Cmin

{{Short description|Minimum blood plasma concentration of a drug during the time between two doses}}

{{DISPLAYTITLE:C_min}}

{{Use dmy dates|date=May 2023}}

{{math|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 {{math|C_trough}}, the concentration immediately prior to administration of the next dose.{{cite book |last1=Weimann |first1=H. J. |last2=Cawello |first2=W. |last3=Brett |first3=M. |last4=Zimmermann |first4=H. |last5=Pabst |first5=G. |last6=Sierakowski |first6=B. |last7=Giesche |first7=R. |last8=Baumann |first8=A. |year=1999 |url=https://books.google.com/books?id=EzqwAAAACAAJ |title=Parameters for Compartment Free Pharmacokinetics: Standardisation of Study Design, Data Analysis and Reporting |chapter=Drug concentrations and directly derived parameters |publisher=Shaker-Verlag |isbn=9783826547676 |oclc=44511664 | location=Aachen, Germany |pages=25–40}} (pages 31–34 in 2003 edition) {{math|C_min}} is the opposite of {{math|C_max}}, the maximum concentration that the drug reaches. {{math|C_min}} must be above certain thresholds, such as the minimum inhibitory concentration (MIC), to achieve a therapeutic effect.{{Cite journal |last=Dalton |first=Bruce R. |date=March 2023 |title=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 |journal=Microorganisms |language=en |volume=11 |issue=3 |pages=567 |doi=10.3390/microorganisms11030567 |pmid=36985141 |pmc=10051726 |issn=2076-2607 |doi-access=free }}

In most cases {{math|C_min}} is directly measurable. At steady state the minimum plasma concentration can also be calculated using the following equation:http://www.pharmpress.com/files/docs/clinical_pharmacokinetics_samplechapter.pdf {{Webarchive|url=https://web.archive.org/web/20180329011004/http://www.pharmpress.com/files/docs/clinical_pharmacokinetics_samplechapter.pdf |date=29 March 2018 }} {{Bare URL PDF|date=March 2022}}

$$C\_\{min\}\; =\; \backslash frac\{SFDk\_a\}\{V\_d(k\_a-k\_e)\}\; \backslash times\; \backslash left(\; \backslash frac\{e^\{-k\_e\backslash tau\}\}\{1-e^\{-k\_e\backslash tau\}\}-\backslash frac\{e^\{-k\_a\backslash tau\}\}\{1-e^\{-k\_a\backslash tau\}\}\; \backslash right)$$

:{{mvar|S}} = Salt factor

:{{mvar|F}} = Bioavailability

:{{mvar|D}} = Dose

:{{math|k{{sub|e}}}} = Elimination rate constant

:{{math|k{{sub|a}}}} = Absorption rate constant

:{{math|V{{sub|d}}}} = Volume of distribution

:{{mvar|τ}} = Dosing interval

{{math|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.[https://web.archive.org/web/20130319082058/http://www.fda.gov/downloads/Drugs/.../Guidances/ucm070124.pdf fda.gov] {{Bare URL PDF|date=March 2022}}