Pharmacokinetics (PK) refers to the movement of a drug product through the body. It assesses drug movement through the time course it takes to be absorbed, distributed, metabolized, and excreted from the body. In other words, pharmacokinetic clinical trials assess the onset, intensity, and duration of a drug’s effect. Hence, pharmacokinetic testing marks a vital milestone in the drug development timeline.
Pharmacokinetic properties depend on the chemical properties of a drug product as well as on the individual patient-related factors. In pharmaceutical drug discovery and development, researchers use patient-related characteristics such as genetic makeup, age, and sex to predict PK parameters in the population. For example, the half-life of some medications will be longer in the older population. Hence, PK evaluations are necessary to adjust prescriptions for diseases so that drugs can meet individual patient needs. The current article discusses the vital process of pharmacokinetic clinical trials and PK testing.
Compartmental models in PK testing
As several processes are involved in drug metabolism, understanding drug movement through the body is very complex. Hence, simple body processes are necessary to understand drug behavior in the body. Scientists apply mathematical principles to study PK characteristics. These principles are one of the simplest ways to assess PK testing.
Scientists use compartmental models to implement mathematical principles in PK testing. As the name suggests, compartmental models are categorized by the number of compartments required to study the drug in the body. One-compartment, two-compartment, and multi-compartmental models are some types of compartmental models in PK analysis. These compartments are not fluid or a specific tissue but represent fluids or a group of similar tissues.
PK testing in clinical trials
Study subjects, study types, and PK/PD data are three crucial elements of PK clinical trials. Let us evaluate each of these aspects individually.
Early-stage PK studies should be conducted with an appropriate number of healthy subjects. If the drug poses risks, sponsors must then conduct PK studies in the target disease population. On the other hand, sponsors must investigate PK properties in target disease populations at the late stages of drug development. Moreover, it is desirable to assess the relationship between therapeutic effects and plasma PK concentration blood drug concentration and drug dosage.
Population pharmacokinetic study and standard pharmacokinetic study are two ways scientists can evaluate the PK properties of a drug product. The standard pharmacokinetic study uses single dose and repeated dose studies to evaluate PK properties. On the other hand, population PK testing uses the blood concentration profile to determine the safety and efficacy of a drug product. Although choosing one ideal method will depend on the study objective and the stage of drug development.
Pharmacokinetic/pharmacodynamic properties are necessary to assess the drug concentrations and pharmacological response levels. This analysis helps clarify the dose-response correlation and relationship between drug concentration, adverse effects, efficacy, and dosage regimens. PK/PD analysis depends on clinical endpoints and drug concentrations to determine the safety/efficacy profile of drug candidates. In some cases, scientists may use a placebo group to compare PK/PD data.
Thus, pharmacokinetic studies are one of the crucial aspects of pharmaceutical drug discovery and development.