Pharmacokinetics, Tissue Distribution, and Druggability Prediction of the Natural Anticancer Active Compound Cytisine N-Isoflavones Combined with Computer Simulation.

Cytisine N-methylene-(5,7-dihydroxy-4'-methoxy)-isoflavone (CNF2) is a new compound isolated from the Chinese herbal medicine Sophora alopecuroides. Preliminary pharmacodynamic studies demonstrated its activity in inhibiting breast cancer cell metastasis. This study examined the pharmacokinetics, absolute bioavailability, and tissue distribution of CNF2 in rats, and combined computer-aided technology to predict the druggability of CNF2. The binding site of CNF2 and the breast cancer target human epidermal growth factor receptor-2 (HER2) were examined with molecular docking technology. Next, ACD/Percepta software was used to predict the druggability of CNF2 based on the quantitative structure-activity relationship (QSAR). Finally, a simple and effective HPLC method was used to determine plasma pharmacokinetics and tissue distribution of CNF2 in rats. Prediction and experimental results show that compared with the positive control HER2 inhibitor SYR127063, CNF2 has a stronger binding affinity with HER2, suggesting that its efficacy is stronger; and the structure of CNF2 complies with the Lipinski's Rule of Five and has good drug-likeness. The residence time of CNF2 in rats is less than 4 h, and the metabolic rate is relatively fast; But the absolute bioavailability of CNF2 in rats was 6.6%, mainly distributed in the stomach, intestine, and lung tissues, where the CNF2 contents were 401.20, 144.01, and 245.82 µg/g, respectively. This study constructed rapid screening and preliminary evaluation of active compounds, which provided important references for the development and further research of such compounds.

Pharmacokinetics of vatinoxan in male neutered cats anesthetized with isoflurane.

OBJECTIVE: To characterize the pharmacokinetics of vatinoxan in isoflurane-anesthetized cats. STUDY DESIGN: Prospective experimental study. ANIMALS: A group of six adult healthy male neutered cats. METHODS: Cats were anesthetized using isoflurane in oxygen. Venous catheters were placed to administer the drug and sample blood. Vatinoxan, 1 mg kg-1, was administered intravenously over 5 minutes. Blood was sampled before and at various times during and up to 8 hours after vatinoxan administration. Plasma vatinoxan concentration was measured using liquid chromatography/tandem mass spectrometry. Compartment models were fitted to the time-concentration data using population methods and nonlinear mixed effect modeling. RESULTS: A three-compartment model best fitted the data. Typical value (% interindividual variability) for the three volumes (mL kg-1), the metabolic clearance and two distribution clearances (mL minute-1 kg-1) were 34 (55), 151 (35), 306 (18), 2.3 (34), 42.6 (25) and 5.6 (0), respectively. Hypotension increased the second distribution clearance to 10.6. CONCLUSION AND CLINICAL RELEVANCE: The pharmacokinetics of vatinoxan in anesthetized cats were characterized by a small volume of distribution and a low clearance. An intravenous bolus of 100 µg kg-1 of vatinoxan followed by constant rate infusions of 55 µg kg-1 minute-1 for 20 minutes, then 22 µg kg-1 minute-1 for 60 minutes and finally 10 µg kg-1 minute-1 for the remainder of the infusion time is expected to maintain the plasma concentration within 90%-110% of the plasma vatinoxan concentration previously shown to attenuate the cardiovascular effects of dexmedetomidine (25 µg kg-1) in conscious cats.

Concentrations of medetomidine enantiomers and vatinoxan, an α2-adrenoceptor antagonist, in plasma and central nervous tissue after intravenous coadministration in dogs.

OBJECTIVE: To quantify the peripheral selectivity of vatinoxan (L-659,066, MK-467) in dogs by comparing the concentrations of vatinoxan, dexmedetomidine and levomedetomidine in plasma and central nervous system (CNS) tissue after intravenous (IV) coadministration of vatinoxan and medetomidine. STUDY DESIGN: Experimental, observational study. ANIMALS: A group of six healthy, purpose-bred Beagle dogs (four females and two males) aged 6.5 ± 0.1 years (mean ± standard deviation). METHODS: All dogs were administered a combination of medetomidine (40 µg kg-1) and vatinoxan (800 µg kg-1) as IV bolus. After 20 minutes, the dogs were euthanized with an IV overdose of pentobarbital (140 mg kg-1) and both venous plasma and CNS tissues (brain, cervical and lumbar spinal cord) were harvested. Concentrations of dexmedetomidine, levomedetomidine and vatinoxan in all samples were quantified by liquid chromatography-tandem mass spectrometry and data were analyzed with nonparametric tests with post hoc corrections where appropriate. RESULTS: All dogs became deeply sedated after the treatment. The CNS-to-plasma ratio of vatinoxan concentration was approximately 1:50, whereas the concentrations of dexmedetomidine and levomedetomidine in the CNS were three- to seven-fold of those in plasma. CONCLUSIONS AND CLINICAL RELEVANCE: With the doses studied, these results confirm the peripheral selectivity of vatinoxan in dogs, when coadministered IV with medetomidine. Thus, it is likely that vatinoxan preferentially antagonizes α2-adrenoceptors outside the CNS.

A Validated Ultra-Performance Liquid Chromatographic Method for the Simultaneous Determination of Nadifloxacin, Mometasone Furoate and Miconazole Nitrate in Their Combined Dosage Form and Spiked Human Plasma Samples.

Nadifloxacin, mometasone furoate and miconazole nitrate are formulated together as a topical antifungal dosage form. In this work, a reversed-phase ultra-performance liquid chromatographic method coupled with a diode array detector (RP-UPLC-DAD) was developed and validated to determine nadifloxacin, mometasone furoate and miconazole nitrate simultaneously in their bulk powder, in pharmaceutical preparation and in spiked human plasma samples. Separation was achieved on an ACQUITY UPLC C18 column of 2.2 µm particle size (2.1 × 100 mm) via isocratic elution using a mobile phase consisting of methanol, acetonitrile and water with ratio (50:20:30; v/v/v) and 0.1 g ammonium acetate, then pH was adjusted to (7.00) using acetic acid, flow rate 0.6 mL/min, temperature 30°C and UV detection at 220 nm. The method is linear in a range from 5 to 400 µg/mL for both nadifloxacin and miconazole nitrate and from 20 to 500 µg/mL for mometasone furoate. The method was validated according to the ICH guidelines then applied successfully to determine the mentioned drugs in their pharmaceutical preparation and spiked human plasma samples. For plasma samples, the results showed that the method can determine nadifloxacin, mometasone furoate and miconazole nitrate in human plasma samples with high accuracy and precision.

Effects of vatinoxan on cardiorespiratory function, fecal output and plasma drug concentrations in horses anesthetized with isoflurane and infusion of medetomidine.

A constant rate infusion (CRI) of medetomidine is used to balance equine inhalation anesthesia, but its cardiovascular side effects are a concern. This experimental crossover study aimed to evaluate the effects of vatinoxan (a peripheral α2-adrenoceptor antagonist) on cardiorespiratory and gastrointestinal function in anesthetized healthy horses. Six horses received medetomidine hydrochloride 7µg/kg IV alone (MED) or with vatinoxan hydrochloride 140µg/kg IV (MED+V). Anesthesia was induced with midazolam and ketamine and maintained with isoflurane and medetomidine CRI for 60min. Heart rate, carotid and pulmonary arterial pressures, central venous pressure, cardiac output and arterial and mixed venous blood gases were measured. Selected cardiopulmonary parameters were calculated. Plasma drug concentrations were determined. Fecal output was measured over 24h. For statistical comparisons, repeated measures analysis of covariance and paired t-tests were applied. Heart rate decreased slightly from baseline in the MED group. Arterial blood pressures decreased with both treatments, but significantly more dobutamine was needed to maintain normotension with MED+V (P=0.018). Cardiac index (CI) and oxygen delivery index (DO2I) decreased significantly more with MED, with the largest difference observed at 20min: CI was 39±2 and 73±18 (P=0.009) and DO2I 7.4±1.2 and 15.3±4.8 (P=0.014)mL/min/kg with MED and MED+V, respectively. Fecal output or plasma concentrations of dexmedetomidine did not differ between the treatments. In conclusion, premedication with vatinoxan induced hypotension, thus its use in anesthetized horses warrants further studies. Even though heart rate and arterial blood pressures remained clinically acceptable with MED, cardiac performance and oxygen delivery were lower than with MED+V.

Simultaneous determination of multiple compounds of Da-Huang-Xiao-Shi decoction in rat plasma by LC-MS/MS and its application in a pharmacokinetic study.

Da-Huang-Xiao-Shi decoction (DHXSD), a traditional Chinese medicinal formula, has been used mainly to treat jaundice for more than 1700 years in China. In this study, we developed a rapid, sensitive, and accurate LC-MS/MS method to simultaneously determine multiple, potentially bioactive compounds of DHXSD, including five alkaloids (berberine, phellodendrine, palmatine, jatrorrhizine, and magnoflorine), five anthraquinones (rhein, aloe-emodin, emodin, chrysophanol, and physcion), two iridoid glycosides (geniposide and genipin 1-gentiobioside), and one iridoid aglycone (genipin) in rat plasma. Plasma samples collected from rats were treated immediately with 5% acetic acid to avoid the degradation of genipin. After protein precipitation with acetonitrile containing 5% acetic acid, the compounds were reconstituted in acetonitrile-water (50:50, v/v) solution containing 6.5% formic acid and separated on the ACQUITY™ UPLC BEH C18 column (2.1 × 100 mm; 1.7 µm) using a mobile phase composed of 2 mM ammonium formate in water (solvent A) and acetonitrile (solvent B) at a flow rate of 0.3 mL/min. Quantitation was performed on a Triple Quand 5500 tandem mass spectrometer coupled with an electrospray ionization (ESI) source. Multiple reaction monitoring (MRM) was used to quantify compounds in positive and negative ion modes. The method validation results showed that the specificity, linearity, precision and accuracy, recovery, matrix effect, and stability of the 13 compounds met the requirements for their quantitation in biological samples. This newly established method was successfully used in a pharmacokinetic study on rats orally treated with DHXSD. Besides, glucuronide and sulfate metabolites were also determined in rat plasma after hydrolysis. This is the first method developed for the simultaneous quantification of multiple compounds of DHXSD in vivo. Our study provides relevant information on the pharmacokinetics of DHXSD and the relationship between the compounds of DHXSD and their therapeutic effects.

Ascending single dose pharmacokinetics of cytisine in healthy adult smokers.

1. Cytisine, a partial agonist for the α4ß2-nAChR, is used as a smoking cessation medication. Cytisine's current dosing is complex and involves taking 1.5 mg several times a day. The aim of this study was to explore the effect of dose on the pharmacokinetics and safety of cytisine after a single dose in healthy adult smokers. 2. Participants were assigned to one of three groups (n = 6 in each group) to receive a single oral dose of 1.5, 3 or 4.5 mg of cytisine. Blood samples were collected up to 24 h post dose. Pulse, blood pressure and respiratory rate were measured. Adverse effects were recorded. 3. Cytisine reached peak plasma concentration 1-2 h post dose in all participants irrespective of dose, with no dose-dependent changes in the elimination phase. Mean (SD) cytisine exposure (AUC0-24h) were 81.9 (15.8), 181.9 (40.8) and 254.5 (48.1) ng.h/mL following 1.5, 3 and 4.5 mg, respectively. 4. Cytisine appears to have predictable pharmacokinetics following a single dose of up to 4.5 mg and may be safe given as a single 4.5 mg dose, which is threefold greater than the recommended dose taken at one time. This study is registered in ClinicalTrials.gov (ID:NCT02585024).

Peripheral α2-adrenoceptor antagonism affects the absorption of intramuscularly coadministered drugs.

OBJECTIVE: We determined the possible effects of a peripherally acting α2-adrenoceptor antagonist, MK-467, on the absorption of intramuscularly (IM) coadministered medetomidine, butorphanol and midazolam. STUDY DESIGN: Randomized, experimental, blinded crossover study. ANIMALS: Six healthy Beagle dogs. METHODS: Two IM treatments were administered: 1) medetomidine hydrochloride (20 µg kg-1) + butorphanol (100 µg kg-1) + midazolam (200 µg kg-1; MBM) and 2) MBM + MK-467 hydrochloride (500 µg kg-1; MBM-MK), mixed in a syringe. Heart rate was recorded at regular intervals. Sedation was assessed with visual analog scales (0-100 mm). Drug concentrations in plasma were analyzed with liquid chromatography-tandem mass spectrometry, with chiral separation of dex- and levomedetomidine. Maximum drug concentrations in plasma (Cmax) and time to Cmax (Tmax) were determined. Paired t-tests, with Bonferroni correction when appropriate, were used for comparisons between the treatments. RESULTS: Data from five dogs were analyzed. Heart rate was significantly higher from 20 to 90 minutes after MBM-MK. The Tmax values for midazolam and levomedetomidine (mean ± standard deviation) were approximately halved with coadministration of MK-467, from 23 ± 9 to 11 ± 6 minutes (p = 0.049) for midazolam and from 32 ± 15 to 18 ± 6 minutes for levomedetomidine (p = 0.036), respectively. CONCLUSIONS AND CLINICAL RELEVANCE: MK-467 accelerated the absorption of IM coadministered drugs. This is clinically relevant as it may hasten the onset of peak sedative effects.

Preliminary pharmacokinetics of intravenous and subcutaneous dolasetron and pharmacodynamics of subcutaneous dolasetron in healthy cats.

Objectives The objectives were to evaluate the pharmacokinetics (PK) of subcutaneous (SC) and intravenous (IV) dolasetron and the pharmacodynamics (PD) of SC dolasetron in healthy cats. Methods Five cats with unremarkable complete blood count, serum biochemistry and urinalyses were utilized. In the PK study, cats received 0.8 mg/kg SC and IV dolasetron in a crossover format. Serum samples were obtained via a jugular catheter at 0, 0.25, 0.5, 1, 2, 4, 8, 12, 24, 36 and 48 h after the administration of dolasetron. Dolasetron and the active metabolite hydrodolasetron were measured using liquid chromatography/tandem mass spectrometry. Non-compartmental PK analysis was performed. In the PD study, SC dolasetron (0.8 mg/kg and 1.0 mg/kg) and saline were administered 30 mins prior to administration of 0.44 mg/kg intramuscular xylazine in a randomized three-way crossover. Number of emetic events, lip licks, time to onset of emesis and visual nausea score were scored by a blinded observer. Results In the PK study, dolasetron was quickly metabolized to the active metabolite hydrodolasetron, limiting assessment of dolasetron PK parameters. Median (range) PK parameters for IV hydrodolasetron were as follows: maximum serum concentration (Cmax) 116 ng/ml (69-316 ng/ml), time to maximum concentration (Tmax) 0.5 h (0.3-0.5 h), half-life 3.3 h (2.9-7.2 h) and area under the curve until the last measurable concentration (AUClast) 323 h/ng/ml (138-454 h/ng/ml). Median (range) PK parameters for SC hydrodolasetron were as follows: Cmax 67.9 ng/ml (60.4-117 ng/ml), Tmax 0.5 h (0.5-1.0 h), half-life 3.8 h (2.9-5.3 h) and AUClast 437 h/ng/ml (221.5-621.8 h/ng/ml). There was no significant difference in exposure to hydrodolasetron between the routes of administration. With regard to PD, when dolasetron was administered prior to xylazine, there was no significant difference in the mean number of emetic events, lip licks, time to onset of emesis or visual nausea score when compared with saline. Conclusions and relevance Administration of 0.8 mg/kg dolasetron does not maintain serum concentrations of active metabolite for 24 h. Administration of dolasetron at 0.8 mg/kg and 1 mg/kg did not prevent xylazine-induced vomiting. Additional feline dose studies are needed to determine if a higher dose is efficacious.

Effect of oxymatrine HSPC liposomes on improving bioavailability, liver target distribution and hepatoprotective activity of oxymatrine.

Oxymatrine (OMT) and matrine (MT) are two naturally occurring alkaloids, both of them provide anti-hepatitis effects. However OMT effect was heavily limited due to its low bioavailability, short half-life and whole body distribution. Herein, we investigated hydrogenated soybean phosphatidylcholine (HSPC) liposomes made by pH gradient active loading to understand the improved hepatoprotective effect mechanisms. Pharmacokinetics researches demonstrated the half-life time of OMT HSPC liposomes was 17.10h in mice. Compared with OMT solution, AUC (0-8) of OMT and MRT (0-8) of MT had been increased 11.8 fold and 14.3 fold in HSPC liposomes. Moreover, tissue distribution revealed the relative AUCs of total alkaloids in liver of OMT HSPC liposomes was as 4.18 times as that of OMT solution. Our data suggested that pathological topical necrosis and mild vacuolar degeneration of liver progressively returned to normal, and serum level of alanine-aminotransferase (ALT) and aspartate-aminotransferase (AST) were significantly reduced after treating with OMT HSPC liposomes in acute liver injury mice induced by CCl4. Pharmacokinetics, biodistribution and pathological researches manifested that HSPC liposomes served as an ideal and potential oxymatrine liver target carrier to prolong OMT retention time and maintain high therapeutically level in liver.

Simultaneous determination of anemoside B4, phellodendrine, berberine, palmatine, obakunone, esculin, esculetin in rat plasma by UPLC-ESI-MS/MS and its application to a comparative pharmacokinetic study in normal and ulcerative colitis rats.

A sensitive and rapid ultra-performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS/MS) method was developed for the simultaneous analysis of anemoside B4, phellodendrine, berberine, palmatine, obakunone, esculin, esculetin, toosendanin (IS1 of anemoside B4), tetrahydropalmatine (IS2 of phellodendrine, berberine, palmatine and obakunone) and scopoletin (IS3 of esculin and esculetin) and to compare the pharmacokinetics of these active ingredients in normal and ulcerative colitis rats. After methanol deproteinization, solvents were evaporated at 40°C under a gentle stream of nitrogen. Chromatography was performed using a C18 column with a gradient elution of 0.1% aqueous formic acid and acetonitrile at 0.4ml/min. Detection and measurement were performed on a 4000 QTRAP UPLC-MS/MS system from AB Sciex in the multiple reaction monitoring (MRM) mode. Phellodendrine, berberine, palmatine, obakunone, esculin, esculetin, tetrahydropalmatine (IS2) and scopoletin (IS3) were monitored under positive ionization conditions. Anemoside B4, and toosendanin (IS1) were monitored under negative ionization conditions. The optimized mass transition ion-pairs (m/z) were 1221.1/750.7 for anemoside B4, 343.2/193.2 for phellodendrine, 337.1/321.0 for berberine, 353.0/336.9 for palmatine, 455.1/161.1 for obakunone, 341.2/179.2 for esculin, 179.1/123.0 for esculetin, 573.4/531.4 for toosendanin (IS1), 356.2/192.2 for tetrahydropalmatine (IS2) and 193.0/133.1 for scopoletin (IS3).

Pharmacokinetic studies of phellodendrine in rat plasma and tissues after intravenous administration using ultra-high performance liquid chromatography-tandem mass spectrometry.

Phellodendrine, a quaternary ammonium alkaloid extracted from the dried bark of Phellodendrom chinensis Schneid and Phellodendrom amurense Rupr, has the effect of suppressing cellular immune response, reducing blood pressure and antinephritis. However, few investigations have been conducted for the pharmacokinetic study of phellodendrine. Thus, a rapid, simple and reliable ultra-high performance liquid chromatography-tandem quadrupole mass spectrometry (UHPLC-QQQ MS/MS) method has been established for quantification of phellodendrine in rat plasma and tissues by using magnoflorine as internal standard. The chromatographic separation was achieved on an Agilent ZORBAX SB-C18 column (4.6mm×50mm, 1.8µm) by gradient elution using 0.1% aqueous formic acid (A) and methanol (B). Triple quadrupole mass detection with multiple reaction monitoring mode was used to monitor the ion transitions, at m/z 342.20→192.20 for phellodendrine and m/z 342.20→58.20 for internal standard, respectively. The developed method was fully validated and successfully applied to the pharmacokinetics and tissue distribution study of phellodendrine after intravenous administration. The lower limits of quantification were 0.5ng/mL for plasma samples, 2.5ng/g for brain and 1ng/g for other tested tissues. Precisions and accuracy values were within the Food and Drug Administration acceptance criteria, the recovery and matrix effects were between 87.8-113.5%. The area under the curve (AUC0-t) ranged from 15.58 to 57.41mg/L min and Cmax were between 1.63-4.93mg/L. The results showed that phellodendrine was eliminated in 120min in plasma and most of tissues and the highest concentrations of phellodendrine were found in the kidney. This study may provide a basis for the further study of phellodendrine.

Pharmacokinetics of dexmedetomidine, MK-467, and their combination following intravenous administration in male cats.

This study characterized the pharmacokinetics of dexmedetomidine, MK-467, and their combination following intravenous bolus administration to cats. Seven 6- to-year-old male neutered cats, weighting 5.1 ± 0.7 kg, were used in a randomized, crossover design. Dexmedetomidine [12.5 (D12.5) and 25 (D25) µg/kg], MK-467 [300 µg/kg (M300)] or dexmedetomidine (25 µg/kg) and MK-467 [75, 150, 300 or 600 µg/kg-only the plasma concentrations in the 600 µg/kg group (D25M600) were analyzed] were administered intravenously, and blood was collected until 8 hours thereafter. Plasma drug concentrations were analyzed using liquid chromatography/mass spectrometry. A two-compartment model best fitted the data. Median (range) volume of the central compartment (mL/kg), volume of distribution at steady state (mL/kg), clearance (mL min/kg) and terminal half-life (min) were 342 (131-660), 829 (496-1243), 14.6 (9.6-22.7) and 48 (40-69) for D12.5; 296 (179-982), 1111 (908-2175), 18.2 (12.4-22.9) and 52 (40-76) for D25; 653 (392-927), 1595 (1094-1887), 22.7 (18.5-36.4) and 48 (35-60) for dexmedetomidine in D25M600; 117 (112-163), 491 (379-604), 3.0 (2.0-4.5) and 122 (99-139) for M300; and 147 (112-173), 462 (403-714), 2.8 (2.1-4.8) and 118 (97-172) for MK-467 in D25M600. MK-467 moderately but statistically significantly affected the disposition of dexmedetomidine, whereas dexmedetomidine minimally affected the disposition of MK-467.

The impact of medetomidine on the protein-binding characteristics of MK-467 in canine plasma.

This study determined the unbound fraction of the peripheral α2 -adrenoceptor antagonist MK-467 alone and combined with medetomidine. MK-467 (0.1, 1 and 10 µm) was incubated in canine plasma with and without medetomidine (molar ratio 20:1), with human serum albumin (HSA) and with α1-acid glycoprotein (AGP). Rapid equilibrium dialysis was used for the measurement of protein binding. All samples were analysed by liquid chromatography and tandem mass spectrometry to obtain the unbound fraction (fu ) of MK-467. Unbound fractions (fu ) of MK-467 in canine plasma (mean ± standard deviation) were 27.6 ± 3.5%, 26.6 ± 0.9% and 42.4 ± 1.2% at 0.1, 1.0 and 10 µm concentrations, respectively. In the presence of medetomidine, fu were 27.5 ± 0.4%, 26.6 ± 0.9% and 41.0 ± 2.4%. The fu of MK-467 in HSA were 50.1 ± 2.5% at 0.1 µm, 49.4 ± 1.2% at 1.0 µm and 56.7 ± 0.5% at 10 µm. fu of MK-467 in AGP was 56.3 ± 3.7% at 0.1 µm, 54.6 ± 5.6% at 1.0 µm and 65.3 ± 0.4% at 10 µm. Protein binding of MK-467 was approximately 70% between 0.1 and 1.0 µm. Medetomidine had no apparent effect on the protein binding of MK-467.

Determination of N-methylcytisine in rat plasma by UPLC-MS/MS and its application to pharmacokinetic study.

In this work, a sensitive and selective UPLC-MS/MS method for determination of N-methylcytisine in rat plasma is developed. After addition of hordenine as an internal standard (IS), protein precipitation by acetonitrile-methanol (9:1, v/v) was used to prepare samples. Chromatographic separation was achieved on a UPLC BEH HILIC (2.1 mm×100mm, 1.7µm) with acetonitrile (containing 10mM ammonium formate) and water (containing 0.1% formic acid and 10mM ammonium formate) as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; multiple reaction monitoring (MRM) mode was used for quantification using target fragment ions m/z 205.1→58.0 for N-methylcytisine, and m/z 166.1→121.0 for IS. Calibration plots were linear throughout the range 2-2000ng/mL for N-methylcytisine in rat plasma. Mean recoveries of N-methylcytisine in rat plasma ranged from 86.1% to 94.8%. RSD of intra-day and inter-day precision were both<13%. The accuracy of the method was between 94.5% and 109.4%. The method was successfully applied to pharmacokinetic study of N-methylcytisine after either oral or intravenous administration. For the first time, the absolute bioavailability of N-methylcytisine was reported as high as 55.5%.

Simultaneous determination of 14-thienyl methylene matrine and matrine in rat plasma by high-performance liquid chromatography-tandem mass spectrometry and its application in a pharmacokinetic study.

A rapid, sensitive and selective high-performance liquid chromatography-tandem mass spectrometric method (HPLC-MS) has been developed and validated for the simultaneous determination of 14-thienyl methylene matrine (TMM) and matrine (MT) in rat plasma in the present study. The analytes were separated on a C18 column (1.9 µm, 2.1 mm × 100 mm) with a security guard C18 column (5 µm, 2.1 mm × 10 mm) and a triple-quadrupole mass spectrometry equipped with an electrospray ionization (ESI) source was applied for detection. With pseudoephedrine hydrochloride as internal standard, sample pretreatment involved in a one-step protein precipitation with isopropanol:ethyl acetate (v/v, 20:80). The method was linear over the concentration ranges of 5-1000 ng/ml for TMM and 10-2000 ng/ml for MT. The intra-day and inter-day relative standard deviations (RSD) were less than 15% and the relative errors (RE) were all within 15%. The proposed method enables unambiguous identification and quantification of TMM and MT in vivo. This was the first report on determination of the TMM and MT in rat plasma after oral administration of TMM. The results provided a meaningful basis for evaluating the clinical applications of the medicine.

Pharmacokinetics of cytisine, an α4 ß2 nicotinic receptor partial agonist, in healthy smokers following a single dose.

Cytisine, an α4 ß2 nicotinic receptor partial agonist, is a plant alkaloid that is commercially extracted for use as a smoking cessation medication. Despite its long history of use, there is very little understanding of the pharmacokinetics of cytisine. To date, no previous studies have reported cytisine concentrations in humans following its use as a smoking cessation agent. A high performance liquid chromatography-ultraviolet (HPLC-UV) method was developed and validated for analysis of Tabex® and nicotine-free oral strips, two commercial products containing cytisine. A sensitive liquid chromatography-mass spectrometry (LC-MS) method was developed and validated for the quantification of cytisine in human plasma and for the detection of cytisine in urine. Single-dose pharmacokinetics of cytisine was studied in healthy smokers. Subjects received a single 3 mg oral dose administration of cytisine. Cytisine was detected in all plasma samples collected after administration, including 15 min post-dose and at 24 h. Cytisine was renally excreted and detected as an unchanged drug. No metabolites were detected in plasma or urine collected in the study. No adverse reactions were reported.

Pharmacokinetic study of multiple active constituents from Kushen-Gancao Decoction after oral administration in rat by HPLC-MS/MS.

Kushen-Gancao Decoction (KGD) is a classic traditional Chinese herb combination in treating viral hepatitis and chronic liver diseases. This study aims to investigate the pharmacokinetic (PK) study of matrine (MT), oxymatrine (OMT), glycyrrhizic acid (GL) and glycyrrhetinic acid (GA) following oral administration of KGD in rats. A rapid, sensitive and reliable HPLC-MS/MS method was successfully developed for the simultaneous determination of MT, OMT, GL and GA in rat plasma. A Inertsil C18 analytical column was used with a gradient mobile phase system of methanol-ammonium acetate (5mM) with a flow rate of 0.5 mL/min. The analysis was performed on a positive and negative ionization electrospray mass spectrometer via multi reaction monitoring (MRM). Linear calibration curves were obtained for the following concentration range: 10-5000 ng/mL for MT, OMT and GL, 50-15,000 ng/mL for GA in rat plasma (R(2)>0.99). The lower limit of quantification (LLOQ) was 5 ng/mL (MT, OMT and GL) and 20 ng/mL (GA). The intra- and inter-day accuracies ranged from -7.91 to 9.10% and precisions (RSD) were within 15%. The analytes were found to be stable under short-term temperature conditions, post-preparative temperature conditions, and after three freeze-thaw cycles conditions. The validated method was successfully applied to a pharmacokinetic study in rats after oral administration of KGD.

Determination of oxymatrine and its active metabolite matrine in human plasma after administration of oxymatrine oral solution by high-performance liquid chromatography coupled with mass spectrometry.

A rapid, sensitive and selective high-performance liquid chromatography mass spectrometric method has been developed and validated for the simultaneous determination of oxymatrine and its active metabolite matrine in human plasma after administration of oxymatrine oral solution. Analytes were extracted from the plasma by liquid-liquid extraction with chloroform. The chromatographic separation was accomplished on a Venusil C18 column (150 mm × 4.6 mm, 5 µm) protected by a C18 guard column (4.0 mm × 2.0 nm; Phenomenex, Torrance, CA, USA). Analytes were detected on a single quadruple mass spectrometer by selected ion monitoring mode via electrospray ionization source. The assay had a lower limit of quantification of 1.5 ng·mL(-1) for oxymatrine and 3 ng·mL(-1) for matrine in plasma. The calibration curves were linear in the measured range. The overall precision and accuracy for all concentrations of quality controls and standards were within ±15%. The proposed method enabled unambiguous identification and quantification of oxymatrine and its active metabolite matrine in vivo. The results provided a meaningful basis for evaluating the clinical applications of the oxymatrine oral solution.

Plasma drug concentrations and clinical effects of a peripheral alpha-2-adrenoceptor antagonist, MK-467, in horses sedated with detomidine.

OBJECTIVE: To investigate plasma drug concentrations and the effect of MK-467 (L-659'066) on sedation, heart rate and gut motility in horses sedated with intravenous (IV) detomidine. STUDY DESIGN: Experimental randomized blinded crossover study. ANIMALS: Six healthy horses. METHODS: Detomidine (10 µg kg(-1) IV) was administered alone (DET) and in combination with MK-467 (250 µg kg(-1) IV; DET + MK). The level of sedation and intestinal sounds were scored. Heart rate (HR) and central venous pressure (CVP) were measured. Blood was collected to determine plasma drug concentrations. Repeated measures anova was used for HR, CVP and intestinal sounds, and the Student's t-test for pairwise comparisons between treatments for the area under the time-sedation curve (AUCsed ) and pharmacokinetic parameters. Significance was set at p < 0.05. RESULTS: A significant reduction in HR was detected after DET, and HR was significantly higher after DET + MK than DET alone. No heart blocks were detected in any DET + MK treated horses. DET + MK attenuated the early increase in CVP detected after DET, but later the CVP decreased with both treatments. Detomidine-induced intestinal hypomotility was prevented by MK-467. AUCsed was significantly higher with DET than DET + MK, but maximal sedations scores did not differ significantly between treatments. MK-467 lowered the AUC of the plasma concentration of detomidine, and increased its volume of distribution and clearance. CONCLUSIONS AND CLINICAL RELEVANCE: MK-467 prevented detomidine induced bradycardia and intestinal hypomotility. MK-467 did not affect the clinical quality of detomidine-induced sedation, but the duration of the effect was reduced, which may have been caused by the effects of MK-467 on the plasma concentration of detomidine. MK-467 may be useful clinically in the prevention of certain peripheral side effects of detomidine in horses.