Development And Evaluation Of The Solubilization System Of Tacrolimus

As a representative drug of the second generation of immunosuppressive agents,tacrolimus?FK 506?has the advantages of strong drug effect,low dosage and good tolerance.But the clinical application of tacrolimus was limited by its poor solubility?2-4?g/mL?and bioavailability?¹8%?.Through the SD,Prograf^?improved the solubility of FK 506,but did not lead to much improvement in bioavailability.Several methods such as SD,SMEDDS,CDICs and nanomedicine have been used to improve the solubility and dissolution of FK 506 in which SD,CDICs and SMEDDS were more popular.The objective of this study was to prepare the tacrolimus loaded SD,SMEDDS and?-CDICs and by in vitro and in vivo evaluation,the best one was chosen for the study of tacrolimus.High-performace liquid chromatography method?HPLC?was develop for the in vitro measurement of content and dissolution test of FK 506.The results of pre-formulation study showed that FK 506 belonged to end absorption and had the strong UV absorption at 210 nm.In addition,FK 506 was instability when the pH of media was above 7.FK 506-SMEDDS was prepared according to our previous study.The formulation of SMEDDS A was 15%of EO,52.5%of Solutol HS 15 and 32.5%of Transcutol P,and the weight ratio of FK 506 and formulation was 1:35.The formulation of SMEDDS B was 28%of Labrafil M1944 CS,48%of Cremophor EL and 24%of Transcutol P,and the weight ratio of FK 506 and formulation was 1:80.Both the particle size of the emulsion droplets of SMEDDS were<50 nm and PDI<0.2.The result of TEM showed that the emulsion droplets of SMEDDS had spherical shapes and narrow size distribution.The dissolution test showed the release of tacrolimus was over 90%at 30 min.Influence factor test showed that with the addition of citric acid,which 0.25%of citric acid was added to FK 506-SMEDDS A and 0.20%of citric acid was added to FK 506-SMEDDS B,the stability of FK506-SMEDDS was improved obviously.The results of DSC and FTIR indicated that tacrolimus could disperse in a molecular or an amorphous state in FK 506-SMEDDS.SD using poloxamer 188 as the carrier material was prepared by the combination of the solvent evaporation method and the freeze drying method which the drug loading was 24.46%and the release of tacrolimus was over 95%at 30 min.With the prescription of FK 506:HPMC AS MF:lactose?5:3:25?,FK 506-HPMC AS MF SD was successfully prepared by the combination of the solvent evaporation method and the vacuum drying method,which the release of tacrolimus was over 90%at 60min when the drug loading was 15.15%.The results of DSC,SEM and FTIR indicated that tacrolimus could disperse in a molecular or an amorphous state in the formulations we prepared.With DM-?-CD as the carrier material,FK 506-DM-?-CDICs was prepared by the combination of the saturated solvent method and the freeze drying method.In vitro dissolution test,the release of tacrolimus was over 90%at 30 min when the drug loading was 1:40 and entrapment rate was over 82%.The results of DSC,SEM and FTIR showed that FK 506-DM-?-CDICs was prepared successfully.The supersaturated stability test showed that the SMEDDS could maintain the stability of tacrolimus while the DM-?-CDICs needed to add the soluplus to maintain the supersaturated stability of tacrolimus.The results of DSC and FTIR showed that the addition of soluplus had no effects on the formation of FK 506-DM-?-CDICs.The in vivo absorption study showed that the value of K_a and P_app of FK 506 in each intestinal segment was significantly improved by three solubilization technologies when comparing with FK 506.Compared to Prograf^?,SMEDDS in the improvement of intestinal absorption of FK 506 was less than that of FK 506-SD and FK 506-DM-?-CDICs while super FK 506-DM-?-CDICs had a higher value of intestinal absorption of FK 506.The pharmacokinetic study showed that FK 506-SMEDDS A and super DM-?-CDICs had a higher value of bioavailability than FK 506-poloxamer 188 SD and compareable with Prograf?.With the consideration of safety and stability,super FK 506-DM-?-CDICs could be used as a new formulation for the study of tacrolimus.