常用参数 Characteristic Description Example value Abbreviation(s) Formula Dose Loading dose (LD),or steady state/maintenance dose(MD) 500mg D design parameter Dosing interval. 24h T design parameter The apparent volume in which a drug is distributed immediately after Volume of distribution it has been injected intravenously and equilibrated between plasma 6.0L =D/Co and the surrounding tissues. Concentration nitial or steady-state concentration of drug in plasma. 83.3μg/mL Co or Css =D/Va Biological halflife The time required for the concentration of the drug to reach half of its 12h original value. t12 In(2)/ke Elimination rate constant The rate at which drugs are removed from the body. 0.0578h1 In(2)/t2=CL/Va Elimination rate Rate of infusion required to balance elimination. 50 mg/h Kin =Css·CL The integral of the concentration-time curve (after a single dose or in AUCo-o Cdt Jo Area under the curve 1320μg/mLxh steady state). AUCTss rt+T Cdt Clearance The volume of plasma cleared of the drug per unit time. 0.38Lh CL = Va·ke=D/AUC AUCpo·D Bioavailability The fraction of drug that is absorbed. 0.8 f AUCn·Dpo Cmax The peak plasma concentration of a drug after oral administration 60.9μgmL Cmar direct measurement Time to reach Cmax. 3.9h direct measurement Cmin The lowest(trough)concentration that a drug reaches before the next 27.7μgfmL dose is administered. Cmin,ss direct measurement =100.Cmaz.ss--Cmm.s】 %PTF Cav,s Fluctuation Peak trough fluctuation within one dosing interval at steady state 41.8% where 生物利用度(bioavailability):制剂中药物被全身利用的程度，药物进入体内吸收后， 进入体循环的药量和给药量的比值，评价相同剂型吸收程度和疗效的重要指标。与脂溶 性和pKa相关常用参数 生物利用度（bioavailability)：制剂中药物被全身利用的程度，药物进入体内吸收后， 进入体循环的药量和给药量的比值，评价相同剂型吸收程度和疗效的重要指标。与脂溶 性和pKa相关