Pharmacokinetics (PK) analysis is a study of how a body processes a drug. There are several biologic factors that a drug can influence. These are ‘ADME’ or Absorption, Distribution, Metabolism, and Excretion. PK testing is the application of various techniques of quantification and modeling to learn the timing of the drug’s ADME. These PK studies help assess whether the drug shows enough success potential or needs further modifications to improve PK parameters. PK studies are instrumental for researchers to decide upon the suitability of a drug’s application in medicine.
Three main PK parameters
● Volume of Distribution
These PK parameters explain the outcomes of a drug’s ADME quantitatively.
PK Testing during Phase I
PK testing is crucial during the FDA application process. PK studies are important right from Phase 1 till then the last phase and beyond. Phase 1 studies help determine the initial dosage regimens. This PK data is essential to gauge the safety and effectiveness of the drug.
FDA considers this data to determine whether the testing and calculations are done correctly. This data might be used for the comparison of the labeled dosages to study results and to make sure that dose adjustments are not required for special populations or food effects.
Importance of PK/PD Modelling
While PK studies how the body processes the drug, PD studies show how the drug affects the body. Data from PD studies help analyse whether the drug actions are as intended and effective.
PK/PD modeling characterizes the relationship between PK studies; concentration vs. time and PD studies; effect vs. time. The use of the PK/PD models right from the early stages of the drug development process helps ease the drug development process. PK/PD relationship data helps in the understanding of the drug action mechanism and may help improve the compound design.
The efficacy and safety ratio of drugs is different among the different population subgroups. These are based on the different ADME parameters. PK studies in such cases during the drug’s premarket stage make a vital risk assessment tool. It helps identify right dosage, drug-drug interactions, and other clinical situations like kidney function or impaired liver, etc.
PK Studies and Dose Regimens
PK studies or PK Testing can help with alterations of dosage schedules of approved drugs as well. Pediatric considerations need more extensive PK studies to ensure the safety of children’s drug dosages. Unless the FDA grants a waiver, it requires PK studies in almost all the cases or stages for supporting dosage regimens and administration for every pediatric subpopulation.
Designing your PK studies properly is critical in the entire process of the drug development process. There have been instances where FDA has into question PK testing data over a four-year time span, which included multiple approvals. PK studies are the most relied upon for proving bioequivalence to reference listed drugs for new drug applications such as generic (505(j) or ANDA) and 505(b)(2). PK studies form an important element during the FDA application process and approvals.