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POPULATION PHARMACOKINETICS

Definition : "Study of the extent, sources and correlates of variability in drug pharmacokinetics within a patient population."

Description

Certain patient characteristics, such as age, body weight, comorbidity and comedication, can alter the pharmacokinetic parameters of a drug. Population pharmacokinetics seeks to assess the extent of the variability of these parameters among a patient population and to identify the factors that are responsible for such variability.

Population pharmacokinetics includes:

  1. Assessment of global variability of the plasma drug concentration profile in a patient population.
  2. Allocation of this variability to pharmacokinetic parameters (e.g. variability of clearance, bioavailability, etc).
  3. Explanation of variability by identifying factors of demographic, pathophysiological, environmental, or concomitant drug-related origin that may influence the pharmacokinetic parameters.
  4. Quantitative estimation of the magnitude of the unexplained variability in the patient population.

Sophisticated pharmacostatistical models are needed to analyze population pharmacokinetics.

Clinical implications

Population pharmacokinetics in the drug development process helps identify differences in drug safety and efficiency among population subgroups.

The mean values of pharmacokinetic parameters allow the elaboration of the standard dosage regimen of the drug. Variability that is due to influencal factors leads to dosage adaptation proposed for patient subsets. Unexplained variability reflects the reproducibility of pharmacokinetics. This is important because the efficacy and safety of a drug may decrease as unexplained variability increases.