Maximum plasma concentration (Cmax)

Maximum plasma concentration, abbreviated Cmax, is the highest level of a substance measured in the blood after a single administration.

Researchers determine Cmax by sampling blood at intervals after dosing and identifying the peak on the concentration-time curve. The time at which that peak occurs is reported separately as Tmax. Together with the area under the curve, Cmax is one of the three standard pharmacokinetic endpoints and is used to compare formulations, routes, and conditions such as fed versus fasted. A higher Cmax usually means a more intense but not necessarily longer exposure.

In cannabidiol studies, Cmax varies widely with formulation and food; oil-based preparations taken with a fatty meal have produced substantially higher peaks than the same amount taken on an empty stomach. Inhaled cannabinoids reach Cmax within minutes, while swallowed ones take hours. Readers meet the term in study tables and product comparison marketing. A Cmax value describes what happened in a study population and does not by itself indicate an effect.