OBJECTIVETo establish a RP-HPLC method for determination of plasma progesterone and to apply the method for pharmacokinetics study of progesterone-loaded lipid nanoparticles after oral administration in rats.

METHODSThe plasma samples were collected from castrated rat after oral administration of progesterone-loaded lipid nanoparticles and extracted by acetic ether. The determination was performed on a Hypersil C18 column (150 mm X 3.9 mm , 5 microm) with a mobile phase consisting of methanol and water (60:40) at a flow-rate of 0.6 ml/min. The UV detector was at 240 nm and danazol was used as internal standard.

RESULTGood linearity was obtained over the range of 0.02-2 microg/ml progesterone in plasma(r=0.9999, n=3). The quantification limit was (0.02 +/-0.004) microg/ml(n=3) and the limit of detection was 0.005 microg.mL(-1)(S/N = or >3). The inter-and intra-day RSDs were all less than 10% for quality control samples at high-, medium- and low-concentrations. The average absolute recovery rate was 90.5 % and the average method recovery was in the range of 93.4 %-107.5%. The plasma concentration-time curves indicated that tmax was delayed after administration of progesterone-loaded lipid nanoparticles, and the bioavailability was increased significantly, compared with contrast solution.

CONCLUSIONThe method developed is stable, simple, rapid, accurate, sensitive and applicable for determining plasma concentrations of progesterone of progesterone-loaded lipid nanoparticles in pharmacokinetic studies.