Metabolism

Metabolism is the set of chemical reactions that convert food into energy and building blocks and transform drugs and other foreign compounds into forms the body can excrete.

In pharmacology the word usually refers to drug metabolism, which takes place mainly in the liver in two phases. Phase one reactions, carried out largely by cytochrome P450 enzymes, add or expose chemical groups, often making a compound less active but sometimes creating an active metabolite. Phase two reactions attach water-soluble molecules so that the product can leave the body in urine or bile. Metabolism determines how long a substance acts and, together with absorption, distribution and excretion, makes up pharmacokinetics.

Cannabinoids are metabolized chiefly by CYP3A4 and CYP2C19 in people, and CBD also inhibits several of these enzymes, which is the basis for its interactions with medications such as clobazam, warfarin and some antiepileptics. Rates differ among individuals because of genetics, age, liver health and other drugs, and they differ between species, which is why dog and cat pharmacokinetics are studied separately. In the broader sense, metabolic health refers to energy balance, blood sugar and lipid regulation, and cannabinoids have been examined in early research on metabolic measures.