| Objective:As a common manifestation of male sexual dysfunction,erectile dysfunction’s(ED)incidence rate has increased year by year and patients are gradually becoming younger,which seriously affects the quality of human life.Tadalafil(TD)is a highly selective reversible inhibitor of phosphodiesterase-5(PDE-5)and is currently recognized as one of the most effective therapeutic drug for ED in the world.However,its solubility is extremely poor,bioavailability is low,and it needs to be taken 2 hours in advance.Long waiting will causes patients emerge some negative emotions,which undoubtedly increases their psychological burden.Moreover,the effective time of TD is long,and adverse reactions such as dizziness,palpitations,and palpitations generally need 24-48 h to dissipate.In addition,TD has irritation,if taken for a long time,it may cause irritation of the gastrointestinal mucosa,lead to symptoms such as bloating,abdominal pain,nausea,vomiting,etc.Therefore,in this study,to prepare TD microparticles without carrier excipients,in order to improve its dispersibility in water,accelerate the release rate and degree in vitro,and improve bioavailability so then;TD microparticles freeze-dried powder is used as the intermediate to prepare orally disintegrating tablets,which are absorbed into the blood through the pregastric mucosa,shortening the effective time,and reducing the irritation to the gastrointestinal mucosa;Evaluate and research the quality of TD microparticles freeze-dried orally disintegrating tablets,provide reference for preparation production,packaging,transportation,and storage;Conduct in vivo bioequivalence studies on TD API orally disintegrating tablets,TD microparticle orally disintegrating tablets and positive drugs in beagles,to provid reference for clinical research.Methods:(1)Preparation and physicochemical properties of tadalafil microparticles:①The pre-prescription study of TD API is carried out:the equilibrium solubility and oil-water partition coefficient of TD in different media are determined by shaking flask and HPLC method;②TD microparticles without carrier excipients are prepared by rapid membrane emulsification-solvent evaporation method.The particle size and enthalpy(measured by DSC)of TD microparticles are used as indexes to investigate the key preparation process by single factor,preliminarily select the optimal preparation conditions;③Conduct research on the physicochemical properties of TD microparticles obtained from validation experiments:Observe the differences in morphology between TD microparticle and API by scanning electron microscopy(SEM),determine the content uniformity of TD microparticles by HPLC and detect the PVA residue in TD microparticles using ultraviolet and visible spectrophotometry(UV).(2)In vitro release study of tadalafil microparticles:Select the release medium closest to the human internal environment of TD after taking medication,and add an reasonable amount of sodium dodecyl sulfate(SDS)to ensure TD release completely.Compare the release behavior of TD microparticles and API in the aforementioned media by direct release method,evaluate the similarities and differences of drug release behavior in vitro.(3)Preparation of tadalafil microparticle orally disintegrating tablets:TD microparticle freeze-dried powder is used as the intermediate of the preparation,and TD microparticle freeze-dried orally disintegrating tablets(referred to as TD microparticle orally disintegrating tablets)are prepared by freeze-drying method.The types of excipients are screened by single factor with the comprehensive evaluation of appearance and disintegration time,as well as the microstructure of orally disintegrated tablets,then the dosage of excipients is optimized by central composite design and response surface methodology,and the optimal prescription can be determined.Inspect the key process parameters in the freeze-drying curve to further optimize the tablets shape and reduce production costs.(4)Quality evaluation of tadalafil microparticle orally disintegrating tablets:The properties,disintegration time limit,weight difference and content uniformity of the selfdeveloped preparation are investigated according to the general principles of Chinese Pharmacopoeia(2020 Edition)and the "Quality Evaluation Method for Freeze-drying Orally Disintegrating Tablets" established by the research group before;Simulate the entire process of drugs entering the human body,establish in vitro dissolution methods,compare the in vitro dissolution behavior of reference formulation(Cialis),TD microparticle orally disintegrating tablets,and TD API orally disintegrating tablets.(5)Research on the bioequivalence of tadalafil in beagle dogs:Qualitative analysis is conducted on the mean blood drug concentration-time curve of positive drugs(10 mg),TD microparticle orally disintegrating tablets(10 mg),and TD API orally disintegrating tablets(10 mg).The pharmacokinetic parameters of the positive drug(10 mg)and TD particulate orally disintegrating tablets(10 mg)in beagle dogs are compared,and provid reference for new drug development and clinical research.Results:(1)Preparation and physicochemical properties of tadalafil microparticles:①Pre-prescription study:A method for the determination of TD is established,and all the methodological studies are qualified;The results of equilibrium solubility and oil-water partition coefficient show that the solubility of TD API is very poor;②The optimized preparation process of TD microparticles is as follows:organic solvent is ethyl acetate,PVA concentration is 3%,drug concentration in oil phase is 0.5%,oil-water phase volume ratio is 1:1,curing solution pH is 4.5,once through the film,and rotavapor solidification.③TD microparticle lyophilized powder is white powder,which could be dispersed by shaking with water.The rehydration property of TD microparticle lyophilized powder is better than that of API;Under the scanning electron microscope,the TD API appears as blocks of varying sizes,which are prone to crystallization;The TD microparticles are in a relatively uniform and elongated shape,with a significant decrease in crystallinity;The particle size of TD microparticles is smaller and their distribution is more uniform.The result of DSC shows that the enthalpy of TD microparticles decreases significantly,and the crystal is more unstable compared to the API,which may be beneficial for dissolution;The average drug content of TD microparticles is 97.32%,and the RSD of TD microparticles content within and between batches is less than 1.5%,and there are almost no PVA residue.(2)In vitro release study of tadalafil microparticles:Acetate buffer containing 0.05%SDS(release medium I,pH 3.6)and phosphate buffer containing 0.1%SDS(release medium II,pH 6.8)are selected as the release medium;The average cumulative release rate of TD microparticles in both release media is more than 60%at 0.5 h,and they are completely released at 6 h,while API is not fully released until 12 h or even 24 h;The drug release behavior of TD microparticles and API in both release media fits the logistic equation best.(3)Preparation of tadalafil microparticle orally disintegrating tablets:Through the optimization of the prescription,the composition of TD microparticle orally disintegrating tablets is determined as follows:the main drug 10 mg,the matrix agent mannitol 20.6 mg,the adhesive pullulan 16.8 mg,Tween-80 10 mg/tablet,menthol 1.5 mg/tablet,WS-3 0.75 mg/tablet.Freeze drying curve:at-60℃ pre-freeze for 30 minutes,enter the freeze drying box at-30℃,maintain for 60 minutes,raise the temperature at a rate of 1 ℃/min to-5℃,maintain for 120 minutes,and then raise the temperature to 25℃at a heating rate of 1℃/min,maintain for 60 minutes.(4)Quality evaluation of tadalafil microparticle orally disintegrating tablets:The shape of TD microparticle orally disintegrating tablets is flat and smooth,with a white and uniform color,no pitting on the surface,there is no crack edge,crack or detachment phenomena;The longitudinal section of the orally disintegrating tablets is uniform in size and arranged in an orderly manner;The weight difference,disintegration time limit,and content uniformity are in accordance with the relevant provisions of the pharmacopoeia.In vitro dissolution behavior:The average cumulative dissolution rates of TD microparticle orally disintegrating tablets and API orally disintegrating tablets in 5 mL of artificial saliva are 3.29%and 2.35%before 5 minutes.At the same time,the average cumulative dissolution rate of reference formulations in 250 mL of artificial gastric fluid is 8.16%;After transferring the freeze-dried orally disintegrated tablets to gastric fluid,they dissolve quickly.And the average cumulative dissolution rate of TD microparticle orally disintegrating tablets is better than TD API orally disintegrating tablets,better than reference formulations too,but their average cumulative dissolution rates are less than 20%;After transferring them to the artificial intestinal fluid,the relationship of average cumulative dissolution rate is following:TD microparticle orally disintegrating tablets are better than reference formulations,also better than TD API orally disintegrating tablets.At 4 h,the average cumulative dissolution rate of TD microparticle orally disintegrating tablets is 98.39%,the reference formulations is 96.20%,and the average cumulative dissolution rate of TD API orally disintegrating tablets is 86.45%.The dissolution behavior of the three is similar.(5)Research on the bioequivalence of tadalafil in beagle dogs:The t1/2 of positive drugs group is(166.32 ± 92.18)min,Tmax is(140.00±56.50)min,and Cmax is(135.16 ±37.98)μg·L-1,AUC0-t is(24776.50 ± 7738.60)μg·L-1·min-1,AUC0-∞ is(33389.39 ± 14039.59)μg·L-1·min-1,MRT(0-t)is(158.75 ± 23.01),MRT(0-∞)is(266.07±81.74),CL is(0.032±0.015)L·min-1·kg-1.The t1/2 of TD microparticle orally disintegrating tablets group is(185.97± 94.93)min,Tmax is(129.38±93.36)min,and Cmax is(173.50± 63.34)μg·L-1,AUC0-t is(36131.50 ± 10865.97)μg·L-1·min-1,AUC0-∞ is(69712.76±30513.13)μg·L-1·min-1,MRT(0-t)is(180.57 ± 9.46),MRT(0-∞)is(275.12 ± 118.08),CL is(0.014 ± 0.005)L·min-1·kg-1.The results showed that the t1/2 of the TD microparticle orally disintegrating tablets group is 1.12 times that of the positive drugs group,Tmax is 0.92 times,Cmax is 1.28 times,AUC0-t is 1.46 times,and AUC0-∞ is 2.09 times.The change of MRT is not significant,and CL reduces to about 2/5 of the original;The blood drug concentration time curve shows that the blood drug concentrations of three groups all show an M-type change trend.The first peak appears time of TD microparticle orally disintegrating tablets group is the same as TD API orally disintegrating tablets group,earlier than positive drugs group,and the relationship of peak blood drug concentration is:positive drugs group higher than TD microparticle orally disintegrating tablets group,higher than TD API orally disintegrating tablets group;There is no significant difference in the time of the second peak among the three groups,the relationship of peak blood drug concentration is:TD API orally disintegrating tablets group higher than TD microparticle orally disintegrating tablets group,higher than positive drugs group.Conclusions:(1)The rapid membrane emulsification process is stable,it can make the microparticles’size smaller,the enthalpy lower than API.At the same time,it can accelerate the dissolution rate and degree of insoluble drugs.Therefore,this method helps to improve the dispersion of insoluble drugs in water and improve their content uniformity during the preparation process.(2)The freeze-drying method is used to prepare the microparticle freeze-dried powder into orally disintegrating tablets,the content is uniform,the tablet shape is full,white,and flat,and the disintegration time and weight difference are in accordance with the relevant provisions of the pharmacopoeia.(3)The in vitro dissolution behavior of orally disintegrating tablets is similar to the reference formulations,but slightly better than it.(4)Orally disintegrating tablets can enable drugs with smaller particle sizes to be absorbed through the oral mucosa and other pregastric mucosa,avoid gastrointestinal irritation,while shortening the effective time and improving bioavailability. |
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