Plasma concentration refers to the concentration of an agent in the plasma which is derived from full blood.
Plasma concentrations are used to define major PK and PK/PD parameters. In most cases, they are good estimates for the distribution of an antibiotic and there is the added advantage of samples of blood being obtained easily. Routine plasma concentration measurements provide information about total blood concentrations and do not differentiate between the plasma protein-bound and free fraction of the drug concentration.
Pharmacokinetics and Pharmacodynamics of Antibacterial Agents (Infectious Disease Clinics of North America, 2009)
Challenges and Potential Solutions – Individualised Antibiotic Dosing at the Bedside for Critically Ill Patients: a structured review (Lancet Infectious Diseases, 2014)
Rational dosing of antibiotics: the use of plasma concentrations versus tissue concentrations (International Journal of Antimicrobial Agents, 2002)