| AIM (1) To investigate the preparation method and optimization technique of nimodipine (NMP) hydrogel microspheres. (2) To study the drug-release characteristics of NMP hydrogel microspheres in vitro and in vivo. (3) To provide scientific basis for preparing ideal sustained-release NMP microspheres. METHODS (1) Hydrogel microspheres were prepared by emulsion method (W/O). Five factors, including stirring rate, amount of cross-linking agent, concentration of polymer solution, concentration of emulsifier and water/oil(W/O) ratio, and four levels for each factor were selected and arranged in an L16 ( 45) orthogonal experimental table to optimize the preparation condition of hydrogel microsphere. The state of microspheres formation and the degree of non-adhesion of microspheres were used as index to evaluate the hydrogel microspheres. The morphology of hydrogel microspheres was observed by scanning electron microscope (SEM). High performance liquid chromatography (HPLC) was introduced to determine the drug loading. (2)The drug release from the NMP hydrogel microspheres in vitro was carried out in a shaking waterbath at 37C. The media used for the release of NMP was 100ml of phosphate buffered saline (pH6.8) with 0.5% of sodium dodecyl sulfate. 0.5mL samples were drawn at 40, 80, 160, 240, 360 and 600min after incubation and the same volume of fresh dissolution media were added to the system immediately. The cumulative release amount of NMP was measured by HPLC. The release data were calculated with zero-order equation, the first-order equation and Higuchi equation. (3) NMP conventional tablets (containing NMP 20mg) and capsules of NMP hydrogel microspheres (containing NMP 14mg) were orally administrated to Beagle dogs respectively. The blood sample were drawn from the vein of dogs in their front legs at 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 8.0, 1 0.0 and 12.0h after drug was orally administrated. The alkalized solution and internal standard were added into the plasma. The NMP in plasma was extracted twice with ether. The organic phase was removed into the tubes and then evaporated in ventilation cabinet. The residue was dissolved in 50 u L of methanol. 20 u L solution was drawn and detected by HPLC. The concentration-time data were analyzed by 3P97 software. RESULTS (1) The sequence of the five factors that affected the preparation of microspheres was as follows: amount of cross-linking agent > concentration of emulsifier > concentration of polymer solution > stirring rate > W/O ratio. Scanning electron micrograph showed that NMP hydrogel microspheres had good shape and smooth surface .The drug loading was (1.40+0.27)%. (2) NMP in PBS was detected by HPLC. The mobile phase consisted of 80% methanol and 20% water. C18 analytical column (250mm X 4.6mm, 5um, phenomenex) were used. The column temperature wasmaintained at 25C. The flow rate was 1 mL min-1 with detection wavelength at 237 nm. Injection volume was 20 u L. The regression equation of standard curve was: Y = - 0.0198+0.0013X (r =0.9997).The linear range was 0.4-1.0 u g mL-1. The results of drug release from the NMP hydrogel microspheres in vitro suggested that the percent of cumulative release of NMP at 40 160 and 360 min were 24.68%, 55.25% and 84.74%,respectivly. The profiles of drug release in vitro were fitted to the first grade equation and Higuchi equation. (3) The concentration of NMP in plasma was determined by HPLC with a mobile phase consisting of 83% methanol and 17% water. The flow rate was 1.0 mL-min"1 and the detection wavelength was 350nm. Under this HPLC condition, NMP was clearly separated from interference. The regression equation of standard curve was: Y= 0.01 7 1+0.0016X (r =0.9995) . The linear range was 0.01 - 0.5 u g-mL-1. The concentration-time data of NMP conventional tablets and NMP hydrogel microsphere were all proved to be consistent with the one-compartment model after being analyzed through 3P97 software package. The pharmacokinetic parameters were as follows: Ke were (0.571 + 0.156) h-1 and ( 0.369+0.037) h-1,...
|
PDF Full Text Request