What is defined as the chemical alteration of drug molecules into metabolites by body cells?

The term that describes the chemical alteration of drug molecules into metabolites by body cells is biotransformation. This process involves enzymes within the cells that modify the structure of the drug, typically making it easier for the body to eliminate it.

Biotransformation is crucial for the pharmacokinetics of drugs, as it can affect the duration and intensity of a drug's therapeutic effects. This process can transform lipophilic compounds into more hydrophilic metabolites, which can then be excreted from the body more easily. It often occurs primarily in the liver, but can take place in other tissues as well.

While metabolism is related and sometimes used interchangeably with biotransformation, it encompasses a broader range of biological processes, including anabolism and catabolism. In this context, biotransformation is specifically focused on the conversion of pharmaceuticals into metabolites. Excretion refers to the elimination of the substances from the body, and active transport pertains to the movement of substances across cell membranes against their concentration gradient, which is not directly related to the chemical alteration of drug molecules.