Determination of vitacoxib, a novel COX-2 inhibitor, in equine plasma using UPLC–MS/MS detection: Development and validation of new methodology

Pharmacokinetics, Tissue Distribution, Metabolism and Excretion of a Novel COX-2 Inhibitor, Vitacoxib, in Rats

The objectives of this study were to elucidate absorption, tissue distribution, excretion, and metabolism of vitacoxib, a novel selective cyclooxygenase-2 inhibitor, in Wistar rats. Vitacoxib was detected in most tissues within 15 min, suggesting that it was well distributed. Moreover, it could cross the intestinal barrier. Vitacoxib was mainly eliminated as two metabolites. Nine proposed metabolites of vitacoxib were found in the plasma, bile, urine, and feces of rats. Two main metabolites, 4-(4-chloro-1-(5-(methyl-sulfonyl) pyridin-2-yl)-1H-imidazol-5-yl) phenyl methanol (M1) and 4-(4-chloro-1-(5-(methyl-sulfonyl) pyridin-2-yl)-1H-imidazol-5-yl) benzoic acid (M2), were identified in rat feces and urine. Further, the authentic standards of M1 and M2 were synthesized to confirm their structures. The carboxylic acid derivative was the major metabolite of vitacoxib excreted in the urine and feces. Hydroxylation of the aromatic methyl group of vitacoxib and additional oxidation of the hydroxymethyl metabolite to a carboxylic acid metabolite were the proposed metabolic pathways. Vitacoxib displayed a high AUC_last (4895.73 ± 604.34 ng·h/ml), long half-life (4.25 ± 0.30 h), slow absorption (T_max, 5.00 ± 2.00 h), and wide tissue distribution in rats. Our findings provide significant information for the further development and investigation of vitacoxib as an effective nonsteroidal anti-inflammatory agent, and highly its potential for use future in a clinical setting.

Development and validation of an HPLC method for determination of rofecoxib in bovine serum albumin microspheres

A simple and reliable HPLC method was developed and validated for determination of rofecoxib in bovine serum albumin microsphere. The analyses were performed on a C18 column (150 x 4.6 mm, 5 μm particle size) at room temperature with UV detection at 272 nm. The mobile phase was composed of acetonitrile-0.1% o-phosphoric acid solution in water (1:1, v/v) mixture, and flow rate was set to 1 mL/min. The method was validated according to the international guidelines with respect to stability, linearity range, limit of quantitation and detection, precision, accuracy, specificity, and robustness. The detection and quantification limit of the method were 1.0 μg/mL and 2.5 μg/mL, respectively. The method was linear in the range of 2.5-25 μg/mL with excellent determination coefficients (R2 >0.99). Intra-day and inter-day precision (<1.76% RSD) and accuracy (<0.55 % Bias) values of the method also fulfilled the required limits. It was concluded that the developed method was accurate, sensitive, precise, and reproducible according to the evaluation of the validation parameters. The applicability of the method was confirmed for in vitro quantification of rofecoxib in bovine serum albumin microspheres.

Non-Linear Mixed-Effects Pharmacokinetic Modeling of the Novel COX-2 Selective Inhibitor Vitacoxib in Cats

The objective of this study was to develop a non-linear mixed-effects (NLME) model to describe the disposition kinetics of vitacoxib in cats following intravenous (I.V) and oral (P.O) (single and multiple) dosing. Data from six consecutive studies with 16 healthy neutered domestic short hair cats were pooled together to build a pharmacokinetic (PK) model using NLME. Population PK parameters were estimated using the stochastic approximation expectation maximization (SAEM) algorithm implemented in Monolix 2019R2. A two-compartment mammillary disposition model with simultaneous zero- and first-order absorption best described the PK of vitacoxib in plasma after oral dosing. The systemic CL of vitacoxib was found to be low (110 ml/h), with a steady-state volume of distribution (VSS) of 3.42 L in cats. Results from the automated covariate search in Monolix 2019R2 showed that bodyweight had a significant effect on the central volume of distribution of vitacoxib. Lastly, using Monte Carlo simulations, we investigated the time course of several dosages of vitacoxib from 0.01 to 8 mg/kg. Using this simulation set, we found a range of reasonable dosages that produce therapeutic plasma concentrations of vitacoxib for 24 h or more in cats.

UPLC-MS/MS Method for Determination of Khasianine in Mouse Blood: Application for Its Pharmacokinetic Study

Background:

The aim of this study was to determine the concentrations of khasianine in mouse whole blood sample and its application for the pharmacokinetics by a rapid, selective and sensitive ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method.

Methods:

The blood samples were preprocessed by one-step protein precipitation with acetonitrile. The study was performed on an ACQUITY I-Class UPLC system with a UPLC BEH column. Lannaconitine (internal standard, IS) and khasianine were gradient eluted by a mixture of acetonitrile and water with 0.1% formic acid at a flow rate of 0.4 mL/min. The mass spectrometer was equipped with an Electrospray Ionization (ESI) source in positive mode. The quantitative detection was performed in a multiple reaction monitoring modes at transitions m/z 722.4→70.7 for khasianine and m/z 585.3→119.9 for the corresponding IS.

Results:

The calibration curve was of good linearity ranging from 0.5 to 1000 ng/mL (r > 0.995). The Lower Limit of Detection (LLOD) and Lower Limit of Quantitation (LLOQ) were 0.2 and 0.5 ng/mL, respectively. The inter-day and intra-day precision (RSD%) were both less than 14%, and the accuracy ranged from 86.6% to 108.3%. The matrix effects were between 98.0% and 103.7%, and the average recovery was better than 67.4%.

Conclusion:

This assay established a sensitive, rapid, selective UPLC-MS/MS method which was successfully used for the pharmacokinetic study of khasianine in mouse blood, and the absolute availability of khasianine was 0.78% which exhibited a poor oral absorption.

Pharmacokinetics of ligustroflavone in rats and tissue distribution in mice by UPLC–MS/MS

An ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) method was developed and validated for quantification of ligustroflavone, which was then applied in pharmacokinetics study in rat and tissue distribution in mouse. Twelve male Sprague Dawley rats were used for pharmacokinetics after intravenous (2 or 8 mg/kg) administration of ligustroflavone, six rats for each dose. Twenty-five mice were randomly divided into 5 groups (5 mice for each group, 1 group for each time point) and received 16 mg/kg ligustroflavone via intraperitoneal administration. The linear range of the calibration curve was over 2–2000 ng/mL for ligustroflavone in rat plasma and mouse tissues. The intra-day and inter-day precision expressed in % RSD were less than 14%, and the accuracy was between 88.5% and 108.4%.

The tissue distribution results indicated that ligustroflavone diffuses rapidly and widely into major organs. The level of ligustroflavone was highest in the mouse liver, followed by the kidney, spleen, and lung. The overwhelming accumulation in the liver indicated that the liver was responsible for the extensive metabolism.

Pharmacokinetics of three formulations of vitacoxib in horses

The pharmacokinetic properties of three formulations of vitacoxib were investigated in horses. To describe plasma concentrations and characterize the pharmacokinetics, 6 healthy adult Chinese Mongolian horses were administered a single dose of 0.1 mg/kg bodyweight intravenous (i.v.), oral paste, or oral tablet vitacoxib in a 3-way, randomized, parallel design. Blood samples were collected prior to and at various times up to 72 hr postadministration. Plasma vitacoxib concentrations were quantified using UPLC-MS/MS, and pharmacokinetic parameters were calculated using noncompartmental analysis. No complications resulting from the vitacoxib administration were noted on subsequent administrations, and all procedures were tolerated well by the horses throughout the study. The elimination half-life (T_1/2λz ) was 4.24 ± 1.98 hr (i.v.), 8.77 ± 0.91 hr (oral paste), and 8.12 ± 4.24 hr (oral tablet), respectively. Maximum plasma concentration (C_max ) was 28.61 ± 9.29 ng/ml (oral paste) and 19.64 ± 9.26 ng/ml (oral tablet), respectively. Area under the concentration-versus-time curve (AUC_last ) was 336 ± 229 ng hr/ml (i.v.), 221 ± 94 ng hr/ml (oral paste), and 203 ± 139 ng hr/ml, respectively. The results showed statistically significant differences between the 2 oral vitacoxib groups in T_max value. T_1/2λz (hr), AUC_last (ng hr/ml), and MRT (hr) were significantly different between i.v. and oral groups. The longer half-life observed following oral administration was consistent with the flip-flop phenomenon.

Nonlinear mixed-effects pharmacokinetic modeling of the novel COX-2 selective inhibitor vitacoxib in dogs

The objective of this study was to develop a nonlinear mixed-effects model of vitacoxib disposition kinetics in dogs after intravenous (I.V.), oral (P.O.), and subcutaneous (S.C.) dosing. Data were pooled from four consecutive pharmacokinetic studies in which vitacoxib was administered in various dosing regimens to 14 healthy beagle dogs. Plasma concentration versus time data were fitted simultaneously using the stochastic approximation expectation maximization (SAEM) algorithm for nonlinear mixed-effects as implemented in Monolix version 2018R2. Correlations between random effects and significance of covariates on population parameter estimates were evaluated using multiple samples from the posterior distribution of the random effects. A two-compartment mamillary model with first-order elimination and first-order absorption after P.O. and S.C. administration, best described the available pharmacokinetic data. Final parameter estimates indicate that vitacoxib has a low-to-moderate systemic clearance (0.35 L hr^-1  kg^-1 ) associated with a low global extraction ratio, but a large volume of distribution (6.43 L/kg). The absolute bioavailability after P.O. and S.C. administration was estimated at 10.5% (fasted) and 54.6%, respectively. Food intake was found to increase vitacoxib oral bioavailability by a fivefold, while bodyweight (BW) had a significant impact on systemic clearance, thereby confirming the need for BW adjustment with vitacoxib dosing in dogs.

Pharmacokinetics of vitacoxib in rabbits after intravenous and oral administration

This study describes the pharmacokinetics of vitacoxib in healthy rabbits following administration of 10 mg/kg intravenous (i.v.) and 10 mg/kg oral. Twelve New Zealand white rabbits were randomly allocated to two equally sized treatment groups. Blood samples were collected at predetermined times from 0 to 36 hr after treatment. Plasma drug concentrations were determined using UPLC-MS/MS. Pharmacokinetic analysis was completed using noncompartmental methods via WinNonlin^™ 6.4 software. The mean concentration area under curve (AUC_last ) for vitacoxib was determined to be 11.0 ± 4.37 μg hr/ml for i.v. administration and 2.82 ± 0.98 μg hr/ml for oral administration. The elimination half-life (T_1/2λz ) was 6.30 ± 2.44 and 6.30 ± 1.19 hr for the i.v. and oral route, respectively. The C_max (maximum plasma concentration) and T_max (time to reach the observed maximum (peak) concentration at steady-state) following oral application were 189 ± 83.1 ng/ml and 6.58 ± 3.41 hr, respectively. Mean residence time (MRT_last ) following i.v. injection was 6.91 ± 3.22 and 11.7 ± 2.12 hr after oral administration. The mean bioavailability of oral administration was calculated to be 25.6%. No adverse effects were observed in any rabbit. Further studies characterizing the pharmacodynamics of vitacoxib are required to develop a formulation of vitacoxib for rabbits.

Pharmacokinetics of the novel COX-2 selective inhibitor vitacoxib in cats: The effects of feeding and dose

The purpose of this study was to determine the pharmacokinetics and dose-scaling model of vitacoxib in either fed or fasted cats following either oral or intravenous administration. The concentration of the drug was quantified by UPLC-MS/MS on plasma samples. Relevant parameters were described using noncompartmental analysis (WinNonlin 6.4 software). Vitacoxib is relatively slowly absorbed and eliminated after oral administration (2 mg/kg body weight), with a T_max of approximately 4.7 hr. The feeding state of the cat was a statistically significant covariate for both area under the concentration versus time curve (AUC) and mean absorption time (MAT_fed ). The absolute bioavailability (F) of vitacoxib (2 mg/kg body weight) after oral administration (fed) was 72.5%, which is higher than that in fasted cats (F = 50.6%). Following intravenous administration (2 mg/kg body weight), Vd (ml/kg) was 1,264.34 ± 343.63 ml/kg and Cl (ml kg^-1  hr^-1 ) was 95.22 ± 23.53 ml kg^-1  hr^-1 . Plasma concentrations scaled linearly with dose, with C_max (ng/ml) of 352.30 ± 63.42, 750.26 ± 435.54, and 936.97 ± 231.27 ng/ml after doses of 1, 2, and 4 mg/kg body weight, respectively. No significant undesirable behavioral effects were noted throughout the duration of the study.

Pharmacokinetic Study of Deltaline in Mouse Blood Based on UPLCMS/ MS

Results:

The UPLC-MS/MS method was sensitive and linear (r>0.995) with a lower limit of quantitation (LLOQ) of 0.1 ng/mL over the range of 0.1-500 ng/mL. Intra- and inter-day precisions were below 13%, the accuracy range was between 88.0% and 108.2%, the recovery was higher than 90.1%, and the matrix effect was between 102.9% and 108.1%.

Conclusion:

The method was sensitive, fast, specific, and has been successfully applied to a pharmacokinetic study of deltaline after intravenous administration.

Evaluation of pharmacokinetic properties of vitacoxib in fasted and fed horses

The pharmacokinetic properties of vitacoxib have not been established completely; current dosage recommendations are based on clinical experiences. The primary objective of this study was to describe plasma concentrations and characterize the pharmacokinetics of vitacoxib formulation following oral administrations in horses. Also, the effect of the state of stomach contents on the absorption of vitacoxib was investigated in fed/fasted horses. Blood samples were collected prior to and at various times up to 72 hr post-administration. Drug concentrations were measured using ultra high-performance liquid chromatography-tandem mass spectrometry. Pharmacokinetic parameters were calculated using Non-Compartmental Analysis Model 200 in WinNonlin™ software. No complications resulting from the vitacoxib administration were noted. All procedures were tolerated well by the horses throughout the study. C_max was 17.5 ± 9.36 ng/ml (fasted) and 9.47 ± 3.53 ng/ml (fed) following oral administrations. AUC_last was 173.7 ± 137.9 ng hr/ml (fasted) and 113.2 ± 70.8 ng h/ml (fed). No significant differences in pharmacokinetic parameters were noted and the results from the pharmacokinetic analysis were similar between the studies, regardless of precision of dosage and fasted and fed conditions. The study extends previous studies describing the pharmacokinetics of vitacoxib following p.o. administration to the horses. Further studies investigating the pharmacokinetics/pharmacodynamics of vitacoxib are necessary to establish adequate therapeutic protocols (optimal dosage and frequency of administration) in horses.

Method development and application for multi-component quantification in rats after oral administration of Longxuetongluo Capsule by UHPLC-MS/MS

Although wide applications towards ischemic stroke in clinic, the therapeutic materials of Longxuetongluo Capsule (LTC) that is composed of total phenolic extract of Chinese dragon's blood, are still largely unclear. Exposure pattern characterization of those drug-derived components in vivo, notably in circulation system has been recommended as a viable approach to disclose the effective components of a given herbal medicine. Herein, we aimed to develop a robust method being capable of multi-component quantification in either rat plasma or tissues following oral administration of LTC, and to clarify the kinetic profiles of 11 primary drug-derived phenolic derivatives. Proteins precipitation was carried out for the plasma as well as homogenized tissue samples with acetonitrile. Chromatographic separations were achieved using UHPLC equipped with a shim-pack XR-ODS II column, and confidence-enhanced detection was accomplished through the joint employment of selected-reaction monitoring and tandem mass spectrometry (SRM-MS/MS) on a hybrid triple quadrupole-linear ion trap mass spectrometer. Diverse validation assays proved the method to be sensitive, precise, and rapid for simultaneous determination of those 11 components. Pharmacokinetic and tissue distribution investigations were subsequently conducted in rat after a single 500 mg/kg oral dose. Rapid absorption (T_max, 11.53-68.27 min) and elimination (T_1/2, 6.893-57.90 min) occurred for all analytes-of-interest. Extensive occurrences were observed for 7,4'-dihydroxy-5-methoxyhomoisoflavanone (C_max, 340.0 ng/mL), thevetiaflavone (C_max, 42.86 ng/mL), 5,7,4'-trihydroxyhomoisoflavanone (C_max, 41.55 ng/mL), and pterostilbene (C_max, 25.49 ng/mL) in plasma. Significant distributions occurred for all analytes in the liver as well as kidney, and several compounds could be found in brain. The findings described are envisioned to provide promising information for the in-depth clarification of the therapeutic entities, and also to offer a practical approach for therapeutic drug monitoring of LTC in clinic.

Safety assessment of vitacoxib: 180-day chronic oral toxicity studies

Vitacoxib, a selective COX-2 inhibitor, is approved for the relief of pain and inflammation associated with orthopedic surgery and osteoarthritis in dogs. In the current study, a chronic toxicity research was performed to evaluate the safety of vitacoxib in male and female rats for long-term. Vitacoxib was dosed orally to groups of rats for 180 days at 1.2, 6, 30 mg/kg bw/day by gavage. The chronic study oral administration of vitacoxib did not show observational or toxicological effects on the body or organ weights, food consumption, hematology and biochemistry at dose 6 mg/kg bw. However, vitacoxib (30 mg/kg) showed minor alterations to histopathology of liver, kidney and stomach related to treatment. These results provide further indication that vitacoxib is safe and well-tolerated in rats after 180 days of daily oral administration at 6 mg/kg bw and the NOAEL for both sexes was 6 mg/kg bw for 180 consecutive days.