Pharmacokinetics. What are Cmax and Cmin?

The following pharmacological definition has been taken from the Pharmacology and Experimental Therapeutics Department Glossary at Boston University School of Medicine.

Cmax, Cmin:

The maximum or “peak” concentration (Cmax) of a drug observed after its administration; the minimum or “trough” concentration (Cmin) of a drug observed after its administration and just prior to the administration of a subsequent dose. For drugs eliminated by first-order kinetics from a single-compartment system, Cmax, after n equal doses given at equal intervals is given by C0(1 – fn )/(1 – f) = Cmax, and Cmin = Cmax – C0.

The time following drug administration at which the peak concentration of Cmax occurs, tp (for any route of administration but the intravenous), is given by tp = (ln ka – ln kel )/(ka – kel). (Remember that ln is the natural logarithm, to the base e, rather than the common logarithm or logarithm to the base 10; ln X=2.303 log X.)

The copyright of the text is held by Trustees of Boston University. Permission has been granted for its use in this blog.

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