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Cmin

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Minimum blood plasma concentration of a drug during the time between two doses

Cmin 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 Ctrough, the concentration immediately prior to administration of the next dose. Cmin is the opposite of Cmax, the maximum concentration that the drug reaches. Cmin must be above certain thresholds, such as the minimum inhibitory concentration (MIC), to achieve a therapeutic effect.

In most cases Cmin is directly measurable. At steady state the minimum plasma concentration can also be calculated using the following equation: C m i n = S F D k a V d ( k a − k e ) × ( e − k e τ 1 − e − k e τ − e − k a τ 1 − e − k a τ ) {\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
ke = Elimination rate constant
ka = Absorption rate constant
Vd = Volume of distribution
τ = Dosing interval

Cmin 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.

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
  4. https://www.fda.gov/downloads/Drugs/.../Guidances/ucm070124.pdf


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