Investigation Of Vaginal Sustained-release Progesterone Gel

Progesterone is a natural progestin,which is mainly used for the treatment of threatened abortion,luteal-phase deficiency and reproductive assistance.At present,the main progesterone preparations on the market are oral capsules,intramuscular oil injection and vaginal gel.Vaginal progesterone gel is gradually favored by the market because of its better bioavailability than oral preparation and no serious side effects compared with oral and intramuscular injection.The progesterone vaginal preparation in domestic market is the vaginal sustained-release progesterone gel Crinone^?which was originally developed by Merck in 1997.Up to date,there is no generic medicine of Crinone^?in China.In this study,vaginal sustained-release progesterone gel was prepared by classical emulsification method,and compared with Crinone^?in pharmaceutics and pharmacokinetics in rats.In this study,a HPLC method for the determination of drug content and in vitro dissolution was established.The progesterone had a good linear relationship in the range of 2.016-252.0μg/mL（y=30.54x-0.6327,r²=1）.The method showed strong specificity and high sensitivity,and could be used as a validated method for the determination of progesterone in vitro.Vaginal sustained release progesterone gel was prepared by emulsification method,and the formulation and preparation process were optimized.The key preparation process factors included swelling time of polymer,method of dispersing drug,emulsifying equipment,and emulsification time.Single factor experiments were used to optimize the above key factors by assessing the appearance,rheology,in vitro dissolution,bioadhesion,pH and physical stability.Single factor experiments were also used to optimize the formulation of progesterone gel by comparing the similarity factor of dissolution results between the developed preparation and Crinone^?.The optimized preparation process contained the following steps:（1）Polymer phase preparation:heating the formulation amount of water and sorbic acid to 75 ℃ to dissolve completely,adding carbomer and polycarbophil after the sorbic acid solution was cooled to room temperature,the polymer phase then being stirred at 800 r/min for 2 hours,the pH value being adjusted to 3.0±0.1 using 1 M NaOH,dispersing the micronized progesterone to the polymer phase,and being heated to 60 ℃.（2）Oil phase preparation:glycerin,light liquid paraffin and Cetyl Palmitate were heated and stirred evenly,and was kept at 60 ℃.（3）Emulsification:the oil phase was added to the polymer phase,and was emulsified by 200 r/min at 60 ℃ for 30min.The optimised formulation of progesterone gel was 8%progesterone（D90<10μm）,1%carbopol,2%polycarbophil,12.9%light liquid paraffin,4.2%glycerol,1%Cetyl Palmitate,and 0.08%sorbic acid.Using the aboved mentioned preparation process and the formulation,generic progesterone gel was developed that was consistent with Crinone^?as proved by the dissolution similarity factor of 64.23.The rheology study showed that the prepared gel was a pseudoplastic non-Newtonian fluid with the property of shear thinning and the gel presented elastic.The bioadhesive time was in the rangd of 1116 s to 1206 s.The above results demonstrated that the developed progesterone gel was consistent with Crinone^?in vitro.The pharmacokinetics of the progesterone preparation developed in this study and Crinone^?were studied in female rats after vaginal administration,and the drug-plasma concentration was determined by LC-MS/MS.The validation of the LC-MS/MS was acceptable.Female rats were divided into three groups（n=6 for each group）,and each group was vaginally administered with blank gel（gel without progesterone）,gel developed in this study（T group）with the dose of 80 mg/kg,and Crinone^?（R group）with the dose of 80 mg/kg,respectively.The pharmacokinetic results showed that the average plasma concentration of the blank group was 8.75±3.67 ng/mL.The plasma progesterone level of both T and R group reached the peak at 1h to 2h,and was significantly higher than that in the blank group.After 12h,the progesterone level of both T and R group was still higher than that of the blank group,indicating that progesterone could be sustained release for 12h in vivo.In R group(Crinone^?group),C_max was136.98±36.90 ng/mL with T_max being 1.83±0.26h,and AUC_0-t was 1224.05±399.95 h*ng/mL,and AUC_0-∞was 1329.98±419.82 h*ng/mL.While in T group,C_max was 133.64±28.10 ng/mL with T_maxbeing 1.60±0.42 h,and AUC_0-6was 1340.61±205.68 h*ng/mL,and AUC_0-∞was1513.78±270.30 h*ng/mL.There was no significant difference between the T and R group in absorption rate(T_max)and absorption degree(C_max,AUC_0-t),indicating that the drug release behavior of self-made preparation and reference preparation was similar in vivo.In conclusion,the in vitro pharmaceutical properties such as the dissolution behavior,rheological properties,bioadhesion were similar between the progesterone gel developed in this study and Crinone^?.After vaginal administration,the progesterone was absorbed rapidly and reached the peak plasma concentration at 1 h-2 h.There was no significant difference between self-made preparation and Crinone^?in absorption rate and absorption degree.This study may provide formulations for the development of generic drug of vaginal sustained-release progesterone gel.