| Biopharmaceutics Classification System(BCS),as a scientific framework based on the drug solubility and permeability measurement,can accurately predict the absorption of drugs and may reduce the costs during the drug development.Due to the inherent physiological differences and the huge differences in the dosage of drugs used in the clinic between humans and other species of animals,it has reached a consensus among researchers all around the world regarding establishing the individual BCS classification standard when BCS is used to veterinary drugs.Based on this,this paper intends to carry out the chicken BCS classification study exampled by 6 antiparasitic drugs.The aim of the study is to establish the BCS framework of commonly used drugs in chicken,and promote the application of BCS in the field of veterinary drugs,accordingly,guide the development of veterinary drugs.1.Metoprolol as classification standard for high/low permeability of commonly used drugs in chickensMetoprolol is a reference standard for the BCS high/low permeability classification of drugs used in human recommended by the FDA,but the pharmacokinetic behavior and intestinal absorption characteristics in chickens are still not be systematically studied and cannot be directly extrapolated as the criteria to the veterinary drugs.In order to explore the applicability of metoprolol as BCS high/low permeability classification standard for chicken commonly used drugs,in this study,the MDCK cells that overexpressed chicken breast cancer resistance gene(Abcg2)or P-glycoprotein gene(Abcbl)were firstly applied to investigate metoprolol’s transmembrane transport characteristics,then the chicken small intestine in situ perfusion model was used to investigate the absorption characteristics of six drugs in chicken jejunum,and finally to investigate the degree of absorption in chickens by measuring the pharmacokinetic parameters and absolute bioavailability of metoprolol.The results of in vitro permeability measurements showed that the apparent permeability(Papp)value of metoprolol(400 μg/mL)from apical to basal in different cell monolayers varies to some extent,but the difference is not significant.Papp is between(6.58±0.23～7.11±0.12)×10-6 cm/s,and the net efflux rate(NER)on each cell line is less than 2.Pharmacokinetic results showed that metoprolol can quickly reach to its highest plasma concentration of(4.42±1.67)μg/mL,which was higher than that of the oral administration group(1.58±0.56 μg/mL).The half-life(T1/2β)was(8.67±3.16)h,longer than the oral administration group(5.77±2.24)h.The area under the curve AUC was significantly increased(6.06±1.97)μg·h/mL,compared to the oral group(5.50±2.15 μg·h/mL).The absolute bioavailability(F)of metoprolol calculated according to the AUCs was 91%,indicating that the absorption of metoprolol in chickens after oral administration is relatively complete.Together with the results of in vitro cell method,in situ perfusion of chicken small intestine and absolute bioavailability,it was confirmed that metoprolol can be used as a reference standard for high/low permeability in the BCS study of chicken commonly used drugs.If the permeability of the tested drugs is equal to or higher than metoprolo,the drug will be taken as a high-permeability drug,otherwise it is a low-permeability drug.2.Determination and classification for intestinal permeability of six commonly used antiparasitic drugs in chickens by monolayer cell method and in situ perfusion modelThis study intends to determine the permeability of six antiparasitic drugs commonly used in veterinary clinics(praziquantel,aminoproline hydrochloride,levamisole hydrochloride,diclazuril,halofuginone,albendazole)based on the physiological characteristics of target animals.Firstly,the MDCK cell lines overexpressing chicken-derived efflux protein BCRP(breast cancer resistance protein)or P-gp(P-glycoprotein)were used for bidirectional transport experiments to determine the apparent permeability coefficient(Papp).And then the chicken in situ perfusion intestinal model was used to determine the effective permeability coefficients(Peff)and study the absorption characteristics of 6 drugs in chicken jejunum.The Papp(×10-6)of praziquantel,albendazole and levamisole hydrochloride was 12.92,15.12 and 14.64 cm/s,respectively,which were higher than metoprolol(6.58×10-6 cm/s),identified as highly permeable drugs.The Peff(×10-4)of the above six drugs were 0.76,0.054,0.66,0.31,1.35,0.93 cm/s,among which the of praziquantel,albendazole and levamisole hydrochloride are all higher than that of metoprolol(0.68×10-4 cm/s),which were mutually verified by the monolayer cell method.The permeability classification results with different cell lines are the same,and although there are still slight difference among different cells.Taking into account of the possible impact of efflux transporters on the absorption,it is suggested using MDCK-chAbcb1/Abcg2 cells that overexpress chicken-derived P-gp and BCRP transporters to determine the permeability,which is more consistent with the high expression of these transporters in chicken small intestine.In conclusion,the permeabilities of six commonly used antiparasitic drugs were determined by the monolayer cell model and the chicken small intestine in situ perfusion model.Among them,praziquantel,albendazole,and levamisole hydrochloride are highly permeable drugs,aminoproline hydrochloride,diclazuril and halofuginone are low permeability drugs.3.The determination of solubility and biopharmaceutics classification of six commonly used drugs in chickensBased on the physiological data of broilers,the solubilities of the above six drugs were measured and classified according to the determining method of human BCS solubility.Then,the six drugs were classified into different BCS types according to the solubility and the permeability.Based on the physiological parameters of chickens measured earlier,the common conditions for determining the solubility of chicken drugs should be in 41℃ and pH 1～8 aqueous buffer solution.And then the equilibrium solubility of each drug was measured to calculate the number of doses(D0).If D0<1,it is a high-solubility drug,that is to say if the highest dose of the drug in a single administration can be dissolved in physiologically relevant buffer of 21 mL(feeding)or 7 mL(fasting),the solubility is high.Using this method,amproline hydrochloride,levamisole hydrochloride,and halofuginone were classified into high-solubility drugs under fasting and eating conditions,however,albendazole,praziquantel and diclazuril were into low solubility drugs.Based on the solubility measured in this test and the permeability measured in the previous chapter,the BCS studies were conducted on these 6 drugs.Levamisole hydrochloride is classified as class I drug.Praziquantel and albendazole are class Ⅱ drugs.Ampicillin hydrochloride and abenzophenone are class III Drugs.Diclazuril is a class IV drug.In summary,we confirmed that metoprolol can be used as a reference standard for the permeability of drugs commonly used in chickens through in vivo and in vitro tests,and the solubility and permeability of 6 drugs were measured and classified respectively.Based on this,the BCS classification of 6 anti-parasitic drugs commonly used in chickens was established.The results can provide important data support for veterinary drug BCS research,and play an important role in promoting the systematization of veterinary drug BCS research. |
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