C_min

$C min$ 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] $C_{min}={\frac {SFDk_{a}}{V_{d}(k_{a}-k_{e})}}\times \left({\frac {e^{-k_{e}\tau }}{1-e^{-k_{e}\tau }}}-{\frac {e^{-k_{a}\tau }}{1-e^{-k_{a}\tau }}}\right)$

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

^ Weimann HJ, Cawello W, Brett M, Zimmermann H, Pabst G, Sierakowski B, et al. (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 978-3-8265-4767-6. OCLC 44511664. (pages 31–34 in 2003 edition)
^ Dalton BR (February 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. PMC 10051726. PMID 36985141.
^ Dhillon S, Gill K (2006). "Basic pharmacokinetics". Clinical pharmacokinetics (PDF). pp. 1–44. Archived from the original (PDF) on 29 March 2018.
^ "Bioavailability and Bioequivalence, Studies for Orally Administered Drug Products — General Considerations" (PDF). Guidance for Industry. Center for Drug Evaluation and Research (CDER), U.S. Food and Drug Administration. March 2003. Archived from the original (PDF) on 19 March 2013.

[1] Weimann HJ, Cawello W, Brett M, Zimmermann H, Pabst G, Sierakowski B, et al. (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 978-3-8265-4767-6. OCLC 44511664. (pages 31–34 in 2003 edition)

[2] Dalton BR (February 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. PMC 10051726. PMID 36985141.

[3] Dhillon S, Gill K (2006). "Basic pharmacokinetics". Clinical pharmacokinetics (PDF). pp. 1–44. Archived from the original (PDF) on 29 March 2018.

[4] "Bioavailability and Bioequivalence, Studies for Orally Administered Drug Products — General Considerations" (PDF). Guidance for Industry. Center for Drug Evaluation and Research (CDER), U.S. Food and Drug Administration. March 2003. Archived from the original (PDF) on 19 March 2013.

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