The field encompasses drug composition and properties, functions, sources, synthesis and drug design, molecular and cellular mechanisms, organ/systems mechanisms, signal transduction/cellular communication, molecular diagnostics, interactions, chemical biology, therapy, and medical applications and antipathogenic capabilities. The two main areas of pharmacology are pharmacodynamics and pharmacokinetics. Pharmacodynamics studies the effects of a drug on biological systems, and pharmacokinetics studies the effects of biological systems on a drug. In broad terms, pharmacodynamics discusses the chemicals with biological receptors, and pharmacokinetics discusses the absorption, distribution, metabolism, and excretion (ADME) of chemicals from the biological systems.
Pharmacology is not synonymous with pharmacy and the two terms are frequently confused. Pharmacology, a biomedical science, deals with the research, discovery, and characterization of chemicals which show biological effects and the elucidation of cellular and organismal function in relation to these chemicals. In contrast, pharmacy, a health services profession, is concerned with the application of the principles learned from pharmacology in its clinical settings; whether it be in a dispensing or clinical care role. In either field, the primary contrast between the two is their distinctions between direct-patient care, pharmacy practice, and the science-oriented research field, driven by pharmacology.
herbalism and natural substances, mainly plant extracts. Medicines were compiled in books called pharmacopoeias. Crude drugs have been used since prehistory as a preparation of substances from natural sources. However, the active ingredient
of crude drugs are not purified and the substance is adulterated with other substances.
Pharmacology developed in the 19th century as a biomedical science that applied the principles of scientific experimentation to therapeutic contexts.
binding affinity of drugs at chemical targets.[14] Modern pharmacologists use techniques from genetics, molecular biology, biochemistry, and other advanced tools to transform information about molecular mechanisms and targets into therapies directed against disease, defects or pathogens, and create methods for preventive care, diagnostics, and ultimately personalized medicine
.
Divisions
The discipline of pharmacology can be divided into many sub disciplines each with a specific focus.
Systems of the body
A variety of topics involved with pharmacology, including neuropharmacology, renal pharmacology, human metabolism, intracellular metabolism, and intracellular regulation
Pharmacology can also focus on specific
renal and endocrine pharmacology. Psychopharmacology is the study of the use of drugs that affect the psyche, mind and behavior (e.g. antidepressants) in treating mental disorders (e.g. depression).[15][16] It incorporates approaches and techniques from neuropharmacology, animal behavior and behavioral neuroscience, and is interested in the behavioral and neurobiological mechanisms of action of psychoactive drugs.[citation needed] The related field of neuropsychopharmacology
focuses on the effects of drugs at the overlap between the nervous system and the psyche.
pharmacogenetics studies how genetic variation gives rise to differing responses to drugs.[citation needed]Pharmacoepigenetics studies the underlying epigenetic marking patterns that lead to variation in an individual's response to medical treatment.[20]
Pharmacology can be applied within clinical sciences. Clinical pharmacology is the application of pharmacological methods and principles in the study of drugs in humans.[21] An example of this is posology, which is the study of how medicines are dosed.[22]
Pharmacology is closely related to toxicology. Both pharmacology and toxicology are scientific disciplines that focus on understanding the properties and actions of chemicals.[23] However, pharmacology emphasizes the therapeutic effects of chemicals, usually drugs or compounds that could become drugs, whereas toxicology is the study of chemical's adverse effects and risk assessment.[23]
Drug discovery is the field of study concerned with creating new drugs. It encompasses the subfields of drug design and development.[24] Drug discovery starts with drug design, which is the inventive process of finding new drugs.[25] In the most basic sense, this involves the design of molecules that are complementary in shape and charge to a given biomolecular target.[26] After a lead compound has been identified through drug discovery, drug development involves bringing the drug to the market.[24] Drug discovery is related to pharmacoeconomics, which is the sub-discipline of health economics that considers the value of drugs[27][28] Pharmacoeconomics evaluates the cost and benefits of drugs in order to guide optimal healthcare resource allocation.[29] The techniques used for the discovery, formulation, manufacturing and quality control of drugs discovery is studied by pharmaceutical engineering, a branch of engineering.[30]Safety pharmacology specialises in detecting and investigating potential undesirable effects of drugs.[31]
The drug discovery cycle
United States Pharmacopoeia. In the European Union, the main body that regulates pharmaceuticals is the EMA, and they enforce standards set by the European Pharmacopoeia
.
The metabolic stability and the reactivity of a library of candidate drug compounds have to be assessed for drug metabolism and toxicological studies. Many methods have been proposed for quantitative predictions in drug metabolism; one example of a recent computational method is SPORCalc.[32] A slight alteration to the chemical structure of a medicinal compound could alter its medicinal properties, depending on how the alteration relates to the structure of the substrate or receptor site on which it acts: this is called the structural activity relationship (SAR). When a useful activity has been identified, chemists will make many similar compounds called analogues, to try to maximize the desired medicinal effect(s). This can take anywhere from a few years to a decade or more, and is very expensive.[33] One must also determine how safe the medicine is to consume, its stability in the human body and the best form for delivery to the desired organ system, such as tablet or aerosol. After extensive testing, which can take up to six years, the new medicine is ready for marketing and selling.[33]
Because of these long timescales, and because out of every 5000 potential new medicines typically only one will ever reach the open market, this is an expensive way of doing things, often costing over 1 billion dollars. To recoup this outlay pharmaceutical companies may do a number of things:[33]
Carefully research the demand for their potential new product before spending an outlay of company funds.[33]
Obtain a patent on the new medicine preventing other companies from producing that medicine for a certain allocation of time.[33]
The inverse benefit law describes the relationship between a drugs therapeutic benefits and its marketing.
When designing drugs, the placebo effect must be considered to assess the drug's true therapeutic value.
Drug development uses techniques from medicinal chemistry to chemically design drugs. This overlaps with the biological approach of finding targets and physiological effects.
Wider contexts
Pharmacology can be studied in relation to wider contexts than the physiology of individuals. For example,
pharmaceuticals and personal care products in the environment.[37]
Drugs may also have ethnocultural importance, so
ethnopharmacology studies the ethnic and cultural aspects of pharmacology.[38]
Emerging fields
Photopharmacology is an emerging approach in medicine in which drugs are activated and deactivated with light. The energy of light is used to change for shape and chemical properties of the drug, resulting in different biological activity.[39] This is done to ultimately achieve control when and where drugs are active in a reversible manner, to prevent side effects and pollution of drugs into the environment.[40][41]
Theory of pharmacology
dose response curves
. Dose response curves are studied extensively in pharmacology.
The study of chemicals requires intimate knowledge of the biological system affected. With the knowledge of cell biology and biochemistry increasing, the field of pharmacology has also changed substantially. It has become possible, through molecular analysis of receptors, to design chemicals that act on specific cellular signaling or metabolic pathways by affecting sites directly on cell-surface receptors (which modulate and mediate cellular signaling pathways controlling cellular function).
Chemicals can have pharmacologically relevant properties and effects.
Network pharmacology is a subfield of pharmacology that combines principles from pharmacology, systems biology, and network analysis to study the complex interactions between drugs and targets (e.g., receptors or enzymes etc.) in biological systems. The topology of a biochemical reaction network determines the shape of drug
dose-response curve[42] as well as the type of drug-drug interactions,[43]
thus can help designing efficient and safe therapeutic strategies. The topology Network pharmacology utilizes computational tools and network analysis algorithms to identify drug targets, predict drug-drug interactions, elucidate signaling pathways, and explore the polypharmacology of drugs.
Pharmacodynamics is defined as how the body reacts to the drugs. Pharmacodynamics theory often investigates the
binding affinity of ligands to their receptors. Ligands can be agonists, partial agonists or antagonists
at specific receptors in the body. Agonists bind to receptors and produce a biological response, a partial agonist produces a biological response lower than that of a full agonist, antagonists have affinity for a receptor but do not produce a biological response.
The ability of a ligand to produce a biological response is termed efficacy, in a dose-response profile it is indicated as percentage on the y-axis, where 100% is the maximal efficacy (all receptors are occupied).
Binding affinity is the ability of a ligand to form a ligand-receptor complex either through weak attractive forces (reversible) or covalent bond (irreversible), therefore efficacy is dependent on binding affinity.
Potency of drug is the measure of its effectiveness, EC50 is the drug concentration of a drug that produces an efficacy of 50% and the lower the concentration the higher the potency of the drug therefore EC50 can be used to compare potencies of drugs.
Medication is said to have a narrow or wide
tumors
.
The effect of drugs can be described with Loewe additivity which is one of several common reference models.[43]
Pharmacokinetics is the study of the bodily absorption, distribution, metabolism, and excretion of drugs.[44]
When describing the pharmacokinetic properties of the chemical that is the active ingredient or active pharmaceutical ingredient (API), pharmacologists are often interested in L-ADME:
Liberation – How is the API disintegrated (for solid oral forms (breaking down into smaller particles), dispersed, or dissolved from the medication?
Distribution – How does the API spread through the organism?
Metabolism – Is the API converted chemically inside the body, and into which substances. Are these active (as well)? Could they be toxic?
Excretion – How is the API excreted (through the bile, urine, breath, skin)?
Drug metabolism is assessed in pharmacokinetics and is important in drug research and prescribing.
Pharmacokinetics is the movement of the drug in the body, it is usually described as 'what the body does to the drug' the physico-chemical properties of a drug will affect the rate and extent of absorption, extent of distribution, metabolism and elimination. The drug needs to have the appropriate molecular weight, polarity etc. in order to be absorbed, the fraction of a drug the reaches the systemic circulation is termed bioavailability, this is simply a ratio of the peak plasma drug levels after oral administration and the drug concentration after an IV administration(first pass effect is avoided and therefore no amount drug is lost). A drug must be lipophilic (lipid soluble) in order to pass through biological membranes this is true because biological membranes are made up of a lipid bilayer (phospholipids etc.) Once the drug reaches the blood circulation it is then distributed throughout the body and being more concentrated in highly perfused organs.
In the United States, the Food and Drug Administration (FDA) is responsible for creating guidelines for the approval and use of drugs. The FDA requires that all approved drugs fulfill two requirements:
The drug must be found to be effective against the disease for which it is seeking approval (where 'effective' means only that the drug performed better than placebo or competitors in at least two trials).
The drug must meet safety criteria by being subject to animal and controlled human testing.
Gaining FDA approval usually takes several years. Testing done on animals must be extensive and must include several species to help in the evaluation of both the effectiveness and toxicity of the drug. The dosage of any drug approved for use is intended to fall within a range in which the drug produces a therapeutic effect or desired outcome.[45]
The safety and effectiveness of prescription drugs in the U.S. are regulated by the federal
from the original on 6 August 2020. Retrieved 21 July 2020.
^Sertürner F (1805). "Untitled letter to the editor". Journal der Pharmacie für Aerzte, Apotheker und Chemisten (Journal of Pharmacy for Physicians, Apothecaries, and Chemists). 13: 229–243. Archived from the original on 17 August 2016.; see especially "III. Säure im Opium" (acid in opium), pp. 234–235, and "I. Nachtrag zur Charakteristik der Säure im Opium" (Addendum on the characteristics of the acid in opium), pp. 236–241.
^Roeland van Wijk et al., Non-monotonic dynamics and crosstalk in signaling pathways and their implications for pharmacology. Scientific Reports 5:11376 (2015) doi: 10.1038/srep11376
^ abMehrad Babaei et al., Biochemical reaction network topology defines dose-dependent Drug–Drug interactions. Comput Biol Med 155:106584 (2023) doi: 10.1016/j.compbiomed.2023.106584
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