Validated liquid chromatography–tandem mass spectrometry method for quantitative determination of dauricine in human plasma and its application to pharmacokinetic study

A highly sensitive and selective LC–MS/MS method was developed and validated for the determination of dauricine in human plasma, using protopine as internal standard (IS). The analyte and IS were extracted by liquid–liquid extraction and analyzed by LC–MS/MS. Chromatographic separation was performed on Agilent TC-C₁₈ column with a mobile phase of methanol–water–glacial acetic acid (60:40:0.8, v/v/v) at a flow rate of 0.7 mL/min. Detection was performed on a triple quadrupole tandem mass spectrum by multiple reaction monitoring (MRM) mode using the electrospray ionization technique in positive mode. The method was linear over the concentration range of 1–200 ng/mL. The lower limit of quantification (LLOQ) was 1 ng/mL in human plasma with acceptable precision and accuracy. The intra- and inter-day precision was less than 5.9% determined from quality control (QC) samples at concentrations of 2.0, 20.0 and 160 ng/mL, and the accuracy was within ±9.9%. This method was successfully applied for the evaluation of pharmacokinetics of dauricine after oral doses of 100, 300 and 600 mg phenolic alkaloids of menispermum dauricum tablet (PAMDT) to 12 Chinese healthy volunteers.     

Development and validation of a liquid chromatography–tandem mass spectrometry method for the determination of goserelin in rabbit plasma

A rapid and sensitive liquid chromatography–electrospray ionization tandem mass spectrometry method (LC–ESI-MS/MS) was developed and validated for the determination of goserelin in rabbit plasma. Various parameters affecting plasma sample preparation, LC separation, and MS/MS detection were investigated, and optimized conditions were identified. Acidified plasma samples were applied to Oasis^® HLB solid-phase extraction (SPE) cartridges. Extracted samples were evaporated under a stream of nitrogen and then reconstituted with 100 μL mobile phase A. The separation was achieved on a Capcell-Pak C18 (2.0 mm × 150 mm, 5 μm, AQ type) column with a gradient elution of solvent A (0.05% acetic acid in deionized water/acetonitrile = 85/15; v/v) and solvent B (acetonitrile) at a flow rate of 250 μL/min. The LC–MS/MS system was equipped with an electrospray ion source operating in positive ion mode. Multiple-reaction monitoring (MRM) of the precursor–product ion transitions consisted of m/z 635.7 → m/z 607.5 for goserelin and m/z 424.0 → m/z 292.1 for cephapirin (internal standard). The proposed method was validated by assessing specificity, linearity, limit of quantification (LOQ), intra- and inter-day precision and accuracy, recovery, and stability. Linear calibration curves were obtained in the concentration range of 0.1–20 ng/mL (the correlation coefficients were above 0.99). The LOQ of the method was 0.1 ng/mL. Results obtained from the validation study of goserelin showed good accuracy and precision at concentrations of 0.1, 1, 5, 10, and 20 ng/mL. The validated method was successfully applied to a pharmacokinetic study of goserelin after a single subcutaneous injection of 3.6 mg of goserelin in healthy white rabbits.     

Determination of Tenacissoside A in rat plasma by liquid chromatography–tandem mass spectrometry method and its application to pharmacokinetic study

A sensitive and specific liquid chromatography–tandem mass spectrometry method was developed and validated for the first time for the estimation of Tenacissoside A in the rats’ plasma, which is the major active constituent in Marsdenia tenacissima. Tenacissoside A was extracted from the rats’ plasma by using liquid–liquid extraction (LLE), medroxyprogesterone acetate was used as the internal standard. An Alltech C18 column (250 mm × 4.6 mm, 5 μm) was used to provide chromatographic separation by detection with mass spectrometry operating in selected ion monitoring (SIM) mode. The method was validated over the concentration range of 1–250 ng/mL for Tenacissoside A. The precisions within and between-batch (CV%) were both less than 15% and accuracy ranged from 90 to 102%. The lower limit of quantification was 1 ng/mL and extraction recovery was 88.3% on average. The validated method was used to study the pharmacokinetic profile of Tenacissoside A in rat after administration.     

Determination of mitoxantrone in rat plasma by liquid chromatography–tandem mass spectrometry method: Application to a pharmacokinetic study

A rapid, sensitive and specific high performance liquid chromatography–tandem mass spectrometric (HPLC–MS/MS) method has been developed for quantification of mitoxantrone in rat plasma. The analyte and palmatine (internal standard) were extracted from plasma samples with diethyl ether–dichloromethane (3:2, v/v) and separated on a C₁₈ column. The chromatographic separation was achieved within 2.5 min using methanol–10 mM ammonium acetate containing 0.1% acetic acid as the mobile phase at a flow rate of 0.2 mL/min. The method was linear over the range of 0.5–500 ng/mL. The lower limit of quantification (LLOQ) was 0.5 ng/mL. Finally, the method was successfully applied to a pharmacokinetic study of mitoxantrone in rats following intravenous administration.     

Development and validation of a quantitative method for the determination of 12 endocannabinoids and related compounds in human plasma using liquid chromatography–tandem mass spectrometry

A sensitive and specific LC–MS/MS method for the quantification of the endocannabinoids and related structures anandamide, 2-arachidonoyl glycerol, 2-arachidonyl glycerol ether, O-arachidonoyl ethanolamide, dihomo-γ-linolenoyl ethanolamide, docosatetraenoyl ethanolamide, N-arachidonoyl dopamine, N-arachidonyl glycine, N-oleoyl dopamine, oleoyl ethanolamide, palmitoyl ethanolamide, and stearoyl ethanolamide in human plasma was developed and validated. Compounds were extracted using acetonitrile followed by solid-phase extraction. Separation was performed on a Xterra C8 column using gradient elution coupled to a triple-quadrupole MS. LLOQ levels ranged from 0.02 to 1.75 μg/mL, LODs ranged from 0.0002 to 0.1266 ng/mL, and accuracies were >80% (except stearoyl ethanolamide at lowest spike level) at all spike levels.     

Simultaneous quantification of venlafaxine and O-desmethylvenlafaxine in human plasma by ultra performance liquid chromatography–tandem mass spectrometry and its application in a pharmacokinetic study

A rapid, selective and sensitive ultra performance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS) method was developed to simultaneously determine venlafaxine (VEN) and O-desmethylvenlafaxine (ODV) in human plasma. Sample pretreatment involved a one-step extraction with diethyl ether of 0.5 mL plasma. The separation was carried out on an ACQUITY UPLC? BEH C₁₈ column with 10 mmol/L ammonium acetate and methanol as the mobile phase at a flow rate of 0.30 mL/min. The detection was performed on a triple–quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) mode via electrospray ionization (ESI) source. The linear calibration curves for VEN and ODV were both obtained in the concentration range of 0.200–200 ng/mL (r² ≥ 0.99) with the lower limit of quantification (LLOQ) of 0.200 ng/mL. The intra- and inter-day precision (relative standard deviation, R.S.D.) values were less than 13% and the accuracy (relative error, R.E.) was within ±5.3% and ±3.6% for VEN and ODV. The method herein described was superior to previous methods in sensitivity and sample throughput and successfully applied to clinical pharmacokinetic study of venlafaxine sustained-release capsule in healthy male volunteers after oral administration.     

Simultaneous determination of m-nisoldipine and its three metabolites in rat plasma by liquid chromatography–mass spectrometry

A simple, sensitive and selective liquid chromatography–tandem mass spectrometry (LC–MS/MS) method for the simultaneous determination of m-nisoldipine and its three metabolites in rat plasma has been developed using nitrendipine as an internal standard (IS). Following liquid–liquid extraction, the analytes were separated using an isocratic mobile phase on a reverse phase C₁₈ column and analyzed by MS in the multiple reaction monitoring (MRM) mode. To avoid contamination by residual sample in the injection syringe, a special injection protocol was developed. We found that m-nisoldipine, metabolite M1 and IS could be ionized under positive or negative electrospray ionization conditions, whereas metabolite M and M2 could only be ionized in the positive mode. The mass spectrometry fragmentation pathways for these analytes are analyzed and discussed herein. The total analysis time required less than 5 min per sample. We employed this method successfully to study the metabolism of m-nisoldipine when it was orally administered to rats at a dose of 9 mg/kg. Three metabolites of m-nisoldipine and an unknown compound of molecular weight 386 were found for the first time in rat plasma. The concentration of the potentially active metabolite was approximately equal to its parent compound concentration.     

Liquid chromatography–tandem mass spectrometry quantification of levosulpiride in human plasma and its application to bioequivalence study

An improved method for determining levels of levosulpiride in human plasma using ultra-performance liquid chromatography–tandem mass spectrometry (UPLC–MS/MS) was developed and validated. The protein precipitation method was used for plasma sample preparation. Levosulpiride and an internal standard (IS) were isocratically separated on a UPLC BEH C₁₈ column with a mobile phase of ammonium formate buffer (1 mM, adjusted to pH 3 with formic acid) and acetonitrile (60:40, v/v). MS/MS detection was performed by monitoring the parent → daughter pair of levosulpiride and the IS at m/z 342 → 112 and 329 → 256, respectively. The method was linear from 2.5 to 200 ng/mL and exhibited acceptable precision and percent recovery. The method was successfully demonstrated in pharmacokinetic and bioequivalence studies of two levosulpiride oral formulations administered to healthy volunteers. When compared to the previous LC–MS methods, the proposed method is faster, well-validated, and uses lesser plasma volume and a similar sensitivity. The use of UPLC allowed rapid and sensitive quantification of levosulpiride, making this method suitable for high-throughput clinical applications.     

Development and validation of a sensitive gas chromatography–ammonia chemical ionization mass spectrometry method for the determination of tabun enantiomers in hemolysed blood and plasma of different species

The aim of this study was to develop and validate a fast, sensitive and easily applicable GC–MS assay for the chiral quantification of the highly toxic organophosphorus compound tabun (O-ethyl-N,N-dimethylphosphoramidocyanidate, GA) in hemolysed swine blood for further use in toxicokinetic and toxicodynamic studies. These requirements were fulfilled best by a GC–MS assay with positive chemical ionization with ammonia (GC–PCI-MS). Separation was carried out on a β-cyclodextrin capillary column (Supelco BetaDex^® 225) after reversed phase (C18) solid-phase extraction. The limit of detection was 1 pg/ml for each enantiomer (approximately 500 fg on column) and the limit of quantification 5 pg/ml. The GC–PCI-MS method was applied for the quantification of tabun enantiomers in spiked swine blood after hemolysis and in spiked plasma of different species including humans.     

A sensitive liquid chromatography–electrospray tandem mass spectrometric method for lancemaside A and its metabolites in plasma and a pharmacokinetic study in mice

A high-performance liquid chromatography tandem mass spectrometry (HPLC–MS/MS) method employing electrospray ionization (ESI) has been developed for simultaneous determination of lancemaside A (3-O-β-d-glucuronopyranosyl-3β, 16α-dihydroxyolean-12-en-28-oic acid 28-O-β-d-xylopyranosyl(1→3)-β-d-xylopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranosyl ester) and its metabolites in mouse plasma. When lancemaside A (60 mg/kg) was orally administered to mice, echinocystic acid was detected in the blood. T_max and C_max of the echinocystic acid were 6.5 ± 1.9 h and 56.7 ± 29.1 ppb. Orally administered lancemaside A was metabolized to lancemaside X (3β, 16α-dihydroxyolean-12-en-28-oic acid 28-O-β-d-xylopyranosyl(1→3)-β-d-xylopyranosyl-(1→4)-α-l-rhamnopyranosyl-(1→2)-α-l-arabinopyranosyl ester) by intestinal microflora in mice, which was metabolized to echinocystic acid by intestinal microflora and/or intestinal tissues. Human intestinal microflora also metabolized lancemaside A to echinocystic acid via lancemaside X. These results suggest that the metabolism by intestinal microflora may play an important role in pharmacological effects of orally administered lancemaside A.     

Improved liquid chromatography–tandem mass spectrometry method for the analysis of eptifibatide in human plasma

A rapid, selective and highly sensitive high performance liquid chromatography–tandem mass spectrometry method (LC–MS/MS) was developed and validated for the determination and pharmacokinetic investigation of eptifibatide in human plasma. Eptifibatide and the internal standard (IS), EPM-05, were extracted from plasma samples using solid phase extraction. Chromatographic separation was performed on a C₁₈ column at a flow rate of 0.5 mL/min. Detection of eptifibatide and the IS was achieved by tandem mass spectrometry with an electrospray ionization (ESI) interface in positive ion mode. Traditional multiple reaction monitoring (MRM) using the transition of m/z 832.6 → m/z 646.4 and m/z 931.6 → m/z 159.4 was performed to quantify eptifibatide and the IS, respectively. The calibration curves were linear over the range of 1–1000 ng/mL with the lower limit of quantitation validated at 1 ng/mL. The intra- and inter-day precisions were within 13.3%, while the accuracy was within ±7.6% of nominal values. The validated LC–MS/MS method was successfully applied for the evaluation of pharmacokinetic parameters of eptifibatide after intravenous (i.v.) administration of a 45 μg/kg bolus of eptifibatide to 8 healthy volunteers.     

Development and validation of a LC–MS/MS method for the determination of clebopride and its application to a pharmacokinetics study in healthy Chinese volunteers

A sensitive and specific liquid chromatography–electrospray ionization-mass spectrometry (LC–ESI-MS/MS) method has been developed and validated for the identification and quantification of clebopride in human plasma using itopride as an internal standard. The method involves a simple liquid–liquid extraction. The analytes were separated by isocratic gradient elution on a CAPCELL MG-III C₁₈ (5 μm, 150 mm × 2.1 mm i.d.) column and analyzed in multiple reaction monitoring (MRM) mode with positive electrospray ionization (ESI) interface using the respective [M+H]⁺ ions, m/z 373.9 → m/z184.0 for clebopride, m/z 359.9 → m/z71.5 for itopride. The method was validated over the concentration range of 69.530–4450.0 pg/ml for clebopride. Within- and between-batch precision (RSD%) was all within 6.83% and accuracy ranged from −8.16 to 1.88%. The LLOQ was 69.530 pg/ml. The extraction recovery was on an average 77% for clebopride. The validated method was used to study the pharmacokinetics profile of clebopride in human plasma after oral administration of clebopride.     

Identification of YH439 and its metabolites in rat urine by gas chromatography–mass spectrometry and liquid chromatography–mass spectrometry

YH439 is a potential drug candidate for the treatment of various hepatic disorders. YH439 and its three metabolites have been identified in rat urine by liquid chromatography–mass spectrometry (LC–MS) and by gas chromatography (GC)–MS. Identification of YH439 and its metabolites was established by comparing their GC retention times and mass spectra with those of the synthesized authentic standards. Both electron impact- and positive chemical ionization MS have been evaluated. The metabolism study was performed in the rat using oral administration of the drug. A major metabolite (YH438) was identified as the N-dealkylation product of YH439. Other identified metabolites were caused by the loss of the methyl thiazolyl amine group (metabolite II) from YH439, the isopropyl hydrogen malonate group (metabolite IV) and the decarboxylated product (metabolite III) of metabolite II.     

Selective and rapid liquid chromatography–mass spectrometry method for the quantification of rofecoxib in pharmacokinetic studies with humans

An easy, rapid and selective method for the determination of rofecoxib in human plasma is presented. The analytical technique is based on reversed-phase high-performance liquid chromatography coupled to atmospheric pressure chemical ionisation mass spectrometry (Finnigan Mat LCQ ion trap). The retention time of rofecoxib was 1.2 min. The method has been validated over a linear range from 1 to 500 μg/l using celecoxib as internal standard. After validation, the method was used to study the pharmacokinetic profile of rofecoxib in 12 healthy volunteers after administration of a single oral dose (12.5 mg). The presented method was sufficient to cover more than 95% of the area under the curve. The pharmacokinetic characteristics (mean±SD) were t_max: 2.4±1.0 h, c_max: 147±34 μg/l, AUC_∞: 2038±581 μg h/l and t_1/2: 11.3±2.1 h.     

Quantitation of itraconazole in rat heparinized plasma by liquid chromatography–mass spectrometry

A liquid chromatographic–mass spectrometric (LC–MS) assay was developed and validated for the determination of itraconazole (ITZ) in rat heparinized plasma using reversed-phase HPLC combined with positive atmospheric pressure ionization (API) mass spectrometry. After protein precipitation of plasma samples (0.1 ml) with acetonitrile containing nefazodone as an internal standard (I.S.), a 50-μl aliquot of the supernatant was mixed with 100 μl of 10 mM ammonium formate (pH 4.0). An aliquot of 25 μl of the mixture was injected onto a BDS Hypersil C₁₈ column (50×2 mm; 3 μm) at a flow-rate of 0.3 ml/min. The mobile phase comprising of 10 mM ammonium formate (pH 4) and acetonitrile (60:40, v/v) was used in an isocratic condition, and ITZ was detected in single ion monitoring (SIM) mode. Standard curves were linear (r²≥0.994) over the concentration range of 4–1000 ng/ml. The mean predicted concentrations of the quality control (QC) samples deviated by less than 10% from the corresponding nominal values; the intra-assay and inter-assay precision of the assay were within 8% relative standard deviation. Both ITZ and I.S. were stable in the injection solvent at room temperature for at least 24 h. The extraction recovery of ITZ was 96%. The validated assay was applied to a pharmacokinetic study of ITZ in rats following administration of a single dose of itraconazole (15 mg/kg).     

Quantitative determination of oxytocin receptor antagonist atosiban in rat plasma by liquid chromatography–tandem mass spectrometry

A kinetic study of atosiban was conducted following repeated intravenous administration in Wistar rats. Sample analysis was performed using liquid chromatography–tandem mass spectrometry (LC–MS/MS) following full validation of an in-house method. Eptifibatide, a cyclic peptide, was used as an internal standard (IS). The analyte and internal standard were extracted using solid phase extraction (SPE) method. Chromatographic separation was carried out using an ACE C18 5 μm 50 mm × 4.6 mm column with gradient elution. Mass spectrometric detection was performed using TSQ Quantum ultra AM. The lower limit of quantification was 0.01 μg/ml when 100 μl rat plasma was used. Plasma concentrations of atosiban were measured at 0 (pre-dose), 2, 15, 30, 45, 60, 120 min at the dosage levels of 0.125 mg/kg (low dose), 0.250 mg/kg (mid dose), and 0.500 mg/kg (high dose), respectively. Atosiban plasma concentration measured at Day 1 showed mean peak atosiban concentration (C_max) 0.40, 0.57, 1.95 μg/ml for low, mid and high dose treated animals and mean peak concentration on Day 28 was 0.41, 0.88, 1.31 μg/ml on Day 28 for low, mid and high dose treated animals.     

Rapid,highly sensitive method for the determination of morphine and its metabolites in body fluids by liquid chromatography–mass spectrometry

A rapid, highly sensitive method for the determination of morphine and its metabolites morphine-3-glucuronide (M3G), morphine-6-glucuronide (M6G) and normorphine has been developed using high-performance liquid chromatography–electrospray mass spectrometry, with the deuterated analogues as internal standards. The analytes were extracted automatically using end-capped C₂ solid-phase extraction cartridges. Baseline separation of morphine, M3G and M6G was achieved on a LiChrospher 100 RP-18 end-capped analytical column (125×3 mm I.D., 5 μm particle size) with water–acetonitrile–tetrahydrofuran–formic acid (100:1:1:0.1, v/v) as the mobile phase. Morphine and normorphine coeluate and were separated mass spectrometrically. The mass spectrometer was operated in the selected-ion monitoring mode using m/z 272 for normorphine, m/z 286 for morphine, m/z 462 for morphine-6-glucuronide. Due to an interfering peak, M3G was measured by tandem mass spectrometry in the daughter-ion mode. The limits of quantitation achieved with this method were 1.3 pmol/ml for morphine, 1.5 pmol/ml for normorphine, 1.0 pmol/ml for M6G and 5.4 pmol/ml for M3G in serum or cerebrospinal fluid. The limits of quantitation achieved in urine were 10 pmol/ml for morphine, 20 pmol/ml for normorphine and M6G and 50 pmol/ml for M3G using a sample size of 100 μl. The method described was successfully applied to the determination of morphine and its metabolites in human serum, cerebrospinal fluid and urine in pharmacokinetic and drug interaction studies.     

Simultaneous determination of active xanthone glycosides,timosaponins and alkaloids in rat plasma after oral administration of Zi-Shen Pill extract for the pharmacokinetic study by liquid chromatography–tandem mass spectrometry

A sensitive and reliable liquid chromatography–electrospray ionization-tandem mass spectrometry (LC–ESI-MS/MS) has been developed and validated for simultaneous determination of active components, i.e., xanthone glycosides (neomangiferin and mangiferin), timosaponins (timosaponin E1, timosaponin B-II and timosaponin B) and alkaloids (palmatine and berberine) in rat plasma after oral administration of Zi-Shen Pill extract. Plasma samples were pretreated by protein precipitation with acetonitrile containing the internal standards ginsenoside Re (for xanthone glycosides and timosaponins) and tetrahydroberberine (for alkaloids). LC separation was achieved on a Zorbax SB-C₁₈ column (150 mm × 2.1 mm I.D., 3.5 μm) with gradient elution using a mobile phase consisting of acetonitrile-0.1% formic acid in water at a flow rate of 0.25 mL/min. The detection was carried out by a triple–quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode via polarity switching between negative (for xanthone glycosides and timosaponins) and positive (for alkaloids) ionization mode. Linear calibration curves were obtained over the concentration range of 5–1000 ng/mL for mangiferin, 0.5–100 ng/mL for neomangiferin, timosaponin E1, timosaponin B-II and timosaponin B, and 0.05–10 ng/mL for palmatine and berberine. The mean recovery of all the analytes ranged from 64.7 to 93.8%. The intra- and inter-day precision (% R.S.D.) was within 11.7% and accuracy (% bias) ranged from ?9.0 to 10.9%. This fully validated method was successfully applied to pharmacokinetic study of the above seven compounds in rats.     

High performance liquid chromatography–tandem mass spectrometry for the determination of bile acid concentrations in human plasma

We report a sensitive and robust method to determine cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), lithocholic acid (LCA), ursodeoxycholic acid (UDCA), and their taurine- and glycine-conjugate concentrations in human plasma using liquid chromatography–tandem mass spectrometry. Activated charcoal was utilized to prepare bile acid-free plasma, which served as the biological matrix for the preparation of standard and quality control samples. Plasma sample preparation involved solid-phase extraction. A total of 16 bile acids and 5 internal standards were separated on a reverse column by gradient elution and detected by tandem mass spectrometry in negative ion mode. The calibration curve was linear for all the bile acids over a range of 0.005–5 μmol/L. The extraction recoveries for all the analytes fell in the range of 88–101%. Intra-day and inter-day coefficients of variation were all below 10%. A stability test showed that all the bile acids were stable in plasma for at least 6 h at room temperature, at least three freeze–thaw cycles, in the −70 °C or −20 °C freezer for 2 months, and also in the reconstitution solution at 8 °C for 48 h. Comparison of the matrix effect of bile acid-free plasma with that of real plasma indicated that the charcoal purification procedure did not affect the properties of charcoal-purified plasma as calibration matrix. This method has been used to determine the bile acid concentrations in more than 300 plasma samples from healthy individuals. In conclusion, this method is suitable for the simultaneous quantification of individual bile acids in human plasma.     

Development and validation of a LC–MS/MS method for the determination of the novel oral 1,14 substituted taxane derivatives,IDN 5738 and IDN 5839, in mouse plasma and its application to the pharmacokinetic study

Two LC-ESI–MS and CID-MS/MS methods were developed and validated for pharmacokinetic studies of the novel oral taxane derivatives IDN 5738 and IDN 5839, used for preclinical evaluation in mice. The analysis requires 100 μL of plasma sample, involves the addition of an internal standard and protein precipitation with 0.1% HCOOH in acetonitrile. The HPLC separation was obtained on Sunfire C18 column and Selected Reaction Monitoring technique was used to quantify the taxanes. The recoveries were more than 90%; the methods were linear over the validated concentrations range of 25–1500 ng/mL for IDN 5738 and 25–5000 ng/mL for IDN 5839 and had a limit of detection of 0.14 and 0.25 ng/mL, respectively. The inter-day coefficient of variation (CV%) of the calibration standards ranged between 1.3 and 7.2% for IDN 5738 and between 0.0 and 9.0% for IDN 5839 and the mean accuracy was in the range 85.3–112.0% for IDN 5738 and between 80.0 and 111.0% for IDN 5839. Moreover, analysing quality control plasma samples on three different days, the methods resulted precise and accurate showing intra- and inter-day CV within 12% for both analytes, and accuracy of 92.0–113.3% and 85.9–105.7% for IDN 5738 and IDN 5839, respectively. With these methods, we studied for the first time, the pharmacokinetics of the two taxanes showing for both, good oral bioavailability (>50%).