is a term used in pharmacokinetics for the minimum blood plasma concentration reached by a drug during a dosing interval, which is the time interval between administration of two doses. This definition is slightly different from , the concentration immediately prior to administration of the next dose. is the opposite of , the maximum concentration that the drug reaches. must be above certain thresholds, such as the minimum inhibitory concentration (MIC), to achieve a therapeutic effect.
In most cases is directly measurable. At steady state the minimum plasma concentration can also be calculated using the following equation:
is also an important parameter in bioavailability and bioequivalence studies, it is part of the pharmacokinetic information recommended for submission of investigational new drug applications.