- Peak drug concentration (Cmax) The highest blood drug concentration after administration. This parameter is an important indicator reflecting the absorption rate and degree of absorption of drugs in the body.
- Peak time (Tmax) the time required to reach the peak concentration of the drug after administration. This parameter reflects the rate at which the drug enters the body. A faster absorption rate means a shorter peak time.
- Terminal elimination rate (Ke) The plasma concentration elimination rate constant of the terminal phase. Take the logarithm of the plasma concentration, and the negative of the slope value obtained after linear regression with time is the terminal elimination rate.
- Terminal elimination half-life (T1/2) The time required for the terminal phase blood drug concentration to drop by half. This parameter intuitively reflects the elimination speed of the drug from the body. The terminal elimination half-life is the reciprocal of the terminal elimination rate in value, that is: terminal elimination half-life=0.693/terminal elimination rate.
- Area under the drug-time curve (AUC) the area enclosed by the blood drug concentration curve against the time axis. This parameter is an important indicator to evaluate the degree of drug absorption, reflecting the exposure characteristics of the drug in the body. Since the blood drug concentration in pharmacokinetic studies can only be observed up to a certain time point t, there are two ways to express AUC: AUC(0-t) and AUC(0-∞), the former is obtained by the trapezoidal area method, and the latter is calculated Formula: AUC(0-∞) = AUC(0-t) + end point concentration/end elimination rate.
- Clearance rate (CL) The apparent volume of distribution of the drug removed from the body in a unit time, the unit is generally L/h. This parameter is an important parameter that reflects the body’s handling characteristics of drugs, and is closely related to physiological factors. The clearance rate is based on the ratio of dose to AUC (0-∞).
- Apparent volume of distribution (Vd) The proportional constant between the amount of the drug in the body and the concentration of the blood drug when the drug reaches dynamic equilibrium in the body. The unit is generally L. This parameter reflects the extent to which the drug is distributed in the body. The higher the value, the wider the distribution. The apparent volume of distribution is numerically derived from the ratio of clearance rate to terminal clearance rate.
- Mean residence time (MRT) The average residence time of drug molecules in the body, which represents the time required to eliminate 63.2% of the drug from the body. This parameter can only be calculated when the pharmacokinetic process has linear characteristics, and its value is obtained by the ratio of AUMC (the integral of the product of drug and time over time t) and AUC (0-∞).
- Bioavailability (F) is a measure of the speed and extent at which a drug is absorbed into the blood circulation, and is an important indicator for evaluating the degree of drug absorption. Bioavailability can be divided into absolute bioavailability and relative bioavailability. The former is used to compare the absorption difference of the two administration routes. The calculation formula is: F = (AUC_extDose_iv)/(AUC_ivDose_ext)100%, Wherein ext means extravascular administration, iv means intravenous administration, and Dose means dose. The latter is used to evaluate the difference in absorption of the two preparations. The calculation formula is: F = (AUC_TDose_R)/(AUC_RDose_T)100%, where T and R are the test preparation and the reference preparation, respectively.