Considerations in the development of an in vitro dissolution condition for lacidipine tablets: in vivo pharmacokinetic evaluation.

In this study, a new discriminative dissolution condition for lacidipine tablets was developed by the established in vitro-in vivo relationship. Series of dissolution media of phosphate buffer solution (PBS) covering the pH range of 1-7.2 and pH 6.8 PBS containing different concentrations of sodium dodecyl sulfate (SDS), were prepared and used to investigate the dissolution behavior of lacidipine tablets. There was an obvious difference in the dissolution profiles of the both brands in pH 6.8 PBS medium containing 0.1% SDS. The pharmacokinetic study of the two lacidipine tablets was carried out in the healthy beagle dogs at a single dose of 4 mg. Statistical comparison of the AUC(0₋24), C(max), and T(max) showed a significant difference in the two brand tablets, coinciding with the dissolution performance with pH 6.8 PBS containing 0.1% SDS. The superiority of the proposed system, pH 6.8 PBS containing 0.1% SDS, could serve as a dissolution medium for lacidipine tablets, and more important it could discriminate the in vivo pharmacokinetic behavior for different brands of products. In summary, in vivo pharmacokinetic evaluation is essential to develop an appropriate in vitro dissolution condition for oral solid dosage forms of poorly soluble drugs.

High-performance liquid chromatography/tandem mass spectrometry for simultaneous determination of four dicaffeoylquinic acids in rat plasma.

A specific and reliable HPLC-MS/MS method was developed and validated for the simultaneous determination of four dicaffeoylquinic acids (DCQA): 3,4-DCQA, 1,5-DCQA, 3,5-DCQA and 4,5-DCQA. The analytes were separated on a C18 column (150 mm × 2.1 mm, 1.8 µm) and a triple-quadrupole mass spectrometry equipped with an electrospray ionization (ESI) source was applied for detection. The plasma sample was prepared by a liquid-liquid extraction method and the recovery for the four analytes was around 80%. The calibration curves were linear over a concentration range of 10.6-1060.0 ng/mL for 3,4-DCQA, 19.2-1920.0 ng/mL for 1,5-DCQA, 14.0-2900.0 ng/mL for 3,5-DCQA, 9.7-970.0 ng/mL for 4,5-DCQA. The intra-day and inter-day precision was less than 15% and the relative error (RE) were all within ±15%. The validated method was successfully applied to a pharmacokinetics study in rats after oral administration of the extracts of Ainsliaea fragrans cham (a traditional Chinese herb).