Study On The Determination Of Lovastation And Lovastatin Acid In Human And The Pharmacokinetics Of Lovastatin Capsule

AIM: To establish a rapid and sensitive method for the quantitation of lovastatin (LV)and lovastatin acid(LVA)by LC-MS/MS in human plasma. The method was used to determine the concentrations of LV and LVA in plasma of 22 volunteers after oral administrations of 40 mg LV capsule.STUDY METHOD: According to a two-period, two-sequence, randomized crossover design, 22 volunteers were divided into 2 groups(R and T)and took both drugs by oral administration, respectively. And four milliliter blood samples were collected before and at 0.5, 1, 1.5, 2, 3, 4, 5, 6, 8, 11, 14, 24, 36 h after administration. Then centrifugated at 3500×g for 10min and transferred the supernatant to a polypropylene tube, stored at -20°C.Plasma samples were thawed at room temperature, then added internal standard simvastatin(SV) and simvastatin acid(SVA) into a certain amount of plasma sample. The mixture was extracted with diethyl ether-dichloromethane (60:40, v/v). And the organic phase was dried by nitrogen. Subsequently, the residue was reconstituted 150μl mobile phase and 20μl of the sample was injected into the LC-MS/MS system. The separation was performed on a Zorbax Eclipse XDB-C8 column(5μm, 4.6×150 mm I.D.)maintained at 30°C using aqueous solution methanol, 10 mmol/l ammonium acetate and formic acid(90:10:0.02,v/v/v)at a flow rate of 1.0 ml·min-?. And the detection of the analyte was by the alternate of positive and negative ion mode. Multiple reaction monitoring was performed using the ion-pairs m/z 427.1?m/z 325.3 and m/z 421.4?m/z 319.2 for LV and LVA, and the ion-pairs m/z 441.3?m/z 325.1 and m/z 435.4?m/z 319.0 for the internal standard respectively. The analytic methodology was evaluated by detecting the specificity, stability, linearity, accuracy, inter and intra-precision, recovery and matrix effects, lower limit of quantization for LV and LVA in plasma according to the SFDA to proved if it fit for the bioequivalence study.After progressing the samples, draw the plasma concentration-time profile of LV and LVA. Based on the concentration data, the pharmacokinetic parameters, such as Tmax, t1/2, Cmax and AUC0-t were obtained using BAPP2.0. Finally, statistical analysis the pharmacokinetic parameters of the two capsule to estimate whether it is or not bioequivalent.RESULTS: This research established a method meet the requirement of SFDA to determination the concentration of LV and LVA in human plasma simultaneously. And the method was rapid,sensitive and reproducible with a low limit of quantization of 0.05 ng·ml-?. The linear range of this method was 0.05 ~ 30 ng·ml-? and the precision and accuracy of the method were all in line with the relevant requirements. There was no significant matrix effects in the plasma interfered the quantitation of LV and LVA. The results of the stability experiments showed that plasma samples were stable enough at room temperature for 6 h, at -20°C for 3 months or after three freeze-thaw cycles. The method corresponded to the relevant norm and could be used for bioequivalence study.After oral administration single dose of LV, the LV's pharmacokinetic parameters of test drug and reference drug were as follows respectively: Tmax: 4.9±4.1 h(Mean ? SD)and 3.8±3.5 h;Cmax: 2.79±1.50 ng·ml-? and 3.38±2.39 ng·ml-?;t1/2: 10.03±3.49 h and 9.69±4.21 h;AUC0-t: 31.33±15.34 and 32.93±23.19 ng·h·ml-?;AUC0–∞: 34.31±15.32 and 30.06±23.58 ng·h·ml-?. By comparison with the reference drug, the relative bioavailability of the test drug was110.5%±55.2%.The LVA's pharmacokinetic parameters of test drug and reference drug were as follows respectively: Tmax: 3.5±1.6 h and 5.2±5.4 h;Cmax: 3.84±2.95 ng·ml-? and 3.94±2.40 ng·ml-?;t1/2: 14.98±11.11 h and 13.97±9.56 h;AUC0-t: 39.81±16.17 and 43.05±18.31 ng·h·ml-?;AUC0–∞: 50.03±24.81 and 51.80±22.14 ng·h·ml-?.By comparison with the reference drug, the relative bioavailability of the test drug was99.7%±32.3%.The results analyzed by BAPP 2.0 of the two formulations were as follows: The Two-One side t-Test shows no significant differences(P>0.05). Under the 90% confidence intervals, the LV of test to reference ratio were 85.9% ~ 117.5%(AUC0-t) and 73.4%±106.8%(Cmax). The LVA of test to reference ratio were 83.7% ~ 106.8%(AUC0-t)and 76.3%±105.6%(Cmax). Based on the statistical results, the test and reference formulations were considered to be bioequivalent.