第 三 单元 药动学（Third unit pharmacokinetics）.docVIP

第 三 单元 药动学（Third unit pharmacokinetics） Third unit pharmacokinetics outline 1. the in vivo process of drugs 2. pharmacokinetics Details 1. the in vivo process of drugs Main points： 1. transmembrane transport of drugs 2. absorption, distribution, excretion of drugs and their influencing factors 3. plasma protein binding rate and enterohepatic circulation of the concept 4. common P450 enzymes and their inhibitors and inducers The in vivo processes include absorption, distribution, metabolism, and excretion. Metabolism: Transformation (I) trans membrane transport of drugs; Methods: passive transport, active transport and membrane transport. 1. passive transport Characteristic： Transfer from the high side to the lower side of the concentration and follow the gradient of concentration through the biofilm. The transport process does not consume energy, there is no need for vectors, and there is no competition inhibition between the drugs, and there is no saturation. When the concentration of drugs on both sides of the biofilm reaches equilibrium state, the transport stops. Methods: simple diffusion, filtration and facilitated diffusion (1) simple diffusion: lipid soluble diffusion Drugs with small molecular weight, small polarity, high lipid solubility and non dissociation are easy to pass through biological membranes. The pH value of the body fluid influences the degree of dissociation of the drug. Weakly acidic drugs: HA=H, ++A- 10 PH-Pka = [A-]/[HA] = [ionic / nonionic] Weakly alkaline drugs: BH, +=H++B 10 Pka-PH = [BH+]/[B] = [ionic / nonionic] Example: the dissociation degree of a weak acid drug in plasma is pKa=8.4 A.10% B.40% C.50% D.60% E.90% [answer number 5006470101: questions for this question] The correct answer, A The formula for the effect of pH on the dissociation of weakly acidic drugs is: 10 pH-pKa=[dissociation type / [non dissociation type], that is, solution The degree of separation is 10 7.4-8.4=10-1=0.1. Example: a weak acid drug, pKa=3.4 According t