Average Elimination Half-life Research Articles

The Rise of Remimazolam: A Review of Pharmacology, Clinical Efficacy, and Safety Profiles.

Anesthesiologists often use benzodiazepines (BZDs) due to their remarkable amnestic and anxiolytic capabilities. Because of this, they are perfect for use during the perioperative phase, when patients' anxiety levels are already high. Remimazolam has replaced certain commonly used intravenous (IV) anesthetics due to its excellent safety profile, rapid onset of action, and short half-life. The four classes of BZDs, 2-keto-benzodiazepines, 3-hydroxy-benzodiazepines, triazolobenzodiazepines, and 7-nitro-benzodiazepines based on chemical structure, provide various levels of drowsiness, forgetfulness, and anxiolysis. Based on their elimination half-life, short-acting BZDs typically have a half-life ranging from one to 12 hours, e.g., oxazepam; intermediate-acting BZDs have an average elimination half-life of 12 to 40 hours, e.g., alprazolam; and long-acting BZDs have an average elimination half-life of more than 40 hours, e.g., diazepam. The chloride ion channel is conformationally shifted by the benzodiazepine molecule resulting in central nervous system (CNS) inhibition and hyperpolarization. Each type of benzodiazepine has a favored use. For example, diazepam is used to treat anxiety. Midazolam is used for its anxiolytic and anterograde amnestic effects during the perioperative phase. Anxiety and epilepsy are two conditions that lorazepam effectively treats. There are now phase II and III clinical studies investigating remimazolam. It is not sensitive to alterations in its surroundings and has a brief half-life so that it may be removed rapidly, even after extensive infusion. Being a soft drug means the body easily breaks it down via metabolism, which explains many features. Remimazolam is hydrolyzed into methanol and its carboxylic acid metabolite CNS 7054 by esterase metabolism. Therefore, remimazolam has a shorter onset time and faster recovery than other BZDs. Remimazolam is metabolized independently of any particular organ. Patients with hepatic and renal problems will not see any changes in metabolism or excretion since the drug's ester moiety makes it a substrate for general tissue esterase enzymes. Like its predecessor, midazolam, it has a high potential for addiction. Some side effects that could occur during infusion include headaches and drowsiness. In clinical trials, hypotension, respiratory depression, and bradycardia were noted in participants. BZDs are helpful when used in conjunction with anesthesia. Remimazolam stands out, thanks to its unique pharmacokinetics, pharmacodynamics, safety profile, and potential medical applications. Its desirable properties make it a potential surgical premedication and sedative in the critical care unit. Anesthesiologists and other doctors could have access to more consistent and safer medication. However, additionalcomprehensive clinical trials are necessary to understand remimazolam's advantages and disadvantages.

Ruxolitinib Pharmacokinetics and Pharmacodynamics in Children with Acute and Chronic Graft-versus-Host Disease

IntroductionWe report pharmacokinetics of oral ruxolitinib in children with steroid refractory acute graft versus host disease (GVHD) (<12y) and chronic GVHD (≤18y) using our published pediatric dosing. MethodsPK sampling before and +2 hours after ruxolitinib was performed in patients with established chronic GVHD. More extensive PK analysis was evaluated in patients with newly diagnosed acute or chronic GVHD before, +0.5, 1, 2, 4 and 6 hours after ruxolitinib in patients >10kg, and before, +3 and +6 hours in children <10kg. We measured pSTAT1, 3 and 5 expression on CD4+ and CD8+ T-cells before and 2 hours after ruxolitinib as a pharmacodynamic marker of JAK/STAT inhibition. ResultsThirteen patients were prospectively enrolled (0-≤18y with existing chronic GVHD(n=8), 0-<12y with new onset steroid refractory acute GVHD(n=4) and newly diagnosed steroid-refractory chronic GVHD(n=1). A large variability in PK was seen. Mean oral clearance (CL/F) was 7.76 ± 4.09 L/h (±SD 4.4; range: 3.1-15.3). The average elimination half-life was 2.32 hours (±SD 1.0). Ruxolitinib clearance was higher in children <2 years versus >2 years (12.1 ± 3.0, vs 5.7 ± 2.8 L/h, p=0.005) and was reduced with concurrent azoles and azithromycin. We saw a variable reduction in pSTAT1/3/5 expression on T-cells at time of peak ruxolitinib absorption (2 hours after dose). ConclusionsChildren<10 kg have lower ruxolitinib exposure, possibly due to inherent increased drug clearance or variabilities in dosing methods leading to decreased drug absorption.

Pharmacokinetic evaluation of 24 representative components of Ling-Gui-Zhu-Gan decoction in acute myocardial infarction model rats via a validated ultrahigh-performance liquid chromatography-tandem mass spectrometry method.

Ling-Gui-Zhu-Gan decoction (LGZGD), one of the 100 herbal classic formulas, is clinically used to treat chronic heart failure with remarkable curative effect. However, LGZGD pharmacokinetic parameters in pathological model rats are poorly understood, in particular for special components. As physicochemical properties are specific to each representative component, no standard sample preparation is available for absolute quantification of representative components of LGZGD in rat plasma. A specific, sensitive and high-throughput ultrahigh-performance liquid chromatography-tandem mass spectrometry (UHPLC/MS/MS) method capturing 24 representative components was developed and applied to evaluate the pharmacokinetic parameters of LGZGD in acute myocardial infarction (AMI) rat plasma after intragastric administration (2.4, 4.8 and 9.6g/kg). Precipitation and extraction were selected and optimized for plasma preparation, and isopropanol precipitation could offer higher recovery and broader coverage. It was expected that AMI could cause less absorption and slower elimination of most of active components of LGZGD. Most of newly reported special components absorbed quickly and eliminated slowly. The average elimination half-life of the 24 representative components was 10.09 h, which is consistent with the dosage of LGZGD (twice daily). The specificity, linearity, precision and accuracy, recovery, matrix effect and stability were validated according to Food and Drug Administration guidance. The validation results demonstrated that the method could be applied to evaluate the pharmacokinetic parameters of LGZGD in AMI rats. The pharmacokinetic parameters showed substantial improvement in quality research of LGZGD, thereby laying the groundwork for preclinical and clinical trials in chronic heart failure clinical efficacy.

Pharmacokinetics of Marbofloxacin Following Oral Administration in Lactic Acid Pretreated Broiler Chickens

Background: It is hypothesized that feeding lactic acid as a feed additive has the potential to alter the pharmacokinetics of many antimicrobial drugs being used for the treatment of infectious disease in general and marbofloxacin in particular; leading to either increased or decreased efficiency. Hence, the present study was planned to explore the effects of lactic acid pre-treatment on the pharmacokinetics of marbofloxacin after oral administration in broiler chickens. Methods: The pharmacokinetics of marbofloxacin was investigated following single dose oral administration (5 mg/kg) in lactic acid pre-treated (8 gm/l each, oral, 10 days) broiler chickens. The plasma concentration of marbofloxacin was determined by ultra-high-performance liquid chromatography to workout pharmacokinetic profile of marbofloxacin using non compartment model. Result: The AUC (area under curve) of marbofloxacin declined from 14.70 ìg·h/mL to 6.16 ìg·h/mL after pre-treatment of lactic acid. Similarly, the average values of maximum plasma concentration (Cmax) of drug decreased from 2.11 ìg/mL to 0.98 ìg/mL and mean body clearance (ClB) increased from 0.47 L/h/kg to 1.03 L/h/kg. The average elimination half-lives (t½â) of marbofloxacin before and after pre-treatment with lactic acid were 4.89 h and 2.81 h, respectively. Furthermore, the investigation revealed alteration of pharmacokinetic parameters evident in lactic acid pre-treated broiler chickens (as compared to non pre-treated birds) requiring adjustment of dosage regimens.

Determination of pharmacokinetics and tissue distribution of a novel lutetium-labeled PSMA-targeted ligand, 177Lu-DOTA-PSMA-GUL, in rats by using LC–MS/MS

Prostate specific membrane antigen (PSMA) is known to be overexpressed in prostate cancer cells, providing as a diagnostic and therapeutic target for prostate cancer. A lutetium-labeled PSMA targeted ligand, 177Lu-DOTA-PSMA-GUL is a novel radiopharmaceutical, which has been developed for the treatment of prostate cancer. While the GUL domain of 177Lu-DOTA-PSMA-GUL binds to the antigen, the beta-emitting radioisotope, 177Lu-labeled DOTA, interacts with prostate cancer cells. However, the in vivo pharmacokinetics of intact 177Lu-DOTA-PSMA-GUL has never been characterized. This study aimed to evaluate the pharmacokinetics and tissue distribution of the radiopharmaceutical in rats by using its stable isotope-labeled analog, 175Lu-DOTA-PSMA-GUL. A sensitive liquid chromatography-tandem mass spectrometry (LC–MS/MS) analysis of 175Lu-DOTA-PSMA-GUL was developed and validated. Following intravenous injection, the plasma concentration–time profiles of 175Lu-DOTA-PSMA-GUL showed a multi-exponential decline with the average elimination half-life of 0.30 to 0.33 h. Systemic exposure increased with the dose and renal excretion is the major elimination route. Tissue distribution of 175Lu-DOTA-PSMA-GUL was most substantial in kidneys, followed by the prostate. The developed LC–MS/MS assay and the in vivo pharmacokinetic data of 175Lu-DOTA-PSMA-GUL would provide helpful information for further clinical studies to be developed as a novel therapeutic agent for prostate cancer.

Preclinical Pharmacokinetics and Bioavailability of Oxypeucedanin in Rats after Single Intravenous and Oral Administration.

Oxypeucedanin, a furanocoumarin extracted from many traditional Chinese herbal medicines, has a variety of pharmacological effects. However, the independent pharmacokinetic characteristics and bioavailability of this compound remains elusive. In this study, a rapid, sensitive, and selective method using ultra-high performance liquid chromatography–tandem mass spectrometry (UPLC/MS/MS) was developed for evaluating the intravenous and oral pharmacokinetics of oxypeucedanin. After intravenous administration of oxypeucedanin (2.5, 5, and 10 mg/kg), and intragastric administration of oxypeucedanin (20 mg/kg), blood samples were collected periodically from the tail vein. The plasma concentration-time curves were plotted, and the pharmacokinetic parameters were calculated using a non-compartmental model analysis. After intravenous administration of oxypeucedanin (single dosing at 2.5, 5, and 10 mg/kg) to rats, the pharmacokinetics fit the linear kinetics characteristics, which showed that some parameters including average elimination half-life (T1/2Z of 0.61~0.66 h), mean residence time (MRT of 0.62~0.80 h), apparent volume of distribution (VZ of 4.98~7.50 L/kg), and systemic clearance (CLZ of 5.64~8.55 L/kg/h) are dose-independent and the area under concentration-time curve (AUC) increased in a dose-proportional manner. Single oral administration of oxypeucedanin (20 mg/kg) showed poor and slow absorption with the mean time to reach the peak concentration (Tmax) of 3.38 h, MRT of 5.86 h, T1/2Z of 2.94 h, and a mean absolute bioavailability of 10.26% in rats. These results provide critical information for a better understanding of the pharmacological effect of oxypeucedanin, which will facilitate its research and development.

Pharmacokinetics of Nafamostat, a Potent Serine Protease Inhibitor, by a Novel LC-MS/MS Analysis.

Nafamostat, a synthetic serine protease inhibitor, has been used for the treatment of inflammatory diseases such as pancreatitis. Recently, an increasing number of studies have shown the promising antiviral effects of nafamostat for the treatment of coronavirus disease-19 (COVID-19). This study aimed to develop a novel liquid chromatography–tandem mass spectrometry (LC-MS/MS) analysis and to characterize the pharmacokinetics of nafamostat in rats. Nafamostat in the rat plasma was extracted by solid phase extraction, and 13C6-nafamostat was used as an internal standard. The quantification limit of nafamostat in the rat plasma was 0.5 ng/mL. The LC-MS/MS method was fully validated and applied to characterize the pharmacokinetics of nafamostat in rats. Following intravenous injection (2 mg/kg), nafamostat in the plasma showed a multiexponential decline with an average elimination half-life (t1/2) of 1.39 h. Following oral administration of nafamostat solutions (20 mg/kg) in 10% dimethyl sulfoxide (DMSO) and in 10% DMSO with 10% Tween 80, nafamostat was rapidly absorbed, and the average oral bioavailability was 0.95% and 1.59%, respectively. The LC-MS/MS method and the pharmacokinetic information of nafamostat could be helpful for the further preclinical and clinical studies of nafamostat.

Pharmacokinetics, Metabolite Measurement, and Biomarker Identification of Dermal Exposure to Permethrin Using Accelerator Mass Spectrometry.

Impregnating military uniforms and outdoor clothing with the insecticide permethrin is an approach to reduce exposure to insect borne diseases and to repel pests and disease vectors such as mosquitos and sandflies, but the practice exposes wearers to prolonged dermal exposure to the pesticide. Key metabolite(s) from a low dose dermal exposure of permethrin were identified using accelerator mass spectrometry. Metabolite standards were synthesized and a high performance liquide chromatography (HPLC) elution protocol to separate individual metabolites in urine was developed. Six human subjects were exposed dermally on the forearm to 25 mg of permethrin containing 1.0 µCi of 14C for 8 h. Blood, saliva and urine samples were taken for 7d. Absorption/elimination rates and metabolite concentrations varied by individual. Average absorption was 0.2% of the dose. Serum concentrations rose until 12-24 h postdermal application then rapidly declined reaching predose levels by 72 h. Maximum saliva excretion occurred 6 h postdosing. The maximum urinary excretion rate occurred during 12-24 h; average elimination half-life was 56 h. 3-Phenoxybenzyl alcohol glucuronide was the most abundant metabolite identified when analyzing elution fractions, but most of the radioactivity was in still more polar fractions suggesting extensive degradative metabolism and for which there were no standards. Analyses of archived urine samples with the ultra performance liquid chromatography-accelerator mass spectrometry-mass spectrometry (UPLC-AMS-MS) system isolated a distinct polar metabolite but it was much diminished from the previous analyses a decade earlier.

Humanized anti-DEspR monoclonal antibody to improve overall survival in xenograft pancreatic peritoneal carcinomatosis nude rat model.

e16262 Background: Pancreatic adenocarcinoma (PDAC) with peritoneal carcinomatosis (PPC) has the worst median overall survival (mOS) among all PDAC metastasis. Novel therapeutic approaches are needed for PPC. The Dual Endothelin-1/VEGF-signal-peptide Receptor (DEspR) is a cell surface receptor which regulates PDAC tumor cell and cancer stem-like cell (CSC) anoikis resistance, tumorigenicity, and tumoral angiogenesis. To translate these findings into a novel anti-cancer therapy, we evaluated the efficacy, empirical safety, pharmacokinetics, and pharmacodynamics of a recombinant, humanized, anti-DEspR hinge-stabilized IgG4S228P monoclonal antibody, hu-6g8, in a PPC xenograft tumor nude rat model. Methods: We used a Panc1 CSC-derived xenograft tumor model of PPC developed via intraperitoneal injection of two million Panc1 CSCs functionally isolated for anoikis resistance. Isolated CSCs had variable DEspR expression, thus modeling CSC-heterogeneity. For efficacy studies, PPC-rats were randomized to receive a single intravenous injection of either 3mg/kg or 15mg/kg hu-6g8, 100mg/kg gemcitabine, or saline, given 3 weeks after CSC injection with palpable PPC tumors. Blood samples were collected to monitor for hematological adverse events (AEs) and vital organs were collected to evaluate for hu-6g8-induced apoptosis. Pharmacokinetics was assessed in a separate study cohort by sequential blood draws after rats received a single dose of 3 mg/kg or 15 mg/kg hu-6g8. In a 3rd cohort, pharmacodynamics were assessed by vital organ collection and immunohistochemistry after rats received either a single-iv injection of 3mg/kg hu-6g8 or IgG4 isotype control. Results: Single dose 15 mg/kg hu-6g8 treatment significantly improved median overall survival (189 days, n = 0.0007) with 3 mg/kg hu-6g8 being comparable to 100 mg/kg gemcitabine (92 vs 115 days, n = 0.62). No hematological AEs were observed in hu-6g8 treated rats, and there was no evidence of increased apoptosis by hu-6g8 in normal tissues by immunohistochemistry of activated Caspase-3. Hu-6g8 demonstrated an average elimination half-life of 46.1 hrs in a two-compartment model. Biodistribution of the antibody showed predominant uptake, albeit heterogenous, and induction of activated caspase 3+ apoptosis in the peritoneal tumors by 24-hours with minimal off-target binding. Conclusions: Treatment with monoclonal hu-6g8 significantly improved survival in a model of PCC with excellent tumor specificity and minimal off-target effect.

Disposition of Oral Cannabidiol-Rich Cannabis Extracts in Children with Epilepsy.

Despite limited evidence, cannabidiol-rich cannabis extracts have been popularly used in pediatrics. With increased use, it is critical to determine basic pharmacokinetic parameters of cannabidiol in these extracts in the pediatric population. The objective of this study was to determine the disposition of oral cannabidiol cannabis extracts and drug interactions in children with pediatric epilepsy. We conducted a prospective observational study evaluating the disposition of oral cannabidiol in children (< 18 years of age) receiving cannabidiol extracts for epilepsy. Subjects underwent serial blood draws after oral cannabidiol administration. Cannabidiol and metabolites, along with anticonvulsant concentrations were determined. Twenty-nine patients had sufficient pharmacokinetic data and were included in the analysis. Mean age was 9.7 years (standard deviation 4.3) and 17 patients (59%) were male. Median peak plasma cannabidiol concentrations was 13.1 ng/mL (interquartile range 6.8-39.3 ngmL); median time to peak of 2.0 h (interquartile range 2.0-4.0 h). Mean acute elimination half-life of oral cannabidiol was 6.2 h (standard deviation 1.8 h). There was an observed half-life of degradation of 533 days noted for cannabidiol concentrations when stored for 0.6-3.1 years. There was some impact on cannabidiol pharmacokinetic parameters when cannabidiol was co-administered with zonisamide (elimination rate constant and V1) and levetiracetam (elimination rate constant). In pediatric patients using oral cannabidiol-rich cannabis extract for epilepsy, the time to peak concentration of plasma cannabidiol and average acute elimination half-life were shorter than those reported for adults. Co-administration of zonisamide and levetiracetam had some impact on cannabidiol pharmacokinetic parameters. There was an observed degradation of plasma cannabidiol in long-term storage. ClinicalTrials.gov Identifer no. NCT02447198.

Pharmacokinetics of Iodine and Fluoride following Application of an Anticaries Varnish in Adults.

Researchers have suggested that combining topical fluoride with an antiseptic to reduce cariogenic bacteria may be more effective than fluoride application alone in preventing dental caries. In previous studies, povidone iodine (PVP-I), a widely used bactericidal antiseptic, and sodium fluoride (NaF), used to foster remineralization of enamel, were applied sequentially topically and shown to be safe and effective. The study aim was to characterize the kinetics of iodine and fluoride following topical application of a single combination PVP-I and NaF anticaries varnish in healthy adults. Sixteen participants (aged 23 to 57 y) participated in a pharmacokinetics study following the application of 0.4 mL varnish containing 10% (w/v) PVP-I and 5% (w/v) NaF. Serum and urine samples were collected at various time points over 24 h following application of varnish. Iodine and fluoride concentrations were analyzed, and for each time point, baseline concentrations were subtracted from observed values. Following varnish application, 2 of 16 participants had nearly undetectable baseline-corrected iodine and fluoride levels, suggesting minimal absorption, lack of release of iodine and fluoride from the varnish, or inconsistent dosing. The average peak concentrations were 57 ± 33 ng/mL iodine and 60 ± 34 ng/mL (0.060 ± 0.034 ppm) fluoride and occurred within 3 h of application. The average elimination half-life was 5.5 ± 1.4 h and 3.1 ± 1.6 h for iodine and fluoride, respectively. Renal clearance of iodine and fluoride was similar to literature values. No adverse events related to the study varnish were observed by the investigative team or reported by the participants. In this study, serum fluoride and iodine transiently increased but were within normal range 24 h after application of the varnish. This study has shown that the combination of PVP-I and NaF in a proposed anticaries varnish was well tolerated. Knowledge Transfer Statement: This clinical study demonstrated that a dental varnish combining 10% (w/v) povidone iodine and 5% (w/v) sodium fluoride is well tolerated. Serum fluoride and iodine transiently increased but were within normal range after 24 h. Further studies should be conducted to assess the efficacy of a combination in preventing dental caries, especially in high-risk populations.

A phase I dose escalation study of SCB01A, a micro-tubular inhibitor with vascular disrupting activity, in patients with advanced solid tumors refractory to standard therapy.

2531 Background: SCB01A is a novel anti-microtubular agent with vascular disrupting activity. The Phase I study aimed to determine the dose-limiting toxicity (DLT), maximum tolerated dose (MTD), safety, and pharmacokinetic (PK) profiles of SCB01A in patients with advanced solid tumor. Methods: This was an open-label, phase I clinical trial with a rapid titration followed by a 3 x 3 study design. Eligible patients would receive a 3-hr intravenous infusion of SCB01A, every 21 days as one cycle. All adverse events were classified according to the CTCAE V4.0. DLT was defined as the occurrence of grade 3 with complications and grade 4 hematoloigcal, or ≥grade 3 non-hematological toxicities. Results: From June 2011 to November 2015, a total of 33 eligible patients were enrolled to eight dose levels: 2 mg/m2 (n = 1), 3 mg/m2 (n = 1), 4 mg/m2 (n = 6), 6.5 mg/m2 (n = 9, with 3 additional subjects were recruited for safety concern), 10 mg/m2 (n = 3), 16 mg/m2 (n = 3), 24 mg/m2 (n = 6) and 32 mg/m2 (n = 4). Six episodes of DLTs were observed in 5 patients (each one in dose levels of 4/6.5/24 mg/m2 and two in dose level of 32 mg/m2), including grade 4 blood creatine phosphokinase elevation (4 mg/m2), grade 3 gastric hemorrhage (6.5 mg/m2), grade 2 venous thrombosis (24 mg/m2), grade 3 peripheral neuropathy manifested as weakness of lower limbs, grade 3 aspartate aminotransferase elevation, and grade 3 hypertension (32 mg/m2). The MTD was determined to be 24 mg/m2. Pharmacokinetic profiles revealed a linear AUC-dose response with an average elimination half-life (t1/2) of 2.5 hours. Partial response was observed in one subject with buccal cancer. A total of 57.6% (19/33) subjects had stable disease for at least 2 cycles. Conclusions: SCB01A is safe and tolerable in patients with solid tumor. The MTD of SCB01A is 24 mg/m2 every 21 days, which deserves further development. Clinical trial information: NCT011159522.

Pharmacokinetics of single-dose oral ponazuril in weanling goats.

Ponazuril (toltrazuril sulfone) is a triazine antiprotozoal agent that targets apicomplexan organisms. Ponazuril may have clinical application in the treatment of clinical coccidiosis due to Eimeria species in goats, along with other protozoal infections. To evaluate the absorption, distribution and elimination characteristics of ponazuril in goats, a sensitive, validated high-pressure liquid chromatography and mass spectroscopy method for ponazuril in caprine plasma was developed. After a single oral dose of ponazuril at 10 mg/kg, plasma samples from seven weanling goats were collected and assayed. Plasma concentrations of ponazuril in the goats peaked at 36 ± 13 h post drug administration at a concentration of 9 ± 2 μg/mL. Concentrations declined to an average of 4.2 ± 0.8 μg/mL after 168 h with an average elimination half-life of 129 ± 72 h post drug administration. This study shows that ponazuril is relatively well absorbed after a single oral dose in goats. Efficacy trials are underway to determine clinical efficacy of ponazuril in the treatment of clinical coccidiosis in goats at 10 mg/kg dosage.

LC-APCI-MS/MS Quantification and Topical Bioavailability of Chloroacetamide in Rats.

Chloroacetamide (CAA) is a preservative used in various cosmetic, personal care and household products. Due to the hazard potential for allergic reaction and reproductive toxicity, CAA is being considered a high priority for screening assessment and toxicological re-evaluation. This study describes the development of a highly specific and sensitive atmospheric pressure chemical ionization tandem mass spectrometry method for the determination of CAA in rat plasma and its application to a topical bioavailability study. Chromatographic separations were achieved on a C8 column using a highly aqueous mobile phase with a binary gradient elution. The assay was linear in the concentration range of 5-2,500 ng/mL (r ≥ 0.995) using a small sample volume (100 µL). Applicability of the assay was demonstrated in a bioavailability study in rats after i.v. injection (0.5 or 2 mg/kg) and topical application (7.02 mg/kg). Average elimination half-life and clearance ranged from 26.6 to 30.5 min and 53.9 to 57.3 mL/min/kg, respectively. Upon topical application, CAA was slowly but steadily absorbed for a prolonged time period (12 h). The topical bioavailability was 53.5 and 48.3% for emulsion and lotion, respectively. The developed assay may be useful to examine the relationship between exposure and toxic potential of CAA in risk assessment.

Population pharmacokinetic meta-analysis of vortioxetine in healthy individuals.

The objective was to describe the pharmacokinetics of vortioxetine and evaluate the effect of intrinsic and extrinsic factors in the healthy population. Data from 26 clinical pharmacology studies were pooled. A total of 21,758 vortioxetine quantifiable plasma concentrations were collected from 887 subjects with corresponding demography. The doses ranged from 2.5 to 75 mg (single dose) and 2.5–60 mg (multiple QD doses). The pharmacokinetics of vortioxetine was best characterised by a two-compartment model with first-order absorption, lag-time and linear elimination, with interindividual error terms for absorption rate constant, oral clearance and central volume of distribution. The population mean was 32.7 L/hr for oral clearance and 1.97·103 L for the central volume of distribution. The average elimination half-life was 65.8 hr. CYP2D6 inferred metabolic status (ultra, extensive, intermediate or poor metabolisers) and age on oral clearance and height on central volume of distribution were identified as statistically significant covariate–parameter relationships. For CYP2D6 poor metabolisers, CL/F was approximately 50% to that seen in CYP2D6 extensive metabolisers. The impact of height on V2/F and age on CL/F was low and not considered to be clinically relevant. The final model was found to be reliable, stable and predictive. A reliable, stable and predictive pharmacokinetic model was developed to characterise pharmacokinetics of vortioxetine in the healthy population.

Pharmacokinetics and Toxicity of Intrathecal Liposomal Cytarabine in Children and Adolescents Following Age-Adapted Dosing

Assessment of the optimal drug dose for intrathecal therapy in children is challenging because of the non-linear increase in cerebrospinal fluid (CSF) volume throughout childhood and potential differences in the elimination rate in children versus adults. The present study was designed to prospectively collect pharmacokinetic and safety data on age-adapted intrathecal liposomal cytarabine in children aged >3years. Sixteen patients with malignant brain tumours were included in the study. Children aged 3-10years received liposomal cytarabine 35mg with concomitant dexamethasone, and those aged >10years received 50mg. Serial CSF and plasma samples were collected before administration and 1h, 12h, 24h, 1week and 2weeks post-dosing. CSF was analysed for free and encapsulated cytarabine, and plasma was analysed for free cytarabine. The average elimination half-life values in children aged 3-10years and in those aged >10years, treated with liposomal cytarabine 35mg and 50mg, respectively, were 40.9 and 43.7h for free cytarabine and 31.5 and 36.4h for encapsulated cytarabine in CSF. Although these values were lower than those previously reported, cytarabine concentrations exceeded the cytotoxic threshold of 0.1mg/L in all patients until 1week post-intraventricular administration. Cytarabine concentrations in plasma were negligible. In general, liposomal cytarabine was well tolerated, with relevant but manageable toxicities. Liposomal cytarabine in doses of 35mg for children aged 3-10years and 50mg for older patients shows sufficient drug exposure for at least 1week and appears to be well tolerated.

Pharmacokinetics of MMB4 DMS in Rats, Rabbits, and Dogs Following a Single IV Administration

Organophosphorus (OP) nerve agents pose tremendous threats to both military and civilian populations. The substance 1,1'-methylenebis[4-[(hydroxyimino)methyl]-pyridinium] (MMB4) is being developed as a replacement for the currently fielded 2-pyridine aldoxime, or pralidoxime (2-PAM) as a treatment for OP nerve agent-induced toxicity. The present study characterized pharmacokinetic (PK) profiles of MMB4 in male and female Sprague-Dawley rats, New Zealand White rabbits, and beagle dogs given a single intravenous (IV) administration of MMB4 dimethanesulfonate (DMS) at 55, 25, and 15 mg/kg dose, respectively. The plasma MMB4 concentration versus time profiles were biphasic for all species tested and fit a 2-compartment model with first-order elimination. There were no overt sex-related differences in the calculated PK parameters. For the rat, rabbit, and dog, the average systemic exposure parameters predicted Cmax (µg/mL) and AUC∞ (µg·h/mL) were 273 and 71.0, 115 and 48.1, and 87.4 and 39.6; the average volume of distribution (mL/kg) values to the central and peripheral compartments were 207 and 143, 242 and 172, and 198 and 213; and the average elimination half-life (hour) and clearance (mL/h/kg) values were 0.18 and 778, 0.29 and 577, and 0.32 and 430, respectively, when the PK parameters for males and females were combined. The current study revealed a similarity in the volume of distribution to the central compartment for MMB4 among the 3 species tested while demonstrating species-related differences in the elimination half-life and clearance of MMB4.

The effect of timing of oral meloxicam administration on physiological responses in calves after cautery dehorning with local anesthesia

Dehorning is a painful husbandry procedure that is commonly performed in dairy calves. Parenteral meloxicam combined with local anesthesia mitigates the physiological and behavioral effects of dehorning in calves. The purpose of this study was to determine the influence of timing of oral meloxicam administration on physiological responses in calves after dehorning. Thirty Holstein bull calves, 8 to 10 wk of age (28–70kg), were randomly assigned to 1 of 3 treatment groups: placebo-treated control group (n=10), calves receiving meloxicam administered orally (1 mg/kg) in powdered milk replacer 12h before cautery dehorning (MEL-PRE; n=10), and calves receiving meloxicam administered as an oral bolus (1 mg/kg) at the time of dehorning (MEL-POST; n=10). Following cautery dehorning, blood samples were collected to measure cortisol, substance P (SP), haptoglobin, ex vivo prostaglandin E2 (PgE2) production after lipopolysaccharide stimulation and meloxicam concentrations. Maximum ocular temperature and mechanical nociceptive threshold (MNT) were also assessed. Data were analyzed using noncompartmental pharmacokinetic analysis and repeated measures ANOVA models. Mean peak meloxicam concentrations were 3.61±0 0.21 and 3.27±0.14μg/mL with average elimination half-lives of 38.62±5.87 and 35.81±6.26h for MEL-PRE and MEL-POST, respectively. Serum cortisol concentrations were lower in meloxicam-treated calves compared with control calves at 4h postdehorning. Substance P concentrations were significantly higher in control calves compared with meloxicam-treated calves at 120h after dehorning. Prostaglandin E2 concentrations were lower in meloxicam-treated calves compared with control calves. Mechanical nociceptive threshold was higher in control calves at 1h after dehorning, but meloxicam-treated calves tended to have a higher MNT at 6h after dehorning. No effect of timing of meloxicam administration on serum cortisol concentrations, SP concentrations, haptoglobin concentrations, maximum ocular temperature, or MNT was observed. However, PgE2 concentrations in MEL-PRE calves were similar to control calves after 12h postdehorning, whereas MEL-POST calves had lower PgE2 concentrations for 3 d postdehorning. These findings support that meloxicam reduced cortisol, SP, and PgE2 after dehorning, but only PgE2 production was significantly affected by the timing of meloxicam administration.

Pharmacokinetics and Bioequivalence Evaluation of Cyclobenzaprine Tablets

The purpose of this study was to investigate cyclobenzaprine pharmacokinetics and to evaluate bioequivalence between two different tablet formulations containing the drug. An open, randomized, crossover, single-dose, two-period, and two-sequence design was employed. Tablets were administered to 23 healthy subjects after an overnight fasting and blood samples were collected up to 240 hours after drug administration. Plasma cyclobenzaprine was quantified by means of an LC-MS/MS method. Pharmacokinetic parameters related to absorption, distribution, and elimination were calculated. Cyclobenzaprine plasma profiles for the reference and test products were similar, as well as absorption pharmacokinetic parameters AUC (reference: 199.4 ng∗h/mL; test: 201.6 ng∗h/mL), Cmax (reference: 7.0 ng/mL; test: 7.2 ng/mL), and T max (reference: 4.5 h; test: 4.6 h). Bioequivalence was evaluated by means of 90% confidence intervals for the ratio of AUC (93%–111%) and C max (93%–112%) values for test and reference products, which were within the 80%–125% interval proposed by FDA. Cyclobenzaprine pharmacokinetics can be described by a multicompartment open model with an average rapid elimination half-life (t (1/2)β) of 3.1 hours and an average terminal elimination half-life (t (1/2)γ) of 31.9 hours.

Florfenicol concentrations in milk of lactating cows postreated by intramuscular or intramammary routes

Objetivo. Determinar la concentración de florfenicol en leche bovina después del tratamiento intramuscular o intramamario, para establecer el tiempo de retiro, la eficacia terapéutica, y su influencia sobre la producción láctea. Materiales y métodos. Se seleccionaron doce vacas Holstein en lactancia de la hacienda de Universidad de Antioquia (Colombia). Se asignaron al azar al grupo control (n=6) o al grupo florfenicol (n=6), al cual se le administró 20 mg/kg de florfenicol por vía intramamaria e intramuscular con 15 días de diferencia entre tratamientos. Resultados. La Tmax y Cmax para la vía intramuscular fueron 6 horas y 2.86 mg/L respectivamente. La Tmax y Cmax para la vía intramamaria, fueron estimados como 0 hora y aproximadamente 20000 mg/L respectivamente por extrapolación de la línea de regresión. La fase de eliminación del florfenicol en leche, tuvo una vida media de eliminación (t½) promedio de 19.8 horas y 4.9 horas para la vía intramuscular e intramamaria respectivamente. Cuando la concentración inhibitoria minima (C.I.M) del florfenicol para Stahphylococcus aureus, fue usada como el valor de referencia, la eficacia terapéutica sólo se alcanzó por la vía intramamaria. No existió diferencia estadística significativa entre las producciones lácteas de las vacas tratadas y no tratadas. Conclusiones. De acuerdo con estos resultados, el tiempo de retiro postratamiento no debe ser menor de 3 días para la administración intramamaria y al menos 7 días para la administración intramuscular. La eficacia terapéutica sólo se alcanzó por la vía intramamaria. Además no existió diferencia estadística significativa en la producción láctea de las vacas tratadas con respecto a las no tratadas.