Pharmacokinetics is the study of drug movement through the body, relating to absorption, distribution, metabolism, and excretion. Pharmacokinetics of a drug depends on patient-related factors as well as the drug’s chemical properties. Application of pharmacokinetic principles is helping to design drug formulation, adjust the administrative dose, and perform therapeutic monitoring. The study of pharmacokinetics is complicated and requires advanced analysis systems, special processing software, and an expert support team, all of which can be provided by the GPD Laboratory.
Pharmacodynamics is broadly defined as the biologic effects resulting from the interaction between drugs and biologic systems. It covers the biochemical, physiologic, and molecular effects of drugs on the body, and involves receptor binding, post-receptor effects, and chemical interactions. A simple and useful distinction is to think of pharmacodynamics as “what the drug does to the body.”
Pharmacodynamics paired with pharmacokinetics helps to explain the relationship between the dose and response. It provides a rational basis to understand the impact of different dosage regimens on the timeline of pharmacologic response.
Bioavailability refers to the extent and rate that the active drug or metabolite enters systemic circulation to access the site of action. Bioavailability is largely determined by the properties of dosage, formulation, and manufacturing. Differences in bioavailability among formulations or delivery methods of a target drug can have clinical significance. The bioavailability value is determined using the area under the concentration-time curve.
Bioequivalence is a term in pharmacokinetics used to assess the expected in vivo biological equivalence of two proprietary preparations of a drug. If two products are said to be bioequivalent, it means that they would be expected to be, for all intents and purposes, the same. The plasma concentration time curve is generally used to assess the rate and extent of absorption. The assessment of bioequivalence of two drug products is based on the fundamental assumption that two drug products are equivalent when the rate and extent of absorption of the products are not significantly different.