Pharmacokinetics

Pharmacokinetics testing or PK bioanalysis helps in establishing how the human body responds to a particular pharmaceutical drug candidate right from the time of its administration to the intended individual. It helps in evaluating the absorption, its biodistribution, metabolism, and finally, elimination from the human body. For establishing the pharmacokinetic vs pharmacodynamic relationship, the concentration of the drug under analysis is evaluated across different biological samples such as urine, plasma, saliva, and serum.

On the other hand, the pharmacodynamics evaluates the molecular, physiological, and biochemical alterations that a pharmaceutical drug candidate produces on the human body. This analysis involves the concepts of receptor binding, inter-chemical interactions, and post-receptor effects. Together, the pharmacokinetics vs pharmacodynamics data assessment explains the relationship existing between the drug and the response generated by the human body. This dose-response relationship becomes an integral part of the designing process of the dose, route, and administration schedule of the pharmaceutical drug candidate under analysis.

Determining both the pharmacokinetic and pharmacodynamic behaviour of the given therapeutic drug candidate has become essential in evaluating both its safety and efficacy. It further assists in the identification of the appropriate dosage form as well its distribution. Pk assay methods plays an important role in determining the concentration time profiles of both the drug and their metabolites in different biological fluids thereby providing the required information for Pk analysis.

One of the key importance of the pharmacokinetics clinical trials assessment and documentation is contributing towards assuring the efficacy and safety of the therapeutic drug in its intended population. Though different parameters are assessed, both the pharmacokinetic vs pharmacodynamic studies shares common comprehensive goals such as safe investigation on establishing safety as well as efficacy of the drug under evaluation. The analytical method employed helps in detecting the presence of the precise amount of the analyte in a given biological matrix under evaluation.

These studies help in determining the drug behaviour within the human body thereby facilitating the critical decision making on the dosage as well as safety levels of the pharmaceutical product under analysis.

Key elements of the Pk bioanalysis –

The following four parameters forms a critical and an undeniable part of the pk bioanalysis –

Absorption –

The first and the foremost parameter of the pk analysis is absorption. This is the stage wherein the pharmaceutical drug candidate enters human body and becomes a part of the systemic circulation. The drug absorption can take place either through nasal, oral, parenteral or dermal routes.

Biodistribution –

This second stage of the pharmacokinetic parameter evaluation is defined as a reversible drug transfer between different points within the human body. The drug distribution is influenced by several different factors such as its plasma or other biological fluid concentration, lipid-solubility, etc.

Metabolism –

This third parameter of the pk assessment is important for the assessment of the conversion ability of the drug candidate into other form or metabolite. This usually is observed in the liver and can be accomplished in two different forms – oxidative metabolism and reductive metabolism.

Elimination

The last parameter is known as the process of excretion of both the pharmaceutical drug candidate and its subsequent metabolites out of the human body. Majority of the toxic substances or the end result of the ADME process of a drug is its elimination out of the human body. The more the soluble the toxic or the waste components are, the more easier it is to eliminate them from the human body.