Pharmacokinetics and Bioequivalence of Dienogest in Healthy Bangladeshi Female Volunteers: An Open-Label, Single-Dose, Randomized, Two-Way Crossover Study

Background: Dienogest is a potential treatment for pelvic pain associated with endometriosis, a condition of significant concern in gynaecology. The current study was conducted as a crossover-randomized bioequivalence assessment of two oral Dienogest 2 mg formulations, aiming to provide valuable insights for healthcare professionals and researchers in this field. Objective: The primary aim of this research was to evaluate and compare the pharmacokinetic characteristics of Dienogest 2 mg tablets. Dinogest (Dienogest 2 mg) tablets, manufactured by Nuvista Pharma Limited in Bangladesh, and Visanne (Dienogest 2 mg) tablets, manufactured by Bayer Pharma in Germany, were the test and reference formulations, respectively. Materials and Method: The study was an open-label, balanced, randomized, two treatments, two sequences, two periods, two-way crossover, laboratory blind, single oral dose bioequivalence study conducted in healthy adult females under fasting conditions. The study was carried out on 13 healthy, non-pregnant female subjects, and all the subjects completed both study periods with a 15-day washout in between. Randomization was used to assign the test and reference formulations to the subjects. Following each oral administration, a series of blood samples were obtained at different time intervals from pre-dose to 72 hours post-dose and analyzed for Dienogest concentrations using a validated bio-analytical method. A standard non-compartmental model was used to analyze the pharmacokinetic parameters. The primary pharmacokinetic parameters were peak plasma drug concentration (Cmax), the area under the plasma concentration-time curve from time zero to time t (AUC0–t), and AUC from t = 0 to infinity (AUC0–∞). The other PK parameters included time to reach Cmax (Tmax), terminal elimination rate constant (Kel), and half-life (t1/2). Result: The ratios and 90% CI for the geometric mean test/reference were 95.53% (86.70% - 105.26%) for Cmax, 101.75% (95.42% - 108.49%) for AUC0−t, and 101.54% (95.59%% - 107.87%) for AUC0−∞. The formulations were bioequivalent since the 90% CIs for the geometric mean test/reference ratios were 80% to 125%, according to the predetermined range of US Food and Drug Administration (FDA) requirements. Conclusion: This single-dose investigation shows that the Dienogest test and reference formulations exhibited a rate and degree of absorption that met the regulatory requirements for bioequivalence.

Bioequivalence Study of Diclofenac 150 mg XR: A Single-Dose, Randomized, Open Label, 2-Period Crossover Study in Healthy Adult Volunteers

Objectives: Evaluate the bioequivalence (BE) of two oral tablets formulations of diclofenac 150 mg in healthy male subjects under fasting condition. This was a phase I, randomized, open label, balanced, two period, two sequences, single oral dose, crossover, analyst blind study. Methods: Twenty four (24) healthy subjects were randomly assigned to one of two sequences protocol: 150 mg XR of reference formulation (R), diclofenac sodium in the first period or the test formulation (T), diclofenac potassium in the second or vice versa. The plasma concentrations were determined using a validated LC-MS/MS method. Pharmacokinetic (PK) parameters included: maximum plasma concentration (Cmax), area under the plasma concentration—time curve from time 0 to the last measurable concentration (AUC0-t), and area under the plasma concentration—time from time 0 to infinity (AUC0-∞), were evaluated for BE. Results: The results showed that 90% confidence intervals for the test/reference geometric mean ratios (GMR) of Cmax (90.43 - 107.17), AUC0-t (93.08 - 116.46) and AUC0-∞ (92.52 - 117.39) were within the BE (80% - 125%) acceptance range. Conclusions: Two formulations, reference product (R) Voltaren® (diclofenac sodium) of Novartis and test product (T), Diklason Bi (diclofenac potassium) of Laboratorios Leti S.A.V., with a single dose of 150 mg XR, under fasting conditions were bioequivalent. No severe, serious or unexpected adverse events (AEs) were reported in this study.

Sensitive and rapid determination of amantadine without derivatization in human plasma by LC–MS/MS for a bioequivalence study

A highly sensitive, rapid and rugged liquid chromatography-tandem mass spectrometw （LC-ESI-MS/MS） method was developed for reliable estimation of amantadine （AMD）, an antiviral drug in human plasma. The analyte and internal standard （IS）, amantadine-d6 （AMD-d6）, were extracted from 200μL plasma by solid phase extraction on Phenomenex Strata-X-C 33 ~t cartridges. Chromatography was performed on Synergi^TM Hydro-RP C18 （150 mm×4.6 mm, 4 μm） analytical column using a mixture of acetonitrile and 10 mM ammonium formate, pH 3.0 （80：20, v/v） as the mobile phase. Detection and quantitation was done by multiple reaction monitoring in the positive ionization mode for AMD （m/z 152.1→ 135.1 ） and IS （m/z 158.0 → 141.1） on a triple quadrupole mass spectrometer. The assay was linear in the concentration range of 0.50-500 ng/mL with correlation coefficient （r^2） 〉 0.9969. The limit of detection of the method was 0.18 ng/mL The intra-batch and inter-batch precisions were 〈 5.42% and the accuracy varied from 98.47% to 105.72%. The extraction recovery of amantadine was precise and quantitative in the range of 97.89%-100.28%. IS-normalized matrix factors for amantadine varied from 0.981 to 1.012. The stability of AMD in whole blood and plasma was evaluated under different conditions. The developed method was successfully applied for a bioequivalence study with 100 mg of AMD in 32 healthy volunteers. The reproducibility of the assay was determined by reanalysis of 134 subject samples.

Quantification of sibutramine and its two metabolites in human plasma by LC-ESI-MS/MS and its application in a bioequivalence study

Obesity can be considered as a chronic illness of epidemic proportion and its incidents have increased exponentially in recent years.The use of anti-obesity drugs such as sibutramine is somewhat helpful.There is a need to quantify such drugs in biological samples,which is generally quite difficult.In this report,we developed and validated a simple,sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the quantification of sibutramine (SB) and its two metabolites N-des methyl sibutramine (DSB) and N-di desmethyl sibutramine (DDSB) in human plasma.Zorbax SBC18 (4.6 mm × 75 mm,3.5 μm,80 (A)) analytical column and 5 mM ammonium formate:acetonitrile (10∶90,v/v) mobile phase were used for chromatographic separation of SB,DSB and DDSB.Multiple reaction monitoring (MRM) in the positive mode was used to detect SB,DSB and DDSB at m/z 280.3/124.9,266.3/125.3 and 252.2/124.9,respectively.Liquid liquid extraction was used for the extraction of analytes and internal standard from human plasma.This method was validated over a linear concentration range of 10.0-10,000.0 pg/mL for SB,DSB and DDSB with correlation coefficients (r) of ≥0.9997.The drug and the two metabolites were stable in plasma samples.The validated method was successfully applied in a bioequivalence and pharmacokinetic study with human volunteers under fasting condition.

Virtual population pharmacokinetic using physiologically based pharmacokinetic model for evaluating bioequivalence of oral lacidipine formulations in dogs

The aim of the present study was to investigate virtual population pharmacokinetic using physiologically based pharmacokinetic(PBPK) model for evaluating bioequivalence of oral lacidipine formulations in dogs. The dissolution behaviors of three lacidipine formulations including one commercial product and two self-made amorphous solid dispersions(ASDs)capsules were determined in 0.07% Tween 80 media. A randomized 3-period crossover design in 6 healthy beagle dogs after oral administration of the three formulations at a single dose of 4 mg was conducted. The PBPK modeling was utilized for the virtual bioequivalence study.In vitro dissolution experiment showed that the dissolution behaviors of lacidipine amorphous solid dispersions(ASDs) capsules, which was respectively prepared by HPMC-E5 or Soluplus, as polymer displayed similar curves compared with the reference formulation in 0.07% Tween 80 media. In vivo pharmacokinetics experiments showed that three formulations had comparable maximum plasma drug concentration(Cmax), and the time(Tmax) to reach Cmax of lacidipine tablet, which was prepared by Soluplus, as polymer was slower than other two formulations in consistency with the in vitro dissolution rate. The 90% confidence interval(CI) for the Cmax, AUC0–24 h and AUC0–∞ of the ratio of the test drug to the reference drug exceeded the acceptable bioequivalence(BE) limits(0.80–1.25). However, the 90% CI of the AUC0–24 h, AUC0–∞ and Cmax of the ratio of test to reference drug were within the BE limit,calculated using PBPK modeling when the virtual subjects reached 24 dogs. The results all demonstrated that virtual bioequivalence study can overcome the inequivalence caused by inter-subject variability of the 6 beagle dogs involved in in vivo experiments.

Quantification of desloratadine in human plasma by LC-ESI-MS/MS and application to a pharmacokinetic study

A simple, sensitive, and specific liquid chromatography tandem mass spectrometry (LC-MS/ MS) method was developed for the quantification of desloratadine (DL) in human plasma using desloratadine-d5 (DLD5) as an internal standard (IS). Chromatographic separation was performed using an Xbridge C18 column (50 mm 4.6 mm, 5 mm) with an isocratic mobile phase composed of 10 mM ammonium formate: methanol (20:80, v/v), at a flow rate of 0.7 mL/min. DL and DLD5 were detected with proton adducts at m/z 311.2-259.2 and 316.2-264.3 in multiple reaction monitoring (MRM) positive modes, respectively. Liquid–liquid extraction (LLE) method was used to extract the drug and the IS. The method was validated over a linear concentration range of 5.0–5000.0 pg/mL with a correlation coefficient of (r2)Z0.9994. This method demonstrated intra- and inter-day precision within 0.7–2.0% and 0.7–2.7%, and an accuracy within 101.4–102.4%, and 99.5–104.8%. DL was found to be stable throughout the freeze–thaw cycles, bench-top, and postoperative stability studies. This method was successfully applied in the analysis of plasma samples following oral administration of DL (5 mg) in 35 healthy Indian male human volunteers under fasting conditions.

Improved simultaneous quantitation of candesartan and hydrochlorthiazide in human plasma by UPLC–MS/MS and its application in bioequivalence studies

A validated ultra-performance liquid chromatography mass spectrometric method （UPLC-MS/MS） was used for the simultaneous quantitation of candesartan （CN） and hydrochlorothiazide （HCT） in human plasma. The analysis was performed on UPLC-MS/MS system using turbo ion spray interface. Negative ions were measured in multiple reaction monitoring （MRM） mode. The analytes were extracted using a liquid-liquid extraction （LLE） method by using 0.1 mL of plasma volume. The lower limit of quantitation for CN and HCT was 1.00 ng/mL whereas the upper limit of quantitation was 499.15 ng/mL and 601.61 ng/mL for CN and HCT respectively. CN d4 and HCT-13Cd2 were used as the internal standards for CN and HCT respectively. The chromatography was achieved within 2.0 min run time using a C18 Pheno-menex, Gemini NX （100 mm ~ 4.6 mm, 5 mm） column with organic mixture：buffer solution （80：20, v/v） at a flow rate of 0.800 mL/min. The method has been successfully applied to establish the bioequivalence of candesartan cilexetil （CNC） and HCT immediate release tablets with reference product in human subjects.

Advance in bioequivalence assessment of topica dermatological products

Bioequivalence(BE) assessment of topical dermatological products is a long standing challenge. The development of generic topical dermatological products has often been hampered due to the limited number of acceptable approaches, which are capable of determining the BE between generic products and reference list products. The aim of this manuscript is to review different BE assessment approaches of topical dermatological products. Besides, the advances in BE evaluation and biowaivers are also provided. Currently, except in the case of dermatological corticosteroids, the golden rule to establish the BE of most topical dermatological products still heavily relied on clinical endpoint trials,which are often unreliable, time-consuming and expensive. The regulatory agencies and pharmaceutical industries are forging ahead to the development of new surrogate BE assessment approaches for other topical dermatological products. These promising approaches include dermatopharmacokinetic study(DPK), dermal microdialysis(DMD), in vitro studies, pharmacokinetic study(PK), near-infrared spectrometry(NIR), and confocal Raman spectroscopy(CRS). In addition, the expansion of biowaivers for topical dermatological products has been explored by pharmaceutical scientists. In conclusion, to accelerate the development and approval of topical dermatological products, emphasis should be put on the following areas, i.e., optimizing and standardizing the existing BE assessment methods, exploring novel alternatives of BE assessment approaches, and expanding biowaivers for topical dermatological products.

Application of an LC–MS/MS method for the analysis of amlodipine,valsartan and hydrochlorothiazide in polypill for a bioequivalence study

A sensitive and selective method has been proposed for the simultaneous determination of amlodipine(AML),valsartan(VAL) and hydrochlorothiazide(HCTZ) in human plasma by liquid chromatography–tandem mass spectrometry(LC–MS/MS). The analytes and their deuterated analogs were quantitatively extracted from100 μL human plasma by solid phase extraction on Oasis HLB cartridges. The chromatographic separation of the analytes was achieved on a Chromolith RP18 e(100 mm × 4.6 mm) analytical column within 2.5 min. The resolution factor between AML and VAL, AML and HCTZ, and VAL and HCTZ was 2.9, 1.5 and 1.4, respectively,under isocratic conditions. The method was validated over a dynamic concentration range of 0.02–20.0 ng/m L for AML, 5.00–10,000 ng/m L for VAL and 0.20–200 ng/m L for HCTZ. Ion-suppression/enhancement effects were investigated by post-column infusion technique. The mean IS-normalized matrix factors for AML, VAL and HCTZ were 0.992, 0.994 and 0.998, respectively. The intra-batch and inter-batch precision(% CV) across quality control levels was ≤ 5.56% and the recovery was in the range of 93.4%–99.6% for all the analytes. The method was successfully applied to a bioequivalence study of 5 mg AML + 160 mg VAL + 12.5 mg HCTZ tablet formulation(test and reference) in 18 healthy Indian males under fasting. The mean log-transformed ratios of C max, AUC0–120 h and AUC0-inf and their 90% CIs were within 90.2%–102.1%. The assay reproducibility was demonstrated by reanalysis of 90 incurred samples.

Quantitation of tadalafil in human plasma using a sensitive and rapid LC-MS/MS method for a bioequivalence study

A highly sensitive liquid chromatography-tandem mass spectrometry（LC-MS/MS） method was developed for the determination of tadalafil（TAD） in human plasma. TAD and its deuterated internal standard（IS）, tadalafil-d3, were extracted from 200 mL plasma using Phenomenex Strata-X-C 33 m extraction cartridges. Chromatographic analysis was carried out on Synergi Hydro-RP C18（100 mm × 4.6 mm, 4 mm）column with a mobile phase consisting of methanol and 10 m M ammonium formate, p H 4.0（90：10, v/v）,delivered at a flow rate of 0.9 m L/min. Quantitation of the protonated analyte was done on a triple quadrupole mass spectrometer using multiple reaction monitoring via electrospray ionization. The precursor to product ions transitions monitored for TAD and TAD-d3 were m/z 390.3-268.2 and m/z393.1-271.2, respectively. The calibration curve was linear over the concentration range of 0.50–500 ng/m L with correlation coefficient, r2 Z 0.9994. Acceptable intra-batch and inter-batch precision（r3.7%） and accuracy（97.8% to 104.1%） were obtained at five concentration levels. The recovery of TAD from spiked plasma was highly precise and quantitative（98.95% to 100.61%）. Further, the effect of endogenous matrix components was minimal. TAD was found to be stable under different storage conditions in human plasma and also in whole blood samples. The validated method was successfully used to determine TAD plasma concentration in a bioequivalence study with 20 mg TAD tablets in 24 healthy volunteers. Method performance was evaluated by reanalyzing 115 study samples.

Simultaneous quantification of prodrug oseltamivir and its metabolite oseltamivir carboxylate in human plasma by LC-MS/MS to support a bioequivalence study

A simple, precise and rapid liquid chromatography-tandem mass spectrometry （LC-MS/MS） method has been developed and validated for the simultaneous determination of oseltamivir and oseltamivir carboxylate, a neuraminidase inhibitor, using their deuterated analogs as internal standards （ISs）. The method involved solid phase extraction of the analytes and ISs from 200 μL human plasma with no reconstitution and drying steps. The chromatographic separation was achieved on a Symmetry C18 （100 mm × 4.6 mm, 5 μm） column using 10 mM ammonium formate and acetonitrile （30：70, v/v） as the mobile phase in a run time of 2.0 min. Quantitation of analytes and ISs were done by multiple reaction monitoring on a triple quadrupole mass spectrometer in the positive ionization mode. The linearity of the method was established in the concentration range of 0.5-200 ng/mL and 2.0-800 ng/mL for oseltamivir and oseltamivir carboxylate respectively. The mean extraction recovery for oseltamivir （94.4%） and oseltamivir carboxylate （92.7%） from spiked plasma samples was consistent and reproducible. The application of this method was demonstratedby a bioequivalence study in 42 healthy Indian subjects with 75 mg oseltamivir phosphate capsules. The assay reproducibility was established by reanalysis of 151 incurred subject samples.

Determination of torasemide in human plasma and its bioequivalence study by high-performance liquid chromatography with electrospray ionization tandem mass spectrometry

A sensitive and selective method using high-performance liquid chromatography coupled with elec- trospray ionization tandem mass spectrometry （HPLC-ESI-MS） to determine the concentration of tor- asemide in human plasma samples was developed and validated. Tolbutamide was chosen as the internal standard （IS）. The chromatography was performed on a GI Sciences Inertsil ODS-3 column （100 mm× 2.1 mm i.d., 5.0 μm） within 5 min, using methanol with 10 mM ammonium formate （60：40, v/ v） as mobile phase at a flow rate of 0.2 mL/min. The targeted compound was detected in negative io- nization at m/z 347.00 for torasemide and 269.00 for IS. The linearity range of this method was found to be within the concentration range of 1-2500 ng/mL （r=0.9984） for torasemide in human plasma. The accuracy of this measurement was between 94.05% and 103.86%. The extracted recovery efficiency was from 84.20% to 86.47% at three concentration levels. This method was also successfully applied in pharmacokinetics and bioequivalence studies in Chinese volunteers.

Determination of lercanidipine in human plasma by an improved UPLC–MS/MS method for a bioequivalence study

An improved and reliable ultra-performance liquid chromatography/tandem mass spectrometry （UPLC- MS/MS） method has been developed and validated for the determination of lercanidipine in human plasma. Plasma samples with lercanidipine-d3 as an internal standard （IS） were prepared by solid phase extraction on Phenomenex Strata-X cartridges using 100 μL of human plasma. Chromatographic analysis was performed on UPLC BEH C18 （50 mm × 2.1 mm, 1.7 μm） column under isocratic conditions. Linear calibration curves were obtained over a wide dynamic concentration range of 0.010-20.0 ng/mL. Matrix effect was assessed by post-column infusion, post-extraction spiking and standard-line slope methods. The mean extraction recovery was 〉 94% for the analyte and IS. Inter-batch and intra-hatch precision （% CV） across five quality controls was 〈 5.8%. Bioequivalence study was performed with 36 healthy sub- jects after oral administration of 10 mg of lercanidipine and the assay reproducibility was evaluated by reanalysis of 133 incurred samples.

Rethinking bioequivalence and equivalence requirements of orally inhaled drug products

Orally inhaled drug products(OIPs),such as corticosteroids and bronchodilators,are at the forefront of asthma and chronic obstructive pulmonary disease treatments,two diseases that afflict worldwide populations.Introducing generics of these products is essential,as the pricing of these medications remain a barrier to adequate patient care.Currently,there is no consensus between regulatory bodies as to the bioequivalence and equivalence requirements of OIPs that are intended for local action in the lungs.This manuscript critically reviews these requirements and presents future directions for clinicians,scientists,and regulators to consider to optimize the development and approval of OIPs.

Pharmacokinetics and Tolerability of Oral Dosage Forms of Huperzine A in Healthy Chinese Male Volunteers: a Randomized,Single Dose, Three-period, Six-sequence Crossover Study

Huperzine A is a potent, reversible, and blood-brain barrier permeable acetylcholinesterase inhibitor. The aim of this study was to compare the pharmacokinetics, tolerability, and bioavailability of two formulations with the established reference formulation of huperzine A in a fasting, healthy Chinese male population. This was a randomized, single-dose, 3-period, 6-sequence crossover study. The plasma concentrations of huperzine A were determined by liquid chromatography tandem mass spectrometry. Tolerability was assessed based on subject interview, vital sign monitoring, physical examination, and routine blood and urine tests. The mean（SD） pharmacokinetic parameters of the reference drug were Cmax, 1.550（0.528） ng/m L; t1/2, 12.092（1.898） h; AUC0-72 h, 17.550（3.794） ng·h/m L. Those of the test formulation A and test formulation B were Cmax, 1.412（0.467）, 1.521（0.608） ng/m L; t1/2, 12.073（2.068）, 12.271（1.678） h; AUC0-72 h, 15.286（3.434） ng·h/mL, 15.673（3.586） ng·h/m L. The 90% confidence intervals for the AUC0-72 h and Cmax were between 0.80 and 1.25. No adverse events were reported by the subjects or found with results of clinical laboratory test. The test and reference products met the regulatory criteria for bioequivalence in these fasting, healthy Chinese male volunteers. All three formulations appeared to be well tolerated.

Determination of metabolite of nicergoline in human plasma by high-performance liquid chromatography and its application in pharmacokinetic studies

A fast, simple and sensitive high performance liquid chromatographic (HPLC) method has been developed for determination of 10a-methoxy-6-methyl ergoline-8b-methanol (MDL, a main metabolite of nicergoline) in human plasma. One-step liquid–liquid extraction (LLE) with diethyl ether was employed as the sample preparation method. Tizanidine hydrochloride was selected as the internal standard (IS). Analysis was carried out on a Diamonsil ODS column (150 mm 4.6 mm, 5 mm) using acetonitrile–ammonium acetate (0.1 mol/L) (15/85, v/v) as mobile phase at detection wavelength of 224 nm. The calibration curves were linear over the range of 2.288–73.2 ng/mL with a lower limit of quantitation (LLOQ) of 2.288 ng/mL. The intra-and inter-day precision values were below 13% and the recoveries were from 74.47% to 83.20% at three quality control levels. The method herein described was successfully applied in a randomized crossover bioequivalence study of two different nicergoline preparations after administration of 30 mg in 20 healthy volunteers.

Bioequivalence of two esomeprazole magnesium enteric-coated formulations in healthy Chinese subjects

BACKGROUND The pharmacokinetics and bioequivalence of esomeprazole in healthy Chinese subjects and the effects of food on the pharmacokinetics have not been well studied.AIM To evaluate the pharmacokinetic characteristics of esomeprazole magnesium(Eso)enteric-coated capsule in the healthy subjects in China and the bioequivalence of the two formulations.METHODS This study was conducted in the Phase I Clinical Trial Unit of the Affiliated Hospital of Changchun University of Chinese Medicine.A total of 64 healthy subjects were enrolled in the study.Thirty-two subjects fasted or fed,took the test or reference formulation Eso enteric-coated capsule by a four-cycle,two-sequence crossover of fasting/fed,self-controlled method.The liquid chromatographymass spectrometry was performed to determine the drug plasma concentration at 16 different time points within 12 h after drug administration.The pharmacokinetic parameters Cmax,area under the curve(AUC)0-t,and AUC0-inf were calculated to evaluate the bioequivalence.RESULTS Pharmacokinetic parameters were evaluated after subjects took the test formulation and control formulation under fasting status.The ratio of geometric means of Cmax was 104.15%,with a confidence interval(CI)of 98.20-110.46%.The ratio of geometric means of AUC0-t was 105.26%,with a CI of 99.80-111.01%.The ratio of geometric means of AUC0-inf was 105.37%,with a CI of 99.97-111.06%.The pharmacokinetic parameters were also evaluated after subjects took the reference formulation of Eso enteric-coated capsule after eating.The upper limit of 95%CI of the geometric mean ratio of pharmacokinetic parameters of Eso enteric-coated capsules in the postprandial state Cmax was-0.1689,and the point estimate was 0.9509(0.80-1.25).The upper limit of 95%CI of the geometric mean ratio of pharmacokinetic parameters of Eso enteric-coated capsules in the postprandial state AUC0-t was-0.1015(≤0),and the point estimate was 0.9003(0.80-1.25).The upper limit of 95%CI of the geometric mean ratio of pharmacokinetic parameters of Eso enteric-coated capsules in the postprandial state AUC0-inf was-0.0593(≤0),and the point estimate was 0.8453(0.80-1.25).The results indicated that the two formulations were bioequivalent under both fasting and fed states.CONCLUSION The two types of esomeprazole tablets were bioequivalent under both fasting and fed states,and both were generally well tolerated.

Determination of asenapine in presence of its inactive metabolites in human plasma by LC-MS/MS

A highly selective and sensitive liquid chromatography-tandem mass spectrometry （LC-MS/MS） assay has been described for the determination of asenapine （ASE） in presence of its inactive metabolites N-desmethyl asenapine （DMA） and asenapine-N-glucuronide （ASG）. ASE, and ASE 13C-d3, used as internal standard （IS）, were extracted from 300 μL human plasma by a simple and precise liquid-liquid extraction procedure using methyl tert-butyl ether. Baseline separation of ASE from its inactive metabolites was achieved on Chromolith Performance RPse （100 mm ×4.6 mm） column using acetonitrile- 5.0 mM ammonium acetate-10% formic acid （90：10：0.1, v/v/v） within 4.5 min. Quantitation of ASE was done on a triple quadrupole mass spectrometer equipped with electrospray ionization in the positive mode. The protonated precursor to product ion transitions monitored for ASE and ASE 13C-d3 were m/z 286.1 → 166.0 and m/z 290.0 → 166.1, respectively. The limit of detection （LOD） and limit of quantitation （LOQ） of the method were 0.0025 ng/mL and 0.050 ng/mL respectively in a linear concentration range of 0.050-20.0 ng/mL for ASE. The intra-batch and inter-batch precision （% CV） and mean relative recovery across quality control levels were 〈 5.8% and 87.3%, respectively. Matrix effect, evaluated as IS-normalized matrix factor, ranged from 1.03 to 1.05. The stability of ASE under different storage conditions was ascertained in presence of the metabolites. The developed method is much simpler, matrix free, rapid and economical compared to the existing methods. The method was suc- cessfully used for a bioequivalence study of asenapine in healthy Indian subjects for the first time.

The study of bioavailability and bioequivalence of oseltamivir in Chinese health volunteers

Objective To evaluate the bioavailability and bioequivalence of oseltamivir capsule in Chinese health male volunteers.Methods A randomized,two period,two treatment,two sequence crossover bioequivalence trial was designed,24 Chinese health volunteers were randomly divided into two groups,each group was orally given single dose oseltamivir phosphate(tamifla)or AMMS 607 capsule.The active metabolite oseltamivir carboxylate of oseltamivir in the plasma were determined by liquid chromatographic-tandem mass spectrometric(LC-MS/MS)method.The pharmacokinetics parameters and relative bioavailability were calculated to evaluate the bioequivalence of AMMS 607 and tamifla.Results Cmax of the AMMS 607 and tamifla were 602.07±153.27 ng·mL-1 and 620.09±132.39 ng·mL-1 respectively;tmax were 4.2±1.1 h and 4.8±1.0 h;t1/2β were 6.60±0.87 h and 6.61±0.83 h;MRT were 10.00±1.77 h and 10.40±1.62 h;AUC0-24 were 6285.88±1083.66 ng·h·mL-1 and 6546.01±1199.32 ng·h·mL-1;Compared with the reference of tamifla capsule,the bioavailability F0-tn of AMMS 607 capsule was 99.5±27.7%.The main pharmacokinetics parameters of AUC0-24,Cmax and Tmax showed no statistically significant difference between the two capsules.Conclusions The AMMS 607 capsule and tamifla capsule are bioequivalent.

Liquid Chromatography-electrospray Ionization Tandem Mass Spectrometry for Simultaneous Determination of Metformin and Glimepiride in Beagle Dog Plasma and Bioequivalence Study

A sensitive and selective liquid chromatography-electrospray ionization tandem mass spectrometry（LC- ES1-MS/MS） was used for the simultaneous determination of metformin and glimepiride in beagle dog plasma with glipizide as internal standard（IS）. After simplified protein precipitation with methanol, both the analytes and IS were chromatographed on a Zorbax CN column via gradient elution with methanol（containing 5 mmol/L ammonium ace- tate） and 5 mmol/L aqueous ammonium acetate as the mobile phase. Detection was performed by multiple reaction monitoring（MRM） scanning via ESI source operated in positive ionization mode. Specificity, linearity, accuracy, pre- cision, recovery, matrix effect and stability were validated for metformin and glimepiride in beagle dog plasma. The calibration curves were linear in a concentration range of 10-10000 ng/mL for metformin and 4-4000 ng/mL for glimepiride with both correlation coefficients higher than 0.99. The recoveries obtained for the analytes and IS were all between 82.7% and 101.2%. The method exhibited excellent performance in terms of selectivity, robustness, short analytical time and simplicity of sample preparation. Finally, the proposed method was applied to a bioequivalence study of self-made bilayer tablet and commercial formulation containing 500 mg of metformin and 1 mg of glimepi- ride in beagle dogs.