Cmax (pharmacology)

Description

Cmax is the opposite of Cmin, which is the minimum (or trough) concentration that a drug achieves after dosing. The related pharmacokinetic parameter tmax is the time at which the Cmax is observed.

After an intravenous administration, Cmax and tmax are closely dependent on the experimental protocol, since the concentrations are always decreasing after the dose. But after oral administration, Cmax and tmax are dependent on the extent, and the rate of drug absorption and the disposition profile of the drug. They could be used to characterize the properties of different formulations in the same subject.

Short term drug side effects are most likely to occur at or near the Cmax, whereas the therapeutic effect of drug with sustained duration of action usually occurs at concentrations slightly above the Cmin.

The Cmax is often measured in an effort to show bioequivalence (BE) between a generic and innovator drug product. According to the FDA, drug quality bioavailability (BA) and BE rely on pharmacokinetic measurements such as AUC and Cmax that are reflective of systemic exposure.

References

References

1. (2004). "Modern pharmacology with clinical applications". Lippincott Williams & Wilkins.
2. (2006). "SAS Conference Proceedings: Pharmaceutical Users Software Exchange".
3. (March 2002). "A short introduction to pharmacokinetics". European Review for Medical and Pharmacological Sciences.
4. (October 2005). "The bioequivalence of highly variable drugs and drug products". International Journal of Clinical Pharmacology and Therapeutics.
5. "Bioavailability and Bioequivalence Studies for Orally Administered Drug Products — General Considerations". Center for Drug Evaluation and Research (CDER), U.S. Food and Drug Administration.