[Simultaneous determination of clevidipine butyrate and its metabolite clevidipine acid in dog blood by liquid chromatography-tandem mass spectrometry].

A rapid, sensitive and simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous determination of clevidipine butyrate and its primary metabolite clevidipine acid in dog blood. After one-step protein precipitation with methanol, the chromatographic separation was carried out on an Ecosil C18 column (150 mm x 4.6 mm, 5 µm) with a gradient mobile phase consisting of methanol and 5 mmol · L(-1) ammonium formate. A chromatographic total run time of 13.0 min was achieved. The quantitation analysis was performed using multiple reaction monitoring (MRM) at the specific ion transitions of m/z 454.1 [M-H]- --> m/z 234.1 for clevidipine butyrate, m/z 354.0 [M-H]- --> m/z 208.0 for clevidipine acid and m/z 256.1 [M-H]- --> m/z 227.1 for elofesalamide (internal standard, IS) in the negative ion mode with electrospray ionization (ESI) source. The linear calibration curves for clevidipine butyrate and clevidipine acid were obtained in the concentration ranges of 0.5-100 ng · mL and 1-200 ng · mL(-1), separately. The lower limit of quantification of clevidipine butyrate and clevidipine acid were 0.5 ng · mL(-1) and 1 ng · mL(-1). The intra and inter-assay precisions were all below 12.9%, the accuracies were all in standard ranges. Stability testing indicated that clevidipine butyrate and clevidipine acid in dog blood with the addition of denaturant methanol was stable under various processing and/or handling conditions. The validated method has been successfully applied to a pharmacokinetic study of clevidipine butyrate injection to 8 healthy Beagle dogs following intravenous infusion at a flow rate of 5 mg · h(-1) for 0.5 h.

The assessment of absorption of periplocin in situ via intestinal perfusion of rats by HPLC.

Periplocin is an important compound of Cortex Periplocae, which shows poor absorption when administered orally. The effective intestinal permeability of periplocin was investigated using single-pass intestinal perfusion technique in male Wistar rats. SPIP was performed in rat jejunum. The samples of perfusate were collected at the designated time points after rat intestinal perfusion and analyzed by HPLC. The specificity of this method was demonstrated by the absence of interference of the drug peak with the intestinal sac artifacts and the components of the KRB solution. Recovery studies, as well as the intra-day and inter-day variations, were within statistical limits. This technique was applied to the study of the intestinal absorption of periplocin. The determined fraction absorbed (F(a)) of periplocin was 0.151 +/- 0.072 (n = 6) at a concentration of 6 microg/mL; the absorption rate constant (K(a)) was 0.0102 +/- 0.0039/min and the effective permeability coefficient (P(eff)) was 0.0021 +/- 0.0012 cm/min. These data suggest that periplocin has high permeability and might be absorbed in rat intestine.