The Study Of Dipfluzine's Pharmacokinetics

Dipfluzine (Dip), a novel piperazines calcium antagonist, selectively dilated vertebral artery, basilar artery and coronary artery. And the effects of Dip were more potent than those of flunarizine. In addition, Dip increased cerebral blood stream , improved brain ischemia, attenuated the infarct size after occlusion , and inhibited platelet aggregation and thrombus formation . Dip may be potentially useful to treat ischemic brain injury. So it is important to clarify the pharmacokinetic characteristic of Dip and to guide the use of clinical drug aright. We studied the pharmacokinetic parameters of Dip using HPLC in rat given drug orally.1 Determination of dipfluzine in rat serum by HPLC and study of its pharmacokinetics.Objective: To establish a method to determine the concentration of Dip in rat serum by HPLC and study the pharmacokinetic parameters of Dip in the bodies of rats.Method: 1) The HPLC consisted of Diamond C18 analytical column(250×4.6mm,5μm),methanol-water(containing 0.01mol.L-1 tetrabutyl ammonium bromide, pH=4.0) as mobile phase at flow rate of 0.8ml.min-1,UV detection at 254 nm. Internal standard was flunarizine. 2) Each rat was given an oral (p.o) dose of Dip equivalent to40mg.kg-1. Blood samples were collected from vein or in the eyepit at different time (15min, 30min, 1h, 2h, 4h, 8h, 12h, 24h) after oral administration. Serum was obtained by centrifugation at 3000r.min-1, 4℃, for 10min. After adding of the internal standard, sample was mixed with alkalescent buffer, then the mixture was extracted with cyclohexane- isopropyl alcohol, hydrochloric acid and methylene dichloride etc. The organic layer was evaporated to dryness under nitrogen. The ratio of peak areas (Dip/Flu) was used for predicting unknown concentrations from the regression equation. The data were handled with 3P97 pharmacokinetic software. The best compartment model was chose by comparising the observed concentrations to the concentrations predicted by the model. The Akaike information Criterion (AIC) was used to identify the best compartment model. The compartment model with the smallest AIC is the most adequate.Result: The mean serum concentration-time curve of Dip after oral administration of Dip in rat was determined. The calibration curve was linear in the range of 0.0625~4μg.ml-1. The regression equation in rat is Y=0.5049X－0.0008,r=0.9999. The lowest detection concentration was 5ng.ml-1. In three different concentration (high, middle, low), the recoveries were 102.1%,99.7% 101.0% , the within-day precisions (RSD) were 0.6% ,3.2% 3.9% and between-day precisions (RSD) were 0.4% ,3.9% ,4.1%. A openone-compartment model in rat was obtained from the mean serum concentrations of Dip after oral administration was confirmed. The parameters:A= 0.827 Ug/ml,Ke= 0.1481/h,Ka= 2.5931/h,T lag =0.035h,t1/2 (Ka) = 0.267h,t1/2 (Ke)= 4.692h,Tmax = 1.172h,Cmax = 0.656 μg/ml,AUC= 5.277 (μg.ml)*h,CL= 7.581 L/Kg/h,V= 51.318 L/kg Conclusions:The measurement of Dip in rat serum samples could be achieved by HPLC method which was sensitive, specific and simple enough to determine the concentration of Dip and to obtain pharmacokinetic parameters. 2 Tissue distribution and excretion of dipfluzine in rats and plasma protein binding of dipfluzine.Objective: To study the tissue distribution and excretion of dipfluzine in rats.Method: 1) Tissue samples (heart, liver, spleen, lung, kidney, brain, pancreas, abdominal fat, and skeletal muscle) were taken at different times (1h, 6h, 24h) after single oral administration (40mg.kg-1), weighed immediately and homogenized. After adding of the internal standard, tissue homogenates were extracted with cyclohexane-ethyl and hydrochloric acid etc. The organic layer was evaporated to dryness under nitrogen. 2) For excretion studies, bile ducts were cannulated with polyethylene tubing under light anaesthesia, and rats were placed in individual metabolism cages. Bile, urine and faeces were collected separately. Andhomogenate...