Studies On The Pharmacokinetics Of 3-n-Butylphthalide In Rats And Rabbits And The Transport Mechanism In Brain

Zhao Chunshun (Major: Pharmaceutics) Advisors: Prof. Zhang Ruhua and Associate Prof. He Zhonggui3-n-Butylphthalide (NBP), a novel cerebral antiischemic agent, was isolated and identified from several plants including celery oil. At present, NBP was synthesized and approved for Phase IV trials in treatment of stroke by the State Drug Administration of China.The main objectives of this research were to study the pharmacokinetics, absolute bioavailability, disposition, intestinal absorption and first-pass effect of NBP in rabbits and rats, to investigate the mechanism of transport of NBP in the blood-cerebrospinal fluid barrier, to research nasal mucosa absorption and nasal ciliotoxicity of NBP in rats, and to develop reasonable delivery system of NBP used in intranasal administration. We also determined the uptake of NBP into the brain after intravenous and intranasal administration in rats.A rapid, sensitive and specific RP-HPLC method was developed for the determination of NBP in rabbits or rats plasma in combination with fluorescence detection at an excitation wavelength of 280 nm and an emission wavelength of 304 nm. Ibuprofen was used as internal standard. Plasma samples were extracted with diethyl ether under acidic conditions. After evaporation of the organic phase, the extract was dissolved in mobile phase and injected into the chromatograph with C18 column and a mobile phase of 0.05mol/L sodium acetate buffer (pH 4.5)-acetonitrile (400:600). The achieved limit of quantification of 0.0212 ug/ml is sufficient to study the pharmacokinetics of NBP in rabbits or rats.The pharmacokinetic investigation were performed on rabbits and rats. NBP exhibited linear pharmacokinetics over the dose range tested (l-10mg/kg) in rabbits and rats after intravenous administration. NBP was rapidly eliminated from the plasma. The mean elimination (T1/2a,10.3-11.3 min and T1/2B, 96-109 min in rabbits; T1/2a, 4.7-9 min and T1/2B, 68-125 min in rats), total plasma clearance, and apparent volume values were independent of doses. The dosage forms had no effect on the pharmacokinetic of NBP in rats. After oral administration to rabbits and rats, NBP reached the peak plasma concentration at a time ranging between 10 to 45 min. Oral bioavailability was lower inrabbits (4.7±1.7%) than in rats (26.3±10.3%) for NBP solution. NBP-HPCD inclusion reduced the bioavailability (15.0±3.7%) of NBP in rats.The distribution of [3H]NBP in tissues was determined at 10, 30, 60, and 90 min after intravenous administration of a single 1, 5, and 10 mg/kg dose to rats by liquid scintillation counter. The highest concentration was found in the liver, and the concentration decreased in the order of liver, kidney, lung, brain, heart and spleen. NBP in tissues is dose-dependent. NBP concentration was not significantly different among cerebrum, cerebellum, olfactory bulb, cerebral ventricle and brain stem.The intestinal transport of NBP was performed by applying single-pass perfusion techniques in situ rats. NBP is a high permeability drug in rat intestine and colon. The apparent permeability, Papp, of NBP was independent of both intestinal region and concentration of NBP present in the perfusion solution. The Papp for NBP in the colon is higher than that in various intestinal regions. The Papp for NBP decreased when HPCD is co-perfused in the intestine and colon. The absorption inhibitor effect of HPCD was concentration dependent and it was supposed that the concentration of free NBP is too low in the perfusion solution when HPCD was added in.The hepatic clearance of NBP during isolated rat liver perfusion were 6.31±0.45, 3.14±0.15, and 2.71±0.48 ml/min for 2, 5, and 10 ug/ml, respectively. The elimination of NBP was inhibited when HPCD is co-perfused in the isolated liver. Liposomes didn't influence the elimination of NBP from the isolated rat liver. Uptake of [3H]NBP by rat primary hepatocytes was rapid and a steady-state was achieved in 15 seconds. The accumulation of [3H]NBP in hepatocytes wasn't inhibited by unlabeled NBP,...