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[[Image:Pharmacologyprism.jpg|thumb|right|300px|A variety of topics involved with pharmacology, including neuropharmacology, renal pharmacology, human metabolism, intracellular metabolism, and intracellular regulation.]]

'''Pharmacology''' (from the [[Greek language|Greek]] φάρμακον, ''pharmakon'', "[[drug]]"; and λόγος, ''logos'', "[[study]]") is the study of how [[drugs]] interact with living [[organisms]] to produce a change in function.<ref name=nagle>{{cite book|last=Nagle|first=Hinter|title=Pharmacology: An Introduction|year=2005|coauthors=Barbara Nagle|publisher=[[McGraw Hill]]|location=[[Boston]]|id=ISBN 0-07-312275-0}}</ref> If substances have [[medication|medicinal]] properties, they are considered '''pharmaceuticals'''. The field encompasses [[drug]] composition and properties, [[interaction]]s, [[toxicology]], therapy, and medical applications and antipathogenic capabilities. Pharmacology is not synonymous with [[pharmacy]], which is the name used for a profession, though in common usage the two terms are confused at times. Pharmacology deals with how drugs interact within biological systems to affect function, while pharmacy is a medical science concerned with the safe and effective use of medicines.

The origins of [[clinical pharmacology]] date back to the [[Middle Ages]] in [[Avicenna]]'s ''[[The Canon of Medicine]]'', [[Peter of Spain]]'s ''Commentary on Isaac'', and John of St Amand's ''Commentary on the Antedotary of Nicholas''.<ref>D. Craig Brater and Walter J. Daly (2000), "Clinical pharmacology in the Middle Ages: Principles that presage the 21st century", ''Clinical Pharmacology & Therapeutics'' '''67''' (5), p. 447-450 [448-449].</ref> Pharmacology as a scientific discipline did not further advance until the mid-19th century amid the great biomedical resurgence of that period.<ref name=rang2006> H P Rang. (2006) The receptor concept: pharmacology's big idea. ''Br J Pharmacol.'' 147 Suppl: S9–S16.</ref>  Before the second half of the nineteenth century, the remarkable potency and specificity of the actions of drugs such as [[morphine]], [[quinine]] and [[digitalis]] were explained vaguely and with reference to extraordinary chemical powers and affinities to certain organs or tissues.<ref name=AHM2002> Andreas-Holger M., Cay-Rüdiger P. and R. F. Halliwell (2002), The emergence of the drug receptor theory. ''Nature Reviews Drug Discovery'' 1, 637-641 </ref> The first pharmacology department was set up by [[Rudolf Buchheim|Buchheim]] in 1847, in recognition of the need to understand how therapeutic drugs and poisons produced their effects.<ref name=rang2006/> 

Early pharmacologists focused on natural substances, mainly plant extracts. Pharmacology developed in the 19th century as a new biomedical science that applied the principles of scientific experimentation to therapeutic contexts.<ref name=rang>{{cite book|last=Rang|first=H.P.|title=Pharmacology|year=2007|coauthors=M.M. Dale, J.M. Ritter, R.J. Flower|publisher=[[Elsevier]]|location=[[China]]|id=ISBN 0-443-06911-5}}</ref> 

==Divisions==
Pharmacology as a chemical science is practiced by pharmacologists. Subdisciplines include 
*''clinical pharmacology'' - the medical field of medication effects on humans
*[[neuropharmacology|''neuro-'']] and ''[[psychopharmacology]]'' (effects of medication on behavior and nervous system functioning), 
*''[[pharmacogenetics]]'' (clinical testing of genetic variation that gives rise to differing response to drugs)
*''[[pharmacogenomics]]'' (application of genomic technologies to new drug discovery and further characterization of older drugs)
*''[[pharmacoepidemiology]]'' (study of effects of drugs in large numbers of people)
*''[[toxicology]]'' study of harmful effects of drugs
*''theoretical pharmacology''
*''posology'' - how medicines are dosed
*''[[pharmacognosy]]'' - deriving medicines from plants

==Scientific background==
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 [[Receptor|receptors]], to design chemicals that act on specific cellular signaling or [[metabolic pathway]]s by affecting sites directly on cell-surface receptors (which modulate and mediate cellular signaling pathways controlling cellular function).

A chemical has, from the pharmacological point-of-view, various properties. [[Pharmacokinetics]] describes the effect of the body on the chemical (e.g. [[half-life]] and [[volume of distribution]]), and [[pharmacodynamics]] describes the chemical's effect on the body (desired or [[toxic]]).

When describing the pharmacokinetic properties of a chemical, pharmacologists are often interested in ''[[ADMET|ADME]]'':
* [[Absorption (digestive)|Absorption]] - How is the medication absorbed (through the [[skin]], the [[intestine]], the [[oral mucosa]])?
* [[Distribution (pharmacology)|Distribution]] - How does it spread through the organism?
* [[Drug metabolism|Metabolism]] - Is the medication converted chemically inside the body, and into which substances. Are these active? Could they be toxic?
* [[Excretion]] - How is the medication eliminated (through the bile, urine, breath, skin)?

Medication is said to have a narrow or wide ''[[therapeutic index]]'' or ''[[therapeutic window]]''. This describes the ratio of desired effect to toxic effect. A compound with a narrow therapeutic index (close to one) exerts its desired effect at a dose close to its toxic dose. A compound with a wide therapeutic index (greater than five) exerts its desired effect at a dose substantially below its toxic dose. Those with a narrow margin are more difficult to dose and administer, and may require [[therapeutic drug monitoring]] (examples are [[warfarin]], some [[antiepileptic]]s, [[aminoglycoside]] [[antibiotics]]). Most anti-[[cancer]] drugs have a narrow therapeutic margin: toxic side-effects are almost always encountered at doses used to kill [[tumor]]s.

==Medicine development and safety testing==
[[Drug development|Development of medication]] is a vital concern to [[medicine]], but also has strong [[economical]] and [[political]] implications. To protect the [[consumer]] and prevent abuse, many governments regulate the manufacture, sale, and administration of medication. In the [[United States]], the main body that regulates pharmaceuticals is the [[Food and Drug Administration]] and they enforce [[standards]] set by the [[United States Pharmacopoeia]]. In the [[European Union]], the main [[body]] that regulates pharmaceuticals is the [[EMEA]] and they enforce standards set by the [[European Pharmacopoeia]].

If the structure of a medicine is altered slightly, this will slightly alter the medicine's properties. This means when a useful activity has been identified, chemists will make many similar compounds called analogues, to attempt and maximise the beneficial effects. This development phase can take up to 3 years and is expensive.<ref name="ReviseALChem">{{cite book|last=Newton|first=David|coauthors=Alasdair Thorpe, Chris Otter|title=Revise A2 Chemistry|publisher=[[Heinemann Educational Publishers]]|date=2004|pages=page 1|month=|isbn =0-435-58347-6}}</ref>

These new analogues need to be developed. It needs to be determined how safe the medicine is for human consumption, its stability in the human body and the best form for dispensing, like tablet or aerosol. After extensive testing, which can take up to 6 years the new medicine is ready for marketing and selling.<ref name="ReviseALChem"/>

As a result of the long time required to develop analogues and test a new medicine and the fact that of every 5000 potential new medicines typically only one will ever reach the open market, this is an expensive way of doing things, costing millions of dollars. To recoup this outlay pharmaceutical companies may do a number of things:<ref name="ReviseALChem"/>
* Carefully research the demand for their potential new product before spending an outlay of company funds.<ref name="ReviseALChem"/>
* Obtain a patent on the new medicine preventing other companies from producing that medicine for a certain allocation of time.<ref name="ReviseALChem"/>

==Drug legislation and safety==
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.
# The drug must meet safety criteria by being subject to extensive animal and controlled human testing.

Gaining FDA approval usually takes several years to attain. 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.<ref name=nagle />

The safety and effectiveness of prescription drugs in the U.S. is regulated by the federal [[Prescription Drug Marketing Act (PDMA)|Prescription Drug Marketing Act of 1987]].

The [[Medicines and Healthcare products Regulatory Agency]] (MHRA) has a similar role in the UK.

==Education==
The study of pharmacology is offered in many universities worldwide.<br />
Again, pharmacology education programs differ from pharmacy programs. Students of pharmacology are trained as researchers, studying the effects of substances in order to better understand the mechanisms which might lead to new drug discoveries for example. Whereas a pharmacy student will eventually work in a pharmacy dispensing medications or some other position focused on the patient, pharmacologist will typically work within a laboratory setting.

Some higher educational institutions combine pharmacology and toxicology into a single program as does
[[Michigan State University]]. Michigan State University offers PhD training in Pharmacology & Toxicology with an optional Environmental Toxicology specialization. They also offer a [[Professional Science Masters]] in Integrative Pharmacology.

== See also ==
{{Portal|Pharmacy and Pharmacology}}
* [[Certain safety factor]]
* [[Cosmeceuticals]] 
* [[Crude drugs]]
* [[Drug design]]
* [[Drug Discovery Hit to Lead]]
* [[Enzyme inhibitor]]s
* [[Galenic formulation]]
* [[Herbalism]]
* [[International Union of Basic and Clinical Pharmacology]]
* [[List of dosage abbreviations]]
* [[List of withdrawn drugs]]
* [[Medicare Part D]] - the new prescription drug plan in the U.S.
* [[Medication]]
* [[Medicinal chemistry]]
* [[Neuropharmacology]] - The Molecular and Behavior study of Disease and Drugs in the Nervous System
* [[Neuropsychopharmacology]] - The detailed comprehensive study of mind, brain and drugs.
* [[Nicholas Culpeper]] - 17th century English Physician who translated and used 'pharmacological texts'.
* [[Pharmaceutical company]]
* [[Pharmacognosy]]
* [[Pharmacopoeia]]
* [[Pharmacotherapy]]
* [[Pharmakos]]
* [[Placebo (origins of technical term)]]
* [[Prescription drug]]
* [[Prescription Drug Marketing Act (PDMA)]]
* [[Psychopharmacology]] - medication for mental conditions
* [[Traditional Chinese Medicine]]

==Footnotes==
{{reflist}}

==External links==
* [http://www.pharmaceutical-business-review.com Pharmaceutical Business Review].
* [http://www.nndb.com/lists/623/000098329/ Pharmaceutical company profiles at NNDB].
* [http://www.ich.org/ International Conference on Harmonisation].
* [http://www.usp.org US Pharmacopeia].
* [http://www.medpharm.blogspot.com/ Medicine updates].
* [http://www.iuphar.org International Union of Basic and Clinical Pharmacology].
* [http://www.iuphar-db.org IUPHAR Committee on Receptor Nomenclature and Drug Classification].

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[[Category:Pharmacology]]
[[Category:Biochemistry]]