药物代谢动力学（英语：Pharmacokinetics），简称药代动力学或药动学，也简称为PK，是药理学的分支，研究药物在机体的影响下所发生的变化及其规律，其中的药物包括药剂、激素、营养素和毒素。药代动力学研究药物的体内过程（包括吸收、分布、代谢和排泄），并运用数学原理和方法阐释药物在机体内的动态规律。

药代动力学阐释在使用某种药物后身体如何吸收和扩散药物，以及药物在身体内发生的化学变化（如通过代谢酶如细胞色素P450或葡萄糖醛酸转移酶），以及药物的效果和排泄方式。 药代动力学属性常常受给药方式和剂量影响，这些原因也会影响吸收率。 药代动力学常与药效学一起研究，后者研究药物在体内的效果。

Pharmacokinetics (from Ancient Greek pharmakon "drug" and kinetikos "moving, putting in motion"; see chemical kinetics), sometimes abbreviated as PK, is a branch of pharmacology dedicated to determining the fate of substances administered externally to a living organism. The substances of interest include pharmaceutical agents, hormones, nutrients, and toxins. It attempts to discover the fate of a drug from the moment that it is administered up to the point at which it is completely eliminated from the body. Pharmacokinetics describes how the body affects a specific drug after administration through the mechanisms of absorption and distribution, as well as the chemical changes of the substance in the body (e.g. by metabolic enzymes such as cytochrome P450 or glucuronosyltransferase enzymes), and the effects and routes of excretion of the metabolites of the drug. Pharmacokinetic properties of drugs may be affected by elements such as the site of administration and the dose of administered drug. These may affect the absorption rate. Pharmacokinetics is often studied in conjunction with pharmacodynamics, the study of a drug's pharmacological effect on the body.