The Pharmacokinetic Study Of M-nisoldipine

M-nisoldipine (m-nis), a new isomer of nisoldipine (nis), is one of dihydropyridines calcium antagonists(DHP-CaA) , being first developed by Department of Organic Chemistry, Hebei Medical University. Pharmacology experiment showed: m-nis was more stable than nis to light and it was ultralente, prompt and powerful. Its main effect was relaxing blood vessel. M-nis showed remarkable effect on hepertension, cardiac angina, etc. we can say that it maybe have powerful potential to being cardiovascular drug. At present, there isn't this product in the market around the world. Therefore, I think that it is important to clarify the pharmacokinetic character of m-nis for guiding clinical medication properly. We studied the pharmacokinetics of m-nis using HPLC in Beagle dog and rat through oral path. 1. Determination of m-nisoldipine in Beagle dog's plasma by RP-HPLC and study the pharmacokinetics of m-nisoldipine. Objective: To establish a method to determine the concentration of m-nis in Beagle dog's plasma by RP-HPLC and study the pharmacokinetics of m-nis in Beagle dog. Methods: â‘´The RP-HPLC consisted of Diamond C18 analytical column(250 ×4.6mm,5 μm) as solid phase, Acetonitrile-20mmol/L KH₂PO₄ (60:40) as mobile phase, flow rate of 1.0ml/min, UV detection wave-length of 237nm. Internal standard was nimodipine. ⑵Beagle dogs were divided into three groups, each group was given different dose of m-nis(1.0,2.5,12.5mg/kg). Blood samples were collected from hindlimb's saphenous vein at different time(15min,30min,1h,1.5h,2h,2.5h,3h,4h,6h,8h,10h,12h,24h)after oral administration. The plasma was obtained by centrifugation at 3000rpm for 10 min at room temperature. After we adding the internal standard to the mixture, the mixture was made alkaline with 0.4ml of 1.0mol/L sodium hydroxide solution and extracted with 5ml of diethyl ether. The organic layer was evaporated to dryness under a nitrogen gas stream and 40μl of methanol was added to the residue. 20μl of sample was injected into the column of the HPLC. ⑶The ratio of peak areas(m-nis/nimo)was used for predicting the unknown concentration from the regression equation. The data was handled with 3P97 pharmacokinetic software. Results: The mean plasma concentration-time curve of m-nis after oral admistration of m-nis in Beagle dog was determined. The calibration curve was linear in the range of 2²00ng/ml. The regression equation in Beagle dog's plasma was Y=0.0258X+0.3146, r=0.9995. The lowest detection concentration was 2ng/ml. In the three different concentrations ( high,middle,low) , the mean recovery of m-nis was 95.65%,96.54%,105.43%; the within-day precision (RSD) was 4.10%,9.10%,10.02% and between-day precision(RSD) was 5.55,7.23%,13.75%. The mean plasma concentration-time curve of m-nis after oral admistration of m-nis in Beagle dog showed double peaks. the pharmacokinetic parameters were: â‘´1.0 mg/kg group: T_peakâ‘´=1h, T_peak⑵=2h, C_maxâ‘´=31 ng/ml, C_max⑵=34.2ng/ml,MRT=5.64h,VRT=43.34h*h, AUC=146( ng/ml )*h, T_1/2β=2.43h, K_e=0.28/h, Cl=6.85 L/h/kg, Vd=24.46L/kg ,K_a=0.47/h, T_1/2α=1.48h; ⑵2.5mg/kg group: T_peakâ‘´=1h, T_peak⑵=2.5h, C_{max â‘´}=63.26ng/ml, C_max⑵=72ng/ml, MRT=4.75h, VRT=30.83h*h, AUC=479.03(ng/ml)*h,T_1/2β=1.34h, K_e=0.52/h, Cl=5.22L/h/kg, Vd=10.04 L/kg,K_a =0.35/h, T_1/2α=1.95h; ⑶12.5mg/kg group: T_peakâ‘´=1h, T_peak⑵=3h, C_maxâ‘´=128.83 ng/ml, C_max=138.58ng/ml,MRT=6.25h,VRT=34.07h,AUC=1257.46(ng/ml)*h,T_1/2β=2.92h, Ke=0.24/h, Cl=9.94 L/h/kg, Vd=41.42L/kg, K_a =0.49/h, T_1/2α=1.41h. Conclusions: The measurement of m-nis in Beagle dog's plasma could be achieved by HPLC method which was more sensitive and higher selective to fit the determination of the m-nis's plasma concentration. The result showed that m-nis was absorbed quickly after oral administration and taken on double peaks: the time reaching to the first peak was 1h, the time reaching to the second peak was 2³h.The plasma concentration was rising with the increasing of administration dose at the same time point of the three groups. 2. Tissue distribution and excretion of m-nisoldipine in ratand plasma protein binding of m-nisoldipine Objective: To study the tissue distribution and excretion of m-nis in rat and plasma protein binding of m-nis. Methods: Tissue samples( heart,liver,spleen,lung,kidney,stomach,small intestine,skeletal muscle,renal fat,brain,metra-ovary,testicle) were taken at different times (5min,30min ,2.5h) after single oral administration of 5mg/kg, weighted, homogenized, centrifuged and got supernature. After we added the internal standard into the supernature, the supernature was made alkaline with 0.4ml of 1.0mol/L sodium hydroxide solution and extracted with 5ml of diethyl ether. The organic layer was evaporated to dryness under a nitrogen gas stream and 40μl of methanol was added to the residue.20μl of sample was injected into the column of the HPLC. ⑵In the excretion studies, under light anaesthesia, bile ducts were cannulated with polyethylene tubing at different time (0⁶h,6¹2h,12²4h) after single oral administration of 5mg/kg; rats were placed in individual metabolism cages after single oral the same dose, urine and faeces were collected separately at different time. The homogenates of bile, urine and faeces were made alkaline with 0.4ml of 1.0mol/L sodium hydroxide solution and extracted with 5ml of diethyl ether. The organic layer was evaporated to dryness under a nitrogen gas stream and 40μl of methanol was added to the residue.20μl of sample was injected into the column of the HPLC. ⑶Plasma protein binding of m-nisoldipine in three...