Effects Of Organic Solvent And Efavirenz On Metabolic Activities Of CYP450 To Probe Substrates

In clinical,many patients may receive more than one drug simultaneously,so physicians must be careful to avoid any drug-drug interactions(DDI).Major DDI concerns are Cytochrome P450 inhibition and induction.CYP inhibition may block the metabolism of victim drug and reduce victim's clearnace so that the exposure of victim is greatly increased to a toxic cocentration.In contrast,CYP induction may increased the metbolism of victim drug and accelerate victim's elimination from body thus reducing the exposure of victim to a low level so that it can not reach the efficacy.Because of the important of DDI,it has become an important concern with the Food and Drug Administration(FDA)and China Food and Drug Administration(CFDA)and at pharmaceutical companies.Both FDA and CFDA have reommended to provide DDI study when submitting IND filing materials.We all known that Cytochrome P450(CYP450)is one of the most important drug metabolic enzymes families which attend to metaolize approximately 75% of drugs.So CYP450 inhibition is a major cause of drug–drug interactions.Commonly used CYP materials are recombinant human CYP isozymes(rh CYP),human liver microsomes(HLM),human liver S9 and hepatocytes.In consideration of compounds' solubility,organic solvents are often required for solubilization of the compounds and addition to an in vitro incubation.However,considering the potential influence of these solvents on cytochrome CYP450 activities,the amount of organic solvents must be controlled within a certain range.We investigated CYP450 inhibition and CYP3A4 activation using human liver microsomes.The thesis includes two major parts:1)Uisng 5-in 1 Cocktail substrates method to investigate the inhibitory effects of three commonly used organic solvents,methanol,acetonitrile,and dimethyl sulfoxide(DMSO)by human liver microsomes.Estimate the effects of these three organic ssolvent on metabolic activities of five major CYPs to their probe substrates.The CYP450 inhibition experimental conditions can be optimized with this investigation.2)During CYP inhibition study using human liver microsome,an abonrmal phenomenon was observed: activity of CYP3A4 was increased rather than been inhibited.We suspected this is one of an atypical CYP kinetics,activation.In order to estabolish a method to evaluate CYP3A4 activation,we investigated the effect of efavirenz on metabolic activities of CYP3A4 probe substrate midazolam.