6 L/h and 13.9 L (for females) and 16.1 L (for males). The median area under the plasma concentration versus time curve (AUC) in children/adolescent patients was 55.1 µg h/L, while in the adult population the median AUC was 61.3 µg h/L, both administered a 1.5 mg/m2 dose regimen with mean (range) BSA for adults = 1.86 (0.90-2.80) vs children/adolescent patients = 1.49 (0.66-2.54). CONCLUSIONS: The adult population pharmacokinetic model adequately described the trabectedin plasma concentrations and its variability in the pediatric population of patients involved in this assessment that mostly comprised adolescents. The trabectedin systemic exposure achieved in this population was comparable (within 12%) to the exposure obtained in adult population when the same dose, expressed in mg/m2, was administered.

Single- and multiple-dose pharmacokinetics and safety of pimodivir, a novel, non-nucleoside polymerase basic protein 2 subunit inhibitor of the influenza A virus polymerase complex, and interaction with oseltamivir: a Phase 1 open-label study in healthy volunteers.

AIMS: The aim of this study was to evaluate the drug-drug interaction between pimodivir, a novel, non-nucleoside polymerase basic protein 2 (PB2) subunit inhibitor of the influenza A virus polymerase complex, and oseltamivir, to assess the feasibility of this combination therapy. Furthermore, single- and multiple-dose pharmacokinetics and safety of pimodivir in healthy volunteers were assessed. METHODS: In Part 1 of this open-label Phase 1 study, healthy volunteers (n = 18) were randomized to one of six cross-over treatment sequences, each comprising administration of oseltamivir 75 mg or pimodivir 600 mg or combination thereof twice daily on Days 1-4, followed by a single morning dose on Day 5. Between each treatment session, there was a minimum 5-day washout period. In Part 2, healthy volunteers (n = 16) randomly received pimodivir 600 mg or placebo (3:1) twice daily on Days 1-9, followed by a single morning dose on Day 10. Pharmacokinetics of pimodivir, oseltamivir and oseltamivir carboxylate, and safety were assessed. RESULTS: In Part 1, co-administration of pimodivir with oseltamivir increased the Cmax of pimodivir by 31% (90% CI: 0.92-1.85) with no change in Cmin or AUC12h . Pimodivir had no effect on oseltamivir or oseltamivir carboxylate pharmacokinetics. In Part 2, after single- and multiple-dose administration of pimodivir, there was a 1.2- and 1.8-fold increase in Cmax and AUC12h , respectively, between Day 1 and Day 10. The most frequently reported treatment-emergent adverse event was diarrhoea (n = 7 each in Part 1 and 2). CONCLUSION: Combination treatment with pimodivir and oseltamivir in healthy volunteers showed no clinically relevant drug-drug interactions. No safety concerns were identified with pimodivir 600 mg twice daily alone or in combination with oseltamivir 75 mg twice daily.

Pharmacokinetics, Antiviral Activity, and Safety of Rilpivirine in Pregnant Women with HIV-1 Infection: Results of a Phase 3b, Multicenter, Open-Label Study.

INTRODUCTION: Physiologic changes during pregnancy may impact the pharmacokinetics of drugs. In addition, efficacy and safety/tolerability concerns have been identified for some antiretroviral agents. METHODS: Human immunodeficiency virus (HIV)-1-infected pregnant women (18-26 weeks gestation) receiving the non-nucleoside reverse transcriptase inhibitor rilpivirine 25 mg once daily were enrolled in this phase 3b, open-label study examining the impact of pregnancy on the pharmacokinetics of rilpivirine when it is given in combination with other antiretroviral agents. Blood samples (collected over the 24-h dosing interval) to assess total and unbound rilpivirine plasma concentrations were obtained during the second and third trimesters (24-28 and 34-38 weeks gestation, respectively) and 6-12 weeks postpartum. Pharmacokinetic parameters were derived using noncompartmental analysis and compared (pregnancy versus postpartum) using linear mixed effects modeling. Antiviral and immunologic response and safety were assessed. RESULTS: Nineteen women were enrolled; 15 had evaluable pharmacokinetic results. Total rilpivirine exposure was 29-31% lower during pregnancy versus postpartum; differences were less pronounced for unbound (pharmacodynamically active) rilpivirine. At study entry, 12/19 (63.2%) women were virologically suppressed; 10/12 (83.3%) women were suppressed at the postpartum visit. Twelve infants were born to the 12 women who completed the study (7 discontinued); no perinatal viral transmission was observed among 10 infants with available data. Rilpivirine was generally safe and well tolerated in women and infants exposed in utero. CONCLUSION: Despite decreased rilpivirine exposure during pregnancy, treatment was effective in preventing mother-to-child transmission and suppressing HIV-1 RNA in pregnant women. Results suggest that rilpivirine 25 mg once daily, as part of individualized combination antiretroviral therapy, may be an appropriate option for HIV-1-infected pregnant women. TRIAL REGISTRATION: ClinicalTrials.gov Identifier, NCT00855335.

Pharmacokinetic Interactions between Simeprevir and Ledipasvir in Treatment-Naive Hepatitis C Virus Genotype 1-Infected Patients without Cirrhosis Treated with a Simeprevir-Sofosbuvir-Ledipasvir Regimen.

Interactions between simeprevir (hepatitis C virus [HCV] NS3/4A protease inhibitor) and ledipasvir (HCV NS5A replication complex inhibitor) were investigated in treatment-naive HCV genotype 1-infected patients without cirrhosis, treated with simeprevir-sofosbuvir-ledipasvir in a two-panel, phase 2, open-label study. Patients had stable background treatment with sofosbuvir (400 mg once daily [QD]). In panel 1 (n = 20), the effect of ledipasvir (90 mg QD) on simeprevir (150 mg QD) was studied. Patients received simeprevir and sofosbuvir from days 1 to 14; steady-state pharmacokinetics (PK) of simeprevir was assessed (day 14). On day 15, ledipasvir was added and steady-state PK of simeprevir in the combination was evaluated (day 28). In panel 2 (n = 20), the effect of simeprevir on ledipasvir was investigated. From days 1 to 14, patients received ledipasvir and sofosbuvir and steady-state PK of ledipasvir was assessed (day 14). On day 15, simeprevir was added and a full PK profile was obtained (day 28). The least-squares mean maximum plasma concentration and area under the concentration-time curve (90% confidence interval) increased 2.3-fold (2.0- to 2.8-fold) and 3.1-fold (2.4- to 3.8-fold) for simeprevir, respectively (panel 1), and 1.6-fold (1.4- to 1.9-fold) and 1.7-fold (1.6- to 2.0-fold) for ledipasvir, respectively (panel 2), in the presence versus the absence of the other drug. All patients achieved sustained virologic responses 12 weeks after treatment end. Adverse events, mainly grade 1/2, occurred in 80% of patients; the most common was photosensitivity (45%). Due to the magnitude of interaction and the limited amount of safety data available, the use of this treatment combination is not recommended. (This study has been registered at ClinicalTrials.gov under registration no. NCT02421211.).

Pharmacokinetics of Total and Unbound Etravirine in HIV-1-Infected Pregnant Women.

BACKGROUND: Treatment of HIV-1-infected women during pregnancy protects maternal health and reduces the risk of perinatal transmission of HIV-1. However, physiologic changes that occur during pregnancy may affect drug pharmacokinetics. This phase IIIb, open-label study evaluated the effects of pregnancy on the pharmacokinetics of the nonnucleoside reverse transcriptase inhibitor etravirine. METHODS: Eligible HIV-1-infected pregnant women (18-26 weeks gestation) on an individualized, highly active antiretroviral therapy regimen including etravirine 200 mg twice daily were enrolled. Blood samples to assess the pharmacokinetics of total and unbound etravirine were obtained at clinic visits during the second and third trimesters (24- to 28-weeks and 34- to 38-weeks gestation, respectively) and 6-12 weeks postpartum. At each time point, plasma concentrations were measured over 12 hours (12-hour time point was obtained before the second daily dose of etravirine); pharmacokinetic parameters were derived using noncompartmental analysis and were compared between pregnancy and postpartum using general linear models. Antiviral and immunologic response and safety were assessed at each visit. RESULTS: Etravirine pharmacokinetic profiles were available for 13 of 15 enrolled women. Exposure to total etravirine was generally higher during pregnancy compared with 6-12 weeks postpartum (1.2- to 1.4-fold); the differences were less pronounced for unbound (pharmacodynamically active) etravirine. Virologic response was generally preserved throughout the study, and no perinatal transmission was observed. Etravirine was generally safe and well tolerated. CONCLUSIONS: Etravirine 200 mg twice daily, as part of individualized combination antiretroviral therapy, may be a treatment option for HIV-1-infected pregnant women.

Evaluation of Three Amorphous Drug Delivery Technologies to Improve the Oral Absorption of Flubendazole.

This study investigates 3 amorphous technologies to improve the dissolution rate and oral bioavailability of flubendazole (FLU). The selected approaches are (1) a standard spray-dried dispersion with hydroxypropylmethylcellulose (HPMC) E5 or polyvinylpyrrolidone-vinyl acetate 64, both with Vitamin E d-α-tocopheryl polyethylene glycol succinate; (2) a modified process spray-dried dispersion (MPSDD) with either HPMC E3 or hydroxypropylmethylcellulose acetate succinate (HPMCAS-M); and (3) confining FLU in ordered mesoporous silica (OMS). The physicochemical stability and in vitro release of optimized formulations were evaluated following 2 weeks of open conditions at 25°C/60% relative humidity (RH) and 40°C/75% RH. All formulations remained amorphous at 25°C/60% RH. Only the MPSDD formulation containing HPMCAS-M and 3/7 (wt./wt.) FLU/OMS did not crystallize following 40°C/75% RH exposure. The OMS and MPSDD formulations contained the lowest and highest amount of hydrolyzed degradant, respectively. All formulations were dosed to rats at 20 mg/kg in suspension. One FLU/OMS formulation was also dosed as a capsule blend. Plasma concentration profiles were determined following a single dose. In vivo findings show that the OMS capsule and suspension resulted in the overall highest area under the curve and Cmax values, respectively. These results cross-evaluate various amorphous formulations and provide a link to enhanced biopharmaceutical performance.

Sample Management: Recommendation for Best Practices and Harmonization from the Global Bioanalysis Consortium Harmonization Team.

The importance of appropriate sample management in regulated bioanalysis is undeniable for clinical and non-clinical study support due to the fact that if the samples are compromised at any stage prior to analysis, the study results may be affected. Health authority regulations do not contain specific guidance on sample management; therefore, as part of the Global Bioanalysis Consortium (GBC), the A5 team was established to discuss sample management requirements and to put forward recommendations. The recommendations from the team concern the entire life span of the sample and include the following: 1. Sampling procedures should be described in the protocol or within the laboratory manual. This information should include the volume of the sample to be collected, the required anticoagulant, light sensitivity, collection and storage containers, and labeling with a unique identifier. 2. The correct procedures for processing and then storing the samples after collection at the clinical/non-clinical testing site and during shipment are also very important to ensure the analyte(s) stability and should be documented. 3. Chain of custody for the samples must be maintained throughout the complete life span of each sample. This is typically maintained via paper and electronic data systems, including Laboratory Information Management Systems (LIMS) where available. 4. Pre- and post-analysis storage location and conditions must also be clearly defined at the analytical laboratory. The storage temperature of the samples must be traceable and controlled by monitoring and warning alerts. The team suggests moving away from using temperatures and to adopt standard terminology of "room temperature," "refrigerator," "freezer," and "ultra-freezer" that have defined and industry-wide accepted temperature ranges. 5. At the end of the study, documentation of the samples' disposal is required.

Determination of tapentadol and tapentadol-O-glucuronide in human serum samples by UPLC-MS/MS.

Tapentadol is a novel, centrally acting analgesic with 2 mechanisms of action, MOR agonism and noradrenaline (NA) reuptake inhibition in a single molecule. It is the first member of a new therapeutic class, MOR-NRI. A high throughput liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay was developed and validated for the quantitative analysis of tapentadol and its O-glucuronide metabolite in human serum. Simultaneous quantification was deemed to be challenging because of the large difference in concentrations between tapentadol and its O-glucuronide metabolite in clinical samples. Therefore, a method was established using a common processed sample, but with different injection volumes and chromatographic conditions for each analyte. Tapentadol and tapentadol-O-glucuronide were determined by protein precipitation of 0.100ml of the samples with acetonitrile. The internal standards used are D6-tapentadol and D6-tapentadol-O-glucuronide. The validated concentration range was 0.200-200 ng/ml (tapentadol) and 10.0-10,000 ng/ml (tapentadol-O-glucuronide). Chromatographic separation was achieved by gradient elution on a Waters Acquity UPLC BEH C18 (1.7 µm, 2.1 × 50 mm) column, with mobile phase consisting of 0.01 M ammonium formate (adjusted to pH 4 using formic acid) (A) and methanol (B). A separate injection was done for measurement of each analyte, with a different gradient and run time. The analytes were detected by using an electrospray ion source on a triple quadrupole mass spectrometer operating in positive ionization mode. The run time was 1.6 min for tapentadol and 1.5 min for tapentadol-O-glucuronide. The high sensitivity and acceptable performance of the assay allowed its application to the analysis of serum samples in clinical trials. The validated method was used for analysis of tapentadol in over 17,000 samples.

Bioavailability and bioequivalence of a darunavir 800-mg tablet formulation compared with the 400-mg tablet formulation.

UNLABELLED: Once-daily darunavir/ritonavir (800/100 mg), plus other antiretrovirals, is recommended for HIV-1-infected patients. Low therapy adherence is linked with poor outcomes. Pill burden can impact adherence. An 800-mg darunavir tablet would reduce pill burden. OBJECTIVES: To assess the relative oral bioavailability (NCT01052883) and bioequivalence (NCT01308658) of a darunavir 800-mg tablet vs. 2 × 400-mg tablets. METHODS: In two phase I, open-label, randomized, crossover, single-center studies, healthy volunteers received once-daily ritonavir (100 mg, days 1 - 5) and a single 800-mg darunavir dose: 2 × 400-mg tablets (reference) or 1 × 800- mg tablet (test) on day 3 and vice versa after a ≥ 7-day wash-out. Each study had fasted (n = 16 (bioavailability); n = 83 (bioequivalence)) and fed panels (n = 16; n = 45, respectively). Pharmacokinetic profiles and tolerability were assessed. RESULTS: No volunteers discontinued for treatment-related reasons. Least-square mean ratios (test vs. reference) for darunavir maximum plasma concentrations (C(max)), area under the concentration-time curve from zero to infinity (AUC(0-∞)) were: 1.06 and 1.15 (bioavailability), and 1.02 and 1.00 (bioequivalence), respectively (fasted); 0.89 and 0.88 (bioavailability), and 0.96 and 0.98 (bioequivalence), respectively (fed). 90% confidence intervals (CI) were within 80.00 - 125.00%, except bioavailability AUC(0-∞) (fed and fasted conditions). Median time to C(max) was comparable for both formulations. No clinically relevant differences in adverse events or laboratory abnormalities occurred between formulations. CONCLUSIONS: Bioequivalence was demonstrated for the 800-mg darunavir tablet (fasted and fed conditions). This formulation can reduce pill burden and potentially increase adherence for HIV-1-infected patients in whom once-daily darunavir/ritonavir 800/100 mg is appropriate.

Pharmacokinetics of darunavir in fixed-dose combination with cobicistat compared with coadministration of darunavir and ritonavir as single agents in healthy volunteers.

This study compared the bioavailability of two candidate fixed-dose combinations (FDCs: G003 and G004) of darunavir/cobicistat 800/150 mg with that of darunavir 800 mg and ritonavir 100 mg coadministered as single agents. Short-term safety and tolerability of the FDC formulations were also assessed. This open-label trial included 36 healthy volunteers and assessed steady-state pharmacokinetics of darunavir over 3 randomized, 10-day treatment sequences, under fed conditions. Blood samples for determination of plasma concentrations of darunavir and cobicistat or ritonavir were taken over 24 hours on day 10 and analyzed by liquid-chromatography tandem mass-spectroscopy. Darunavir AUC24h following administration of the FDCs (G003: 74,780 ng ∙ h/mL and G004: 76,490 ng ∙ h/mL) was comparable to that following darunavir/ritonavir (78,410 ng ∙ h/mL), as was Cmax (6,666 and 6,917 ng/mL versus 6,973 ng/mL, respectively). Modestly lower C0h (1,504 and 1,478 ng/mL versus 2,015 ng/mL) and Cmin (1,167 and 1,224 ng/mL versus 1,540 ng/mL) values were seen with the FDCs. Short-term tolerability of the FDCs was comparable to that of darunavir/ritonavir when administered as single agents. The most common adverse events reported were headache, gastrointestinal upset, or rash. Cobicistat is an effective pharmacoenhancer of darunavir when administered as an FDC. Short-term administration of darunavir/ritonavir or darunavir/cobicistat was generally well tolerated.

Pharmacokinetic evaluation of tapentadol extended-release tablets in healthy subjects.

OBJECTIVE: To evaluate serum pharmacokinetics of tapentadol administered to healthy subjects as extended-release (ER) tablets. DESIGN: Seven single-dose studies (five randomized, crossover, bioequivalence studies; a study in Japanese men; and a randomized, crossover, effects-of-food study) and one repeated-dose study. SETTING: Clinical research settings in the United States and The Netherlands. PATIENTS OR PARTICIPANTS: Healthy males and females were enrolled into seven studies; one study enrolled only Japanese males. INTERVENTIONS: In the bioequivalence studies, subjects first received one polyethylene oxide- or hypromellose-based tapentadol ER tablet (50, 100, 150, 200, or 250 mg; one dose per study), then (after washout) the other formulation (matching dose). In all other studies, subjects received polyethylene oxide-based tapentadol ER tablets. In the repeated-dose study, subjects received one 250 mg tablet, then (after washout) one 250 mg tablet every 12 hours (five doses). In the food-effect study, subjects received one 250 mg tablet within 30 minutes after a high-fat meal or after 10 hours of fasting. In the study in Japanese men, subjects received one 100 mg tablet. MAIN OUTCOME MEASURES: Maximum tapentadol concentrations (Cmax) were typically observed 5 hours after dosing. Mean terminal half-life values ranged from 4.4 to 5.9 hours. Tapentadol Cmax and AUC values increased proportionally following single ER (polyethylene oxide-based tablets) doses of 50 to 250 mg. Trough tapentadol concentrations increased during repeat dosing until reaching steady-state by the third dose. Serum Cmax and area under the concentration-time curve (AUC) values at steady state were 1.6 and 1.9 times higher relative to single-dose administration. Coadministration of the 250 mg dose with a high-fat meal increased Cmax and AUC values by an average of < 17 percent. CONCLUSIONS: The pharmacokinetics of tapentadol ER are consistent after repeated and single-dose administration. Tapentadol ER may be administered without regard to food intake. No clinically significant differences were observed in the pharmacokinetics of tapentadol between Japanese and Caucasian subjects.

Postmortem redistribution of fentanyl in the rabbit blood.

Postmortem redistribution of fentanyl in the rabbit was investigated after application of the 50-µg/h Durogesic pain patch. Patches were applied for 48 hours. Two cycles of patch administration were used before characterization of the postmortem redistribution. Fentanyl showed marked redistribution into the femoral and pulmonary veins of the rabbit through 48 hours after the animals were humanely killed and the pain patches removed. The plasma concentration of 2.34 ng/mL in the femoral blood before killing the animals increased 5.6-fold by 48 hours after patch removal to 13.2 ng/mL. This postmortem concentration is approximately 3-fold the C(max) determined during antemortem pharmacokinetic analysis, 4 ng/mL, which was achieved 24 hours after the application of the second 50-µg/h Durogesic pain patch. After blood sampling for 48 hours after animal termination with patch removal compared with sampling for 48 hours from animals not terminated and with patch removal, the exposure ratios in the terminated animals were approximately 30-fold, indicating that between the postmortem redistribution of fentanyl and the cessation of hepatic clearance of fentanyl in the rabbit, the postmortem redistribution of fentanyl leads to an elevated measures of postmortem blood concentrations relative to antemortem blood concentrations.