Cmin

Cmin is a term used in pharmacokinetics that usually refers to the minimum plasma 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.Cmin has direct relationships with other minimum concentrations such as MIC and is required to be higher than those concentrations to achieve the minimum efficacy.

In most cases Cmin is directly measurable. At steady state the minimum plasma concentration can also be calculated using the following equation: $$C_{p min}= \frac{SFD k_a}{V_d(k_a-k)}\times\{\frac{e^{-k\tau}}{1-e^{-k\tau}}-\frac{e^{-k_a\tau}}{1-e^{-k_a\tau}}\}$$

Cmin is also a very important parameter in BA/BE studies, it is part of the pharmacokinetic information recommended for submission of IND.