C_max is a term used in pharmacokinetics refers to the maximum (or peak) concentration that a drug achieves in tested area after the drug has been administrated and prior to the administration of a second dose. C_max is the opposite of C_min

Cmin

Cmin is a term used in pharmacology refers to the minimum concentration that a drug achieves in tested area after the drug has been administrated and prior to the administration of a second dose. Cmin is the opposite of Cmax, which is the maximum concentration that a drug achieves after dosing....

, which is the minimum (or trough) concentration that a drug achieves after dosing.

Short term drug side effect

Adverse drug reaction

An adverse drug reaction is an expression that describes harm associated with the use of given medications at a normal dosage. ADRs may occur following a single dose or prolonged administration of a drug or result from the combination of two or more drugs...

s are most likely to occur at or near the C_max whereas the therapeutic effect of drug with sustained duration of action usually occurs a concentrations slightly above the C_min.

The C_max is often measured in an effort to show bioequivalence

Bioequivalence

Bioequivalence is a term in pharmacokinetics used to assess the expected in vivo biological equivalence of two proprietary preparations of a drug...

between a generic and innovator drug product.