A Quick Guidance of Pharmacodynamics: Biochemical and Physiologic Effects of Drugs


A Quick Guidance of Pharmacodynamics

Pharmacokinetics (PK) is the analysis and description of the disposition of a drug in the body, encompassing development of the mathematical description of all depositional processes in the body, defined as ADME – absorption, distribution, metabolism, and elimination. Pharmacodynamics is the relationship between plasma and tissue drug and/or metabolite concentrations, time, and therapeutic response. Simply put, PK describes what the body does to the drug, and PD describes what the drug does to the body. Pharmacodynamics definition – It  is the study of the biochemical and physiologic effects of drugs, including the mechanisms of drug action, drug effects, and the relationship between drug concentration and effect. Pharmacodynamics describes what happens to the body when a particular drug is introduced into the body. Pharmacodynamics represents how a drug behaves in the body: how it affects cells, organs, or processes within the body.

Pharmacokinetics is the analysis and description of the disposition of a drug in the body, encompassing development of the mathematical description of all depositional processes in the body, defined as ADME – absorption, distribution, metabolism, and elimination. Closely related fields in the biochemical pharmacology discipline include clinical pharmacokinetics, pharmacodynamics, pharmacology, and toxicokinetics.

Drug discovery is the process by which new candidate medications are discovered. Historically, drugs were discovered through identifying the active ingredient from traditional remedies or by serendipitous discovery. Modern drug discovery involves the identification of screening hits, medicinal chemistry and optimization of those hits to increase the affinity, selectivity, efficacy, oral bioavailability and/or metabolic stability. Once a compound that fulfills all of these requirements has been identified, it will begin the process of drug development prior to clinical trials. One or more of these steps may in turn, be repeated in cases where more compounds have been identified than initially expected (and consequently, not all compounds were sufficiently explored) or if previous lead compounds appear to have been optimized to an inadequate degree.

In the past, drugs were found through identifying the active ingredient from traditional remedies or by serendipitous discovery. Scientists did tests with testing on animals and a few humans. Modern drug research is at a stage where the choice of appropriate animal models is often guided by knowledge of human genetics and by direct testing on human tissue, but there are still many cases where knowledge gained from an animal model is critical for success.

Drug development cycle involves multiple stakeholders, including pharmaceutical companies, microbiologists and virologists, physicians, researchers, regulators (including the Food and Drug Administration), government bodies, and venture capitalists to make sure that investment is in the best interest of companies and patients. It typically takes about 12 years for a new medication to be discovered, tested for safety in preclinical experiments with computer models or animals (i.e., mice and rats), approved for human testing in clinical trials for safety, shown to be effective in clinical trials with human subjects, receive approval from the FDA or other regulatory agencies such as the EMA (European Medicines Agency) or PMDA (Pharmaceuticals and Medical Devices Agency) in Japan before being listed on the market.


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