Pharmacokinetics and safety of niraparib in patients with moderate hepatic impairment

PURPOSE

The purpose of this study is to characterize niraparib pharmacokinetics (PK) and safety in patients with normal hepatic function (NHF) versus moderate hepatic impairment (MHI).

METHODS

Patients with advanced solid tumors were stratified by NHF or MHI (National Cancer Institute-Organ Dysfunction Working Group criteria [bilirubin > 1.5-3 × upper limit of normal and any aspartate aminotransferase elevation]). In the PK phase, all patients received one 300 mg dose of niraparib. In the extension phase, patients with MHI received niraparib 200 mg daily; patients with NHF received 200 or 300 mg based on weight (< 77 kg, ≥ 77 kg)/platelets (< 150,000/µL, ≥ 150,000/µL). PK parameters included maximum concentration (C_max), area under the curve to last measured concentration (AUC_last) and extrapolated to infinity (AUC_inf). Safety was assessed in both phases. Exposure-response (E-R) modeling was used to predict MHI effects on exposure and safety of niraparib doses ≤ 200 mg or 300/200 mg or 200/100 mg weight/platelet regimens.

RESULTS

In the PK phase (NHF, n = 9; MHI, n = 8), mean niraparib C_max was 7% lower in patients with MHI versus NHF. Mean exposure (AUC_last, AUC_inf) was increased by 45% and 56%, respectively, in patients with MHI without impacting tolerability. In the extension phase (NHF, n = 8; MHI, n = 7), the overall safety profile was consistent with previous trials. In patients with MHI, E-R modeling predicted niraparib 200 mg reduced Grade ≥ 3 thrombocytopenia incidence, whereas a 200/100 mg regimen yielded exposures below efficacy-associated levels in 15% of patients.

CONCLUSION

These findings support adjusting the 300 mg niraparib starting dose to 200 mg QD in patients with MHI.

TRIAL REGISTRATION

NCT03359850; registered December 2, 2017.

Pepper Alkaloids and Processed Meat Intake: Results from a Randomized Trial and the European Prospective Investigation into Cancer and Nutrition (EPIC) Cohort

SCOPE

Processed meat intake has been associated with adverse health outcomes. However, little is known about the type of processed meat more particularly responsible for these effects. This study aims to identify novel biomarkers for processed meat intake.

METHODS AND RESULTS

In a controlled randomized cross-over dietary intervention study, 12 healthy volunteers consume different processed and non-processed meats for 3 consecutive days each. Metabolomics analyses are applied on post-intervention fasting blood and urine samples to identify discriminating molecular features of processed meat intake. Nine and five pepper alkaloid metabolites, including piperine, are identified as major discriminants of salami intake in urine and plasma, respectively. The associations with processed meat intake are tested for replication in a cross-sectional study (n = 418) embedded within the European Prospective Investigation into Cancer and Nutrition (EPIC) cohort. Three of the serum metabolites including piperine are associated with habitual intake of sausages and to a lesser extent of total processed meat.

CONCLUSION

Pepper alkaloids are major discriminants of intake for sausages that contain high levels of pepper used as ingredient. Further work is needed to assess if pepper alkaloids in combination with other metabolites may serve as biomarkers of processed meat intake.

Effects of naringenin on the pharmacokinetics of tofacitinib in rats

Context: Naringenin and tofacitinib are often used together for treatment of rheumatoid arthritis in Chinese clinics.Objective: This experiment investigates the effect of naringenin on the pharmacokinetics of tofacitinib in rats.Materials and methods: Twelve Sprague-Dawley rats were randomly divided into two groups (experimental group and control group). The experimental group was pre-treated with naringenin (150 mg/kg/day) for two weeks before dosing tofacitinib, and equal amounts of CMC-Na solution in the control group. After a single oral administration of 5 mg/kg of tofacitinib, 50 μL blood samples were directly collected into 1.5 mL heparinized tubes via the caudal vein at 0.083, 0.5, 1, 2, 3, 4, 6, 8, 10, 12 and 24 h. The plasma concentration of tofacitinib was quantified by UPLC/MS-MS.Results: Results indicated that naringenin could significantly affect the pharmacokinetics of tofacitinib. The AUC_0-24 of tofacitinib was increased from 1222.81 ± 222.07 to 2016.27 ± 481.62 ng/mL/h, and the difference was significant (p < 0.05). Compared with the control group, the T_max was increased from 0.75 ± 0.29 to 3.00 ± 0.00 h (p < 0.05), and the MRT_(0-24) was increased from 4.90 ± 0.51 to 6.57 ± 0.66 h (p < 0.05), but the clearance was obviously decreased from 4.10 ± 0.72 to 2.42 ± 0.70 L/h/kg (p < 0.05) in experimental group. Although the C_max and t_1/2 of tofacitinib were increased, there were no significant differences (p > 0.05).Conclusions: This research demonstrated a drug-drug interaction between naringenin and tofacitinib possibly when preadministered with naringenin; thus, we should pay attention to this possibility in the clinic.

Modeling of [18F]FEOBV Pharmacokinetics in Rat Brain

PURPOSE

[¹⁸F]Fluoroethoxybenzovesamicol ([¹⁸F]FEOBV) is a radioligand for the vesicular acetylcholine transporter (VAChT), a marker of the cholinergic system. We evaluated the quantification of [¹⁸F]FEOBV in rats in control conditions and after partial saturation of VAChT using plasma and reference tissue input models and test-retest reliability.

PROCEDURE

Ninety-minute dynamic [¹⁸F]FEOBV PET scans with arterial blood sampling were performed in control rats and rats pretreated with 10 μg/kg FEOBV. Kinetic analyses were performed using one- (1TCM) and two-tissue compartmental models (2TCM), Logan and Patlak graphical analyses with metabolite-corrected plasma input, reference tissue Patlak with cerebellum as reference tissue, standard uptake value (SUV) and SUV ratio (SUVR) using 60- or 90-min acquisition. To assess test-retest reliability, two dynamic [¹⁸F]FEOBV scans were performed 1 week apart.

RESULTS

The 1TCM did not fit the data. Time-activity curves were more reliably estimated by the irreversible than the reversible 2TCM for 60 and 90 min as the influx rate K_i showed a lower coefficient of variation (COV, 14-24 %) than the volume of distribution V_T (16-108 %). Patlak graphical analysis showed a good fit to the data for both acquisition times with a COV (12-27 %) comparable to the irreversible 2TCM. For 60 min, Logan analysis performed comparably to both irreversible models (COV 14-32 %) but showed lower sensitivity to VAChT saturation. Partial saturation of VAChT did not affect model selection when using plasma input. However, poor correlations were found between irreversible 2TCM and SUV and SUVR in partially saturated VAChT states. Test-retest reliability and intraclass correlation for SUV were good.

CONCLUSION

[¹⁸F]FEOBV is best modeled using the irreversible 2TCM or Patlak graphical analysis. SUV should only be used if blood sampling is not possible.

Enantioselective LC-MS/MS method for the determination of cloperastine enantiomers in rat plasma and its pharmacokinetic application

Cloperastine is a central antitussive used to reduce the frequency and intensity of coughing on a short-term basis. In this study, a reliable chiral LC-MS/MS technology has been developed for the quantification of cloperastine enantiomers in the rat plasma. Carbinoxamine was selected as the internal standard. The enantioseparation of cloperastine was performed on a Chiralpak IA column with a mobile phase composed of acetonitrile-water-ammonium hydroxide (80:20:0.1, v/v/v) at a flow rate of 0.6 mL/min. Cloperastine enantiomers were detected by mass spectrometry in multiple reaction monitoring mode with a positive electrospray ionization source. The method was validated over the linear concentration range of 0.05 to 10.0 ng/mL (5.0 × 10^-4 ng to 0.10 ng) for both enantiomers. The lower limit of quantification (LLOQ) for each analyte was determined as 0.05 ng/mL. The relative standard deviations (RSDs) of intraday and interday precision was less than 13.9%, and the relative error (RE) of accuracy ranged from -5.4% to 6.1%, which were within the acceptance criteria. Finally, an application to the stereoselective pharmacokinetics of cloperastine in rats was successfully realized in our assay. The developed method on a commercially available Chiralpak IA column under isocratic mobile phase is advantageous to analyze cloperastine enantiomers in plasma samples collected for enantioselective metabolism or drug interaction studies.

Development and validation of a Level A in-vitro in-vivo correlation for tofacitinib modified-release tablets using extrudable core system osmotic delivery technology

PURPOSE

To determine if a validated Level A in-vitro in-vivo correlation (IVIVC) could be achieved with the extrudable core system (ECS) osmotic tablet platform. Tofacitinib is an oral JAK inhibitor for the treatment of rheumatoid arthritis.

METHODS

Fast-, medium-, and slow-release modified-release formulations of 11 mg tofacitinib ECS tablets, and one formulation of 22 mg tofacitinib ECS tablet, were manufactured. In vitro dissolution of the tofacitinib ECS tablets was performed using USP Apparatus 2 (paddles) and in vivo pharmacokinetic (PK) data were obtained from a Phase 1 study in healthy volunteers. A 5 mg immediate-release formulation tablet was included to support deconvolution of the tofacitinib ECS PK tablet data to obtain the in vivo absorption profiles. A linear, piecewise correlation and a simple linear correlation were used to build and validate two IVIVC models.

RESULTS

The prediction errors (PEs) for the linear, piecewise correlation met the Food and Drug Administration's criteria for establishing a Level A IVIVC, with a maximum absolute individual internal PE of 4.6%, a maximum absolute average internal PE of 3.9%, and a maximum absolute external PE of 8.4% obtained.

CONCLUSIONS

This study demonstrates that the tofacitinib ECS osmotic tablet platform can achieve a Level A IVIVC, similar to other osmotic delivery systems.

Open-label, single-center, phase I trial to investigate the mass balance and absolute bioavailability of the highly selective oral MET inhibitor tepotinib in healthy volunteers

Tepotinib (MSC2156119J) is an oral, potent, highly selective MET inhibitor. This open-label, phase I study in healthy volunteers (EudraCT 2013-003226-86) investigated its mass balance (part A) and absolute bioavailability (part B). In part A, six participants received tepotinib orally (498 mg spiked with 2.67 MBq [¹⁴C]-tepotinib). Blood, plasma, urine, and feces were collected up to day 25 or until excretion of radioactivity was <1% of the administered dose. In part B, six participants received 500 mg tepotinib orally as a film-coated tablet, followed by an intravenous [¹⁴C]-tepotinib tracer dose (53–54 kBq) 4 h later. Blood samples were collected until day 14. In part A, a median of 92.5% (range, 87.1–96.9%) of the [¹⁴C]-tepotinib dose was recovered in excreta. Radioactivity was mainly excreted via feces (median, 78.7%; range, 69.4–82.5%). Urinary excretion was a minor route of elimination (median, 14.4% [8.8–17.7%]). Parent compound was the main constituent in excreta (45% [feces] and 7% [urine] of the radioactive dose). M506 was the only major metabolite. In part B, absolute bioavailability was 72% (range, 62–81%) after oral administration of 500 mg tablets (the dose and formulation used in phase II trials). In conclusion, tepotinib and its metabolites are mainly excreted via feces; parent drug is the major eliminated constituent. Oral bioavailability of tepotinib is high, supporting the use of the current tablet formulation in clinical trials. Tepotinib was well tolerated in this study with healthy volunteers.

Development of novel response surface methodology-assisted micellar enhanced synchronous spectrofluorimetric method for determination of vandetanib in tablets, human plasma and urine

A highly sensitive and accurate novel response surface methodology (RSM)-assisted micellar enhanced synchronous spectrofluorimetric method was developed and validated for determination of vandetanib (VDB) in tablets, human plasma and urine. The method relied on enhancement of the fluorescence behavior of VDB in polyoxyethylene hydrogenated castor oil 40 (HCO 40) micellar medium and measuring the fluorescence using synchronous scan approach (Δλ = 50 nm). Key factors affecting VDB fluorescence were optimized by RSM using Box-Behnken design. These factors were the type and volume of surfactant and pH of the buffer medium. Under the optimum conditions, the fluorescence-concentration plot was linear over the range 40-600 ng mL^-1; the limits of detection and quantification were 5.22 and 15.82 ng mL^-1, respectively. The suggested method was successfully applied to the analysis of laboratory-prepared tablets, spiked human plasma and urine samples. The results were statistically compared with those acquired by a pre-validated liquid chromatography-tandem mass spectrometric reference method and the results obtained from both methods were found to be in good agreement.

Quantification of afatinib, alectinib, crizotinib and osimertinib in human plasma by liquid chromatography/triple-quadrupole mass spectrometry; focusing on the stability of osimertinib

The development and full validation of a sensitive and selective ultra-performance liquid chromatography/tandem mass spectrometry (UPLC-MS/MS) method are described for the simultaneous analysis of afatinib, alectinib, crizotinib and osimertinib in human lithium heparinized plasma. Afatinib-d6, crizotinib-d5 and erlotinib-d6 were used as internal standards. Given osimertinib's instability in plasma and whole blood at ambient temperature, samples should be solely processed on ice (T = 0 °C). Chromatographic separation was obtained on an Acquity UPLC ® BEH C18; 2.1 × 50 mm, 1.7 μm column, which was eluted with 0.400 mL/minute flow on a linear gradient, consisting of 10 mM ammonium formate (pH 4.5) and acetonitrile. Calibration curves for all compounds were linear for concentration ranges of 1.00 to 100 ng/mL for afatinib and 10.0 to 1000 ng/mL for alectinib, crizotinib and osimertinib, herewith validating the lower limits of quantification at 1.00 ng/mL for afatinib and 10.0 ng/mL for alectinib, crizotinib and osimertinib. Within-run and between-run precision measurements fell within 10.2%, with accuracy ranging from 89.2 to 110%.

Effects of food and grapefruit juice on single-dose pharmacokinetics of blonanserin in healthy Chinese subjects

PURPOSE

The purpose of this study was to investigate the potential effects of a meal and grapefruit juice on the pharmacokinetics of blonanserin and its metabolite N-desethyl blonanserin in healthy Chinese volunteers.

METHODS

This was a single-centre, open-label, fixed-sequence study, where 12 healthy Chinese volunteers received a single dose of 8 mg blonanserin after an overnight fast in period 1 (reference), a high-fat meal during period 2 and with co-administration of 250 mL of grapefruit juice in period 3. The washout period was 7 days. Series of plasma samples were collected after each dose to determine concentrations of blonanserin and its metabolite N-desethyl blonanserin using liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were estimated by non-compartmental analysis and compared between periods by standard average bioequivalence ANOVA. Adverse events were monitored throughout the study.

RESULTS

All subjects completed the study. High-fat meals significantly increased blonanserin exposure (AUC_t) 2.58-fold (90% CI 2.21, 3.02), relative to the reference period. Co-administration of blonanserin with grapefruit juice remarkably prolonged elimination half-life of blonanserin (from 9.7 to 21.4 h) and significantly increased exposures to blonanserin and N-desethyl blonanserin by 5.82-fold (90% CI 4.57, 7.42) and 1.81-fold (90% CI 1.65, 1.98), respectively.

CONCLUSIONS

These results suggested that blonanserin was largely metabolised in the intestinal tract before becoming systemically available, and both food and grapefruit juice enhanced exposure to blonanserin and N-desethyl blonanserin. Grapefruit juice increased bioavailability and may have reduced systemic clearance of blonanserin. Further intestinal CYP3A4 and hepatic CYP3A4 might be postulated to explain the delayed elimination of blonanserin. Dose adjustment of blonanserin is needed on the basis of co-intake of known strong CYP3A4 inhibitor. Patients taking high-dose blonanserin also need to be cautious about the ingestion of grapefruit juice.

Relationship between blood remifentanil concentration and stress hormone levels during pneumoperitoneum in patients undergoing laparoscopic cholecystectomy

OBJECTIVE

The effect of remifentanil on stress response to surgery is unclear. However, there are not clinical studies investigating the relationship between blood remifentanil concentrations and stress hormones. Therefore, the aim of the present study was to assess the association between blood remifentanil concentrations measured after pneumoperitoneum and cortisol (CORT) or prolactin (PRL) ratio (intraoperative/preoperative value), in patients undergoing laparoscopic cholecystectomy.

PATIENTS AND METHODS

Patients did not receive any pre-anesthetic medication. Anesthesia induction was standardized. Anesthesia maintenance was performed with inhaled sevoflurane at age-adjusted 1.0 minimum alveolar concentration and intravenous remifentanil at infusion rate ranging from 0.1 to 0.4 mcg/kg/min. Blood samples were withdrawn before anesthesia induction and 5 min after achieving a pneumoperitoneum pressure of 12 mmHg. Correlation analyses were performed to evaluate the relationship between measured blood remifentanil concentrations, CORT or PRL ratio (intraoperative/preoperative value) and remifentanil dose delivered by the pump.

RESULTS

A significant inverse correlation was found between CORT ratio and measured blood remifentanil concentration (p=0.03) or planned remifentanil dose (p=0.04). No correlations were found between blood remifentanil concentration and PRL ratio (p=0.83).

CONCLUSIONS

Our data suggest that the CORT response to surgical stress is more efficiently counteracted by increased blood remifentanil concentration.

Alectinib versus crizotinib in patients with ALK-positive non-small-cell lung cancer (J-ALEX): an open-label, randomised phase 3 trial

BACKGROUND

Alectinib, a potent, highly selective, CNS-active inhibitor of anaplastic lymphoma kinase (ALK), showed promising efficacy and tolerability in the single-arm phase 1/2 AF-001JP trial in Japanese patients with ALK-positive non-small-cell lung cancer. Given those promising results, we did a phase 3 trial to directly compare the efficacy and safety of alectinib and crizotinib.

METHODS

J-ALEX was a randomised, open-label, phase 3 trial that recruited ALK inhibitor-naive Japanese patients with ALK-positive non-small-cell lung cancer, who were chemotherapy-naive or had received one previous chemotherapy regimen, from 41 study sites in Japan. Patients were randomly assigned (1:1) via an interactive web response system using a permuted-block method stratified by Eastern Cooperative Oncology Group performance status, treatment line, and disease stage to receive oral alectinib 300 mg twice daily or crizotinib 250 mg twice daily until progressive disease, unacceptable toxicity, death, or withdrawal. The primary endpoint was progression-free survival assessed by an independent review facility. The efficacy analysis was done in the intention-to-treat population, and safety analyses were done in all patients who received at least one dose of the study drug. The study is ongoing and patient recruitment is closed. This study is registered with the Japan Pharmaceutical Information Center (number JapicCTI-132316).

FINDINGS

Between Nov 18, 2013, and Aug 4, 2015, 207 patients were recruited and assigned to the alectinib (n=103) or crizotinib (n=104) groups. At data cutoff for the second interim analysis, 24 patients in the alectinib group had discontinued treatment compared with 61 in the crizotinib group, mostly due to lack of efficacy or adverse events. At the second interim analysis (data cutoff date Dec 3, 2015), an independent data monitoring committee determined that the primary endpoint of the study had been met (hazard ratio 0·34 [99·7% CI 0·17-0·71], stratified log-rank p<0·0001) and recommended an immediate release of the data. Median progression-free survival had not yet been reached with alectinib (95% CI 20·3-not estimated) and was 10·2 months (8·2-12·0) with crizotinib. Grade 3 or 4 adverse events occurred at a greater frequency with crizotinib (54 [52%] of 104) than alectinib (27 [26%] of 103). Dose interruptions due to adverse events were also more prevalent with crizotinib (77 [74%] of 104) than with alectinib (30 [29%] of 103), and more patients receiving crizotinib (21 [20%]) than alectinib (nine [9%]) discontinued the study drug because of an adverse event. No adverse events with a fatal outcome occurred in either treatment group.

INTERPRETATION

These results provide the first head-to-head comparison of alectinib and crizotinib and have the potential to change the standard of care for the first-line treatment of ALK-positive non-small-cell lung cancer. The dose of alectinib (300 mg twice daily) used in this study is lower than the approved dose in countries other than Japan; however, this limitation is being addressed in the ongoing ALEX study.

FUNDING

Chugai Pharmaceutical Co, Ltd.

Application of Physiologically-Based Pharmacokinetic Modeling for the Prediction of Tofacitinib Exposure in Japanese

Tofacitinib (3-[(3R,4R)-4-methyl-3-[methyl(7H-pyrrolo[2,3-d]pyrimidin-4-yl)amino]piperidin-1-yl]-3 -oxopropanenitrile) is an oral Janus kinase inhibitor that is approved in countries including Japan and the United States for the treatment of rheumatoid arthritis, and is being developed across the globe for the treatment of inflammatory diseases. In the present study, a physiologically-based pharmacokinetic model was applied to compare the pharmacokinetics of tofacitinib in Japanese and Caucasians to assess the potential impact of ethnicity on the dosing regimen in the two populations. Simulated plasma concentration profiles and pharmacokinetic parameters, i.e. maximum concentration and area under plasma concentration-time curve, in Japanese and Caucasian populations after single or multiple doses of 1 to 30 mg tofacitinib were in agreement with clinically observed data. The similarity in simulated exposure between Japanese and Caucasian populations supports the currently approved dosing regimen in Japan and the United States, where there is no recommendation for dose adjustment according to race. Simulated results for single (1 to 100 mg) or multiple doses (5 mg twice daily) of tofacitinib in extensive and poor metabolizers of CYP2C19, an enzyme which has been shown to contribute in part to tofacitinib elimination and is known to exhibit higher frequency in Japanese compared to Caucasians, were also in support of no recommendation for dose adjustment in CYP2C19 poor metabolizers. This study demonstrated a successful application of physiologically-based pharmacokinetic modeling in evaluating ethnic sensitivity in pharmacokinetics at early stages of development, presenting its potential value as an efficient and scientific method for optimal dose setting in the Japanese population.

Pharmacokinetics of LBPT and its primary metabolites, as well as tolerability in the first-in-human study

BACKGROUND

LBPT is a novel platelet-activating factor (PAF) receptor antagonist that is developed for the treatment of rheumatoid arthritis. The purpose of this first-in-human study was to evaluate the tolerability and safety of LBPT, to investigate the pharmacokinetics of LBPT and its primary metabolites, as well as to assess the food effect on the pharmacokinetics in healthy Chinese subjects.

MATERIALS AND METHODS

LBPT was evaluated in 2 clinical studies. The first study was a double blind, placebo-controlled and ascending dose study. Eighty-five healthy Chinese subjects received oral dose of 2, 4, 6, 8, 15, 25, 50, 75, 100, 125, 150, 225, 300, 400 or 500mg of LBPT or placebo. The pharmacokinetics of LBPT and its primary metabolites were investigated in the last 4 dose cohorts. The tolerability was evaluated by monitoring adverse events (AEs), physical examinations, 12-lead electrocardiograms (ECG) and laboratory tests. The second study was an open-label, 2-period cross-over study with a washout interval of 3days. Twelve subjects received 300mg of LBPT after an overnight fasting or a high-fat breakfast. The pharmacokinetics of LBPT in subjects under fasted and fed conditions were compared.

RESULTS

LBPT was well tolerated up to 500mg-dose and there were no serious AEs in the study. The incidence and severity of AEs were closely related to dose. Following single oral administration of 225, 300, 400 and 500mg of LBPT, plasma C_max was reached at 0.5h and the mean t_1/2 was 0.6-1.6h. Plasma exposure increased with dose escalation but proportionality was not observed. LBPT was eliminated in forms of metabolites and 20-40% of the given dose was recovered in urine. Compared with the subjects under fasting conditions, AUC and C_max were lower and t_max was delayed in the fed subjects.

CONCLUSION

LBPT was well tolerated in healthy subjects with a pattern of dose-related AEs. The pharmacokinetics was non-linear and was impacted by food intake.

Effect of chongmyungtang, a traditional Korean polyherbal formula, on the Pharmacokinetic profiles of donepezil in rats

Chongmyungtang (CMT) is a famous Korean herbal medicine for improving learning and memory, which has been reported to have anti-cholinergic and neuroprotective effects. Therefore, drug-drug interactions were examined between CMT and donepezil as a first screening of combination therapy for cognitive deficits. Rats received oral co-administration of donepezil with distilled water as a control or donepezil with CMT as a combination. The distilled water or CMT was co-administered at intervals within 5min after donepezil or 1.5h intervals. The plasma samples were analyzed for donepezil concentration and its pharmacokinetic parameters of T_max, C_max, AUC, t_1/2 and MRT_inf. In the single co-administration at intervals within 5min, donepezil was detected lower in the combination than control at 0.5h and 2h post-treatment (P<0.05). In addition, the combination showed significant increases in MRT_inf compared to the control (P<0.05). This suggests drug-drug interactions between donepezil and CMT in the co-administration within 5 min. However, no meaningful differences were found in the pharmacokinetic profiles of donepezil by single dosing with CMT at 1.5h intervals and even by the repeated dosing for a week at 1.5h intervals potential combination therapy of donepezil with CMT.

Altered pharmacokinetics and pharmacodynamics of repaglinide by ritonavir in rats with healthy, diabetic and impaired hepatic function

BACKGROUND

Ritonavir is an antiretroviral drug to treat HIV AIDS and inhibits cytochrome P450 3A4. To treat diabetes mellitus in HIV, repaglinide is coadministered with ritonavir in the clinic. Multiple cytochrome P450 (CYP) isoforms are involved in the metabolism of repaglinide like CYP2C8 and CYP 3A4. In order to predict and understand drug-drug interactions of these two drugs, the pharmacokinetics and pharmacodynamics (PK/PD) of repaglinide and ritonavir were studied in normal, diabetic and hepatic impaired rats. The purpose of the study was to assess the influence of ritonavir on the PK/PD of repaglinide in rats with normal, diabetic and impaired hepatic function.

METHODS

Human oral therapeutic doses of ritonavir and repaglinide were extrapolated to rats based on the body surface area. Ritonavir (20 mg/kg, p.o.), alone and along with repaglinide (0.5 mg/kg, p.o.), was given to normal, diabetic and hepatic impaired rats, and the PK/PD were studied.

RESULTS

The pharmacokinetic parameters like peak plasma concentration (Cmax), area under the plasma concentration time profile (AUC) and elimination half life of repaglinide were significantly (p<0.0001) increased when compared to repaglinide control rats. The repaglinide clearance (CL) was significantly (p<0.0001) decreased in the presence of ritonavir treatment. In the presence of ritonavir, repaglinide hypoglycemic activity was increased significantly (p<0.0005) when compared with repaglinide control group.

CONCLUSIONS

The significant difference in the PK/PD changes have been due to the increased plasma exposure and decreased total body clearance of repaglinide, which may be due to the inhibition of the CYP P450 metabolic system and organic anion-transporting polypeptide transporter by ritonavir.

Development of easy-to-use reverse-phase liquid chromatographic methods for determining PRE-084, RC-33 and RC-34 in biological matrices. The first step for in vivo analysis of sigma1 receptor agonists

Over the years there has been a growing interest in the therapeutic potential for central nervous system pathologies of sigma receptor modulators. The widely studied PRE-084 and our compounds RC-33 and RC-34 are very potent and selective sigma 1 receptor agonists that could represent promising drug candidates for Amyotrophic Lateral Sclerosis (ALS). Herein, we develop and validate robust and easy-to-use reverse-phase chromatographic methods suitable for detecting and quantifying PRE-084, RC-33 and RC-34 in mouse blood, brain and spinal cord. An HPLC/UV/ESI-MS system was employed for analyzing PRE-084 and an HPLC/UV-PDA system for determining RC-33 and RC-34. Chromatographic separations were achieved on Waters Symmetry RP18 column (150 × 3.9 mm, 5 µm), eluting with water and acetonitrile (both containing 0.1% formic acid) in gradient conditions. The recovery of PRE-084, RC-33 and RC-34 was >95% in all the considered matrices. Their limits of quantitation and detection were also determined. Validation proved the methods be suitable for separating tested compounds from endogenous interferences, being characterized by good sensitivity, linearity, precision and accuracy. A preliminary central nervous system distribution study showed a high distribution of RC-33 in brain and spinal cord, with concentration values well above the determined limit of quantitation. The proposed methods will be used in future preclinical investigations.

Altered mental status and end organ damage associated with the use of gacyclidine: a case series

INTRODUCTION

Over the past decade, there has been a sharp increase in the number of newly identified synthetic drugs. These new drugs are often derivatives of previously abused substances but have unpredictable toxicity. One of these drugs is gacyclidine, a derivative of phencyclidine (PCP). Gacyclidine has been studied as a neuroprotective agent in trauma and as a therapy of soman toxicity. There are no previous reports of its use as a drug of abuse.

CASE REPORTS

During a two-month period in the summer of 2013, a series of patients with severe agitation and end-organ injury were identified in an urban academic Emergency Department (ED). A urine drug of abuse screen was performed on all patients, and serum samples were sent for comprehensive toxicology analysis. A total of five patients were identified as having agitation, rhabdomyolysis, and elevated troponin (Table 1). Three of the five patients reported use of methamphetamine, and all five patients had urine drug screens positive for amphetamine. Comprehensive serum analysis identified methamphetamine in three cases, cocaine metabolites in one case, and a potential untargeted match for gacyclidine in all five cases. No other drugs of abuse were identified.

DISCUSSION

This is the first series of cases describing possible gacyclidine intoxication. The possible source of the gacyclidine is unknown but it may have been an adulterant in methamphetamine as all patients who were questioned reported methamphetamine use. These cases highlight the importance of screening for new drugs of abuse when patients present with atypical or severe symptoms. Gacyclidine has the potential to become a drug of abuse both by itself and in conjunction with other agents and toxicity from gacyclidine can be severe. It is the role of the medical toxicology field to identify new agents such as gacyclidine early and to attempt to educate the community on the dangers of these new drugs of abuse.

No correlation between remifentanil blood, cerebrospinal fluid and cerebral extracellular fluid levels and TCI prediction: a pharmacokinetic study

BACKGROUND

The aims of this paper were to elucidate the difference in concentration among remifentanil blood, cerebrospinal fluid and cerebral extracellular fluid levels, and to verify the presumable existence of a correlation between arterial and cerebral remifentanil. We used brain microdialysis to shed light on this aspect of the pharmacokinetic and to correlate these findings with Minto's model.

METHODS

The study population was formed by 9 patients scheduled for elective intracranial surgery for cerebral supratentorial neoplasia. All patients received general anaesthetic; 100 microliters of dialysate were collected. Furthermore, arterial blood samples of 3 mL each were collected, respectively one at the beginning and one at the end of the sampling period. We determined the concentration of remifentanil and its main metabolite, remifentanil acid, in the blood and in the brain. The predictive performance of the Minto pharmacokinetic parameter set was evaluated by examining the performance error.

RESULTS

The mean Performance Error was -45.13% (min -21.80, max -88.75) for the first series of arterial samples, -38.29% (min -6.57, max -79.17) for the second one and 67.73% (min 7, max -93.12) for the extra cellular fluid sample. The concentration of remifentanil set pumps was correlated with blood concentration for both series of samples. Neither the set concentration, nor the arterial samples were correlated with extra cellular fluid values.

CONCLUSION

There was a wide interindividual variability with regard both to blood and cerebral remifentanil concentration. Moreover, the ratio between arterial blood and cerebral remifentanil was not consistent among our patients in spite of a stable infusion rate of remifentanil; at the end we found a trend of over prediction in the ratio between the various compartments examined.

Acute toxicity associated with the recreational use of the novel dissociative psychoactive substance methoxphenidine

INTRODUCTION

Methoxphenidine is a novel dissociative designer drug of the diarylethylamine class which shares structural features with phencyclidine (PCP), and is not at present subject to restrictive regulations. There is very limited information about the acute toxicity profile of methoxphenidine and the only sources are anonymous internet sites and a 1989 patent of the Searle Company. We report a case of analytically confirmed oral methoxphenidine toxicity.

CASE DETAILS

A 53-year-old man was found on the street in a somnolent and confusional state. Observed signs and symptoms such as tachycardia (112 bpm), hypertension (220/125 mmHg), echolalia, confusion, agitation, opisthotonus, nystagmus and amnesia were consistent with phencyclidine-induced adverse effects. Temperature (99.1°F (37.3°C)) and peripheral oxygen saturation while breathing room air (99%) were normal. Laboratory analysis revealed an increase of creatine kinase (max 865 U/L), alanine aminotransferase (72 U/L) and gamma-glutamyl transpeptidase (123 U/L). Methoxphenidine was identified by a liquid chromatography tandem mass spectrometry toxicological screening method using turbulent flow online extraction in plasma and urine samples collected on admission. The clinical course was favourable and signs and symptoms resolved with symptomatic treatment.

CONCLUSION

Based on this case report and users' web reports, and compatible with the chemical structure, methoxphenidine produces effects similar to those of the arylcyclohexylamines, as PCP.

Effect of deprotenizing agent and quantification of donepezil hydrochloride in human plasma

The effect of deprotenizing agents on recovery of donepezil hydrochloride in the development of a simple, rapid, selective and sensitive high performance liquid chromatography method for quantification of donepezil hydrochloride in human plasma was described. The deprotenizing agents were comprised of, perchloric acid, methanol, acetonitrile, chloroform and their mixtures. The chromatographic separation was carried out using reversed phase C18 column (Agilent Eclipse Plus C18) with UV detection at 268 nm. The mobile phase was comprised of 0.01 M potassium dihydrogen phosphate buffer, methanol and acetronitrile (50:30:20, v/v) adjusted to pH 2.7 with phosphoric acid (80%). A combination of perchloric acid and methanol gave a cleaner sample with a good recovery of donepezil hydrochloride of above 96%. The method showed intraday precision and accuracy in the range of 6.82% to 1.5% and 3.13% to 1.12% respectively, while interday precision and accuracy ranged between 1.06% to 4.71% and 13.01% to 6.43% respectively. The standard calibration curve was linear from 30ng/mL to 4000ng/mL, with a correlation coefficient of 0.9965±0.0034. The retention time of donepezil was 5.9 min with a run time of 7.0 min. The method can be applied to analyze large batch plasma samples in pharmacokinetic studies.

Determination of LBPT in human plasma by high performance liquid chromatography-tandem mass spectrometry

A rapid and selective HPLC-MS/MS method was developed for the determination of LBPT in human plasma. The analyte was extracted from plasma samples by solid-phase extraction and then chromatographed on a C18 analytical column. The mobile phase consisted of acetonitrile-10mM ammonium formate in 0.1% formic acid (30:70, v/v) and the flow rate was 0.2 mL/min. The detection was performed on a triple quadrupole tandem mass spectrometer in multiple reactions monitoring (MRM) mode using positive electrospray ionization (ESI). The method was validated over the concentration range of 0.2-100 ng/mL. Inter- and intra-day precision (RSD %) were less than 9.2% and the accuracy (RE %) ranged from 0 to 11.0%. The lower limit of quantitation (LLOQ) was 0.2 ng/mL. The extraction recovery was on average 75% and the detection was not affected by the matrix. The method was successfully applied to the pharmacokinetic study of LBPT in healthy Chinese subjects.

Donepezil nanosuspension intended for nose to brain targeting: In vitro and in vivo safety evaluation

The present study was to develop donepezil loaded nanosuspension for direct olfactory administration which reaches the brain and determining safety profile in Sprague-Dawley rats. Nanosuspension was prepared by ionic-crosslinking method. The developed nanosuspension was intranasally instilled into the nostrils of rats with the help of cannula (size 18/20) so that drug reached into the brain directly via nose to brain pathway. The nanosuspension had an average size of 150-200nm with a polydispersity index of 0.341. The donepezil concentration was estimated in the brain homogenate using HPLC method. The Cmax showed concentration of donepezil in brain and plasma as 7.2±0.86 and 82.8±5.42ng/ml, respectively, for drug suspension and concentration of donepezil in brain and plasma as 147.54±25.08 and 183.451±13.45ng/ml, respectively, for nanosuspension at same dose of 0.5mg/ml when administered intranasally (p<0.05). The in vivo safety evaluation studies showed that no mortality, hematological changes, body weight variations and toxicity in animals was observed, when nanosuspension was administered in different doses as compared to control group (normal saline). Donepezil loaded chitosan nanosuspension is a potential new delivery system for treatment of Alzheimer's disease, when transported via olfactory nasal pathway to the brain.

Reduced physiologically-based pharmacokinetic model of repaglinide: impact of OATP1B1 and CYP2C8 genotype and source of in vitro data on the prediction of drug-drug interaction risk

PURPOSE

To investigate the effect of OATP1B1 genotype as a covariate on repaglinide pharmacokinetics and drug-drug interaction (DDIs) risk using a reduced physiologically-based pharmacokinetic (PBPK) model.

METHODS

Twenty nine mean plasma concentration-time profiles for SLCO1B1 c.521T>C were used to estimate hepatic uptake clearance (CLuptake) in different genotype groups applying a population approach in NONMEM v.7.2.

RESULTS

Estimated repaglinide CLuptake corresponded to 217 and 113 μL/min/10(6) cells for SLCO1B1 c.521TT/TC and CC, respectively. A significant effect of OATP1B1 genotype was seen on CLuptake (48% reduction for CC relative to wild type). Sensitivity analysis highlighted the impact of CLmet and CLdiff uncertainty on the CLuptake optimization using plasma data. Propagation of this uncertainty had a marginal effect on the prediction of repaglinide OATP1B1-mediated DDI with cyclosporine; however, sensitivity of the predicted magnitude of repaglinide metabolic DDI was high. In addition, the reduced PBPK model was used to assess the effect of both CYP2C8*3 and SLCO1B1 c.521T>C on repaglinide exposure by simulations; power calculations were performed to guide prospective DDI and pharmacogenetic studies.

CONCLUSIONS

The application of reduced PBPK model for parameter optimization and limitations of this process associated with the use of plasma rather than tissue profiles are illustrated.

Regional brain imaging of vesicular acetylcholine transporter using o-[125 I]iodo-trans-decalinvesamicol as a new potential imaging probe

In this study, the regional rat brain distribution of radioiodinated o-iodo-trans-decalinvesamicol ([(125) I]OIDV) was determined in vivo to evaluate its potential as a single-photon emission computed tomography (SPECT) imaging probe for vesicular acetylcholine transporter (VAChT). Following intravenous injection, [(125) I]OIDV passed freely across the blood-brain barrier and accumulated in rat brain. The accumulation of [(125) I]OIDV in rat brain was significantly reduced by coadministration of (+/-)-vesamicol (0.125 µmol). In contrast, the coadministration of σ-receptor ligands, such as (+)-pentazocine (0.125 µmol) as a σ-1 receptor ligand and (+)-3-(3-hydroxyphenyl)-N-propylpiperidine (0.125 µmol) as a σ-1 and σ-2 receptor ligands, barely affected the accumulation of [(125) I]OIDV in rat brain. These findings in vivo were corroborated by autoradiographic analysis ex vivo. The authors found that the tracer binds with pharmacological selectivity to VAChT in rat brain and predicted that it may likewise serve in translational SPECT imaging studies of this marker in the integrity of cholinergic innervations.

[Simultaneous determination of repaglinide and pravastatin sodium in rat plasma by LC-ms/MS and its application on pharmacokinetic interactions study]

The study aims to establish a method for simultaneous determination of repaglinide and pravastatin sodium in rat plasma by LC-MS/MS and to study its pharmacokinetic interactions. Eighteen male SD rats were divided into repaglinide group, pravastatin sodium group and co-administration group. Blood samples were collected at different times after oral administration. Repaglinide and pravastatin sodium in rat plasma were separated by Agilent HC-C18 with the mobile phase consisting of methanol-0.1% formic acid (80 : 20). Detection and quantification were performed by using ESI-MS. The detector was operated in selected Reaction-monitoring mode at m/z 453.3-->230.1 for repaglinide, m/z 447.2-->327.4 for pravastatin sodium and m/z 285.1-->192.9 for diazepam as the internal standard. The calibration curve obtained was linear (R2>0.99) over the concentration range of 9.77-10,000 ng.mL-1 for repaglinide and 4.88-625 ng.mL-1 for pravastatin sodium. Compared with the single administration group, Cmax and AUC0-6h of repaglinide increased significantly (P<0.05) and tmax of pravastatin sodium prolonged (P<0.05) in co-administration group. The method is found to be simple, sensitive and accurate for determining the concentration of repaglinide and pravastatin sodium in rat plasma. There exists pharmacokinetic interactions in the co-administration of repaglinide and pravastatin sodium.

Body composition variation and impact of low skeletal muscle mass in patients with advanced medullary thyroid carcinoma treated with vandetanib: results from a placebo-controlled study

OBJECTIVES

Vandetanib was approved by the U.S. Food and Drug Association for the treatment of advanced medullary thyroid cancer (MTC). Because body weight (BW) loss is observed in MTC and because low skeletal muscle mass (SM) is associated with drug toxicity, this study assessed effects of vandetanib on SM and adipose tissue (AT) and explored the association between SM, toxicity, and serum concentration of vandetanib.

METHODS

Thirty-three patients with MTC received vandetanib (n = 23) or placebo (n = 10) in the ZETA study. Visceral AT (VAT), sc AT (SAT), and SM were assessed with computed tomography imaging by measuring tissue cross-sectional areas (square centimers per square meter). Dose-limiting toxicities (DLTs) were prospectively recorded.

RESULTS

Early at 3 months, compared with placebo group who lost BW, muscle, and SAT, patients treated with vandetanib gained 1.5 kg BW (P = 0.02), 1.3 cm(2)/m(2) (∼0.7 kg) of SM (P = 0.009), and 4.5 cm(2)/m(2) (∼0.5 kg) of SAT (P = 0.004) and gained more VAT, 5.1 cm(2)/m(2) (∼0.7 kg) (P = 0.02). Patients with DLT had lower SM index (37.2 vs 44.3 cm(2)/m(2), P = 0.003) and a higher vandetanib serum concentration (1091 vs 739 ng/mL, P = 0.03). Patients with SM index <43.1 cm(2)/m(2) had a higher probability of DLT (73% vs 14%, P = 0.004) and a higher vandetanib serum concentration (1037 vs 745 ng/mL, P = 0.04). Patients with the highest compared with the intermediate and lower levels of vandetanib serum concentration experienced more DLT, respectively, 78% vs 40% vs 20% (P = 0.04).

CONCLUSIONS

Muscle and adipose tissues are restored after only 3 months of vandetanib treatment. Patients with low muscle mass had high vandetanib serum concentration and high incidence of toxicities.

Effect of pitavastatin in different SLCO1B1 backgrounds on repaglinide pharmacokinetics and pharmacodynamics in healthy Chinese males

The effect of pitavastatin and SLCO1B1 genetic background on the pharmacokinetic and pharmacodynamic properties of repaglinide was investigated. In this randomized, placebo-controlled, crossover study, twelve healthy Chinese males were administered with pitavastatin 4 mg/d or the placebo for 5 d followed by repaglinide 4 mg given orally on d 5. Plasma repaglinide and glucose levels were measured by liquid chromatography-tandem mass spectrometry (LC/MS/MS) and the glucose oxidase method, respectively. Treatment with pitavastatin significantly increased the peak plasma concentration (Cmax) of repaglinide (P=0.003) in SLCO1B1*1b homozygotes (P=0.015) and SLCO1B1*15 carriers (P=0.031). Treatment with pitavastatin led to a marginal increase in the area under plasma concentration-time curve from 0 h to infinity (AUC0⇒∞) of repaglinide (P=0.091). There was no significant difference in pharmacokinetic parameters or hypoglycemic effects of repaglinide among SLCO1B1 genotypes in either the pitavastatin or control group. Pitavastatin increased the Cmax of the plasma concentration of repaglinide in an SLCO1B1 genotype dependent manner, but had no apparent effect on the pharmacodynamics of repaglinide in healthy volunteers. The p values for this statement were not reported.

Liquid chromatography-tandem mass spectrometry simultaneous determination of repaglinide and metformin in human plasma and its application to bioequivalence study

A simple, sensitive, selective, and reproducible liquid chromatography-tandem mass spectrometric method was developed for the simultaneous determination of repaglinide and metformin in human plasma using d5-repaglinide and d6-metformin as internal standards (ISs). After a simple protein precipitation using acetonitrile as the precipitation solvent, both analytes and ISs were separated on a Venusil ASB C 18 (150 mm x 4.6 mm, 5 microm) via gradient elution using acetonitrile--10 mmol x L(-1) ammonium acetate as the mobile phase. A chromatographic total run time of 7.5 min was achieved. Mass spectrometric detection was conducted with atmospheric pressure chemical ionization under positive-ion and multiple-reaction monitoring modes. The method was linear over the 0.2 to 60.0 ng x mL(-1) concentration range for repaglinide and over the 4 to 1 000 ng x mL(-1) range for metformin. For both analytes, the intra- and inter-accuracies and precisions were within the +/- 15% acceptable limit across all concentrations. The validated method was successfully applied to a clinical bioequivalence study.

The Effects ofGinkgo bilobaExtracts on the Pharmacokinetics and Pharmacodynamics of Donepezil

The effects of ginkgo supplementation on the steady-state plasma concentration of donepezil and the activity of cholinesterase in red blood cells and cognitive function were examined. Fourteen inpatients with Alzheimer's disease received donepezil 5 mg/day, supplemented with extracts of Ginkgo biloba 90 mg/day for 30 days. Blood samples were collected before and during ginkgo supplementation and 30 days after its discontinuation, together with an assessment of cognitive function. Plasma drug concentration was measured using high-performance liquid chromatography (HPLC), and cholinesterase in red blood cells was measured using Ellman methods. Cognitive function was evaluated using the Mini-Mental Scale Examination (MMSE). Plasma concentration of donepezil during ginkgo supplementation (mean +/- SD [95% confidence interval]; 24.4 +/- 12.6 ng/mL [17.1-31.7 ng/mL]) was not significantly different from that before ginkgo supplementation (22.7 +/- 10.3 ng/mL [16.8-28.7 ng/mL]) or that 4 weeks after its discontinuation (25.0 +/- 12.9 ng/mL [17.6-32.4 ng/mL]). There was no significant difference between cholinesterase in red blood cells before ginkgo supplementation (1.75 +/- 0.21 U [1.63-1.87 U]), during ginkgo supplementation (1.91 +/- 0.27 U [1.76-2.07 U]), and 4 weeks after its discontinuation (1.83 +/- 0.29 U [1.66-2.00 U]). Ginkgo supplementation did not alter MMSE scores throughout the study. The present study shows that ginkgo supplementation does not have major impact on the pharmacokinetics and pharmacodynamics of donepezil.

Combination of remifentanil with isoflurane or propofol: effect on the surgical stress response

BACKGROUND

Hormonal and metabolic changes following surgery are markers of the stress response to surgery. We compared hemodynamic parameters and stress response markers (glucose, cortisol, and C-reactive protein) in two groups of patients receiving either propofol or isoflurane combined with remifentanil for maintenance of anesthesia.

METHODS

We randomly assigned 100 women (ASA I-II) scheduled for diagnostic gynecologic laparoscopy to receive either isoflurane (0.8% end-tidal) or propofol (100 mg/kg/min) in addition to remifentanil (0.25 mg/ kg/min). Heart rate and mean arterial pressure were recorded after induction, 30 seconds after intubation, at four time points after incision, and 60 min after surgery. Serum C-reactive protein, cortisol and glucose concentrations were measured before induction, one hour after incision, and one hour after surgery.

RESULTS

After induction, heart rate decreased significantly from baseline in both groups, and remained below baseline until the end of surgery. Mean arterial pressure also decreased significantly in both groups. C-reactive protein levels were not significantly different between groups. In the propofol group, cortisol decreased significantly one hour after incision, but increased in the isoflurane group. Glucose increased significantly in both groups, but was significantly lower in the propofol group one hour after the incision and one hour after surgery.

CONCLUSION

An anesthetic regimen combining propofol and remifentanil attenuates two indicators of the stress response more efficiently than a isoflurane - remifentanil combination.

Characterization of cognitive deficits in a transgenic mouse model of Alzheimer's disease and effects of donepezil and memantine

Alzheimer's disease is characterized by a progressive decline in cognitive function and involves β-amyloid (Aβ) in its pathogenesis. To characterize cognitive deficits associated with Aβ accumulation, we analyzed PS1/APP mice overexpressing mutant presenilin-1 (PS1, M146L; line 6.2) and amyloid precursor protein (APP, K670N/M671L; line Tg2576), a mouse model of Alzheimer's disease with accelerated Aβ production. Age-dependent changes in working and spatial memory behaviors were investigated using Y-maze and Morris water maze tasks, respectively, in female PS1/APP mice at ages of 2, 4, 6, and 12 months. Significant deficits in working and spatial memory were observed from 4 and 6 months of age, respectively. Acute single-dose administrations of memantine, a low-to-moderate-affinity N-methyl-d-aspartate (NMDA) antagonist, showed improvements in working memory deficits at 4 months of age, whereas donepezil, an acetylcholinesterase (AChE) inhibitor, did not. However, both drugs improved spatial memory dysfunction at 6 months of age at therapeutically relevant doses. No age-related dramatic changes were observed in expression levels of several proteins relating to memory dysfunction and also the mechanisms of donepezil and memantine in the cerebral cortex of PS1/APP mice until 6 months of age. Taken together, these results suggest dysfunctions in cholinergic and/or glutamatergic transmissions may be involved in the cognitive deficits associated with Aβ toxicity. Since donepezil and memantine have been widely used for treating patients of Alzheimer's disease, these results also suggest that cognitive deficits in PS1/APP mice assessed in the Y-maze and Morris water maze tasks are a useful animal model for evaluating novel Alzheimer's disease therapeutics.

[Determination of donepezil enantiomer in human plasma by normal-HPLC-MS/MS]

OBJECTIVE

To develop and validate a normal phase HPLC-MS/MS method for the determination of donepezil enantiomer in human plasma.

METHODS

Donepezil was extracted from plasma by n-hexane:isopropanol (98:2, V/V) with lidocaine serving as an internal standard. The analytes went through the column of CHIRALCEL OJ-H (250 mm x 4.6 mm, 5 microm) with mobile phase n-hexane:n-propanol:diethylamine (60:40: 0.1, V/V/V). Donepezil enantiomer was determined by API 3000 in MRM mode.

RESULTS

The retention time of S-DN and R-DN were 15.56 min and 18.41 min, respectively. The calibration curves were linear in a range from 0.051 to 7.596 ng/mL for S-DN, and from 0.049 to 7.404 ng/mL for R-DN, respectively, both with more than 0.99 correlation coefficients. The relative recovery were 95.10%-103.70% for S-DN and 93.58%-98.00% for R-DN, respectively; the pretreatment recovery were 58.42%-61.08% for S-DN and 53.24%-61.87% for R-DN, respectively; the within-day RSD ranged from 8.35% to 11.28% for S-DN and from 6.78% to 11.58% for R-DN, respectively; the between-day RSD ranged from 5.82% to 9.02% for S-DN and from 6.87% to 9.19% for R-DN, respectively.

CONCLUSION

This normal phase HPLC-MS/MS method is simple, rapid, sensitive and accurate for the determination of donepezil enantiomer in human plasma and is suitable for pharmacokinetic studies of donepezil enantiomers.

Selective cannabinoid-1 receptor blockade benefits fatty acid and triglyceride metabolism significantly in weight-stable nonhuman primates

The goal of this study was to determine whether administration of the CB₁ cannabinoid receptor antagonist rimonabant would alter fatty acid flux in nonhuman primates. Five adult baboons (Papio Sp) aged 12.1 ± 4.7 yr (body weight: 31.9 ± 2.1 kg) underwent repeated metabolic tests to determine fatty acid and TG flux before and after 7 wk of treatment with rimonabant (15 mg/day). Animals were fed ad libitum diets, and stable isotopes were administered via diet (d₃₁-tripalmitin) and intravenously (¹³C₄-palmitate, ¹³C₁-acetate). Plasma was collected in the fed and fasted states, and blood lipids were analyzed by GC-MS. DEXA was used to assess body composition and a hyperinsulinemic euglycemic clamp used to assess insulin-mediated glucose disposal. During the study, no changes were observed in food intake, body weight, plasma, and tissue endocannabinoid concentrations or the quantity of liver-TG fatty acids originating from de novo lipogenesis (19 ± 6 vs. 16 ± 5%, for pre- and posttreatment, respectively, P = 0.39). However, waist circumference was significantly reduced 4% in the treated animals (P < 0.04), glucose disposal increased 30% (P = 0.03), and FFA turnover increased 37% (P = 0.02). The faster FFA flux was consistent with a 43% reduction in these fatty acids used for TRL-TG synthesis (40 ± 3 vs. 23 ± 4%, P = 0.02) and a twofold increase in TRL-TG turnover (1.5 ± 0.9 vs. 3.1 ± 1.4 μmol·kg⁻¹·h⁻¹, P = 0.03). These data support the potential for a strong effect of CB₁ receptor antagonism at the level of adipose tissue, resulting in improvements in fasting turnover of fatty acids at the whole body level, central adipose storage, and significant improvements in glucose homeostasis.

Presynaptic selectivity of a ligand for serotonin 1A receptors revealed by in vivo PET assays of rat brain

A novel investigational antidepressant with high affinity for the serotonin transporter and the serotonin 1A (5-HT(1A)) receptor, called Wf-516 (structural formula: (2S)-1-[4-(3,4-dichlorophenyl)piperidin-1-yl]-3-[2-(5-methyl-1,3,4-oxadiazol-2-yl)benzo[b]furan-4-yloxy]propan-2-ol monohydrochloride), has been found to exert a rapid therapeutic effect, although the mechanistic basis for this potential advantage remains undetermined. We comparatively investigated the pharmacokinetics and pharmacodynamics of Wf-516 and pindolol by positron emission tomographic (PET) and autoradiographic assays of rat brains in order to elucidate their molecular interactions with presynaptic and postsynaptic 5-HT(1A) receptors. In contrast to the full receptor occupancy by pindolol in PET measurements, the binding of Wf-516 to 5-HT(1A) receptors displayed limited capacity, with relatively high receptor occupancy being achieved in regions predominantly containing presynaptic receptors. This selectivity was further proven by PET scans of neurotoxicant-treated rats deficient in presynaptic 5-HT(1A) receptors. In addition, [(35)S]guanosine 5'-O-[γ-thio]triphosphate autoradiography indicated a partial agonistic ability of Wf-516 for 5-HT(1A) receptors. This finding has lent support to reports that diverse partial agonists for 5-HT(1A) receptors exert high sensitivity for presynaptic components. Thus, the present PET data suggest a relatively high capacity of presynaptic binding sites for partial agonists. Since our in vitro and ex vivo autoradiographies failed to illustrate these distinct features of Wf-516, in vivo PET imaging is considered to be, thus far, the sole method capable of pharmacokinetically demonstrating the unique actions of Wf-516 and similar new-generation antidepressants.

Simultaneous UFLC-ESI-MS/MS determination of piperine and piperlonguminine in rat plasma after oral administration of alkaloids from Piper longum L.: application to pharmacokinetic studies in rats

The alkaloids from Piper longum L. showed protective effects on Parkinson's disease models in our previous study and piperine and piperlonguminine were the two main constituents in the alkaloids. The present study aimed at developing a rapid, sensitive, and accurate UFLC-ESI-MS/MS method and validating it for the simultaneous determination of piperine and piperlonguminine in rat plasma using terfenadine as the internal standard. The analytes and internal standard (IS) were extracted from rat plasma using a simple protein precipitation by adding methanol/acetonitrile (1:1, v/v). A Phenomenex Gemini 3 u C18 column (20 mm × 2.00 mm, 3 μm) was used to separate the analytes and IS using a gradient mode system with a mobile phase consisting of water with 0.1% formic acid (mobile phase A) and acetonitrile with 0.1% formic acid (mobile phase B) at a flow rate of 0.4 mL/min and an operating column temperature of 25°C. The total analytical run time was 4 min. The detection was performed using the positive ion electrospray ionization (ESI) in multiple reaction monitoring (MRM) mode with transitions at m/z 286.1-201.1 for piperine, m/z 274.0-201.1 for piperlonguminine, and m/z 472.4-436.4 for the IS. The calibration curves were both linear (r>0.995) over a concentration range of 1.0 to 1000 ng/mL; the lower limit of quantification (LLOQ) was 1.0 ng/mL for both piperine and piperlonguminine. The intra-day and inter-day precisions (RSD %) were <12.1%, accuracies ranged from 86.6 to 120%, and recoveries ranged from 90.4 to 108%. The analytes were proven stable in the short-term, long-term, and after three freeze-thaw cycles. The method was successfully applied to pharmacokinetic studies of piperine and piperlonguminine in rats after oral administration of alkaloids from P. longum L.

Ultra-low flow liquid chromatography assay with ultraviolet (UV) detection for piperine quantitation in human plasma

A robust and sensitive ultra-low flow liquid chromatography (UFLC) method that can reproducibly, at reasonable cost, detect low concentrations of piperine from human plasma is necessary. Piperine in plasma was separated and quantified by a gradient method using ultraviolet detection at a maximal absorbance wavelength of 340 nm. An aliquot was injected onto a reversed-phase column Waters SymmetryShield, 2.1 x 100 mm, 3.5 microm, C(18) column, attached to a Waters absorbosphere, 4.6 x 30 mm, C(18) guard column and eluted with a mobile phase containing a mixture of acetonitrile/water/acetic acid (25:74.9:0.1, v/v/v) on line A and acetonitrile/acetic acid (99.9:0.1, v/v) on line B. The flow rate was 0.3 mL/min. The gradient method consisted of an opening condition of 20% pump B, with a linear increase to 37% pump B over 8 min, then a linear increase to 100% pump B at 11 min, 2 min at 100% pump B, and then a return to the opening condition (20% pump B) via a linear gradient over 2 min, followed by 5 min re-equilibration at opening conditions. The total run time was 20 min for each sample. All samples were processed protected from ambient light to avoid isomerization of piperine. The plasma assay was linear with R = 0.9995, with a lower limit of detection [signal-to-noise (S/N) > 5:1] of 100 pg of piperine loaded into the analytical system with acceptable accuracy and precision. Extraction recoveries of piperine from human plasma were 88% for quality control high (QCH), 93% for quality control medium (QCM), and 90% for quality control low (QCL), and the matrix effect was <12%. Piperine was quantifiable from a 50 mg oral dose given to human volunteers. A UFLC method for the rapid assay of human plasma with sensitivity to detect as low as 5 ng/mL piperine was developed. The method sensitivity equals that of liquid chromatography/tandem mass spectrometry (LC/MSMS) methods with much less cost.

A pharmacokinetic/pharmacodynamic model for a platelet activating factor antagonist based on data arising from Phase I studies

A nonlinear mixed-effects modelling approach was used to analyse pharmacokinetic and pharma-codynamic data from two Phase I studies of a platelet activating factor (PAF) antagonist under development for the treatment of seasonal allergic rhinitis. Data for single-dose (8 subjects) and multiple-dose (9 subjects) administration were available for analysis with a program based on an EM algorithm. Pharmacokinetic analyses of plasma drug concentrations were performed using a biexponential model with first-order absorption. PAF response data were modelled with a hyperbolic Emax model. The drug showed nonlinear pharmacokinetics, with the clearance decreasing from 46.0 to 27.1 L h−1 over a dose range of 160–480 mg. There was an apparent dose dependency within the C50 (concentration producing 50% of the maximum effect) but at higher doses most of the data was above the estimated C50 and when the data was analysed simultaneously a value of 17.57 ng mL−1 was obtained for C50, with considerable intersubject variability (103%). Consistent results were obtained from the two studies and the population and individual pharmacodynamic parameter estimates from the analyses provided predicted responses that were in good agreement with the observed data. The results were used to simulate a 320-mg twice-daily dosing regimen.

Inhibition of neointimal hyperplasia by a specific thrombin inhibitor

OBJECTIVE

Restenosis secondary to neointimal hyperplasia remains the major limiting factor after vascular interventions. Thrombin generated in high concentrations at the site of vascular injury plays a central role in thrombosis and hemostasis. Thrombin has also been implicated as a mitogen for smooth muscle cell proliferation that contributes to restenosis. This study was designed to determine the effects of a specific thrombin inhibitor on neointimal hyperplasia after balloon injury in a rat carotid artery model.

DESIGN

A total of 47 male Sprague-Dawley rats were divided into five groups. All groups underwent balloon injury of the left carotid artery. A specific thrombin inhibitor, inogatran, was given in four different regimens: low and high dose injections, short-term infusion for 3 h, and long-term infusion for 1 week. After 2 weeks the animals were killed and the carotid neointima/media area ratio and the luminal narrowing were calculated.

RESULTS

All treatments significantly reduced the neointimal hyperplasia. Inogatran given as a long-term infusion for 1 week had the lowest neointima/media ratio compared with the other groups. The percentage of lumen narrowing was also significantly lower in all treatment groups compared with the control group.

CONCLUSION

A specific direct thrombin inhibitor, inogatran, reduces neointimal hyperplasia after arterial injury in rats. A more prolonged administration of the thrombin inhibitor gave a further reduction of the neointimal hyperplasia. It seems that inhibition of thrombin activity is not only important early after injury, but also later. This could have clinical implications in the treatment of restenosis and needs to be further evaluated.

Repaglinide-loaded long-circulating biodegradable nanoparticles: rational approach for the management of type 2 diabetes mellitus

BACKGROUND

Repaglinide (RPG) is an oral hypoglycemic agent with excellent bioavailability (90-98%) and a short plasma half-life (2-6 h). A full dose of RPG is required before each meal; hence, therapy may become inconvenient. Thus, the aim of the present study was to design a novel delivery system to maintain peak plasma levels of RPG for the long-term management of diabetes mellitus.

METHODS

Two nanoparticle formulations were prepared by combining RPG with poly (lactic-co-glycolic) acid alone or as a copolymer with methoxypolyethylene glycol (RPGNP1 and RPGNP2, respectively); both formulations were subjected to in vitro and in vivo characterization. In vivo characterization was performed in a streptozotocin (STZ)-induced diabetic male albino rats.

RESULTS

The mean particle size of the RPGNP1 and RPGNP2 formulations was 387.8 ± 11.9 and 310.2 ± 12.4 nm, respectively, with a zeta potential of -27.4 ± 0.7 and -15.7 ± 0.5 mV, respectively. The entrapment efficiency and drug content of RPGNP1 (58.7 ± 1.3% and 27.4 ± 2.3%, respectively) was better than that of RPGNP2 (45.8 ± 1.2% and 24.3 ± 1.1%, respectively). Blood glucose levels of RPGNP1- and RPGNP2-treated STZ-diabetic rats were reduced significantly (to normal levels) compared with untreated STZ-diabetic rats (P < 0.05), but there was no difference between the two treatment groups (P > 0.05). However, whereas RPGNP1 was effective for a period of only 24 h, RPGNP2 was effective for up to 1 week.

CONCLUSIONS

The results of the present study show that RPGNP2 effectively manages type 2 diabetes mellitus for up to 1 week. Surface-modified NPs could be used to improve patient compliance with drug treatment as a result of decreased dosing frequency.

Pharmacokinetic-directed dosing of vandetanib and docetaxel in a mouse model of human squamous cell carcinoma

Docetaxel, usually administered according to maximum tolerated dose (MTD), can inhibit endothelial cell proliferation at low nanomolar concentrations. Docetaxel may exert antiangiogenic effects if dosed so plasma levels are maintained at low nanomolar concentrations over a prolonged time. We evaluated metronomic and MTD-based dosing of docetaxel with and without vandetanib, a vascular endothelial growth factor receptor-2 and epidermal growth factor receptor tyrosine kinase inhibitor with antiangiogenic and antitumor activity, in a head and neck xenograft model. A murine physiologically based pharmacokinetic model was modified to predict docetaxel distribution following i.p. administration to design dosing regimens that target prespecified plasma concentrations, for antiendothelial effects (metronomic), or exposure, to mimic 30 mg/m2 (weekly/MTD) docetaxel in humans. Animals were treated for 28 days with 1 mg/kg/d (DTX1) or 6 mg/kg q4d (DTX6) docetaxel with or without vandetanib (15 mg/kg/d p.o.) in mice bearing UMSCC2 tumor xenografts. The DTX1 dosing scheme was adjusted to treatment for 10 days followed by 9 days off due to severe gastrointestinal toxicity. All treatment groups significantly reduced tumor volume, tumor proliferation (Ki-67), and tumor endothelial cell proliferation (Ki-67/von Willebrand factor) compared with control. Addition of vandetanib to docetaxel treatment significantly enhanced tumor growth inhibition over single-agent therapy. A positive correlation of tumor endothelial cell proliferation with tumor growth rates demonstrates vandetanib and docetaxel antiangiogenic effects. Due to the morbidity observed with DTX1 treatment, it is difficult to clearly ascertain if metronomic schedules will be effective for treatment. Docetaxel with vandetanib is effective in treating UMSCC2 xenografts at concentrations relevant to exposures in humans.

Effect of nitrous oxide on desflurane MACBAR at two target-controlled concentrations of remifentanil

BACKGROUND

The aim of this prospective, randomized, double-blind study was to determine the effect of nitrous oxide on the desflurane requirement for blunting sympathetic response following surgical incision (MACBAR) when desflurane was combined with two different target-controlled concentrations of remifentanil (1 and 3 ng/mL).

METHODS

A total of 103 patients, aged 20-50 years, ASA physical status I, scheduled to undergo general anesthesia for elective abdominal surgery, were randomly allocated to receive anesthesia with desflurane alone (Group A, n = 53), or with the addition of 60% nitrous oxide (Group N, n = 50). Patients of both groups were further assigned to receive a target-controlled plasma concentration of 1 ng/mL (Group A1, n = 27; Group N1, n = 26) or 3 ng/mL remifentanil (Group A3, n = 26, Group N3, n = 24). Sympathetic responses to surgical incision were determined after a 20 min period of constant end-tidal desflurane and target-controlled remifentanil concentrations. Predetermined end-tidal desflurane concentrations and the MACBAR for each group were determined using an up-and-down sequential allocation technique.

RESULTS

A total of 98 patients completed the study. The MACBAR of desflurane was 5.2% (95% confidence interval [CI95: 4.9-5.5%]) in Group A1 and 2.7% (CI95: 2.6-2.8%) in Group N1 (P<0.001), while in Groups A3 and N3 the MACBAR of desflurane was 2.2% (CI95:2-2.4%) and 2% (CI95:1.9-2.2%), respectively (P<0.01). When considering a minimum anesthetic concentration (MAC) value with a contribution of 60% nitrous oxide (0.55 MAC) in this population, the combined MACBAR values (expressed as multiples of the MAC) were 1.9 MAC for group A1, 1 MAC for group N1, 0.8 MAC for group A3, and 0.7 MAC for group N3.

CONCLUSION

The addition of 60% nitrous oxide reduces the MACBAR of desflurane by 52% when using a remifentanil concentration of 1 ng/mL, and reduces the MACBAR by 10% when using a remifentanil concentration of 3 ng/mL.

Determination of endocannabinoid receptor antagonist SR141716 (rimonabant) in plasma by liquid chromatograph tandem mass spectrometry

SR141716 (rimonabant) is an endocannabinoid receptor antagonist. Endocannabinoids are a class of chemicals that affect neurotransmission via G-protein coupled CB1 (brain) and CB2 (peripheral tissue) receptors. Numerous animal studies have shown that SR141716 binds with the CB1 receptor in the brain, resulting in several biological consequences including reduced alcohol intake and reward as well as reduced food consumption. In this work, an analytical method based on liquid chromatography and electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS) has been developed and validated for the quantitative measurement of SR141716 in both human and rat plasma to support the investigation of this compound. A suitable internal standard (AM251) has been chosen and the experimental conditions have been optimized for the separation and detection of singly charged positive ions of SR141716 and the internal standard. A protein precipitation protocol has been developed for extraction of SR141716 and the internal standard from plasma samples. Quantitation was achieved using multiple-reaction-monitoring (MRM) mode for SR141716 (m/z 463-->m/z 363) and the internal standard (m/z 555-->m/z 455) and calibration curve over the concentration range of 5.00-1000 ng/ml was plotted using the peak-area ratio versus the concentration of SR141716 with a LOD and LLOQ of 1.09 and 3.62 ng/ml, respectively. The method developed has been used to analyze SR141716 in rat plasma samples from an animal study.

[Pharmacokinetic simulations of remifentanil]

Remifentanil has short half-lives: the values of alpha and beta decay are about 2 and 15 min, respectively. Therefore, the time for remifentanil concentration to reach its steady state concentration (Css) is shorter than those of other anesthetic drugs such as propofol and fentanyl. The Css and the time course of plasma concentration as well as effect-site concentration (Ce) during the continuous infusion of remifentanil could be helpful in our clinical practice. Css is strongly affected by weight and age with Minto's pharmacokinetic parameters of remifentanil. Css increases by a factor of 1.8 when the weight doubles, and Css in a 75-year-old is 1.5 times higher than Css in a 25-year-old. We tried to simulate the time courses of remifentanil Ce and fentanyl Ce during induction, maintenance, and emergence phases of anesthesia. Because of the short half-lives, remifentanil concentration could be well-controlled. However, remifentanil concentration does not reach the Css immediately with constant rate infusion. For example, it will take about 5 min for remifentanil effect-site concentration to decrease from Css to a half of Css. It is considered that anesthetic management with remifentanil is superior to that without it.

Parenteral vs. oral sumatriptan and naratriptan: plasma levels and efficacy in migraine. a comment

The clinical efficacy in migraine was compared for oral and subcutaneous sumatriptan and naratriptan. Doses of the two administration forms were chosen as resulting in comparable blood concentrations. Subcutaneous administrations of the drugs were superior for efficacy than the oral forms. This most likely due to a quicker rise in blood concentrations after subcutaneous injections.. In designing new therapies for migraine one should aim at a quick absorption of the drug, which will probably result in an increased efficacy.

Remifentanil versus remifentanil with paracervical block on plasma remifentanil concentrations and pulmonary function tests for transvaginal ultrasound-guided oocyte retrieval

STUDY OBJECTIVE

The aim of this study is to compare plasma remifentanil concentrations and pulmonary function tests in subjects receiving remifentanil infusion (RI) versus RI with paracervical block (PCB) during transvaginal ultrasound-guided oocyte retrieval (TUGOR).

DESIGN

Prospective, randomized.

SETTING

Assisted Conception Unit.

PATIENTS

Forty American Society ofAnesthesiologists I subjects requiring TUGOR.

INTERVENTION

After ovarian hyperstimulation, subjects were randomly allocated into two groups to receive either RI (Group RI, n = 20) or RI with PCB (Group RI + PCB, n = 20).

MEASUREMENTS

Heart rate (HR), mean arterial pressure (MAP), peripheral oxygen saturation (SpO2), end tidal carbon dioxide (ETCO2) tension, forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC), and amount of remifentanil used were collected. Plasma remifentanil concentrations were calculated with STANPUMP software.

MAIN RESULTS

HR, MAP, ETCO2, SpO2, FEV1, and FVC did not differ between the groups. Total amount of remifentanil used were 486 +/- 1.81 microg and 321 +/- 0.87 microg in groups RI and RI + PCB, respectively, (p < 0.05). In Group RI, plasma remifentanil concentrations were 4.7 ng mL(-1) and 4.2 ng mL(-1) during the second transvaginal puncture, and at the end of TUGOR, respectively, whereas corresponding plasma remifentanil concentrations were 3.1 ng mL(-1) and 2.6 ng mL(-1) in Group RI + PCB (p < 0.05).

CONCLUSION

Both anesthesia regimens provided satisfactory analgesia without affecting FEV1 and FVC, but significantly higher plasma remifentanil concentrations were calculated when only RI was used as an anesthetic technique.