The Study Of Pharmacokinetics And Relative Bioavailability Of Spironolatone Metabolite Canrenone In Healthy Chinese Volunteers

Spironolactone, the first used aldosterone receptor antagonist, has a very similar chemical structure with aldosterone, and it's now being wildly used on patients with edema with aldosterone elevation, congestive heart failure, and hypertension etc. As people are acquiring more and more knowledge in the physiopathology of aldosterone, the research of the pharmacological action of spironolactone will be pushed further, making it a broader future in clinical use. Having a short metabolism rate, spironolactone has a low plasma concentration rate in human body. Its metabolite is canrenone, which has no pharmacokinetics study reported in our country yet. The pharmacokinetics about canrenone, metabolites of spironolactone (both Jiangsu Yixing Qianjin medical co. and Jiangsu Changjiang medical co.) ,in Chinese healthy volunteers is reported in this thesis and it will provide academic foundation for the development andclinical use of spironolactone.Objective To study pharmacokinetics academic foundation and clinical use ofcanrenone.Methods A single oral dose 200mg of two spironolactone oral solutions was given two 18 healthy volunteers in a randomized cross-over study. The interval was 2 weeks. None of the subjects had a history of significant medical illness or hypersensitivity to any drugs. They were not alcohol addicted and were none-smoker. None of them had taken any other drugs during the study. Their normal health status were judged on the basis of a physical examination with screening blood chemistries,including a complete blood count and liver function test,urinalysis and eletrocardiogram performed before the study. After overnight fast,each of them took a single 200mg oral dose of spironolactone with 200ml water. A standardized meal was served separately at 4 hours after the drug ingestion. Venous blood samples(4ml each) were collected into heparin zed tubes,immediately before the drug administration and at 0.5, 1, 1.5, 2, 2.5, 3, 4, 6, 8, 12, 24, 48, 72 hours after dosing. The sample were spun immediately after the collection, centrifuged for 10 min at 3000 r/min, and the plasma samples were stored at -20℃until assayed.Then 1.0 ml plasma was taken to a clean tube, 4ml ethyl acetate was added to each tube for extraction, tube were vortexed vigorously for 5 min, centrifuged for 10 min at 3000 r/min, and the 3ml organic layer was evaporated at 40℃under conditions of a mild nitrogen. When the tube was dry, acetonitrile:0.02M ammonium dibasic phosphater(45:55), PH 5.6, was added for reconstitution. Tubes were vortexed vigorously for 1 min,and 40μL was injected via Agilient Crop.The sample was delivered using a mobile phase composed of 45% acetonitrile and 55% 0.05M monobasic ammonium phosphate at 280 nm.The plasma concentration-time data were disposed with 3P97 program. The peak connection (C_max) and the peak time (T_max) of nevirapine were determined from the respective observed concentration-time data. The area under the curve(AUC) was calculated by the linear trapezoidal method. The data are expressed as mean values±SD throughout the paper. Difference in pharmacokinetics data of two formulation were evaluated statistically by use of a two-one side t test. P value of >0.05 was considered to statistically significant.Results The results showed that this method was specific and selective for canrenone in plasma and impurity substance in plasma didn' t intefere with determination of canrenone. Obtained linear regression equation of metformin was: C=0.7671A+3.3992 (r = 0.9999) . The method was validated for a linear range of 9.375～300μg·L^-1 for canrenone. Difference intra-day, intra-day and relative recoveries, all meet with the examination of living creature sample.The study result showed that the data of the two formulations were fitted to a one-compartment open model in healthy volunteers. Compared with standard reference formulation, the relative bioavailability of canrenone. The main pharmacokinetics parameters two canrenone were as follows: T_max were (4.2±1.2)h and (4.7±1.6)h, C_max were (159.8±46.6)μg·L^-1 and (149.7±43.4)μg·L^-1, T_1/(2ke) were (18.18±4.88)h and (19.07±3.88)h, AUC₀^t were (3168.5±688.4)μg·L^-1 and (3266.7±626.9)μg·L^-1, AUC₀^∞were (3610.7±768.4)μg·L^-1 and (3758.9±641.9)μg·L^-1,respectively. The relative bioavailability of F₀^t was (106.3±26.0)%, and F₀^∞was (107.6±25.9)%. The results of ANOVA and twoone-side t test statically analysis showed that the two spironolactone werebioequivalent.Conclusions1. The process show the pharmacokinetics academic foundation of canrenonein healthy volunteers.2 The spironolactone (both Jiangsu Yixing Qianjin medical co. and JiangsuChangjiang medical co.) have the similar pharmacokinetics parameters, and theyare bioequivalent.