Determination of Prostaglandin E1 in dog plasma using liquid chromatography-tandem mass spectrometry and its application to a pharmacokinetic study

Development, Optimization, and Characterization of PEGylated Nanoemulsion of Prostaglandin E1 for Long Circulation

Lipo-PGE1 is the most widely used formulation of PGE1 in clinic. However, PGE1 is easier to leak out from lipo-PGE1 and this will lead to the phlebophlogosis when intravenous injection. The stability of lipo-PGE1 in storage and in vivo is also discounted. The aim of this study is to develop a long-circulating prostaglandin E1-loaded nanoemulsion modified with 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[methoxy(polyethylene glycol)-2000] (DSPE-PEG) to improve the stability and pharmacokinetics profiles of lipo-PGE1. PEGylated PGE1 nanoemulsion was prepared using a dispersing-homogenized method. The stability of nanoemulsion in 1 month was investigated. Pharmacokinetic studies were employed to evaluate the in vivo profile of the optimized nanoemulsion. The optimized nanoemulsion PGE1-PEG2000(1%)-NE showed an oil droplet size <100 nm with a surface charge of -14 mV. Approximately, 97% of the PGE1 was encapsulated in the nanoemulsion. The particle size, zeta potential, and drug loading of PGE1-PEG2000(1%)-NE were stable in 1 month. After PGE1-PEG2000(1%)-NE was intravenously administered to rats, the area under curve (AUC) and half-life of PGE1 were, respectively, 1.47-fold and 5.98-fold higher than those of lipo-PGE1 (commercial formulation). PGE1-PEG2000(1%)-NE was an ideal formulation for prolonging the elimination time of PGE1. This novel parenteral colloidal delivery system of PGE1 has a promising potential in clinic use.

Simultaneous determination of carboprost methylate and its active metabolite carboprost in dog plasma by liquid chromatography-tandem mass spectrometry with positive/negative ion-switching electrospray ionization and its application to a pharmacokinetic study

A liquid chromatography-tandem mass spectrometric (LC-MS/MS) method using positive/negative electrospray ionization (ESI) switching for the simultaneous quantitation of carboprost methylate and carboprost in dog plasma has been developed and validated. After screening, the esterase inhibitor, dichlorvos was added to the whole blood at a ratio of 1:99 (v/v) to stabilize carboprost methylate during blood collection, sample storage and LLE. Indomethacin was added to plasma to inhibit prostaglandins synthesis after sampling. After liquid-liquid extraction of 500μL plasma with ethyl ether-dichloromethane (75:25, v/v), analytes and internal standard (IS), alprostadil-d4, were chromatographed on a CAPCELL PAK Phenyl column (150×2.0mm, 5μm) using acetonitrile-5mM ammonium acetate as mobile phase. Carboprost methylate was detected by positive ion electrospray ionization followed by multiple reaction monitoring (MRM) of the transition at m/z 400.5→329.3; the carboprost and IS were detected by negative ion electrospray ionization followed by MRM of the transitions at m/z 367.2→323.2, and 357.1→321.2, respectively. The method was linear for both analytes in the concentration range 0.05-30ng/mL with intra- and inter-day precisions (as relative standard deviation) of ≤6.75% and accuracy (as relative error) of ≤7.21% and limit of detection (LOD) values were 10 and 20pg/mL, respectively. The method was successfully applied to a pharmacokinetic study of the analytes in beagle dogs after intravaginal administration of a suppository containing 0.5mg carboprost methylate.