Determination of thymopentin in beagle dog blood by liquid chromatography with tandem mass spectrometry and its application to a preclinical pharmacokinetic study.

The pentapeptide thymopentin (Arg-Lys-Asp-Val-Tyr, RKDVY) corresponds to amino acids 32-36 of the 49 amino acid immunomodulatory polypeptide, thymopoietin, whose biological activity is partially reproduced. Thymopentin is widely used in the clinic and represents a promising target for drug design but bioanalytical and pharmacokinetic data are limited due to its enzymatic instability. This paper reports a rapid and sensitive method based on liquid chromatography with tandem mass spectrometry for the determination of thymopentin in beagle dog blood. To inactivate peptidases and stabilize thymopentin, acetonitrile was added to blood samples immediately after collection followed by addition of stable isotope-labeled thymopentin as internal standard and washing with dichloromethane. Chromatography was carried out on an Ascentis Express Peptide ES-C18 column using gradient elution with methanol and aqueous 0.1% formic acid at a flow rate of 0.6 mL/min. Positive electrospray ionization mass spectrometry with selected reaction monitoring achieved linearity in the range of 1.5-800 ng/mL with good accuracy/precision and minimal matrix effects. The method was successfully applied to a pharmacokinetic study in beagle dogs after intravenous administration of 0.2 mg/kg thymopentin.

Effect of fluvoxamine on the pharmacokinetics and pharmacodynamics of clopidogrel in rats.

1. Fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), is often coprescribed with clopidogrel for the treatment of ischemic vascular diseases. The aim of this study was to explore the effect of fluvoxamine on the pharmacokinetics and pharmacodynamics of clopidogrel. 2. Twelve male rats were employed to investigate the effect of fluvoxamine on the pharmacokinetics of clopidogrel in vivo. Clopidogrel carboxylic acid was used for the pharmacokinetic study of clopidogrel. 3. After pretreatment with high dose of fluvoxamine (27 mg/kg), there were significant increases in the AUC0-t (from 9850±4060 to 27,300±6910 µg/l h; p<0.05), AUC0-∞ (from 9850±4060 to 27,600±6800 µg/l h; p<0.05) and t1/2 (from 2.07±0.0942 to 7.49±1.22 h; p<0.05) of clopidogrel carboxylic acid. The pharmacokinetic data for clopidogrel carboxylic acid showed significant decreases in VLz/F (from 0.765±0.299 to 0.256±0.0594 l/kg; p<0.05) after pretreatment with high dose of fluvoxamine. Pharmacodynamic studies that measure platelet aggregation percentage (from 21.63±6.05% to 45.98±5.11%; p<0.01) show that high doses of fluvoxamine significantly inhibit the effect of clopidogrel. 4. In conclusion, the pharmacokinetics and pharmacodynamics of clopidogrel were significantly affected by high doses of fluvoxamine. This study indicated that potential drug-drug interaction between fluvoxamine and clopidogrel should be taken into consideration in clinical use.

Determination of a deuterohemin-peptide conjugate in rat plasma by liquid chromatography-tandem mass spectrometry and application to a preclinical pharmacokinetic study.

The deuterohemin-peptide conjugate (DhHP-6) is a microperoxidase mimetic, which has demonstrated substantial benefits in vivo as a scavenger of reactive oxygen species. This paper reports the development of a sensitive and rapid liquid chromatography tandem mass spectrometry (LC-MS/MS) method for the determination of DhHP-6 in rat plasma using triptorelin as an internal standard (IS). 50µL plasma was used in sample preparation, and a simple protein precipitation procedure with acetonitrile was involved. Satisfactory peak shapes of analyte and IS were obtained on an Agilent HC-C18 column by using a gradient elution with 10mM ammonium acetate-0.5% formic acid (v:v) and acetonitrile, there was no significant interference impacting the determination. A calibration curve obtained from this method was linear within the concentration range 10-3000ng/mL with intra- and inter-day precisions of 4.2-6.8% and 3.2-8.9%, respectively and accuracy of -1.3% to 2.1%. The recovery was above 80% with low matrix effects. The method was successfully applied to support a preclinical pharmacokinetic study in rat.