
Pharmacodynamics (PD) is the study of the
biochemical
Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology an ...
and
physiologic
Physiology (; ) is the scientific study of functions and mechanisms in a living system. As a sub-discipline of biology, physiology focuses on how organisms, organ systems, individual organs, cells, and biomolecules carry out the chemical ...
effects of
drug
A drug is any chemical substance that causes a change in an organism's physiology or psychology when consumed. Drugs are typically distinguished from food and substances that provide nutritional support. Consumption of drugs can be via insuffla ...
s (especially
pharmaceutical drug
A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy (pharmacotherapy) is an important part of the medical field and re ...
s). The effects can include those manifested within
animal
Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...
s (including humans),
microorganism
A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...
s, or combinations of
organism
In biology, an organism () is any living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy into groups such as multicellular animals, plants, and ...
s (for example,
infection
An infection is the invasion of tissues by pathogens, their multiplication, and the reaction of host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmissible disease or communicable dise ...
).
Pharmacodynamics and
pharmacokinetics
Pharmacokinetics (from Ancient Greek ''pharmakon'' "drug" and ''kinetikos'' "moving, putting in motion"; see chemical kinetics), sometimes abbreviated as PK, is a branch of pharmacology dedicated to determining the fate of substances administered ...
are the main branches of
pharmacology
Pharmacology is a branch of medicine, biology and pharmaceutical sciences concerned with drug or medication action, where a drug may be defined as any artificial, natural, or endogenous (from within the body) molecule which exerts a biochemica ...
, being itself a topic of
biology
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...
interested in the study of the interactions between both endogenous and exogenous chemical substances with living organisms.
In particular, pharmacodynamics is the study of how a drug affects an organism, whereas pharmacokinetics is the study of how the organism affects the drug. Both together influence
dosing
Dosing generally applies to feeding chemicals or medicines when used in small quantities.
For medicines the term '' dose'' is generally used. In the case of inanimate objects the word dosing is typical. The term dose titration, referring to stepw ...
, benefit, and
adverse effect
An adverse effect is an undesired harmful effect resulting from a medication or other intervention, such as surgery. An adverse effect may be termed a "side effect", when judged to be secondary to a main or therapeutic effect. The term complica ...
s. Pharmacodynamics is sometimes abbreviated as PD and
pharmacokinetics
Pharmacokinetics (from Ancient Greek ''pharmakon'' "drug" and ''kinetikos'' "moving, putting in motion"; see chemical kinetics), sometimes abbreviated as PK, is a branch of pharmacology dedicated to determining the fate of substances administered ...
as PK, especially in combined reference (for example, when speaking of
PK/PD models PK/PD modeling (pharmacokinetic/pharmacodynamic modeling) (alternatively abbreviated as PKPD or PK-PD modeling) is a technique that combines the two classical pharmacologic disciplines of pharmacokinetics and pharmacodynamics. It integrates a pharm ...
).
Pharmacodynamics places particular emphasis on
dose–response relationship
The dose–response relationship, or exposure–response relationship, describes the magnitude of the response of an organism, as a function of exposure (or doses) to a stimulus or stressor (usually a chemical) after a certain exposure time. ...
s, that is, the relationships between drug
concentration
In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', ''molar concentration'', ''number concentration'', an ...
and effect. One dominant example is drug-receptor interactions as modeled by
:
L + R <=> LR
where ''L'', ''R'', and ''LR'' represent ligand (drug), receptor, and ligand-receptor complex concentrations, respectively. This equation represents a simplified model of
reaction dynamics
Reaction dynamics is a field within physical chemistry, studying why chemical reactions occur, how to predict their behavior, and how to control them. It is closely related to chemical kinetics, but is concerned with individual chemical events on ...
that can be studied mathematically through tools such as
free energy maps.
Basics
There are four principle protein targets with which drugs can interact:
*
Enzymes- (e.g.
neostigmine
Neostigmine, sold under the brand name Bloxiverz, among others, is a medication used to treat myasthenia gravis, Ogilvie syndrome, and urinary retention without the presence of a blockage. It is also used in anaesthesia to end the effects of n ...
and
acetyl cholinesterase)
**
Inhibitors
**
Inducers
**
Activators
*
Membrane carriers- Reuptake">nowiki/>Reuptake vs Reverse transport">Efflux
Efflux may refer to:
* Efflux (microbiology), a mechanism responsible for moving compounds out of cells
* e-flux, a publishing platform and archive
See also
* Efflux time, part of a measure of paint viscosity
* Flux (biology)
In general, flux ...
] (e.g. Tricyclic antidepressant, tricyclic antidepressants and catecholamine uptake-1)
** Reuptake enhancer, Enhancer (RE)
** Reuptake inhibitor, Inhibitor (RI)
** Releasing agent, Releaser (RA)
*