Cmin

C_min 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 C_trough , the concentration immediately prior to administration of the next dose. ^[1] C_min is the opposite of C_max , the maximum concentration that the drug reaches. C_min must be above certain thresholds, such as the minimum inhibitory concentration (MIC), to achieve a therapeutic effect. ^[2]

In most cases C_min is directly measurable. At steady state the minimum plasma concentration can also be calculated using the following equation: ^[3] $${\displaystyle C_{min}={\frac {SFDk_{a}}{V_{d}(k_{a}-k_{e})}}\times \left({\frac {e^{-k_{e}\tau }}{1-e^{-k_{e}\tau }}}-{\frac {e^{-k_{a}\tau }}{1-e^{-k_{a}\tau }}}\right)}$$

S = Salt factor

F = Bioavailability

D = Dose

k_e = Elimination rate constant

k_a = Absorption rate constant

V_d = Volume of distribution

τ = Dosing interval

C_min 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. ^[4]

References

1. Weimann, H. J.; Cawello, W.; Brett, M.; Zimmermann, H.; Pabst, G.; Sierakowski, B.; Giesche, R.; Baumann, A. (1999). "Drug concentrations and directly derived parameters". Parameters for Compartment Free Pharmacokinetics: Standardisation of Study Design, Data Analysis and Reporting. Aachen, Germany: Shaker-Verlag. pp. 25–40. ISBN   9783826547676. OCLC   44511664. (pages 31–34 in 2003 edition)
2. Dalton, Bruce R. (March 2023). "What Is the Best Vancomycin Therapeutic Drug Monitoring Parameter to Assess Efficacy? A Critical Review of Experimental Data and Assessment of the Need for Individual Patient Minimum Inhibitory Concentration Value". Microorganisms. 11 (3): 567. doi: 10.3390/microorganisms11030567 . ISSN   2076-2607. PMC   10051726 . PMID   36985141.
3. http://www.pharmpress.com/files/docs/clinical_pharmacokinetics_samplechapter.pdf Archived 29 March 2018 at the Wayback Machine ^{[ bare URL PDF ]}
4. fda.gov ^{[ bare URL PDF ]}