| Objective:?1?Using the flunarizine hydrochloride as a model drug,prepared it into the ophthalmic organogels,screened the best prescription and evaluated its in vivo and in vitro quality system.?2?To observe the changes concentration in blood and brain tissue and distribution characteristics of rats after drops administration,intravenous administration,intragastric administration and organogel administration,in order to explore feasibility of systemic transport after the interocular administration and further evaluate the feasibility of organogels for systemic delivery.?3?To observe the changes concentration in the thalamus,olfactory bulb,hippocampus,cerebral cortex,and cerebellum and distribution characteristics of rats after after drops administration,intravenous administration,intragastric administration and to provide a theoretical basis for the study of the eye-brain drug transport mechanism.Methods:?1?Through examining the effects of the oil phase,gel factorand anticoagulant on the gelling time,in vitro release and related factors of flunarizine hydrochloride,the best formulation was determined;Salt buffer?containing 2%Tween80?was used as the release medium to investigate its in vitro release.Rabbits were used to investigate the retention time and irritation of the drug in the eyes.?2?The concentration of Flunarizine Hydrochloride in rat plasma and brain was determined by HPLC.The rats were randomly divided into 4 groups.They were divided into interocular drops administration group,organoge administrationl group,intravenous administration group and gavage administration group.The dosage of drops administration,organogel administration and gavage administration was 14 mg?kg-1,and the dosage of intravenous administration was 5 mg?kg-1.After administration,plasma and brain samples were collected and processed at a specific time point.The concentration of Flunarizine Hydrochloride in the samples was determined and the main pharmacokinetic parameters were calculated.?3?The rats were randomly divided into three groups:interocular drops administration group,intravenous administration group and gavage administration group.The dosage of nterocular drops administration and gavage administration was 14 mg?kg-1,and the dosage of intravenous administration was 5 mg?kg-1.After administration,rats were killed at a specific time point to take out the brain tissue and wash it and separate the thalamus,olfactory bulb,hippocampus,cerebral cortex,cerebellum and other brain areas.LC-MS method was used to determine the concentration of Flunarizine Hydrochloride in different brain areas and calculate the main pharmacokinetic parameters.Results:?1?The equilibrium solubility of Flunarizine Hydrochloride in different p H aqueous phase,the oil-water partition coefficients of Flunarizine Hydrochloride in different oil phases?glycerin,injected soybean oil,castor oil,medium chain fatty acid,liquid paraffin?and different p H were determined by HPLC.The solubility of Flunarizine Hydrochloride in phosphate buffer solution of p H 2.0,p H 5.0,p H 6.0,p H7.0,p H 8.0 and p H 9.0 is 2.69 mg?m L-1?2.47 mg?m L-1?2.24 mg?m L-1?1.96 mg?m L-1?1.68 mg?m L-1?1.21 mg?m L-1,The solubility of Flunarizine Hydrochloride in glycerol,injected soybean oil,castor oil,medium chain fatty acid and liquid paraffin are 1.39mg?g-1?1.79 mg?g-1?2.06 mg?g-1?2.78 mg?g-1?0.24 mg?g-1,Under the conditions of p H9.0,p H 7.0,p H 5.0 and p H 2.0,the oil-water partition coefficients log P of flunarizine hydrochloride were 1.40,1.35,0.92 and 0.70.?2?The best formulation of flunarizine hydrochloride gel was injected soybean oil:stearic acid:N-methyl pyrrolidone?NMP??10:1:3,v/w/v?,and the drug loading was 30mg?m L-1.The gel was prepared at room temperature,it is a pale yellow transparent liquid,which could be rapidly converted to semi solid after being applied to the eyes.The p H was about 7.The stability test shows that the product could maintain long-term stability under room temperature.In vitro release test of organogel shows that drug exhibits good zero order release kinetics process,and FNZ is detected by fluorescence labeling.The duration of in-situ organogels in eye retention was 45 min,while the retention time of the drops was 120 min.The retention time of organogel was significantly longer than that of drops.After single and multiple administration,no obvious eye irritation was observed.?3?The pharmacokinetic parameters of plasma after intraocular administration were as follows:Cmax was 0.48 mg?L-1,AUC0-t was?74.40±8.93?mg?L-1?min-1;F%was 18.67%;The pharmacokinetic parameters of brain after intraocular administration were as follows:Cmax was 0.21?g?g-1,AUC0-t was?50.34±6.32??g?g-1?min-1;F%was 34.27%;The main pharmacokinetic parameters of plasma after intragastric administration were as follows:Cmax was 0.43 mg?L-1,AUC0-t was?57.98±4.19?mg?L-1?min-1;F%was14.32%;The main pharmacokinetic parameters of brain after intragastric administration were as follows:Cmax was 0.14?g?g-1,AUC0-t was?31.67±3.24??g?g-1?min-1;F%was21.56%.The main pharmacokinetic parameters of plasma after intravenous administration were as follows:Cmax was 3.14 mg?L-1,AUC0-t was?142.31±3.71?mg?L-1?min-1;the main pharmacokinetic parameters of brain after intravenous administration were as follows:Cmax was 0.62?g?g-1,AUC0-t was?52.46±2.31??g?g-1?min-1;Flunarizine hydrochloride could be absorbed into the systemic circulation after intraocular administration.?4?The pharmacokinetic parameters of plasma after organogel administration were as follows:Cmaxwas 1.44?g?m L-1,AUC0-twas?74.40±8.93?mg·L-1·min-1;;F%was66.12%;The pharmacokinetic parameters of brain after organogel administration were as follows:Cmaxwas 1.01?g?g-1,AUC0-twas?160.95±3.97?mg·L-1·min-1;F%was76.71%.Compared the plasma with the intraocular solution-administration group,the organogel-FNZ-administration group showed a 0.5-fold increase in Tmax,3-fold increase in Cmax,5.1-fold increase in AUC0–t and 3.5-fold increase in absolute bioavailability.In our research,for the group of FNZ solution,the drug concentration almost declined to zero after 6 h.For the group of organogel-FNZ,the plasma of rats could maintain a higher drug concentration 8 h after a single dose.Compared with the intraocular drop-administration group,the organogel-FNZ-administration group took the same time to reach Tmax,and had a 4.8-fold increase in Cmax,3.2-fold increase in AUC0–t,and2.2-fold increase in absolute bioavailability?5?Comparing the pharmacokinetic parameters of rat brain regions?thalamus,olfactory bulb,hippocampus,cerebral cortex,cerebellum?after different routes of administration,the results showed that Cmax,AUC0-t,and F%in each brain tissue were greater than the perfusion gastric administration group.Conclusion:The p H,viscosity and osmotic pressure of FNZ organogels were all within the scope.The preparation had a certain sustained-release effect and could prolong the action time of the drug in vivo.There was no obvious irritation to cornea,conjunctiva,iris and retina.It is proved that the safety of ophthalmic administration is good.According to the experimental results of brain area distribution,FNZ has the highest concentration in the hippocampus,followed by thalamus,olfactory bulb,cerebellum and cortex after eye administration,which were higher than those in the corresponding brain area after gavage administration.Therefore,it could be inferred that there may be multiple pathways to brain tissue after interocular administration,which provides a theoretical basis for further exploration of eyes to brain absorption mechanism. |
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