Development Of PH-time Dependent Pellets For Colon-specific Delivery Of 5-fluorouracil

Objective: Colon cancer is common in gastrointestinal cancer. recently, the incidence of colon cancer is rising,so its treatment has attracted wide attention.5-Fluorouracil is one of the most widely used agents in the first-line chemotherapy of colon cancer.After oral administration, the absorption of the drug is poor,the drug which reach the colon is few.It also has serious adverse effects and toxic side effects.Oral colon-specific drug delivery system(OCDDS) is the appropriate ways to prevent drugs release in the stomach,duodenum,jejunum and ileum end,but effect an abrupt onset of drug release upon entry into the ileocecal.pH-time dependent pellets for colon-specific delivery of 5- fluorouracil release drugs located in the colon,not only improving the local therapeutic concentrations, but aslo reducing the systemic absorption and toxicity.Methods:Pellet cores containing 5-fluorouracil and microcrystalline cellulose were prepared by the process of extrusion-spheronization.The mixture of pore former(HPMC E5) and surelease was used as time dependent film coat.Eudragit S100 of ethanol solution was used as pH-dependent film coat.Coating was performed using fluidized bed coater.The optimization of technique was definite with the colligation evaluation of formation, the orthogonal experiment was designed to screen technique in which the speed of extrusion, speed of spheronization and the time of spheronization were taken as three influential factors and three different levels were selected to part, each conformation of technique was selected refer to the L₉(3³) orthogonal design table.The single factor experiment was designed to screen technique in the concentration of coating liquor ,pressure of spray ,temperature of in air.Single-factor analysis was carried out to find out the main factors(amount of pore former,weight gain of time dependent layer and pH dependent layer)affecting the drug release.HPLC method was established to determine the content and the release of 5-fluorouracil in the coated pellets.HPLC conditions:Chromatogram column:KromasilC₁₈(5μm,250mm×4.6mm);mobilephase:0.01mol·L^-1 potassium dihydrogen phosphate buffer;column temperature:25℃; flow rate: 1ml·min ^-1;detection wavelength:265nm;injection volume:20μl.Drug release studies carried out using C.P2005 XC dissolution rate test apparatus(apparatus 1, 100rpm ,37℃).Initial studies were carried out in 1000 ml of 0.1mol·L ^-1 HCl for 2h, then turn to pH6.8 phosphate buffer saline for 4h ,after this turn to pH7.8-8.0 phosphate buffer saline to 24h.At different time intervals, 5ml of the sample withdrawn and replaced with 5 ml of fresh dissolution medium.The samples were analysed by HPLC as described previously.The chemical and physical stability of pH-time dependent pellets for colon-specific delivery of 5-fluorouracil was investigated under the conditions of strong light ,high temperature and high humidity.Then the formulation was observed for change in physical appearance ,drug content and drug release rate.SD rats were administered orally uncoated and coated pellets via a polyethylence cannula under light ether anesthesia, respectively, at a dosage of 30mg·mg^-1.The 5-fluorouracil concentrarions in the gastrointestinal tract,cecum tissue and its contents,colon tissue and its contents,plasma were determined using HPLC method described previously.Results:The pellet core were prepared by the process of extrusion- spheronization.:speed of extrusion 30r·min^-1;speed of spheronization 40r·min^-1;time of spheronization 4 min.Time lag layer coating condition: temperature of in air 40℃,pressure of spray 0.05MPa,spray speed 1mL·min^-1. pH dependent layer coating condition:temperature of in air 50℃,pressure of spray 0.05MPa,spray speed 1ml·min^-1.The optimization of the colonic coating prescription was 5% HPMC E5 of solid content, 5% weight gain of time dependent layer and 55% weight gain of pH dependent layer .The reserve time of 5-fluorouracil was about 7.5min,the recoveries were 98.65¹00.28%, the within-day precision was 0.86¹.74%, the between-day precision was 0.92¹.13%.The method could determine the content of 5-fluorouracil accurately and precisely.Under the condition of RH92.5% for 5 days, the weight increasing ratio of pellets was 6.2%.There was no significant difference in the physical appearance and content and percent of release of the pellets at the end of the strong light,high humidity(75%) and the accelerated experiment.pH-time dependent pellets for colon-specific delivery of 5-fluorouracil (tested group)released little drug in the stomach and small intestine and most in cecum and colon tissues.But the uncoated pellets(controlled group)released most drug in the stomach and small intestine.The mean peak 5-fluorouracil concentrations in cecum tissue,cecal contents,colon tissue and colon contents,respectively,were 64.764±22.535μg·g^-1,618.949±201.641μg·g^-1, 44. 271±10.765μg·g^-1 and 458.147±93.821μg·g^-1 for 5-fluorouracil released from the coated pellets,and 4.537±1.548μg·g^-1,30.027±12.843μg·g^-1, 1.824±0.615μg·g^-1 and 17.425±5.233μg·g^-1 for the administration of the uncoated pellets.In plasma, the relatively low and flat drug concentration profile from coated pellets was in contrast to the high and sharp pharmacokinetic profile obtained from drug released from uncoated pellets.The mean Cmax from the coated pellets group (0.120±0.025μg·ml^-1) was lower than that of the uncoated pellets group (1.383±0.215μg·ml^-1).The mean Tmax of the coated pellets group(12h) was longer than that of the uncoated pellets group(1h).The AUC values of coated pellets and uncoated pellets were 1.042±0.132μg·h^-1·ml^-1 and 1.838±0.217μg·h^-1·ml^-1.The relative bioavailability of the coated pellets from the uncoated pellets is 56.69%.Conclusions: pH-time dependent pellets for colon targeted delivery of 5- fluorouracil may provide the necessary protection to a drug in stomach and small intestine while allowing drug release in the colon.In contrast to uncoated pellets dispersal along stomach and small intestine, 5-fluorouracil was largely released from the the coated pellets in cecum and colon,not only improving the local therapeutic concentrations, but aslo reducing the systemic absorption and toxicity.