In order to investigate the effects of methomyl poisoning on the metabolic capacity of cytochrome P450 (CYP) enzymes, a cocktail method was employed to evaluate the activities of CYP2B1, CYP2D1, CYP1A2, CYP3A2, CYP2C11. The rats were randomly divided into methomyl group and control group. The methomyl group rats were given 4 mg/kg methomyl by intraperitoneal administration. After 7 days, five probe drugs bupropion, metroprolol, phenacetin, testosterone and tolbutamide were given to rats through intragastric administration, and the plasma concentrations were determined by UPLC-MS/MS. Statistical pharmacokinetics difference for metroprolol, phenacetin, testosterone and tolbutamide in rats were observed by comparing methomyl group with control group. Methomyl poisoning inhibits the activities of CYP2D1 and CYP1A2 of rats. Enzyme inhibition by methomyl poisoning can increase the risk of adverse reactions. Induction of drug metabolizing enzyme CYP3A2 and CYP2C11 by methomyl poisoning would reduce the efficacy of other drug. Additionally, methomyl poisoning may cause hepatotoxicity.

Azilsartan is a novel angiotensin II type 1 (AT1) receptor blocker ARB introduced in the early 2011. It is for treatment of hypertension, and is the 8th ARB to appear on the clinical market. In this study, a sensitive and selective liquid chromatography mass spectrometry (LC-MS) method for the determination of azilsartan in rat plasma has been developed. After addition of diazepam as internal standard (IS) and protein precipitation by acetonitrile-methanol (90/10, v/v), chromatographic separation was achieved on a C8 (2.1 x 50 mm, 5 mu m) column with acetonitrile-0.1% formic acid in water as mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; selective ion monitoring (SIM) mode was used for quantification. Calibration plots were linear over the range of 5-5000 ng/mL for azilsartan in rat plasma. Mean recoveries of azilsartan in rat plasma were in the range of 87.1-97.0%. RSD of intra-day and inter-day precision were both less than 12%. The accuracy of the method ranged from 97.5 to 108.8%. The method was successfully applied to pharmacokinetic study of azilsartan after oral and intravenous administration in rats. The bioavailability of azilsartan was 34.1% in rats.

In this work, a sensitive and selective ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for determination of colchicine in rat plasma was developed and validated. After addition of diazepam 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 C18 column (2.1 x 100 mm, 1.7 mu m) with 0.1% formic acid and acetonitrile as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; multiple reactions monitoring (MRM) mode was used for quantification using target fragment ions m/z 400.2 -> 310.1 for colchicine, and m/z 285.1 -> 193.1 for IS. Calibration plots were linear throughout the range 2-2000 ng/mL for colchicine in rat plasma. Mean recoveries of colchicine in rat plasma ranged from 76.2% to 88.8%. RSD of intra-day and inter-day precision were both < 11%. The accuracy of the method was between 94.1% and 106.9%. The method was successfully applied to pharmacokinetic study of colchicine after intravenous administration.

A sensitive and selective liquid chromatography mass spectrometry (LC-MS) method for the determination of tirofiban in rat plasma has been developed. Tirofiban, a small molecule, non-peptide tyrosine derivative, belongs to the family of glycoprotein (GP) IIb/IIIa receptor inhibitor (GPI), which is approved by the US Food and Drug Administration for the treatment of patients with acute coronary syndromes (ACS). After addition of diazepam as internal standard (IS) and protein precipitation by acetonitrile-methanol (90/10, v/v), chromatographic separation was achieved on a C-8 (2.1 x 50 mm, 5 mu m) column with acetonitrile-0.1% formic acid in water as mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; selective ion monitoring (SIM) mode was used for quantification. Calibration plots were linear over the range of 5-5000 ng/mL for tirofiban in rat plasma. Mean recoveries of tirofiban in rat plasma were in the range of 91.4-9%. RSD of intra-day and inter-day precision were both less than 15%. The accuracy of the method ranged from 92.4 to 111.6%. The method was successfully applied to pharmacokinetic study of tirofiban after oral and intravenous administration in rats. The bioavailability of tirofiban is 2.2% in rats.

Tenacissoside G, as a major C21 steroidal glycoside, is abundant in Marsdenia tenacissima. In this work, a sensitive and selective UPLCMS/MS method for determination of tenacissoside G in rat plasma is developed. After addition of tenacissoside I 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 C18 column (2.1 mm x 100 mm, 1.7 mu m) with 0.1% formic acid and methanol as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; multiple reactions monitoring (MRM) mode was used for quantification using target fragment ions m/z 815.3 -> 755.4 for tenacissoside G, and m/z 837.3 -> 85.0 for IS. Calibration plots were linear throughout the range 2 2000 ng/mL for tenacissoside G in rat plasma. Mean recoveries of tenacissoside G in rat plasma ranged from 84.2% to 92.3%. RSD of intra day and inter day precision were both <12%. The accuracy of the method was between 97.9% and 107.8%. The method was successfully applied to pharmacokinetic study of tenacissoside G after either oral or intravenous administration. For the first time, the absolute bioavailability of tenacissoside G was reported as high as 29.2%.

Sceptridium ternatum Lyon, a common Chinese herb, has been used in treatment of allergic asthma and whooping cough. In order to investigate the effects of Sceptridium ternatum on the metabolic capacity of cytochrome P450 (CYP) enzymes, a cocktail method was employed to evaluate the activities of CYP2B1, CYP2D1, CYP1A2, CYP3A2, CYP2C11. The rats were randomly divided into Sceptridium ternatum group (Low, High) and control group. The Sceptridium ternatum group rats were given 1.2, 12 g/kg (Low, High) Sceptridium ternatum by continuous intragastric administration for 7 days. Five probe drugs bupropion, metroprolol, phenacetin, testosterone and tolbutamide were given to rats through intragastric administration, and the plasma concentrations were determined by UPLC-MS/MS. Statistical pharmacokinetics difference for bupropion, metroprolol, phenacetin and tolbutamide in rats were observed by comparing Sceptridium ternatum group with control group. Continuous 7 days-intragastric administration of Sceptridium ternatum may induce the activities of CYP2B1, CYP2D1, CYP1A2 and CYP2C11 of rats. Induction of drug metabolizing enzyme would reduce the efficacy of other drug. Additionally, Sceptridium ternatum did not cause hepatotoxicity.

CI-994 (N-acetyldinaline, PD 123654) is a novel oral agent active in a broad variety of murine and human tumor xenografts. A sensitive and selective liquid chromatography mass spectrometry (LC-MS) method for quantification of CI-994 in rat plasma was developed. After addition of carbamazepine as internal standard (IS), protein precipitation by acetonitrile-methanol (9:1, v/v) was used as sample preparation. Chromatographic separation was achieved on a Zorbax SB-C18 (2.1 x 150 mm, 5 pm) column with acetonitrile-0.1% formic acid in water as mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; selective ion monitoring mode was used for quantification. Calibration plots were linear over the range of 20-2000 ng/mL for CI-994 in rat plasma. Mean recovery of CI-994 in plasma was in the range of 73.7-80.4%. Coefficient of variation of intra-day and inter-day precision were both <14%. The bioavailability of CI-994 in rat was 54.5%.

Cabozantinib S-malate is a vascular endothelial growth factor receptor 2, c-MET, and RET multi-targeted tyrosine kinase inhibitor that has antiangiogenic and antitumorigenic properties with potential efficacy for the treatment of several cancers. In order to investigate the effects of cabozantinib on the metabolic capacity of cytochrome P450 (CYP) enzymes, a cocktail method was employed to evaluate the activities of CYP2B1, CYP2D1, CYP1A2, CYP3A2, CYP2C11. The rats were randomly divided into cabozantinib group (Low, Medium, High) and control group. The cabozantinib group rats were given 10, 20, 30 mg/kg (Low, Medium, High) cabozantinib by continuous intragastric administration for 7 days. Five probe drugs bupropion, metroprolol, phenacetin, testosterone and tolbutamide were given to rats through intragastric administration, and the plasma concentrations were determined by UPLCMS/MS. Statistical pharmacokinetics difference for bupropion, phenacetin and testosterone in rats were observed by comparing cabozantinib group with control group. Combined with PCR results, continuous 7 days-intragastric administration of cabozantinib inhibits the activities of CYP2B1 and CYP1A2 of rats. Enzyme inhibition by co-administered drugs and genetic variations of their expression can increase the risk of adverse reactions. Additionally, high dosage cabozantinib may cause hepatotoxicity.

Ramelteon, it is mainly for the treatment of difficult to sleep insomnia, chronic insomnia and also have a definite effect to short-term insomnia. In this study, a sensitive and selective liquid chromatography mass spectrometry method for the determination of ramelteon in rat plasma has been developed. After addition of diazepam as internal standard (IS) and protein precipitation by acetonitrile-methanol (90/10, v/v), chromatographic separation was achieved on a C8 (2.1 x 50 mm, 5 mu m) column with acetonitrile-0.1% formic acid in water as mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; selective ion monitoring (SIM) mode was used for quantification. Calibration plots were linear over the range of 5-2000 ng/mL for ramelteon in rat plasma. Mean recoveries of ramelteon in rat plasma were in the range of 87.8-96.9%. RSD of intra-day and inter-day precision were both less than 15%. The accuracy of the method ranged from 93.9 to 107.6%. The method was successfully applied to pharmacokinetic study of ramelteon after oral and intravenous administration in rats. The bioavailability of ramelteon is 52.1% in rats.

Methomyl a carbamate insecticide, has been classified as a highly toxic pesticide for aquatic organism, widely used in many agricultural countries for crop protection and soil or plant treatment. The rats were randomly divided into methomyl group and activated carbon treatment group. The concentration of methomyl in rat plasma was determined by a simple high performance liquid chromatograph method over the range of 50-1000 mu g/mL. Chromatographic separation was achieved on a C18 (4.6 x 150 mm, 5 mu m) column with acetonitrile-0.1% trifluoroacetic acid in water (50: 50, v/v) as mobile phase. Protein precipitation with acetonitrile, then freeze-drying for 24 h, and re-suspension in methanol was used as sample preparation. Statistical toxicokinetics difference in rats was observed by comparing methomyl group with activated carbon treatment group (10 min, 1000 mg/kg), AUC((0-t)) decreased (p < 0.05), MRT(0-infinity) increased (p < 0.05), t(1/2) increased (p < 0.05), and V increased (p < 0.01). The results shown that treatment by activated carbon could relieve acute methomyl poisoning in rats.

Dextromethorphan at high doses has phencyclidine-like effects on the NMDA receptor system; recreational use of high doses has been found to cause mania and hallucinations. In order to investigate the effects of dextromethorphan on the metabolic capacity of cytochrome P450 (CYP) enzymes, a cocktail method was employed to evaluate the activities of CYP2B1, CYP2D1, CYP1A2, CYP3A2, CYP2C11. The rats were randomly divided into dextromethorphan group (Low, Medium, High) and control group. The dextromethorphan group rats were given 12, 24, 48 mg/kg (Low, Medium, High) dextromethorphan by continuous intragastric administration for 7 days. Five probe drugs bupropion, metroprolol, phenacetin, testosterone and tolbutamide were given to rats through intragastric administration, and the plasma concentrations were determined by UPLC-MS/MS. Statistical pharmacokinetics difference for metroprolol, phenacetin and testosterone in rats were observed by comparing dextromethorphan group with control group. Continuous 7 days-intragastric administration of dextromethorphan inhibits the activities of CYP2D1 of rats. Enzyme inhibition by co-administered drugs and genetic variations of their expression can increase the risk of adverse reactions. Additionally, continuous 7 days-intragastric administration of dextromethorphan may not cause hepatotoxicity.

Tramadol is a synthetic opioid analgesic with multiple pharmacological actions, and has been widely used for acute, chronic, and neuropathic pain. In this study, a sensitive and selective liquid chromatography mass spectrometry method for the determination of tramadol in rat plasma has been developed. After addition of diazepam as internal standard (IS) and protein precipitation by acetonitrilemethanol (90/10, v/v), chromatographic separation was achieved on a C18 (2.1 mm x 50 mm, 5 mu m) column with acetonitrile-0.1% formic acid in water as mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; selective ion monitoring (SIM) mode was used for quantification. Calibration plots were linear over the range of 5-2000 ng/mL for tramadol in rat plasma. Mean recoveries of tramadol in rat plasma were in the range of 88.7-94.6%. RSD of intra-day and inter-day precision were both less than 11%. The accuracy of the method ranged from 95.6 to 112.3%. The method was successfully applied to pharmacokinetic study of tramadol after intravenous (5, 10 mg/kg) and oral administration (10, 200 mg/kg) in rats. The bioavailability of tramadol was 59.8% in rats.

Flos Daturae, known as "baimantuoluo" or "yangjinhua" in China, has been used for centuries in Traditional Chinese Medicine for the treatment of asthma, convulsions, pain, and rheumatism. To investigate the influences of Flos Daturae on the activities of rat CYP450 enzymes (CYP1A2, CYP2C9, CYP2C19, CYP2B6, CYP2D6 and CYP3A4) using cocktail probe drugs in vivo. A cocktail solution at a dose of 5 mL/kg, which contained phenacetin (10 mg/kg), tolbutamide (1 mg/kg), omeprazole (10 mg/kg), bupropion (10 mg/kg), metoprolol (10 mg/kg) and testosterone (10 mg/kg), was intragastric administered to rats treated with a single low or high dose of Flos Daturae decotion for 7days. Blood samples collected at a series of time-points in plasma were determined by UPLC-MS/MS. The corresponding pharmacokinetic parameters were calculated by the software of DAS 3.0. The results from the present in vivo study showed that Flos Daturae induce the activity of CYP2D6 enzyme with the decreased Cmax, AUC(0-∞) (P < 0.05) and the increased CL (P < 0.05). However, there were no significant differences of other probe drugs in plasma concentration and pharmacokinetic parameters. There were no significant effects on rat CYP1A2, CYP3A4, CYP2B6, CYP2C9 and CYP2C19 by Flos Daturae. Therefore, the resulting data suggested that caution was needed when Flos Daturae was co-administered with CYP2D6 substrates, which may result in treatment failure and herb-drug interactions.

Macitentan is a novel, orally active dual endothelin receptor antagonist, which is currently under investigation for the treatment of diseases associated with endothelin dysfunction, including pulmonary arterial hypertension (PAH). In this work, a sensitive and selective ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for determination of macitentan in rat plasma was developed and validated. After addition of diazepam 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 C18 column (2.1 x 100 mm, 1.7 mu m) with 0.1% formic acid and methanol as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; multiple reactions monitoring (MRM) mode was used for quantification using target fragment ions m/z 588.9 -> 203.4 for macitentan, and m/z 285.1 -> 193.1 for IS. Calibration plots were linear throughout the range 10-4000 ng/mL for macitentan in rat plasma. Mean recoveries of macitentan in rat plasma ranged from 80.2 to 93.0%. RSD of intra-day and inter-day precision were both < 12%. The accuracy of the method was between 893 and 105.1%. The method was successfully applied to pharmacokinetic study of macitentan after either oral or intravenous administration. The bioavailability of macitentan was reported as 79.6%.

Imperialine is the major biologically active isosteroidal alkaloid present in Bulbus Fritillaria. In this work, a sensitive and selective UPLC-MS/MS method for determination of imperialine in rat plasma was developed and validated. After addition of hupehenine 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 C18 column (2.1 mm x 100 mm, 1.7 mu m) with 0.1% formic acid and acetonitrile 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 430.3 -> 4382 for imperialine, and m/z 416.3 -> 98.0 for IS. Calibration plots were linear throughout the range 2-2000 ng/mL for imperialine in rat plasma. Mean recoveries of imperialine in rat plasma ranged from 93.9 to 97.0%. RSD of intra-day and inter-day precision were both < 6%. The accuracy of the method was between 96.5% and 106.5%. The method was successfully applied to pharmacokinetic study of imperialine after either oral or intravenous administration. The bioavailability of imperialine was reported as 48.5%.

Miltefosine is a new oral drug to treat leishmaniasis, with relatively high efficacy rates reported for treatment of New World cutaneous, mucocutaneous, and visceral leishmaniasis. In this work, a sensitive and selective ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for determination of miltefosine in rat plasma was developed and validated. After addition of diazepam 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 C18 column (2.1 mm x100 mm, 1.7 mu m) with 0.1% formic acid and methanol as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; multiple reactions monitoring (MRM) mode was used for quantification using target fragment ions m/z 408.2 -> 86.1 for miltefosine, and m/z 285.1 -> 193.1 for IS. Calibration plots were linear throughout the range 10-4000 ng/mL for miltefosine in rat plasma. Mean recoveries of miltefosine in rat plasma ranged from 86.7% to 96.4%, matrix effect of miltefosine in rat plasma ranged from 99.2% to 110.2%. RSD of intra-day and inter-day precision were both < 7%. The accuracy of the method was between 93.7% and 105.2%. The method was successfully applied to pharmacokinetic study of miltefosine after either oral or intravenous administration.

Vorinostat (suberoylanilide hydroxamic acid, SAHA) is the first approved histone deacetylase (HDAC) inhibitor for the treatment of cutaneous T-cell lymphoma after progressive disease following two systemic therapies. The rats were randomly divided into SAHA groups (low, medium and high dosage) and control group. The SAHA group rats were given 12.3, 24.5, and 49 mg/kg SAHA, respectively, by continuous intragastric administration for 7 days. The influence of SAHA on the activities of CYP450 isoforms CYP2B6, CYP1A2, CYP2C19, CYP2D6 and CYP2C9 were evaluated by cocktail method, they were responsed by the changes of pharmacokinetic parameters of bupropion, phenacetin, tolbutamide, metroprolol and omeprazole. The five probe drugs were given to rats through intragastric administration, and the plasma concentration were determined by UPLC-MS/MS. The result of SAHA group compared to control group, there were statistical pharmacokinetics difference for bupropion, phenacetin, tolbutamide and metroprolol. Continuous intragastric administration for 7 days may induce the activities of CYP2C19 of rats, inhibit CYP1A2 and slightly inhibit CYP2B6 and CYP2D6 of rats. This may give advising for reasonable drug use after co-used with SAHA. The results indicated that drug co-administrated with SAHA may need dose adjustment. Furthermore, continuous intragastric administration of SAHA for 7 days, liver cell damaged, causing liver cell edema, in liver metabolism process.

In order to investigate the effects of diphenoxylate on the metabolic capacity of cytochrome P450 (CYP) enzymes, a cocktail method was employed to evaluate the activities of CYP2B6, CYP2D6, CYP2C19, CYP1A2, CYP3A4, CYP2C9. The rats were randomly divided into diphenoxylate group (Low, Medium, High) and control group. The diphenoxylate group rats were given 12, 24, 48 mg/kg (Low, Medium, High) diphenoxylate by continuous intragastric administration for 7 days. Six probe drugs bupropion, metroprolol omeprazole, phenacetin, testosterone and tolbutamide were given to rats through intragastric administration, and the plasma concentrations were determined by UPLC-MS/MS. Statistical pharmacokinetics difference for omeprazole, phenacetin and tolbutamide in rats were observed by comparing diphenoxylate group with control group. Continuous 7 days-intragastric administration of diphenoxylate induces the activities of CYP2C19, CYP1A2 and CYP2C9 of rats. Induction of drug metabolizing enzyme by diphenoxylate would reduce the efficacy of other drug. Additionally, high dosage diphenoxylate may cause hepatotoxicity.

In this work, a sensitive and selective ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for determination of hupehenine in rat plasma was developed and validated. After addition of imperialine 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 C18 column (2.1 × 100 mm, 1.7 µm) with 0.1% formic acid and acetonitrile as the mobile phase with gradient elution. An electrospray ionization source was applied and operated in positive ion mode; multiple reaction monitoring mode was used for quantification using target fragment ions m/z 416.3 → 98.0 for hupehenine, and m/z 430.3 → 138.2 for IS. Calibration plots were linear throughout the range 2-2000 ng/mL for hupehenine in rat plasma. Mean recoveries of hupehenine in rat plasma ranged from 92.5 to 97.3%. Relative standard deviations of intra-day and inter-day precision were both <6%. The accuracy of the method was between 92.7 and 107.4%. The method was successfully applied to a pharmacokinetic study of hupehenine after either oral or intravenous administration. For the first time, the bioavailability of hupehenine was reported as 13.4%.

Cephalomannine, a naturally occurring diterpene alkaloid, was originally isolated from Taxus wallichiana. A sensitive and selective ultra-performance liquid-chromatography with tandem mass spectrometry (UPLC-MS/MS) method for determination of cephalomannine in rat plasma was developed. After addition of diazepam as internal standard (IS), protein precipitation by acetonitrile-methanol (9: 1, v/v) was used as sample preparation. Chromatographic separation was achieved on a CORTECSTM C18 column (2.1 mm x 100 mm, 1.6 mu m) with acetonitrile-0.1% formic acid in water as 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 832.4 -> 264.1 for cephalomannine and m/z 285.1 -> 193.1 for IS. Calibration plots were linear over the range of 2-2000 ng/mL for cephalomannine in rat plasma. Mean recoveries of cephalomannine in rat plasma were in the range of 90.6-97.0%. RSD of intra-day and inter-day precision were both < 12%. The accuracy of the method ranged from 89.5 to 108.7%. The method was successfully applied to pharmacokinetic study of cephalomannine after intravenous administration of single dosage 2 mg/kg in rats.