Randomized two‐way cross‐over bioequivalence study of two amoxicillin formulations and inter‐ethnicity pharmacokinetic variation in healthy Malay volunteers

The objectives of this study were to develop a new deproteinization method to extract amoxicillin from human plasma and evaluate the inter‐ethnic variation of amoxicillin pharmacokinetics in healthy Malay volunteers. A single‐dose, randomized, fasting, two‐period, two‐treatment, two‐sequence crossover, open‐label bioequivalence study was conducted in 18 healthy Malay adult male volunteers, with one week washout period. The drug concentration in the sample was analyzed using high‐performance liquid chromatography (UV–vis HPLC). The mean (standard deviation) pharmacokinetic parameter results of Moxilen® were: peak concentration (C_max), 6.72 (1.56) µg/mL; area under the concentration–time graph (AUC_0–8), 17.79 (4.29) µg/mL h; AUC_0–∞, 18.84 (4.62) µg/mL h. Those of YSP Amoxicillin® capsule were: C_max, 6.69 (1.44) µg/mL; AUC_0–8, 18.69 (3.78) µg/mL h; AUC0_0–∞, 19.95 (3.81) µg/mL h. The 90% confidence intervals for the logarithmic transformed C_max, AUC_0–8 and AUC_0–∞ of Moxilen® vs YSP Amoxicillin® capsule was between 0.80 and 1.25. Both C_max and AUC met the predetermined criteria for assuming bioequivalence. Both formulations were well tolerated. The results showed significant inter‐ethnicity variation in pharmacokinetics of amoxicillin. The C_max and AUC of amoxicillin in Malay population were slightly lower compared with other populations. Copyright © 2014 John Wiley & Sons, Ltd.     

Comparative pharmacokinetics studies of benzoylhypaconine,benzoylmesaconine, benzoylaconine and hypaconitine in rats by LC‐MS method after administration of Radix Aconiti Lateralis Praeparata extract and Dahuang Fuzi Decoction

A rapid and sensitive high‐performance liquid chromatography–mass spectrometric (HPLC‐MS) method was developed and validated for simultaneous determination of benzoylhypaconine (BHA), benzoylmesaconine (BMA), benzoylaconine (BAC) and hypaconitine (HA) in rat plasma for the first time. The analytes were separated on a Kromasil C₁₈ column with a total running time of 11 min. The validation data demonstrated a sound feasibility for the newly developed method and it was then applied to the pharmacokinetic study of these analytes in rats. Pharmacokinetic behaviors of BHA, BMA, BAC and HA in rats were studied after oral administration of Radix Aconiti Lateralis Praeparata extract (FZ) and Dahuang Fuzi Decoction (DFD). The main parameters for the two groups of subjects were compared, and significant differences between Radix Aconiti Lateralis Praeparata extract group and Dahuang Fuzi Decoction group in calculated parameters, such as the area under the plasma concentration–time from zero to the last quantifiable time‐point (AUC_0–t), the area under the plasma concentration–time curve from zero to infinity (AUC_0–∞), peak plasma concentration (C_max), half‐life of elimination (T_1/2), mean retention time (MRT_0–t), plasma clearance (CL), volume of distribution (V_d) and time to reach C_max (T_max), were found. After oral administration of DFD, the AUC_0–t, AUC_0–∞ and C_max of BHA, BMA, BAC and HA decreased remarkably (p < 0.05) compared with those of the FZ extract group. V_d and CL values of BHA, BMA, BAC and HA increased, two of which showed significant difference (p < 0.05). T_1/2 and MRT_0–t values of BHA, BMA and BAC in the DFD group were significantly delayed compared with those of FZ extract group. Only the T_max of HA, the toxic ingredient in FZ, delayed significantly in DFD group compared with the value of FZ group. All these pharmacokinetic parameters were statistically compared, and the rationality of the combination for DFD was clearly demonstrated. Copyright © 2013 John Wiley & Sons, Ltd.     

Metabolic characteristics and pharmacokinetic differences of Qiwei Tongbi oral liquid in rheumatoid arthritis rats

Qiwei Tongbi oral liquid (QWTB), a classical traditional Chinese medicine formula, is widely used to treat arthritis-related diseases in clinical practice. Currently, in vivo metabolic characteristics and pharmacokinetic studies are lacking. This study analyzed the prototype components of QWTB absorbed in the blood and their metabolic transformation process after intragastric administration and compared the differences in pharmacokinetic properties between healthy and rheumatoid arthritis model rats. In sum, 17 prototype components and 21 related metabolites were identified in the plasma and urine of the treated rats. Metabolites were derived from sinomenine and magnoflorine. Through systematic methodology verification, an accurate and stable detection method for sinomenine and magnoflorine in plasma samples was established and applied to pharmacokinetic research of QWTB. At the three dose levels, the AUC_0–∞ (area under the curve) of the two components showed a good positive correlation with the dose (R² > 0.9). Compared with healthy rats, the T_max, t_1/2z, and AUC of sinomenine were markedly increased, and C_max was decreased in rheumatoid arthritis model rats, indicating that the rate of absorption and elimination rate decreased, but the body exposure increased. However, there were no significant differences in the pharmacokinetic parameters of magnoflorine under healthy and pathological conditions. In summary, the main active ingredients of QWTB are sinomenine and magnoflorine, which exhibit linear kinetic characteristics within a set dose range, and the rheumatoid arthritis pathological state is more conducive to the absorption and efficacy of sinomenine. The results of this study demonstrate the rationality of the clinical application of the QWTB.     

LC Determination and Pharmacokinetic Study of Sinomenine in Dog Plasma

A simple HPLC method has been developed for determination of sinomenine in dog plasma and has been used to evaluate the pharmacokinetics of sinomenine tablets in dogs. Chromatographic separation was performed on a reversed-phase column with 0.78% (w/v) NaH₂PO₄-acetonitrile, 88:12 (v/v), as mobile phase, delivered at a flow rate of 1.5 mL min^?1. Detection was performed at 265 nm. The limit of quantification was 5.0 ng mL^?1. The calibration range was from 5.0 to 1000 ng mL^?1. The developed method was applied to pharmacokinetic studies of sinomenine sustained-release tablets (test preparation) and sinomenine conventional tablets (reference preparation) in six dogs. Pharmacokinetic data t _max, C _max, AUC _0-t , AUC _0-∞, and t _1/2 for both preparations were determined from plasma concentration-time profiles. The method was sufficiently sensitive, simple, and repeatable for use in pharmacokinetic studies.     

Comparative pharmacokinetics of nine major bioactive components in normal and ulcerative colitis rats after oral administration of Lizhong decoction extracts by UPLC–TQ–MS/MS

Lizhong decoction (LZD), a classic formula, has been used to treat ulcerative colitis (UC) for thousands of years in clinical practice. However, the pharmacokinetic characteristics of its major bioactive components in rats under different physiological and pathological states are not clear. Thus, in this study, a rapid and sensitive analytical method, ultra‐performance liquid chromatography coupled with mass spectrometry (UPLC–MS/MS) method, was developed and applied to simultaneously determine glycyrrhizic acid, liquiritin, isoliquiritin, glycyrrhizin, isoliquiritigenin, 6‐gingerol, ginsenoside Rg1, ginsenoside Rb1 and ginsenoside Re in normal and UC rats after oral administration of LZD extract. A Waters BEH C₁₈ UPLC column was used for chromatographic separation, while acetonitrile and 0.1% formic acid were selected as mobile phase. The linearity of nine analytes was >0.9920. Inter‐ and intra‐day accuracy was ≤ 11.4% and precision was from 1.1 to 12.7%. Additionally, stable and suitable extraction recoveries were also obtained. The established method was validated and found to be specific, accurate and precise for nine analytes. Furthermore, it was successfully applied to the pharmacokinetic investigation of nine major components after oral administration of LZD extracts to normal and model rats, respectively. The results showed that the pharmacokinetic parameters (C_max, T_max, AUC_0–t, AUC_0–∞) in the plasma of UC rats were significantly different from those of normal rats, which could provide a reference for the clinical application of LZD.     

Comparative pharmacokinetic study of the main components of cortex fraxini after oral administration in normal and hyperuricemic rats

Cortex Fraxini is an important traditional Chinese herbal medicine used for the treatment of gout and hyperuricemia. An efficient and rapid ultra‐performance liquid chromatography mass spectrometry method was developed and validated for simultaneous quantitation of six coumarins (aesculin, fraxin, aesculetin, fraxetin, sopoletin and 7‐hydroxycoumarin) in normal and hyperuricemic rats plasma after oral administration of Cortex Fraxini. The method could successfully be applied for pharmacokinetics studies. The pharmacokinetic behavior of six coumarins in normal and hyperuricemia rats plasma was determined. Results showed that, for some of analytes, the pharmacokinetic parameters (AUC_0–t , AUC_0–∞, C _max, T _max and CL ) were significantly different between normal and hyperuricemic rats. The different pharmacokinetic parameters might result from renal impairment or a change of metabolic enzymes in the pathological state. The pharmacokinetic study in pathological state could provide more useful information to guide the clinical use of traditional Chinese herbal medicine.     

Pharmacokinetic properties of wogonin and its herb–drug interactions with docetaxel in rats with mammary tumors

Docetaxel, frequently used for the treatment of breast cancer, is mainly metabolized via hepatic cytochrome P450 (CYP) 3A in humans and is also a substrate of P‐glycoprotein (P‐gp). Wogonin has been shown to be able to modulate the activities of CYPs and P‐gp, and it could serve as an adjuvant chemotherapeutic agent. However, the impacts of co‐administration of wogonin and docetaxel on their pharmacokinetics have not been studied because of a lack of an analytical method for their simultaneous measurement. In the present study, we established an HPLC–MS/MS method for simultaneous measurement of wogonin and docetaxel in rat plasma, and it was then utilized to explore the pharmacokinetics of wogonin and the herb–drug interactions between wogonin and docetaxel after their combined administration in rats with mammary tumors. The rats received 10, 20 and 40 mg/kg wogonin via oral administration, with or without docetaxel intravenously administered at 10 mg/kg, and the plasma concentrations of wogonin and docetaxel were measured using the established and validated HPLC–MS/MS method. The C_max and AUC_0–t of wogonin were proportionally increased in the dose range from 10 to 40 mg/kg, suggesting a linear pharmacokinetics of wogonin. Moreover, the C_max and AUC_0–t of docetaxel and the AUC_0–t of wogonin were increased after co‐administration (p < 0.05), indicating increased in vivo exposures of both wogonin and docetaxel, which might lead to an increase in not only therapeutic but also toxic effects. Thus the alterations of pharmacokinetics should be taken into consideration when wogonin and docetaxel are co‐administered.     

A rapid and sensitive LC–MS/MS method for analysis of iguratimod in human plasma: Application to a pharmacokinetic study in Chinese healthy volunteers

A rapid, sensitive and reproducible LC–MS/MS method was developed and validated to determine iguratimod in human plasma. Sample preparation was achieved by protein precipitation with acetonitrile. Chromatographic separation was operated on an Ultimate® XB‐C₁₈ column (2.1 × 50 mm, 3.5 μm, Welch) with a flow rate of 0.400 mL/min, using a gradient elution with acetonitrile and water which contained 2 mm ammonium acetate and 0.1% formic acid as the mobile phase. The detection was performed on a Triple Quad™ 5500 mass spectrometer coupled with an electrospray ionization interface under positive‐ion multiple reaction monitoring mode with the transition ion pairs of m/z 375.2 → 347.1 for iguratimod and m/z 244.3 → 185.0 for agomelatine (the internal standard), respectively. The method was linear over the range of 5.00–1500 ng/mL with correlation coefficients ≥0.9978. The accuracy and precision of intra‐ and inter‐day, dilution accuracy, recovery and stability of the method were all within the acceptable limits and no matrix effect or carryover was observed. As a result, the main pharmacokinetic parameters of iguratimod were as follows: C_max, 1074 ± 373 ng/mL; AUC_0–72, 13591 ± 4557 ng h/mL; AUC_0–∞, 13,712 ± 4613 ng h/mL; T_max, 3.29 ± 1.23 h; and t_1/2, 8.89 ± 1.23 h.     

Pharmacokinetics of anthraquinones in rat plasma after oral administration of a rhubarb extract

A sensitive and specific LC‐MS/MS method was developed for simultaneous determination of aloe‐emodin, rhein, emodin, chrysophanol and physcion and their conjugates in rat plasma. The lower limit of quantitation of each anthraquinone was 0.020–0.040 µm . Intra‐day and inter‐day accuracies were 90.1–114.3% and the precisions were <14.6%. The matrix effects were 104.0–113.2%. The method was successfully applied to a pharmacokinetic study in rats receiving a rhubarb extract orally. The area under the concentration–time curve (AUC_0–t) and peak concentration (C_max) of free aloe‐emodin and emodin in rat plasma were much lower than those of rhein. The amounts of chrysophanol and physcion were too low to be continuously detected. After treating the plasma samples with β‐glucuronidases, each anthraquinone was detectable throughout the experimental period (36 h) and showed much higher plasma concentrations and AUC_0–t. The free/total ratios of aloe‐emodin, rhein and emodin were 6.5, 49.0 and 1.7% for C_max and 3.7, 32.5 and 1.1% for AUC_0–t, respectively. The dose‐normalized AUC_0–t and C_max of the total of each anthraquinone were in the same descending order: rhein > emodin > chrysophanol > physcion > aloe‐emodin. These findings reveal phase II conjugates as the dominant in vivo existing forms of rhubarb antharquinones and warrant a further study to evaluate their contribution to the herbal activity. Copyright © 2013 John Wiley & Sons, Ltd.     

Quantitative analysis and pharmacokinetic comparison of multiple bioactive components in rat plasma after oral administration of Qi-Shen-Ke-Li formula and its single-herb extracts using ultra-high-performance liquid chromatography–tandem mass spectrometry

Qi-Shen-Ke-Li (QSKL), a traditional Chinese formula prepared from six herbs, has long been used for the treatment of coronary heart disease and chronic heart failure. However, the herbal combination mechanism and underlying material basis of this multi-herbal formula are not clear. In this study, an ultra-high-performance liquid chromatography–tandem mass spectrometry (UHPLC–MS/MS) method to simultaneously determine multiple bioactive compounds in QSKL was established and validated. Using the developed method, 18 bioactive components in rat plasma after oral administration of QSKL formula and its single herb extracts were quantified. Based on these results, pharmacokinetic (PK) parameters (T_1/2, T_max, C_max, AUC_0–48h, and AUC_0–∞) of the 18 bioactive components were analyzed and compared using PKSlover 2.0 PK software. The experimental data suggested that significant changes in PK profiles were observed between the QSKL formula and its single-herb extracts. The herbal combination in QSKL significantly influences the system exposure and the PK behaviors of the 18 bioactive components, indicating multicomponent interactions among the herbs. This study provides insight into the herbal combination mechanism and underlying material basis of the QSKL formula.     

Comparative pharmacokinetics of prim-O-glucosylcimifugin and cimifugin by liquid chromatography-mass spectrometry after oral administration of Radix Saposhnikoviae extract, cimifugin monomer solution and prim-O-glucosylcimifugin monomer solution to rats

A sensitive and reliable liquid chromatography–mass spectrometry method has been developed and validated for simultaneous determination of cimifugin and prim‐O‐glucosylcimifugin in rat plasma after oral administration of Radix Saposhnikoviae (RS) extract, prim‐O‐glucosylcimifugin monomer solution and cimifugin monomer solution. Plasma samples were pretreated by protein precipitation with acetonitrile containing the internal standards puerarin and daidzein. LC separation was achieved on a Zorbax SB‐C₁₈ column (150 × 4.6 mm i.d., 5 µm) with 0.1% formic acid in water and methanol by isocratic elution. The detection was carried out in select‐ion‐monitoring mode with a positive electrospray ionization interface. The fully validated method was successfully applied to the pharmacokinetic study of the analytes in rats. A bimodal phenomenon appeared in the concentration–time curve of prim‐O‐glucosylcimifugin and cimifugin after oral administration of RS extract. Prim‐O‐glucosylcimifugin mainly transformed to cimifugin when it was absorbed into blood. Both absorption and elimination of cimifugin after oral administration of RS were longer than after administration of single cimifugin. The pharmacokinetic parameters (AUC_0–t, AUC_0–∞ and t_1/2) of prim‐O‐glucosylcimifugin and cimifugin by giving cimifugin monomer solution, prim‐O‐glucosylcimifugin monomer solution and RS extract had significant differences (P < 0.05). Copyright © 2012 John Wiley & Sons, Ltd.     

LC–ESI/MS Analysis of Levodopa and Methyldopa (IS) in Beagle Dog Pharmacokinetic Study after Oral Administration and Domperidone Given in Advance

A simple, sensitive and accurate method was developed for the quantification of levodopa and methyldopa (IS) in beagle dog plasma by LC–ESI/MS, chromatographic separation was carried out by a Diamonsil C18 column (150 mm × 4.6 mm i.d., 5 mm) with an ODS guard column maintained at 30 °C. The mobile phase was methanol (A) and 0.5% formic acid aqueous solution (B) system in the gradient elution profile, the retention time of levodopa and IS were 4.8 and 6.1 min, respectively, linear range for levodopa concentration was 0.08‐20.0 μg/mL in plasma samples with a correlation coefficient(r) of 0.9978, the limit of detection was 32 ng/mL. CV of intra‐day and inter‐day assays were all less than 15%, mean recoveries of levodopa were all more than 90% in 0.32, 1.6 and 16.0 μg/mL concentrations of levodopa (n = 3). The validated method was successfully applied to the determination of levodopa in plasma samples, pharmacokinetic of levodopa following a single oral dose of compound levodopa tablets and antiemetic drug – domperidone administrated to beagle dogs has been carried out, the main pharmacokinetic parameters of levodopa with domperidone were as follows: T_max (0.50 ± 0.18) h, C_max (39.72 ± 7.91) μg/mL, t_l/2 (0.65 ± 0.07) h, AUC_o‐t (49.01 ± 12.13) μg·h/mL , AUC_o‐∞ (49.10 ± 12.16) μg·h/mL, we also evaluated the effect of domperidone on pharmacokinetics of levodopa in beagle dog. We thought non‐oral sustained‐release formulations should be a very good choice instead of this common oral dosage forms on the market, the test results can provide a reference for clinical trials on drug therapy of Parkinson‘s disease.     

UPLC–MS/MS simultaneous determination of seven active ingredients of Yaobitong capsule in rat plasma and its integrated pharmacokinetic application

A reliable and sensitive UPLC–MS/MS method was first established and validated for the simultaneous determination of seven active ingredients of Yaobitong capsule in rat plasma: ginsenoside Rg1, ginsenoside Rb1, osthole, tetrahydropalmatine, paeoniflorin, albiflorin, and ferulic acid. And this method was further applied for the integrated pharmacokinetic study of Yaobitong capsule in rats after oral administration. Plasma samples (100 μL) were precipitated with 300 μL of methanol using carbamazepine as internal standard. Chromatographic separation was achieved using an Aquity UPLC BEH C18 column (100 × 2.1 mm, 1.7 μm), with the mobile phase consisting of 0.1% formic acid and acetonitrile. The method was validated using a good linear relationship (r ≥ 0.991), and the lower limit of quantification of the analytes ranged from 0.5 to 40 ng/mL. In the integrated pharmacokinetic study, the weight coefficient was calculated by the ratio of AUC_0–∞ of each component to the total AUC_0–∞ of the seven active ingredients. The integrated pharmacokinetic parameters C_max, T_max, and t_1/2 were 81.54 ± 9.62 ng/mL, 1.00 ± 0.21 h, and 3.26 ± 1.14 h, respectively. The integration of pharmacokinetic parameters showed a shorter t_1/2 because of fully considering the contribution of the characteristics of each active ingredient to the overall pharmacokinetics.     

A self‐contrast approach to evaluate the inhibitory effect of chrysosplenetin,in the absence and presence of artemisinin,on the in vivo P‐glycoprotein‐mediated digoxin transport activity

In this study, we used a self‐contrast method, which excluded the individual difference, to evaluate the inhibitory effect of chrysosplentin (CHR) in the presence or absence of artemisinin (ART) on the P‐glycoprotein (P‐gp) transport activity. A sensitive and rapid UHPLC–MS/MS method was applied for quantification of digoxin, a P‐gp‐specific substrate, in rat plasma. A pharmacokinetic study was carried out: first after an oral administration of digoxin at a dose of 0.09 mg/kg (first period), followed by a 20‐day wash‐out, then after another administration of digoxin (second period). During the second period, test compounds were orally given three times per day for seven consecutive days. Results showed that the t_1/2 of digoxin in all the groups had no significant difference between the first and second periods. The AUC_0–24, C_max, t_max, and Cl_z/F of the negative control and ART alone groups showed no difference. However, the AUC_0–24 and C_max in the CHR alone, CHR–ART (1:2) and verapamil (positive control) groups showed 2.34‐, 3.04‐, 1.79‐, and 1.81‐, 1.99‐, 2.06‐fold increases along with 3.50‐, 3.84‐ and 4.76‐fold decreases for CL_z/F, respectively. The t_max in the CHR–ART (1:2) group increased 3.73‐fold. In conclusion, our self‐contrast study suggested that CHR, especially when combined with ART in a ratio of 1:2, inhibited P‐gp activity while ART alone has no effect. Copyright © 2016 John Wiley & Sons, Ltd.     

Simultaneous quantification of ligustilide,dl‐3‐n‐butylphthalide and senkyunolide A in rat plasma by GC–MS and its application to comparative pharmacokinetic studies of Rhizoma Chuanxiong extract alone and Baizhi Chuanxiong Decoction

The herb couple has special clinical significance in reducing the toxicity and increasing the efficacy of drugs. The combination of Radix Angelicae Dahuricae (Baizhi, BZ) and Rhizoma Chuanxiong (ChuanXiong, CX) is a traditional herb couple. The combination performs better than the CX extract alone in the treatment of migraine and has been used for thousands of years. However, the specific compatibility mechanisms are still unclear. Ligustilide, dl ‐3‐n‐butylphthalide and senkyunolide A are the major active ingredients in CX and BZ–CX decoction. However, a comprehensive study of the pharmacokinetics of CX has not been carried out. A gas chromatography–mass spectroscopy (GC–MS) method with high selectivity, sensitivity and accuracy was developed. An SH‐Rxi‐5Sil (30 m × 0.25 mm i.d., and 0.25 μm film thickness) column was employed in the GC separation. Selectivity, linearity, precision, accuracy, recovery, matrix effect and stability were used to validate the current GC–MS method. Using the validated method, this is the first time to study on the comparative pharmacokinetics of ligustilide, dl ‐3‐n‐butylphthalide and senkyunolide A from CX alone and BZ–CX decoction in rat plasma. The pharmacokinetic parameters (C_max, T_max, T_1/2, AUC_0–t, AUC_0–∞ and CLz/F) of all of the detected ingredients showed significant differences between the two groups (P < 0.05). The results are helpful for further investigation of the compatibility mechanism of BZ–CX decoction.     

The application of HPLC‐MS/MS to studies of pharmacokinetics and interconversion of isoliquiritigenin and neoisoliquiritigenin in rats

A specific and sensitive HPLC‐MS/MS method was developed and validated for the simultaneously quantification of isoliquiritigenin (ISL) and neoisoliquiritin (NIS) in rat plasma by oral administration. Analytes were analyzed on an Agilent 6460 LC‐MS/MS system (Agilent, USA) using an Agilent Zorbax SB‐C₁₈ column (4.6 × 150 mm, 5 μm). Gradient elution was applied for the analyte separation using a mobile phase composed of 0.1% formic acid aqueous solution and methanol at a flow rate of 1.0 mL/min with a total running time of 12 min. The calibration curves for ISL and NIS showed good linearity in the concentrations ranging from 0.001 to 4.000 μg/mL with correlation coefficients >0.998. The precision, accuracy, recovery and stability were deemed acceptable. The method was applied to the pharmacokinetics study of ISL and NIS in rats by single and combination administration. The result showed that C_max and AUC_0→t of ISL were markedly increased from 0.53 to 1.20 μg/mL, and from 69.63 to 200.74 min μg/mL by combination administration. The mean t_1/2 value was also prolonged from 64.55 to 203.74 min in the combination group. These results indicated that NIS may have been metabolized to ISL which increased the absorption and extended the elimination of ISL. However, little difference was found for NIS pharmacokinetics parameters between single NIS and the combination group, which suggested that there was no significant biotransformation of ISL to NIS. Copyright © 2015 John Wiley & Sons, Ltd.     

Liquid chromatography tandem mass spectrometry method for the quantification of sarpogrelate, a selective 5-HT(₂A) receptor antagonist, in plasma: application to a pre-clinical pharmacokinetic study

A simple LC‐MS/MS method was developed and validated for the estimation of sarpogrelate in 50 µL of rat plasma. The analyte and internal standard (IS) were extracted from rat plasma by acetonitrile precipitation and they were separated on a reversed‐phase C₈ column with gradient program. The MS acquisition was performed with multiple reaction monitoring mode using m/z 430.2 to m/z 135.0 for analyte and m/z 448.2 to m/z 285.3 for IS. The calibration curves were linear over the range of 1–1000 ng/mL with the correlation coefficient greater than 0.999. With dilution integrity up to 20‐fold, the upper limit of quantification was extendable up to 15,000 ng/mL. The method was successfully applied to the analysis of rat plasma samples after single dose oral administration of sarpogrelate at 5 mg/kg to rats for the determination of its pharmacokinetics. Following oral administration the maximum mean concentration in plasma (C_max, 11514 ng/mL) was achieved at 0.25 h (T_max) and the area under curve (AUC_0–24) was 11051 ± 3315 ng h/mL. The half‐life (t_1/2) and clearance (Cl) were 2.9 ± 1.1 h and 490 ± 171 mL/h/kg, respectively. We believe that development of a method in rodent plasma would facilitate the ease of adaptability of sarpogrelate in human plasma. Copyright © 2010 John Wiley & Sons, Ltd.     

Pharmacokinetics of luteolin and tetra‐acetyl‐luteolin assayed by HPLC in rats after oral administration

Accurate and reproducible HPLC methods were developed and validated for the determination of concentrations of luteolin (LT) and tetra‐acetyl‐luteolin (TALT) in rat plasma. HPLC analyses were performed on an Agilent TC‐C₁₈ column protected by a guard Agilent Zorbax Eclipse Plus. The mobile phase for LT was a binary mixture of acetonitrile–water (40:60, v/v) containing 0.5% phosphoric acid at a flow rate of 1.0 mL/min, and that for TALT was a binary mixture of methanol–water (70 : 30, v/v) containing 0.5% glacial acetic acid at the same flow rate. The UV detection wavelength for both analytes was set at 350 nm. The calibration curve was linear over the range of 40–1800 ng/mL, the lower limit of quantitation was 40 ng/mL and the lower limit of detection was 20 ng/mL for both LT and TALT. The intra‐ and inter‐day precision (RSD) values for all samples were within 7.9%. The concentration–time curves of LT and TALT after oral administration (30 mg/kg) were both fitted to a two‐compartment model. The pharmacokinetic characteristics of TALT were better than that of LT in the maximum plasma concentration (C_max) and the area under the concentration–time curve (AUC). Copyright © 2010 John Wiley & Sons, Ltd.     

Development and validation of a rapid and sensitive LC-ESI-MS/MS method for ondansetron quantification in human plasma and its application in comparative bioavailability study

The validation of a high throughput and specific method using a high‐performance liquid chromatography coupled to electrospray (ES+) ionization tandem triple quadrupole mass spectrometric (LC‐ESI‐MS/MS) method for ondansetron quantification in human plasma is described. Human plasma samples were extracted by liquid–liquid extraction (LLE) using methyl tert‐butyl ether and analyzed by LC‐ESI‐MS/MS. The limit of quantification was 0.2 ng/mL and the method was linear in the range 0.2–60 ng/mL. The intra‐assay precisions ranged from 1.6 to 7.7%, while inter‐assay precisions ranged from 2.1 to 5.1%. The intra‐assay accuracies ranged from 97.5 to 108.2%, and the inter‐assay accuracies ranged from 97.3 to 107.0%. The analytical method was applied to evaluate the relative bioavailability of two pharmaceutical formulations containing 8 mg of ondansetron each in 25 healthy volunteers using a randomized, two‐period crossover design. The geometric mean and respective 90% confidence interval (CI) of ondansetron test/reference percent ratios were 90.15% (81.74–99.44%) for C_max and 93.11% (83.01–104.43%) for AUC_0–t. Based on the 90% confidence interval of the individual ratios (test formulation/reference formulation) for C_max and AUC_0‐inf, it was concluded that the test formulation is bioequivalent to the reference one with respect to the rate and extent of absorption of ondansetron. Copyright © 2010 John Wiley & Sons, Ltd.     

Pharmacokinetics of aconitine in rat skin after oral and transdermal gel administrations

The purpose of this study was to evaluate percutaneous penetration and arrhythmogenic effects of aconitine after transdermal administration, compared with the oral route. Skin penetration of aconitine was tested by a microdialysis technique in rats and in vivo recovery was determined by retrodialysis. After oral and transdermal administration of aconitine, dialysate was sampled at 20 min intervals until the end of the experiment for the determination of concentration of aconitine in skin. Blood samples were collected and analyzed using a validated HPLC‐MS/MS method. In addition, we concurrently recorded the electrocardiogram (ECG). The in vivo recovery of aconitine in the skin was calculated to be 39.59%. The C_max values for aconitine absorbed into the skin after oral and transdermal administration were 1.51 ± 0.53 and 2723.8 ± 848.8 ng/mL, respectively, and within the plasma, 215.86 ± 79.29 and 20.92 ± 3.15 ng/mL. The C_max value for the plasma concentration of aconitine after oral administration was approximately 10 times higher than with the transdermal route. For oral administration, the ECG revealed various types of arrhythmias at a period of T_max, which is normal in transdermal gel administration. These results indicate that transdermal aconitine gel is a safe formulation that can deliver the drug in sufficient amounts and safe concentrations to produce therapeutic action in rats. Copyright © 2011 John Wiley & Sons, Ltd.