Clearance

Clearance is the volume of blood plasma from which a substance is completely removed per unit of time, expressed in units such as liters per hour.

The concept describes how efficiently the body eliminates a compound, mainly through liver metabolism and kidney excretion. A substance with high clearance is removed quickly and needs to be given more often to maintain a level; one with low clearance lingers. Clearance, together with the volume of distribution, determines half-life, and researchers calculate it from dose and area under the concentration-time curve.

Cannabidiol is cleared primarily by liver enzymes of the cytochrome P450 family, so anything that changes enzyme activity, including other medications and liver disease, can change its clearance. Because CBD is fat-soluble and stored in adipose tissue, its apparent clearance after repeated use differs from that after a single dose. Readers meet the term in pharmacokinetic study tables. It is a population-level measurement and varies from one individual to another.