| Solubility and permeability are the key factors which determine drug absorption.Biopharmaceutics classification system(BCS)is a drug classification and prediction system based on these factors.Currently,FDA,WHO and EMA have approved it to be applied as a science-based approach for the waiver of in vivo bioequivalence of the drugs used in human.In recent years,some researchers have tried to introduce BCS into the field of veterinary medicine.However,due to the interspecies differences,the BCS of human medicine cannot be directly extrapolated to animals,so the methods used to detect the dug solubility and permeability should be based on the physiological conditions of the target animals to ensure the accuracy of classification and the correlation between in vitro and in vivo.This study aims at establishing a method for determining the solubility of chicken BCS by measuring the physiological parameters of the chicken,the MDCK cell line overexpressing chicken-derived intestinal efflux protein is used as a tool for permeability measurement.The permeabilities of commonly used drugs are measured,and the effects of pH conditions on permeability detection are discussed.Finally,the absorption performance of florfenicol micro-powder and crystal was compared with API from in vitro and in vivo.1.Establishment of a method for determining the physiological solubility of commonly used drugs in chickensThe high physiological solubility is defined by FDA as the highest dose can be completely dissolved in 250 mL(50 mL of gastric fluid volume with 200 mL of water for drug delivery)in human drugs.In this experiment,AA white feather broilers aged 1-day were selected and raised to 8 weeks old.During this period,the physiological parameters including body temperature,pH of the gastrointestinal tract and gastrointestinal volume,were measured at different ages.Chicken BCS solubility classification method was initially established based on these,then conducted the measurement and classification of 16 drugs.The results showed that the body temperature of the chicken at different ages was 41℃,the pH of the gastrointestinal tract ranged from 2.03 to 8.23,and the gastrointestinal volume was positively correlated with the body weight,the volume of the chicken weighting 1 Kg in feding condition was 20.40 mL,while the fasting condition was 6.73 mL.Therefore,the condition of determining the solubility were based on chicken body temperature and the pH of the gastrointestinal tract.The results of solubility in this study were higher than the solubility data recorded in the pharmacopoeia due to the differences in experimental temperature and pH.When classified under the conditions of feding and fasting,3 of the 16 drugs were found inconsistent classification,which indicates that the different gastrointestinal volumes has the effect on the classification.when compared the "human BCS" and "chicken BCS",2 of the 7 drugs was found to be inconsistent in solubility classification.Therefore,the human BCS cannot be directly extrapolated to chicken,and the effect of fasting should be considered when establishing the classification of chicken BCS solubility.In summary,the solubility of commonly used drug in chicken is measured in 41℃ and buffer solutions which pH were 1,3,5,7 and 8,while the high solubility of chicken BCS is defined as the highest dose of the drug can be completely dissolved in 20.40 mL(feding)or 6.73 mL(fasting).2.Establishment of an in vitro permeability determination method for commonly used drugs in chickensThe methods for permeability measurement are diverse,considering ethical issues and in vitro-in vivo correlation with chicken,MDCK cell and MDCK cells overexpressing chicken-derived BCRP or P-gp were initially selected as the assay for measuring of drug permeability,firstly comparing the Papp of metoprolol tartrate or propranolol hydrochloride between MDCK cell lines and Caco-2 cell,the results showed that the Papp of AP-BL and BL-AP permeability in same drug were different,and the variety trend of different drugs Papp in the two cells is also different,indicating that the two cells cannot replace each other.Then the recommended high-permeability drug metoprolol tartrate is classified as a standard drug,the 1/10 highest dose of each drug was used as the transport concentration on the MDCK cell,MDCK-chAbcg2 cell,and MDCK-chAbcg2/Abcb1 cell at pH conditions of 5.5 and 7.4,respectively,to investigate the differences between cell lines and the effect of pH on permeability measurements.The results showed that pH would certain influence the apparent permeability coefficient of the drugs.8 of the 16 drugs were significant differences in Papp under different pH conditions,but the effect of pH on drug classification was only reflected in individual drugs.Then,on different cell lines,the Papp of 10 and 13 drugs were significant differences under pH 5.5 and 7.4,respectively,but 14 of 16 drugs were classified identically on different cell lines.In addition,when the classification results were compared with the chicken bioavailability,the correlation was found to be good,and only 2 of the 16 drugs showed non-conformity.In summary,in order to simulate the conditions of chicken small intestine and establish a good correlation between in vitro and in vivo,we chose an appropriate permeability measurement method for chicken commonly used drugs,which is the 1/10 highest dose of each drug was used as the transport concentration on the MDCK-chAbcg2/Abcb1 cell lines at pH 7.4.And the high permeability of chicken drugs was defined as the apparent permeability coefficient greater than the Papp of metoprolol tartrate under the same experimental conditions.3.In vitro permeability and in vivo pharmacokinetic study of florfenicol-optimized formula based on BCS conceptFlorfenicol was a poor absorption drug based on BCS concept,we compared the in vitro and in vivo absorption between florfenicol API and two kinds of formula including florfenicol micropowder or crysta1.The results showed that at 10 μmol/L,the Papp(AP-BL)of the drug substance on MDCK-chAbcb1/Abcg2 cells was 0.27×10-6 cm/s,and the efflux rate was 5.6,while the Papp(AP-BL)of micropowder and crystal were significantly higher than that of the drug substance(P<0.05),0.46 and 0.42×10-6 cm/s,respectively,and the efflux rate was 3.35 and 3.27,respectively,which were significantly lower than the ER of the drug substance(P<0.05).The difference between the two preparations and the drug substance was similar to 10 μmol/L at 50 μmol/L,and the Papp(AP-BL)of the drug substance,micropowder and crystal were 0.33,0.44 and 0.51(×10-6 cm/s),respectively.And the efflux rates were 5.11,4.12 and 3.95,respectively.In addition,after the same dose was administered to the chickens,the Cmax of the drug substance was 5.48(μg/mL,the T1/2β was 1.95 h,the CL was 1.09 mL/h/kg,and the AUC of the drug was 18.67μg·h/mL.The Cmax and T1/2β of the micropowder and crystal are higher than these of the drug substance,Cmax is 1.5-and 1.2-folds of the drug substance,respectively,and T1/2β is 1.1-and 1.9-folds,respectively,and the clearance was significantly lower than that of the drug substance(P<0.05),and the two formulations had a larger AUC,was 1.2-and 1.3-folds of the drug substance,respectively,and the relative bioavailability was up to 121.4 and 129.8%,respectively.The above results indicate that the solubility-modified florfenicol preparations can effectively improve the absorption and bioavailability of FFC in chickens.In summary,we initially established a classification method for solubility and permeability of chickens drugs applied to BCS and successfully classified 16 drugs.The effects of chicken feding and fasting conditions on solubility classification methods as well as different cell lines and pH values on permeability classification methods were analyzed and finally compared the results with human drug BCS.In all words,it is necessary to establish a physiologically based BCS classification method for chickens drugs.In addition,to discuss the guiding role of BCS in the transformation of old drugs,we compared the in vitro and in vivo absorption between florfenicol API and the FFC micropowder or crystal. |
PDF Full Text Request