Development of a Rapid LC-MS/MS Method for Simultaneous Quantification of Donepezil and Tadalafil in Rat Plasma: Its Application in a Pharmacokinetic Interaction Study after Oral Administration in Rats.

This study aimed to establish a simple and sensitive analytical method to simultaneously quantify donepezil (DPZ) and tadalafil (TAD) in rat plasma using lansoprazole (LPZ) as an internal standard (IS) by using liquid chromatography tandem mass spectrometry. The fragmentation pattern of DPZ, TAD, and IS was elucidated using multiple reaction monitoring in electrospray ionization positive ion mode for the quantification of precursor to production at m/z 380.1 → 91.2 for DPZ, m/z 390.2 → 268.1 for TAD, and m/z 370.3 → 252.0 for LPZ. The extracted DPZ and TAD from plasma using acetonitrile-induced protein precipitation was separated using Kinetex C18 (100 × 2.1 mm, 2.6 µm) column with a gradient mobile phase system consisting of 2 mM ammonium acetate and 0.1% formic acid in acetonitrile at a flow rate of 0.25 mL/min for 4 min. The selectivity, lower limit of quantification, linearity, precision, accuracy, stability, recovery, and matrix effect of this developed method was validated according to the guidelines of the U.S. Food and Drug Administration and the Ministry of Food and Drug Safety of Korea. The established method achieved acceptance criteria in all validation parameters, ensuring reliability, reproducibility, and accuracy, and was successfully implemented in a pharmacokinetic study on the co-administration of DPZ and TAD orally in rats.

A Validated Chiral LC-MS/MS Method for the Enantioselective Determination of (S)-(+)- and (R)-(-)-Ibuprofen in Dog Plasma: Its Application to a Pharmacokinetic Study.

The purpose of this study was to develop a method for simultaneously separating ibuprofen enantiomers using electrospray ionization (ESI) liquid chromatography with tandem mass spectrometry (LC-MS/MS). LC-MS/MS was operated with negative ionization and multiple reaction monitoring modes; transitions were monitored at m/z of 205.1 > 160.9 for ibuprofen enantiomers, 208.1 > 163.9 for (S)-(+)-ibuprofen-d3 [internal standard 1 (IS1)], and 253.1 > 208.9 for (S)-(+)-ketoprofen (IS2), respectively. In a one-step liquid-liquid extraction, 10 µL plasma was extracted with ethyl acetate:methyl tertiary-butyl ether of 7:3. Enantiomer chromatographic separation was carried out with an isocratic mobile phase consisting of 0.008% formic acid in water-methanol (v/v) at a flow rate of 0.4 mL/min on a CHIRALCEL® OJ-3R column (150 × 4.6 mm, 3 µm). This method was fully validated for each enantiomer and results were in compliance with the regulatory guidelines of the U.S. Food and Drug Administration and the Korea Ministry of Food and Drug Safety. The validated assay was executed for nonclinical pharmacokinetic studies after oral and intravenous administration of racemic ibuprofen and dexibuprofen in beagle dogs.

Pharmacokinetic Comparison of Ginsenosides between Fermented and Non-Fermented Red Ginseng in Healthy Volunteers.

Fermentation of red ginseng (RG) produces fermented red ginseng (FRG), thereby increasing the relative amount of downstream ginsenosides, including compound Y (CY), F2, Rh2, compound K (CK), compound O, protopanaxadiol (PPD), and protopanaxatriol (PPT). These downstream ginsenosides have beneficial pharmacological effects, and are easily absorbed by the human body. Based on these expectations, a randomized, single-dose, two-period, crossover clinical trial was planned to compare the pharmacokinetic characteristics of seven types (Rb1, CY, F2, CK, Rh2, PPD, and PPT) of ginsenoside components after FRG and RG administration. The safety and tolerability profiles were assessed in this clinical trial. Sixteen healthy Korean male subjects were administered 6 g of FRG or RG. All ginsenosides except Rb1 showed higher systemic exposure after FRG administration than after RG administration, based on comparisons of ginsenoside Cmax and area under the concentration-time curve (AUC) between FRG and RG. CK, the main ginsenoside component produced during the fermentation process, had 69.23/74.53-fold higher Cmax/AUClast after administration of FRG than RG, and Rh2 had 20.27/18.47-fold higher Cmax/AUClast after administration of FRG than RG. In addition, CY and F2 were detected in FRG; however, all plasma concentrations of CY and F2, except in one subject, were below the lower limit of quantification in RG. There were no clinically significant findings with respect to clinical laboratory tests, blood pressures, or adverse events. Therefore, regular administration of FRG may exert better pharmacological effects than RG.

A Pharmacokinetic Study of Ephedrine and Pseudoephedrine after Oral Administration of Ojeok-San by Validated LC-MS/MS Method in Human Plasma.

A sensitive and reproducible liquid chromatography-tandem mass spectrometry (LC-MS/MS) system was developed and fully validated for the simultaneous determination of ephedrine and pseudoephedrine in human plasma after oral administration of the herbal prescription Ojeok-san (OJS); 2-phenylethylamine was used as the internal standard (IS). Both compounds presented a linear calibration curve (r2 ≥ 0.99) over a concentration range of 0.2-50 ng/mL. The developed method was fully validated in terms of selectivity, lower limit of quantitation, precision, accuracy, recovery, matrix effect, and stability, according to the regulatory guidelines from the U.S. Food and Drug Administration and the Korea Ministry of Food and Drug Safety. This validated method was successfully applied for the pharmacokinetic assessment of ephedrine and pseudoephedrine in 20 healthy Korean volunteers administered OJS.

Ginsenoside Absorption Rate and Extent Enhancement of Black Ginseng (CJ EnerG) over Red Ginseng in Healthy Adults.

Red ginseng (RG) and black ginseng (BG, CJ EnerG) were prepared from fresh ginseng using one and nine cycles of steaming and drying, respectively. This process reduces the molecular weight (MW) of ginsenoside-active compounds in ginseng by removing sugar moieties from their dammaranes. We compared the pharmacokinetic characteristics of ginsenosides between BG comprising mainly low-MW ginsenosides (Rg3, Rg5, Rk1, and Rh1) and RG that predominantly contains high-MW ginsenosides (Rb1, Rb2, Rc, Rd, Re, and Rg1). The safety profiles and tolerability were also studied using a randomized, double-blind, single-dose, crossover clinical trial. A combination of Rb1, Rg1, and Rg3, well-known representative and functional RG components, exhibited a 1 h faster absorption rate (Tmax) and 58% higher exposure (24 h area under the concentration-time curve, AUC24) in BG than in RG. Furthermore, the combination of Rg3, Rg5, and Rk1, the major and most efficient components in BG, displayed 824% higher absorption (AUC24) in BG than in RG. The total ginsenoside showed a 5 h rapid intestinal absorption (Tmax) and 79% greater systemic exposure (AUC24) in BG than in RG. No clinically significant findings were observed in terms of safety or tolerability. Thus, BG extract was more effective than RG extract.

Development and Validation of an LC-MS/MS Assay to Quantitate 2',4',6'-Trihydroxyacetophenone in Rat and Dog Plasma and its Application to a Pharmacokinetic Study.

In the present study, a simple, rapid, and reliable bioanalytical method was developed using liquid chromatography with tandem-mass spectrometry (LC-MS/MS) to quantify 2',4',6'-trihydroxyacetophenone (THAP) in rat and dog plasma with 2',4',6'-trihydroxybenzaldehyde as an internal standard (IS). The LC-MS/MS instrument was operated in the multiple reaction monitoring (MRM) mode to detect THAP at m/z transition 166.89 > 82.8 and IS at 152.89 > 82.8, respectively. A simple, one-step protein precipitation (PP) method was employed with acetonitrile for sample preparation. Utilizing a Gemini C18 column, THAP and IS were separated with an isocratic mobile phase consisting of 10 mM ammonium acetate and methanol (10:90, v/v) at a flow rate of 0.2 mL/min. Total chromatographic run time was 2.5 min per sample injection. The standard calibration curve for THAP was linear (r2 ≥ 0.9987) over the concentration range of 0.1 to 100 µg/mL with the lower limit of quantitation (LLOQ) of 0.1 µg/mL (S/N ratio > 10). According to the regulatory guidelines from the U.S. Food and Drug Administration (FDA) and the Korea Ministry of Food and Drug Safety (MFDS), our newly developed biomedical analytical method was fully and adequately validated in terms of selectivity, sensitivity, linearity, intra- and inter-day precision and accuracy, recovery, matrix effect, stability, and dilution integrity. Our validated assay was successfully utilized in a nonclinical pharmacokinetic study of THAP in rats and dogs.

Quantitation of plasma and biliary cefpiramide concentrations in human samples using high-performance liquid chromatography.

Cefpiramide is frequently used to treat biliary infections. However, no bioanalytical method has been validated to quantitate cefpiramide in human samples, particularly in bile. Therefore, this study was conducted to develop a simple, selective and validated high-performance liquid chromatographic method to determine cefpiramide in human plasma and bile. A protein precipitation procedure was used to extract cefpiramide and cefoperazone (internal standard, IS) from 200 µl of plasma and bile. Utilizing a Capcell Pak C18 column (4.6 × 250 mm), cefpiramide and IS were separated using the timed-gradient mobile phase consisting of 0.1 m sodium acetate (pH 5.2) and acetonitrile at a flow rate of 1 ml/min with photodiode array detector (wavelength set at 273 nm). The calibration curves showed linearity at concentrations ranging from 1 to 150 µg/ml in both plasma and bile (r2 > 0.999). The within- and between-run coefficients of variation (CVs) for plasma samples were 0.570-4.43 and 1.10-2.76%, respectively; for bile samples, the within- and between-day precision (CV) was 0.814-6.34 and 2.05-4.00%, respectively. Our newly developed bioanalytical method was successfully employed to quantify cefpiramide concentrations in both plasma and bile at multiple time points in patients with acute cholangitis.

A Pharmacokinetic Drug Interaction Between Fimasartan and Linagliptin in Healthy Volunteers.

OBJECTIVE: Fimasartan, an angiotensin II type 1 receptor blocker, and linagliptin, a dipeptidyl-peptidase-4 inhibitor, are frequently coadministered to treat patients with hypertension and diabetes, respectively. This study sought to evaluate the pharmacokinetic interactions between fimasartan and linagliptin after co-administration in healthy Korean subjects. METHODS: The overall study was divided into two separate parts, with each part designed as an open-label, multiple-dose, two-period, and single-sequence study. In Part A, to investigate the effect of linagliptin on fimasartan, 25 subjects received 120 mg fimasartan alone once daily for seven days during Period I, and 120 mg fimasartan with 20 mg linagliptin for seven days during Period II. In Part B, to examine the effect of fimasartan on linagliptin, 12 subjects received only linagliptin once daily for seven days during Period I, followed by concomitant administration of fimasartan for seven days during Period II, at the same doses used in Part A. Serial blood samples were collected at scheduled intervals for up to 24 h after the last dose to determine the steady-state pharmacokinetics of both drugs. RESULTS: Thirty-six subjects completed the study. The geometric mean ratio and 90% confidence intervals for maximum plasma concentration at steady state (Cmax,ss) and area under the concentration-time curve at steady state (AUCτ,ss) of fimasartan with or without linagliptin were 1.2633 (0.9175-1.7396) and 1.1740 (1.0499-1.3126), respectively. The corresponding values for Cmax,ss and AUCτ,ss of linagliptin with or without fimasartan were 0.9804 (0.8480-1.1336) and 0.9950 (0.9322-1.0619), respectively. A total of eight adverse events (AEs) were reported and the incidence of AEs did not increase significantly with co-administration of the drugs. CONCLUSION: Our results suggest that there are no clinically significant pharmacokinetic interactions between fimasartan and linagliptin when co-administered. Treatments were well tolerated during the study, with no serious adverse effects. CLINICAL TRIAL REGISTRY: http://clinicaltrials.gov, NCT03250052.

Quantification of metronidazole in human bile fluid and plasma by liquid chromatography-tandem mass spectrometry.

This study was conducted to develop a highly selective, sensitive, and validated method for quantifying metronidazole in human plasma and bile fluid. Metronidazole and metronidazole-d4 (internal standard) were extracted from 100 µL of plasma and bile fluid by liquid-liquid extraction. Liquid chromatography with a Hydrosphere C18 column (50 × 2.0 mm) was performed using 10 mM ammonium formate (pH 4.0) and acetonitrile (20:80, v/v) as the mobile phase. Triple quadrupole mass spectrometry was operated with an electrospray ionization interface in multiple reaction monitoring and positive ion modes. The calibration curves were linear for bile and plasma samples over the range of 50-20,000 ng/mL (r2 > 0.999). The intra- and inter-day coefficients of variation (CVs) for plasma ranged from 2.50% to 7.85% and 3.11% to 16.9%, respectively; for bile, the intra-and inter-run precision (CVs) ranged from 2.76% to 13.2% and 3.16% to 11.5%, respectively. The mean extraction recovery for metronidazole ranged from 76.5% to 82.1% in plasma and from 78.8% to 87.8% in bile, respectively. Our proposed analytical method was successfully applied to determine metronidazole concentrations in bile as well as in plasma at multiple time points in a patient with acute cholangitis.

Development and Validation of Simple LC-MS-MS Assay for the Quantitative Determination of Ticagrelor in Human Plasma: its Application to a Bioequivalence Study.

A sensitive, rapid, reproducible and reliable high-performance liquid chromatography-electrospray ionization tandem mass spectrometric method has been developed and fully validated for the determination of ticagrelor in human plasma using ticagrelor-d7 as an internal standard (IS) after one-step liquid-liquid extraction with ethyl acetate. Ticagrelor and IS were detected in the multiple reaction monitoring mode at m/z transition 523.4 > 127.0 and 530.4 > 127.0, respectively. Chromatographic separation was performed on a Phenomenex Luna® C18 column using a mobile phase consisting of 0.1% formic acid in water-acetonitrile (20:80, v/v) at a flow rate of 0.2 mL/min. The retention times of ticagrelor and IS were 1.03 min and 1.02 min, respectively. The calibration curve was linear [correlation coefficient (r) ≥ 0.9991] over the concentration range of 2-1,500 ng/mL. Intra- and inter-day precisions ranged from 1.0% to 4.9% and from 1.8% to 8.7%, and the accuracy ranged from 97.0% to 105.9% and from 97.5% to 102.9%, respectively. The developed method was fully validated with respect to selectivity, linearity, lower limit of quantitation, recovery, matrix effect and stability. This validated method was successfully applied to the bioequivalence study of ticagrelor in 44 healthy Korean male volunteers.

Pharmacokinetics and bioequivalence of two fenofibrate choline formulations in healthy subjects under fed and fasted condition
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OBJECTIVE: The objective of this study was to evaluate the pharmacokinetics and bioequivalence of two formulations (the original capsule ("reference") and the new tablet ("test") formulations) of 135-mg choline fenofibrate under fed and fasted conditions. MATERIALS AND METHODS: This was an open-label, randomized, single-dose, crossover bioequivalence study in healthy Korean males. A total of 40 individuals were separately enrolled in the high-fat fed and the fasting study, respectively, and were randomized in a 1:1 ratio into two sequences. Serial blood samples were collected over 72 hours after drug administration. Plasma concentrations of fenofibric acid were determined by a validated LC-MS/MS method. Pharmacokinetic (PK) parameters were estimated using noncompartmental methods. RESULTS: Overall, 37 and 35 individuals completed the fed and the fasting study, respectively, as planned. The estimated Cmax, AUC0-∞, and AUC0-last were comparable between the test and the reference formulations in both fed and fasting studies (p > 0.05). The 90% confidence intervals for the geometric mean ratios of Cmax, AUC0-∞, and AUC0-last were 0.92 - 1.06, 0.95 - 1.01, and 0.95 - 1.01 in the fed study; and 0.94 - 1.12, 0.94 - 1.00, and 0.94 - 1.00 in the fasting study, respectively. For both formulations, tmax was significantly prolonged under fed condition compared to fasting condition (p < 0.0001); all other PK parameters were comparable between the fed and the fasting studies (p > 0.05). CONCLUSION: The reference and the test formulations of 135 mg choline fenofibrate show comparable pharmacokinetic profiles of fenofibric acid under both fed and fasted conditions and are considered bioequivalent.
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Pharmacokinetic and bioequivalence study comparing a fimasartan/rosuvastatin fixed-dose combination with the concomitant administration of fimasartan and rosuvastatin in healthy subjects.

PURPOSE: A new fixed-dose combination (FDC) formulation of 120 mg fimasartan and 20 mg rosuvastatin was developed to increase therapeutic convenience and improve treatment compliance. METHODS: A randomized, open-label, single-dose, two-treatment, two-way crossover study with a 7-day washout period was conducted to compare the pharmacokinetic (PK) characteristics and bioequivalence between an FDC of fimasartan/rosuvastatin and the separate co-administration of fimasartan and rosuvastatin in healthy Korean volunteers. The plasma concentrations of fimasartan and rosuvastatin were analyzed by a validated liquid chromatography-tandem mass spectrometry method, for which serial blood samples were collected for up to 48 hours post-administration of fimasartan and 72 hours post-administration of rosuvastatin, in each period. The PK parameters were calculated using a non-compartmental method. RESULTS: A total of 78 subjects completed the study. All the 90% CIs of the geometric mean ratios (GMRs) fell within the predetermined acceptance range. The GMR and 90% CI for the area under the plasma concentration-time curve from time 0 to the last measurement (AUC0-t) and the maximum plasma concentration (Cmax) for fimasartan were 0.9999 (0.9391-1.0646) and 1.0399 (0.8665-1.2479), respectively. The GMR and 90% CI for the AUC0-t and Cmax for rosuvastatin were 1.0075 (0.9468-1.0722) and 1.0856 (0.9944-1.1852), respectively. Treatment with fimasartan and rosuvastatin was generally well tolerated without serious adverse events. CONCLUSION: The new FDC formulation of 120 mg fimasartan and 20 mg rosuvastatin can be substituted for the separate co-administration of fimasartan and rosuvastatin, for the advantage of better compliance with convenient therapeutic administration.

Development of a simple and sensitive HPLC-MS/MS method for determination of diazepam in human plasma and its application to a bioequivalence study.

We developed a simple, sensitive, and effective ultra-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) method with an electrospray ionization (ESI) interface in multiple reaction monitoring (MRM) and positive ion modes to determine diazepam concentrations in human plasma using voriconazole as an internal standard (IS). Diazepam and IS were detected at transition 285.2→193.1 and 350.2→127.1, respectively. After liquid-liquid extraction (LLE) using 1.2 ml of ethyl acetate:n-hexane (80:20, v/v), diazepam and IS were eluted on a Phenomenex Cadenza CD-C18 column (150 × 3.0 mm, 3 µm) with an isocratic mobile phase (10 mM ammonium acetate in water:methanol [5:95, v/v]) at a flow rate of 0.4 mL/min. The peak retention time was 2.32 min for diazepam and 2.01 min for IS, respectively. The lower limit of quantitation (LLOQ) was 0.5 ng/mL (S/N > 10) using 50 µL of plasma, and no interferences were observed in chromatograms. Our analytical method was fully validated and successfully applied to a bioequivalence study of two formulations of diazepam in healthy Korean volunteers.

Enhanced Absorption Study of Ginsenoside Compound K (20-O-ß-(D-Glucopyranosyl)-20(S)-protopanaxadiol) after Oral Administration of Fermented Red Ginseng Extract (HYFRG™) in Healthy Korean Volunteers and Rats.

To evaluate the pharmacokinetics of compound K after oral administration of HYFRG and RG in humans, an open-label, randomized, single-dose, fasting, and one-period pharmacokinetic study was conducted. After oral administration of a single 3 g dose of HYFRG and RG to 24 healthy Korean males, the mean (±SD) of AUC0-t and C max of compound K from HYFRG were 1466.83 ± 295.89 ng·h/mL and 254.45 ± 51.20 ng/mL, being 115.2- and 80-fold higher than those for RG (12.73 ± 7.83 ng·h/mL and 3.18 ± 1.70 ng/mL), respectively; in case of Sprague Dawley rats the mean (±SD) of AUC0-t and C max of compound K from HYFRG was 58.03 ± 32.53 ng·h/mL and 15.19 ± 10.69 ng/mL, being 6.3- and 6.0-fold higher than those from RG (9.21 ± 7.52 ng·h/mL and 2.55 ± 0.99 ng/mL), respectively. T max of compound K in humans and rats was 2.54 ± 0.92 and 3.33 ± 0.50 h for HYFRG and 9.11 ± 1.45 and 6.75 ± 3.97 hours for RG, respectively. In conclusion, the administration of HYFRG resulted in a higher and faster absorption of compound K in both humans and rats compared to RG.

Development and validation of an LC-MS/MS method for the determination of pelubiprofen and its active metabolite, trans-alcohol, in human plasma and its application to pharmacokinetic study.

A suitable liquid chromatography tandem mass spectrometry (LC-MS/MS) method is required to determine pelubiprofen and its active metabolite, trans-alcohol (M-D), in human plasma for pharmacokinetic studies of pelubiprofen preparations. After one-step liquid-liquid extraction (LLE) using methyl tert-butyl ether (MTBE), pelubiprofen, M-D, and tolbutamide (the internal standard, IS) were eluted from a Capcellpak C18 ACR column using a gradient mobile phase consisting of 0.1% formic acid in water and acetonitrile at a flow rate 0.35mL/min. The achieved lower limits of quantitation (LLOQ) of pelubiprofen and M-D were both 15ng/mL (S/N>10) and the standard calibration curves for pelubiprofen and M-D were linear (correlation coefficients >0.99) over the studied concentration range (15-2000ng/mL). Intra- and inter-day precisions were within 7.62% for all analytes and the deviation of assay accuracies was within ±13.23%. The developed method was successfully applied to a pharmacokinetic study of pelubiprofen in healthy Korean male volunteers.

Development of simple and rapid LC-MS/MS method for determination of celecoxib in human plasma and its application to bioequivalence study.

A suitable liquid chromatography tandem mass spectrometry (LC-MS/MS) method to determine celecoxib in human plasma is needed for bioequivalence and pharmacokinetic studies of celecoxib preparations. The present study describes a simple, rapid, reproducible, and reliable LC-MS/MS method to determine celecoxib concentrations in human plasma. After one-step liquid-liquid extraction (LLE) using methyl tert-butyl ether (MTBE), celecoxib and atorvastatin (internal standard, IS) were eluted on a Luna HILIC column with an isocratic mobile phase, consisting of 10mM ammonium formate buffer (adjusted to pH 3.0 with formic acid):methanol (5:95, v/v) at a flow rate of 0.2 mL/min. The achieved lower limit of quantitation (LLOQ) was 10 ng/mL (S/N>10) and the standard calibration curve for celecoxib was linear (correlation coefficients were >0.9995) over the studied concentration range (10-2000 ng/mL). The inter- and intra-assay coefficients of variation ranged from 1.15% to 4.93% and 1.08% to 7.81%, respectively. The chromatographic run time for each plasma sample was <2 min. The developed method was successfully applied to a bioequivalence study of celecoxib in healthy Korean male volunteers.