Quantitative study of the time course of the absorption, distribution, biotransformation and excretion of chemical substances, called toxicokinetics, referred to as toxicokinetics, or toxicokinetics, called pharmacokinetics for drugs . Applying these time courses described in mathematical models, it is possible to obtain predictions of body load and retention time after termination of the contact chemicals, as well as other relevant information. These data help to select species and evaluate the harm of chemical substances to human body.
In order to quantitatively analyze these kinetic processes, it is necessary to adopt appropriate models to simplify complex biological systems and describe their models with mathematical formulas. The establishment of the dynamic model is to regard the body as a system, and the interior of the system is divided into several chambers according to the dynamic characteristics. The transport speed of the site is the same and can be classified as one compartment. In the toxicokinetic model, poisons can enter and exit this compartment, which is called an open system. Usually can be divided into open one-compartment model and open two-compartment model.
The open one-compartment model is the simplest model and assumes that the body consists of one compartment. Immediately after exposure, the poison can be evenly distributed throughout the chamber and eliminated from the chamber at a certain rate. In the toxicokinetic test, some poisons can draw a poison-time curve according to this model, and apply the curve and other calculation formulas to obtain the apparent volume, elimination rate, half-life, clearance rate and the area under the poison-time curve, etc. parameter. However, some poisons require a two-compartment model to fit the curve and calculate the toxicokinetic parameters.
Toxicokinetics has practical value in the safety evaluation of chemicals, poisoning treatment and prevention. Through these parameters, it is possible to understand the degree of absorption of the compound from various routes and its absorption rate, metabolism rate and excretion rate. If the poison is quickly excreted in large quantities and has a high clearance rate, chronic toxicity will not occur. However, compounds with very low clearance rate are only partially excreted for a long time, and about 50% are excreted within 7 days, so most of them will remain in the body; this may be due to the reversible combination of toxicants with lipids and proteins. Hepatic circulation, or irreversible interactions of active metabolites with important tissue components; such results predict chronic toxicity or carcinogenicity.