This article is about the science. For the book type ("a pharmacology"), see Materia medica.
Pharmacology is the branch of biology concerned with the study of drug action, where a drug can be broadly defined as any man-made, natural, or endogenous (from within body) molecule which exerts a biochemical or physiological effect on the cell, tissue, organ, or organism (sometimes the word pharmacon is used as a term to encompass these endogenous and exogenousbioactive species). More specifically, it is the study of the interactions that occur between a living organism and chemicals that affect normal or abnormal biochemical function. If substances have medicinal properties, they are considered pharmaceuticals.
The field encompasses drug composition and properties, synthesis and drug design, molecular and cellular mechanisms, organ/systems mechanisms, signal transduction/cellular communication, molecular diagnostics, interactions, toxicology, 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 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 are their distinctions between direct-patient care, for pharmacy practice, and the science-oriented research field, driven by pharmacology.
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. Clinical pharmacology owes much of its foundation to the work of William Withering. Pharmacology as a scientific discipline did not further advance until the mid-19th century amid the great biomedical resurgence of that period. 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. The first pharmacology department was set up by Rudolf Buchheim in 1847, in recognition of the need to understand how therapeutic drugs and poisons produced their effects.
Early pharmacologists focused on natural substances, mainly plant extracts. Pharmacology developed in the 19th century as a biomedical science that applied the principles of scientific experimentation to therapeutic contexts. Today pharmacologists use genetics, molecular biology, chemistry, and other advanced tools to transform information about molecular mechanisms and targets into therapies directed against disease, defects or pathogens, and create methods for preventative care, diagnostics, and ultimately personalized medicine.
The discipline of pharmacology can be divided into many sub disciplines each with a specific focus.
Clinical pharmacology is the basic science of pharmacology with an added focus on the application of pharmacological principles and methods in the medical clinic and towards patient care and outcomes.
Neuropharmacology is the study of the effects of medication on central and peripheral nervous system functioning.
Psychopharmacology, also known as behavioral pharmacology, is the study of the effects of medication on the psyche (psychology), observing changed behaviors of the body and mind, and how molecular events are manifest in a measurable behavioral form. Psychopharmacology is an interdisciplinary field which studies behavioral effects of psychoactive drugs. 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. Another goal of behavioral pharmacology is to develop animal behavioral models to screen chemical compounds with therapeutic potentials. People in this field (called behavioral pharmacologists) typically use small animals (e.g. rodents) to study psychotherapeutic drugs such as antipsychotics, antidepressants and anxiolytics, and drugs of abuse such as nicotine, cocaine and methamphetamine. Ethopharmacology (not to be confused with ethnopharmacology) is a term which has been in use since the 1960s and derives from the Greek word ἦθος ethos meaning character and "pharmacology" the study of drug actions and mechanism.
Cardiovascular pharmacology is the study of the effects of drugs on the entire cardiovascular system, including the heart and blood vessels.
Pharmacogenetics is clinical testing of genetic variation that gives rise to differing response to drugs.
Pharmacogenomics is the application of genomic technologies to drug discovery and further characterization of older drugs.
Pharmacoepidemiology is the study of the effects of drugs in large numbers of people.
Safety pharmacology specialises in detecting and investigating potential undesirable pharmacodynamic effects of new chemical entities (NCEs) on physiological functions in relation to exposure in the therapeutic range and above.
Systems pharmacology is the coding system principles in the field of pharmacology.
Toxicology is the study of the adverse effects, molecular targets, and characterization of drugs or any chemical substance in excess (including those beneficial in lower doses).
Theoretical pharmacology is a relatively new and rapidly expanding field of research activity in which many of the techniques of computational chemistry, in particular computational quantum chemistry and the method of molecular mechanics, are proving to be of great value. Theoretical pharmacologists aim at rationalizing the relation between the activity of a particular drug, as observed experimentally, and its structural features as derived from computer experiments. They aim to find structure—activity relations. Furthermore, on the basis of the structure of a given organic molecule, the theoretical pharmacologist aims at predicting the biological activity of new drugs that are of the same general type as existing drugs. More ambitiously, it aims to predict entirely new classes of drugs, tailor-made for specific purposes.
Posology is the study of how medicines are dosed. This depends upon various factors including age, climate, weight, sex, elimination rate of drug, genetic polymorphism and time of administration. It is derived from the Greek words πόσος posos meaning "how much?" and -λογία -logia "study of".
Pharmacognosy is a branch of pharmacology dealing especially with the composition, use, and development of medicinal substances of biological origin and especially medicinal substances obtained from plants.
Environmental pharmacology is a new discipline. Focus is being given to understand gene–environment interaction, drug-environment interaction and toxin-environment interaction. There is a close collaboration between environmental science and medicine in addressing these issues, as healthcare itself can be a cause of environmental damage or remediation. Human health and ecology are intimately related. Demand for more pharmaceutical products may place the public at risk through the destruction of species. The entry of chemicals and drugs into the aquatic ecosystem is a more serious concern today. In addition, the production of some illegal drugs pollutes drinking water supply by releasing carcinogens. This field is intimately linked with Public Health fields.
Experimental pharmacology involves the study of pharmacology through bioassay, to test the efficacy and potency of a drug.
Dental pharmacology relates to the study of drugs commonly used in the treatment of dental disease.
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).
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 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?
- Absorption – How is the API absorbed (through the skin, the intestine, the oral mucosa)?
- 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)?
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 antiepileptics, aminoglycosideantibiotics). Most anti-cancer drugs have a narrow therapeutic margin: toxic side-effects are almost always encountered at doses used to kill tumors.
Medicine development and safety testing
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 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.[dead link] If the chemical structure of a medicinal compound is altered slightly, this could slightly or dramatically alter the medicinal properties of the compound depending on the level of alteration as it relates to the structural composition of the substrate or receptor site on which it exerts its medicinal effect, a concept referred to as the structural activity relationship (SAR). This means that when a useful activity has been identified, chemists will make many similar compounds called analogues, in an attempt to maximize the desired medicinal effect(s) of the compound. This development phase can take anywhere from a few years to a decade or more and is very expensive.
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 delivery to the desired organ system, like tablet or aerosol. After extensive testing, which can take up to 6 years, the new medicine is ready for marketing and selling.
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, often costing over 1 billion dollars. To recoup this outlay pharmaceutical companies may do a number of things:
- Carefully research the demand for their potential new product before spending an outlay of company funds.
- Obtain a patent on the new medicine preventing other companies from producing that medicine for a certain allocation of time.
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 (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.
The safety and effectiveness of prescription drugs in the U.S. is regulated by the federal Prescription Drug Marketing Act of 1987.
The Medicines and Healthcare products Regulatory Agency (MHRA) has a similar role in the UK.
Students of pharmacology are trained as biomedical scientists, studying the effects of drugs on living organisms. This can lead to new drug discoveries, as well as a better understanding of the way in which the human body works.
Students of pharmacology must have detailed working knowledge of aspects in physiology, pathology and chemistry. During a typical degree they will cover areas such as (but not limited to) biochemistry, cell biology, basic physiology, genetics and the Central Dogma, medical microbiology, neuroscience, and depending on the department's interests, bio-organic chemistry, or chemical biology.
Modern Pharmacology is highly interdisciplinary. Graduate programs accept students from most biological and chemical backgrounds. With the increasing drive towards biophysical and computational research to describe systems, pharmacologists may even consider themselves mainly physical scientists. In many instances, Analytical Chemistry is closely related to the studies and needs of pharmacological research. Therefore, many institutions will include pharmacology under a Chemistry or Biochemistry Department, especially if a separate Pharmacology Dept. does not exist. What makes an institutional department independent of another, or exist in the first place, is usually an artifact of historical times.
Whereas a pharmacy student will eventually work in a pharmacy dispensing medications, a pharmacologist will typically work within a laboratory setting. Careers for a pharmacologist include academic positions (medical and non-medical), governmental positions, private industrial positions, science writing, scientific patents and law, consultation, biotech and pharmaceutical employment, the alcohol industry, food industry, forensics/law enforcement, public health, and environmental/ecological sciences.
The word "pharmacology" is derived from Greekφάρμακον, pharmakon, "drug, poison, spell" and -λογία, -logia "study of", "knowledge of" (cf. the etymology of pharmacy).
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WRITING A CLASSIFICATION PAPER
Classification is sorting things into groups or categories on a single basis of division. A classification paper says something meaningful about how a whole relates to parts, or parts relate to a whole. Like skimming, scanning, paraphrasing, and summarizing, classification requires the ability to group related words, ideas, and characteristics.
Prewriting and purpose
It is a rare writer, student or otherwise, who can sit down and draft a classification essay without prewriting. A classification paper requires that you create categories, so prewriting for a classification paper involves grouping things in different ways in order to discover what categories make the most sense for the purpose you intend.
An important part of creating useful categories is seeing the different ways that things can be grouped. For example, a list of United States presidents may be grouped in any number of ways, depending on your purpose. They might be classified by political party, age on taking office, or previous occupations, but you could just as well, depending on your purpose, classify them by the pets they keep or how they keep physically fit. If your purpose was to analyze presidential administrations, you would group information focusing on the presidents' more public actions–say, cabinet appointments and judicial nominations. On the other hand, if you intended to write about the private lives of presidents, you might select information about personal relationships or hobbies.
Make sure the categories you create have a single basis of classification and that the group fits the categories you propose. You may not, for example, write about twentieth century presidents on the basis of the kinds of pets they kept if some of those presidents did not keep pets. The group does not fit the category. If you intend to talk about all the presidents, you must reinvent the categories so that all the presidents fit into it. In the example below, the group is "all U.S. presidents" and the two categories are "those who kept pets and those who did not":
Some U.S. presidents have indulged their love of pets, keeping menageries of animals around the White House, and others have preferred the White House pet-free.
Alternatively, in the following example, the group is "twentieth century U.S. presidential pet-keepers" and the three categories are "dog lovers, cat lovers, and exotic fish enthusiasts."
Among the twentieth century presidents who kept pets, presidential pet-keepers can be classified as dog-lovers, cat-lovers, or exotic fish enthusiasts (for who can really love a fish?).
Developing a thesis
Once you have decided on your group, purpose, and categories, develop a thesis statement that does the following three things:
- names what group of people or things you intend to classify
- describes the basis of the classification
- labels the categories you have developed
Here is a thesis statement for a classification paper written for a Health and Human Fitness class that includes all three of the above elements, underlined:
Our last five U.S. presidents have practiced physical fitness regimens that varied from the very formal to the informal. They have been either regular private gym-goers, disciplined public joggers, or casual active sports enthusiasts.
Order is the way you arrange ideas to show how they relate to one another. For example, it is common to arrange facts and discussion points from most- to least-important or from least- to most-important, or from oldest to most recent or longest to shortest. The example thesis statement above is ordered from most- to least-formal physical fitness activities. There is no one right way; use an ordering system that seems best to suit your purpose and the type of information you are working with.
For example, suppose you are writing about the last five U.S. presidents for a psychology class. If you wish to show that these presidents' public decisions spring directly from negative issues in their personal relationships, you might order your information from most private to more public actions to clearly establish this connection. Or, if you wish to give the reader the impression that he is moving into increasingly intimate knowledge of personal presidential foibles, you may choose the reverse, ordering your information from public to private.
Signal phrases, or transitions, typically used for classification papers include the following:
- this type of...
- several kinds of...
- in this category...
- can be divided into...
- classified according to...
- is categorized by...
These phrases signal to the reader your intention to divide and sort things. They also contribute to the unity of the paper.
Classification requires that you invent (or discover) abstract categories, impose them on a concrete whole, and derive something new-a tall order that you can, nevertheless, manage if you resist the temptation to skip the brainstorming steps. Remember that clinical dissection is never an aim in itself; the point of classification is to reveal and communicate something meaningful.