Simplified molecular-input line-entry system
The simplified molecular-input line-entry system is a specification in the form of a line notation for describing the structure of chemical species using short ASCII strings. SMILES strings can be imported by most molecule editors for conversion back into two-dimensional drawings or three-dimensional models of the molecules; the original SMILES specification was initiated in the 1980s. It has since been extended. In 2007, an open standard called. Other linear notations include the Wiswesser line notation, ROSDAL, SYBYL Line Notation; the original SMILES specification was initiated by David Weininger at the USEPA Mid-Continent Ecology Division Laboratory in Duluth in the 1980s. Acknowledged for their parts in the early development were "Gilman Veith and Rose Russo and Albert Leo and Corwin Hansch for supporting the work, Arthur Weininger and Jeremy Scofield for assistance in programming the system." The Environmental Protection Agency funded the initial project to develop SMILES. It has since been modified and extended by others, most notably by Daylight Chemical Information Systems.
In 2007, an open standard called "OpenSMILES" was developed by the Blue Obelisk open-source chemistry community. Other'linear' notations include the Wiswesser Line Notation, ROSDAL and SLN. In July 2006, the IUPAC introduced the InChI as a standard for formula representation. SMILES is considered to have the advantage of being more human-readable than InChI; the term SMILES refers to a line notation for encoding molecular structures and specific instances should be called SMILES strings. However, the term SMILES is commonly used to refer to both a single SMILES string and a number of SMILES strings; the terms "canonical" and "isomeric" can lead to some confusion when applied to SMILES. The terms are not mutually exclusive. A number of valid SMILES strings can be written for a molecule. For example, CCO, OCC and CC all specify the structure of ethanol. Algorithms have been developed to generate the same SMILES string for a given molecule; this SMILES is unique for each structure, although dependent on the canonicalization algorithm used to generate it, is termed the canonical SMILES.
These algorithms first convert the SMILES to an internal representation of the molecular structure. Various algorithms for generating canonical SMILES have been developed and include those by Daylight Chemical Information Systems, OpenEye Scientific Software, MEDIT, Chemical Computing Group, MolSoft LLC, the Chemistry Development Kit. A common application of canonical SMILES is indexing and ensuring uniqueness of molecules in a database; the original paper that described the CANGEN algorithm claimed to generate unique SMILES strings for graphs representing molecules, but the algorithm fails for a number of simple cases and cannot be considered a correct method for representing a graph canonically. There is no systematic comparison across commercial software to test if such flaws exist in those packages. SMILES notation allows the specification of configuration at tetrahedral centers, double bond geometry; these are structural features that cannot be specified by connectivity alone and SMILES which encode this information are termed isomeric SMILES.
A notable feature of these rules is. The term isomeric SMILES is applied to SMILES in which isotopes are specified. In terms of a graph-based computational procedure, SMILES is a string obtained by printing the symbol nodes encountered in a depth-first tree traversal of a chemical graph; the chemical graph is first trimmed to remove hydrogen atoms and cycles are broken to turn it into a spanning tree. Where cycles have been broken, numeric suffix labels are included to indicate the connected nodes. Parentheses are used to indicate points of branching on the tree; the resultant SMILES form depends on the choices: of the bonds chosen to break cycles, of the starting atom used for the depth-first traversal, of the order in which branches are listed when encountered. Atoms are represented by the standard abbreviation of the chemical elements, in square brackets, such as for gold. Brackets may be omitted in the common case of atoms which: are in the "organic subset" of B, C, N, O, P, S, F, Cl, Br, or I, have no formal charge, have the number of hydrogens attached implied by the SMILES valence model, are the normal isotopes, are not chiral centers.
All other elements must be enclosed in brackets, have charges and hydrogens shown explicitly. For instance, the SMILES for water may be written as either O or. Hydrogen may be written as a separate atom; when brackets are used, the symbol H is added if the atom in brackets is bonded to one or more hydrogen, followed by the number of hydrogen atoms if greater than 1 by the sign + for a positive charge or by - for a negative charge. For example, for ammonium. If there is more than one charge, it is written as digit.
Route of administration
A route of administration in pharmacology and toxicology is the path by which a drug, poison, or other substance is taken into the body. Routes of administration are classified by the location at which the substance is applied. Common examples include intravenous administration. Routes can be classified based on where the target of action is. Action may be enteral, or parenteral. Route of administration and dosage form are aspects of drug delivery. Routes of administration are classified by application location; the route or course the active substance takes from application location to the location where it has its target effect is rather a matter of pharmacokinetics. Exceptions include the transdermal or transmucosal routes, which are still referred to as routes of administration; the location of the target effect of active substances are rather a matter of pharmacodynamics. An exception is topical administration, which means that both the application location and the effect thereof is local. Topical administration is sometimes defined as both a local application location and local pharmacodynamic effect, sometimes as a local application location regardless of location of the effects.
Administration through the gastrointestinal tract is sometimes termed enteral or enteric administration. Enteral/enteric administration includes oral and rectal administration, in the sense that these are taken up by the intestines. However, uptake of drugs administered orally may occur in the stomach, as such gastrointestinal may be a more fitting term for this route of administration. Furthermore, some application locations classified as enteral, such as sublingual and sublabial or buccal, are taken up in the proximal part of the gastrointestinal tract without reaching the intestines. Enteral administration can be used for systemic administration, as well as local, such as in a contrast enema, whereby contrast media is infused into the intestines for imaging. However, for the purposes of classification based on location of effects, the term enteral is reserved for substances with systemic effects. Many drugs as tablets, capsules, or drops are taken orally. Administration methods directly into the stomach include those by gastric feeding tube or gastrostomy.
Substances may be placed into the small intestines, as with a duodenal feeding tube and enteral nutrition. Enteric coated tablets are designed to dissolve in the intestine, not the stomach, because the drug present in the tablet causes irritation in the stomach; the rectal route is an effective route of administration for many medications those used at the end of life. The walls of the rectum absorb many medications and effectively. Medications delivered to the distal one-third of the rectum at least avoid the "first pass effect" through the liver, which allows for greater bio-availability of many medications than that of the oral route. Rectal mucosa is vascularized tissue that allows for rapid and effective absorption of medications. A suppository is a solid dosage form. In hospice care, a specialized rectal catheter, designed to provide comfortable and discreet administration of ongoing medications provides a practical way to deliver and retain liquid formulations in the distal rectum, giving health practitioners a way to leverage the established benefits of rectal administration.
The parenteral route is any route, not enteral. Parenteral administration can be performed by injection, that is, using a needle and a syringe, or by the insertion of an indwelling catheter. Locations of application of parenteral administration include: central nervous systemepidural, e.g. epidural anesthesia intracerebral direct injection into the brain. Used in experimental research of chemicals and as a treatment for malignancies of the brain; the intracerebral route can interrupt the blood brain barrier from holding up against subsequent routes. Intracerebroventricular administration into the ventricular system of the brain. One use is as a last line of opioid treatment for terminal cancer patients with intractable cancer pain. Epicutaneous, it can be used both for local effect as in allergy testing and typical local anesthesia, as well as systemic effects when the active substance diffuses through skin in a transdermal route. Sublingual and buccal medication administration is a way of giving someone medicine orally.
Sublingual administration is. The word "sublingual" means "under the tongue." Buccal administration involves placement of the drug between the cheek. These medications can come in the form of films, or sprays. Many drugs are designed for sublingual administration, including cardiovascular drugs, barbiturates, opioid analgesics with poor gastrointestinal bioavailability and vitamins and minerals. Extra-amniotic administration, between the endometrium and fetal membranes nasal administration (th
A receptor antagonist is a type of receptor ligand or drug that blocks or dampens a biological response by binding to and blocking a receptor rather than activating it like an agonist. They are sometimes called blockers. In pharmacology, antagonists have affinity but no efficacy for their cognate receptors, binding will disrupt the interaction and inhibit the function of an agonist or inverse agonist at receptors. Antagonists mediate their effects by binding to the active site or to the allosteric site on a receptor, or they may interact at unique binding sites not involved in the biological regulation of the receptor's activity. Antagonist activity may be reversible or irreversible depending on the longevity of the antagonist–receptor complex, which, in turn, depends on the nature of antagonist–receptor binding; the majority of drug antagonists achieve their potency by competing with endogenous ligands or substrates at structurally defined binding sites on receptors. The English word antagonist in pharmaceutical terms comes from the Greek ἀνταγωνιστής – antagonistēs, "opponent, villain, rival", derived from anti- and agonizesthai.
Biochemical receptors are large protein molecules that can be activated by the binding of a ligand such as a hormone or a drug. Receptors can be membrane-bound, as cell surface receptors, or inside the cell as intracellular receptors, such as nuclear receptors including those of the mitochondrion. Binding occurs as a result of non-covalent interactions between the receptor and its ligand, at locations called the binding site on the receptor. A receptor may contain one or more binding sites for different ligands. Binding to the active site on the receptor regulates receptor activation directly; the activity of receptors can be regulated by the binding of a ligand to other sites on the receptor, as in allosteric binding sites. Antagonists mediate their effects through receptor interactions by preventing agonist-induced responses; this may be accomplished by binding to the allosteric site. In addition, antagonists may interact at unique binding sites not involved in the biological regulation of the receptor's activity to exert their effects.
The term antagonist was coined to describe different profiles of drug effects. The biochemical definition of a receptor antagonist was introduced by Ariens and Stephenson in the 1950s; the current accepted definition of receptor antagonist is based on the receptor occupancy model. It narrows the definition of antagonism to consider only those compounds with opposing activities at a single receptor. Agonists were thought to turn "on" a single cellular response by binding to the receptor, thus initiating a biochemical mechanism for change within a cell. Antagonists were thought to turn "off" that response by'blocking' the receptor from the agonist; this definition remains in use for physiological antagonists, substances that have opposing physiological actions, but act at different receptors. For example, histamine lowers arterial pressure through vasodilation at the histamine H1 receptor, while adrenaline raises arterial pressure through vasoconstriction mediated by alpha-adrenergic receptor activation.
Our understanding of the mechanism of drug-induced receptor activation and receptor theory and the biochemical definition of a receptor antagonist continues to evolve. The two-state model of receptor activation has given way to multistate models with intermediate conformational states; the discovery of functional selectivity and that ligand-specific receptor conformations occur and can affect interaction of receptors with different second messenger systems may mean that drugs can be designed to activate some of the downstream functions of a receptor but not others. This means efficacy may depend on where that receptor is expressed, altering the view that efficacy at a receptor is receptor-independent property of a drug. By definition, antagonists display no efficacy to activate the receptors they bind. Antagonists do not maintain the ability to activate a receptor. Once bound, antagonists inhibit the function of agonists, inverse agonists, partial agonists. In functional antagonist assays, a dose-response curve measures the effect of the ability of a range of concentrations of antagonists to reverse the activity of an agonist.
The potency of an antagonist is defined by its half maximal inhibitory concentration. This can be calculated for a given antagonist by determining the concentration of antagonist needed to elicit half inhibition of the maximum biological response of an agonist. Elucidating an IC50 value is useful for comparing the potency of drugs with similar efficacies, however the dose-response curves produced by both drug antagonists must be similar; the lower the IC50 the greater the potency of the antagonist, the lower the concentration of drug, required to inhibit the maximum biological response. Lower concentrations of drugs may be associated with fewer side-effects; the affinity of an antagonist for its binding site, i.e. its ability to bind to a receptor, will determine the duration of inhibition of agonist activity. The affinity of an antagonist can be determined experimentally using Schild regression or for competitive antagonists in radioligand binding studies using the Cheng-Prusoff equation. Schild regression can be used to determine the nature of antagonism as beginning either competitive or non-competitive and Ki determination is independent of the affinity, efficacy or concentration of the agonist used.
However, it is important. The effects of receptor desensitization on reaching equilibrium must als
Reuptake is the reabsorption of a neurotransmitter by a neurotransmitter transporter located along the plasma membrane of an axon terminal or glial cell after it has performed its function of transmitting a neural impulse. Reuptake is necessary for normal synaptic physiology because it allows for the recycling of neurotransmitters and regulates the level of neurotransmitter present in the synapse, thereby controlling how long a signal resulting from neurotransmitter release lasts; because neurotransmitters are too large and hydrophilic to diffuse through the membrane, specific transport proteins are necessary for the reabsorption of neurotransmitters. Much research, both biochemical and structural, has been performed to obtain clues about the mechanism of reuptake; the first primary sequence of a reuptake protein was published in 1990. The technique for protein sequence determination relied upon the purification and cloning of the transporter protein in question, or expression cloning strategies in which transport function was used as an assay for cDNA species coding for that transporter.
After separation, it was realized. Further exploration in the field of reuptake proteins found that many of the transporters associated with important neurotransmitters within the body were very similar in sequence to the GABA and norepinephrine transporters; the members of this new family include transporters for dopamine, serotonin, proline and GABA. They were called Na+/Cl− dependent neurotransmitter transporters. Sodium and chloride ion dependence will be discussed in the mechanism of action. Using the commonalities among sequences and hydropathy plot analyses, it was predicted that there are 12 hydrophobic membrane spanning regions in the ‘Classical’ transporter family. In addition to this, the N- and C-termini exist in the intracellular space; these proteins all have an extended extracellular loop between the third and fourth transmembrane sequences. Site-directed chemical labeling experiments verified the predicted topological organization of the serotonin transporter. In addition to neurotransmitter transporters, many other proteins in both animals and prokaryotes were found with similar sequences, indicating a larger family of Neurotransmitter:Sodium Symporters.
One of these proteins, LeuT, from Aquifex aeolicus, was crystallized by Yamashita et al. with high resolution, revealing a molecule of leucine and two Na+ ions bound near the center of the protein. They found that the transmembrane helices 1 and 6 contained unwound segments in the middle of the membrane. Along with these two helices, TM helices 3 and 8 and the areas surrounding the unwound sections of 1 and 6 formed the substrate and sodium ion binding sites; the crystal structure revealed pseudo-symmetry in LeuT, in which the structure of TM helices 1-5 is reflected in the structure of helices 6-10. There is an extracellular cavity in the protein, into which protrudes a helical hairpin formed by extracellular loop EL4. In TM1, an aspartate distinguishes monoamine NSS transporters from amino acid transporters which contain a glycine at the same position. External and internal “gates” were assigned to pairs of negatively and positively charged residues in the extracellular cavity and near the cytoplasmic ends of TM helices 1 and 8.
The classic transporter proteins use transmembrane ion gradients and electrical potential to transport neurotransmitter across the membrane of the presynaptic neuron. Typical neurotransmitter sodium symport transporters, which are Na+ and Cl− ion dependent, take advantage of both Na+ and Cl− gradients, inwardly directed across the membrane; the ions flow down their concentration gradients, in many cases leading to transmembrane charge movement, enhanced by the membrane potential. These forces pull the neurotransmitter substrate into the cell against its own concentration gradient. At a molecular level, Na+ ions stabilize amino acid binding at the substrate site and hold the transporter in an outward-open conformation that allows substrate binding; the role of the Cl− ion in the symport mechanism has been proposed to be for stabilizing the charge of the symported Na+. After ion and substrate binding have taken place, some conformational change must occur. From the conformational differences between the structure of TMs 1-5 and that of TMs 6-10, from the identification of a substrate permeation pathway between the binding site of SERT and the cytoplasm, a mechanism for conformational change was proposed in which a four-helix bundle composed of TMs 1, 2, 6 and 7 changes its orientation within the rest of the protein.
A structure of LeuT in the inward-open conformation subsequently demonstrated that the major component of the conformational change represents movement of the bundle relative to the rest of the protein. The main objective of a reuptake inhibitor is to decrease the rate by which neurotransmitters are reabsorbed into the presynaptic neuron, increasing the concentration of neurotransmitter in the synapse; this increases neurotransmitter binding to pre- and postsynaptic neurotransmitter receptors. Depending on the neuronal system in question, a reuptake inhibitor can have drastic effects on cognition and behavior. Non-competitive inhibition of the bacterial homologue LeuT by tricyclic antidepressants resulted from binding of these inhibitors in the extracellular permeation pathway. However, the competitive nature of serotonin transport inhibition by antidepressants suggests that in neurotransmitter transporters, they bind in a site overlapping the substrate site. Horschitz et al. examined reuptake inhibitor selectivity among the rat serotonin reuptake protein expressed in human em
Spain the Kingdom of Spain, is a country located in Europe. Its continental European territory is situated on the Iberian Peninsula, its territory includes two archipelagoes: the Canary Islands off the coast of Africa, the Balearic Islands in the Mediterranean Sea. The African enclaves of Ceuta, Peñón de Vélez de la Gomera make Spain the only European country to have a physical border with an African country. Several small islands in the Alboran Sea are part of Spanish territory; the country's mainland is bordered to the south and east by the Mediterranean Sea except for a small land boundary with Gibraltar. With an area of 505,990 km2, Spain is the largest country in Southern Europe, the second largest country in Western Europe and the European Union, the fourth largest country in the European continent. By population, Spain is the fifth in the European Union. Spain's capital and largest city is Madrid. Modern humans first arrived in the Iberian Peninsula around 35,000 years ago. Iberian cultures along with ancient Phoenician, Greek and Carthaginian settlements developed on the peninsula until it came under Roman rule around 200 BCE, after which the region was named Hispania, based on the earlier Phoenician name Spn or Spania.
At the end of the Western Roman Empire the Germanic tribal confederations migrated from Central Europe, invaded the Iberian peninsula and established independent realms in its western provinces, including the Suebi and Vandals. The Visigoths would forcibly integrate all remaining independent territories in the peninsula, including Byzantine provinces, into the Kingdom of Toledo, which more or less unified politically and all the former Roman provinces or successor kingdoms of what was documented as Hispania. In the early eighth century the Visigothic Kingdom fell to the Moors of the Umayyad Islamic Caliphate, who arrived to rule most of the peninsula in the year 726, leaving only a handful of small Christian realms in the north and lasting up to seven centuries in the Kingdom of Granada; this led to many wars during a long reconquering period across the Iberian Peninsula, which led to the creation of the Kingdom of Leon, Kingdom of Castile, Kingdom of Aragon and Kingdom of Navarre as the main Christian kingdoms to face the invasion.
Following the Moorish conquest, Europeans began a gradual process of retaking the region known as the Reconquista, which by the late 15th century culminated in the emergence of Spain as a unified country under the Catholic Monarchs. Until Aragon had been an independent kingdom, which had expanded toward the eastern Mediterranean, incorporating Sicily and Naples, had competed with Genoa and Venice. In the early modern period, Spain became the world's first global empire and the most powerful country in the world, leaving a large cultural and linguistic legacy that includes more than 570 million Hispanophones, making Spanish the world's second-most spoken native language, after Mandarin Chinese. During the Golden Age there were many advancements in the arts, with world-famous painters such as Diego Velázquez; the most famous Spanish literary work, Don Quixote, was published during the Golden Age. Spain hosts the world's third-largest number of UNESCO World Heritage Sites. Spain is a secular parliamentary democracy and a parliamentary monarchy, with King Felipe VI as head of state.
It is a major developed country and a high income country, with the world's fourteenth largest economy by nominal GDP and sixteenth largest by purchasing power parity. It is a member of the United Nations, the European Union, the Eurozone, the Council of Europe, the Organization of Ibero-American States, the Union for the Mediterranean, the North Atlantic Treaty Organization, the Organisation for Economic Co-operation and Development, Organization for Security and Co-operation in Europe, the Schengen Area, the World Trade Organization and many other international organisations. While not an official member, Spain has a "Permanent Invitation" to the G20 summits, participating in every summit, which makes Spain a de facto member of the group; the origins of the Roman name Hispania, from which the modern name España was derived, are uncertain due to inadequate evidence, although it is documented that the Phoenicians and Carthaginians referred to the region as Spania, therefore the most accepted etymology is a Semitic-Phoenician one.
Down the centuries there have been a number of accounts and hypotheses: The Renaissance scholar Antonio de Nebrija proposed that the word Hispania evolved from the Iberian word Hispalis, meaning "city of the western world". Jesús Luis Cunchillos argues that the root of the term span is the Phoenician word spy, meaning "to forge metals". Therefore, i-spn-ya would mean "the land where metals are forged", it may be a derivation of the Phoenician I-Shpania, meaning "island of rabbits", "land of rabbits" or "edge", a reference to Spain's location at the end of the Mediterranean. The word in question means "Hyrax" due to Phoenicians confusing the two animals. Hispania may derive from the poetic use of the term Hesperia, reflecting the Greek perception of Italy as a "western land" or "land of the setting sun" (Hesperia
Regulation of therapeutic goods
The regulation of therapeutic goods, drugs and therapeutic devices, varies by jurisdiction. In some countries, such as the United States, they are regulated at the national level by a single agency. In other jurisdictions they are regulated at the state level, or at both state and national levels by various bodies, as is the case in Australia; the role of therapeutic goods regulation is designed to protect the health and safety of the population. Regulation is aimed at ensuring the safety and efficacy of the therapeutic goods which are covered under the scope of the regulation. In most jurisdictions, therapeutic goods must be registered. There is some degree of restriction of the availability of certain therapeutic goods depending on their risk to consumers. Modern drug regulation has historical roots in the response to the proliferation of universal antidotes which appeared in the wake of Mithridates' death. Mithridates had brought together physicians and shamans to concoct a potion that would make him immune to poisons.
Following his death, the Romans became keen on further developing the Mithridates potion's recipe. Mithridatium re-entered western society through multiple means; the first was through the Leechbook of the Bald, written somewhere between 900 and 950, which contained a formula for various remedies, including for a theriac. Additionally, theriac became a commercial good traded throughout Europe based on the works of Greek and Roman physicians; the resulting proliferation of various recipes needed to be curtailed in order to ensure that people were not passing off fake antidotes, which led to the development of government involvement and regulation. Additionally, the creation of these concoctions took on ritualistic form and were created in public and the process was observed and recorded, it was believed that if the concoction proved unsuccessful, it was due to the apothecaries’ process of making them and they could be held accountable because of the public nature of the creation. In the 9th century, many Muslim countries established an office of the hisba, which in addition to regulating compliance to Islamic principles and values took on the role of regulating other aspects of social and economic life, including the regulation of medicines.
Inspectors were appointed to employ oversight on those who were involved in the process of medicine creation and were given a lot of leigh weigh to ensure compliance and punishments were stringent. The first official'act', the'Apothecary Wares and Stuffs' Act was passed in 1540 by Henry VIII and set the foundation for others. Through this act, he encouraged physicians in his College of Physicians to appoint four people dedicated to inspecting what was being sold in apothecary shops. In conjunction with this first piece of legislation, there was an emergence of standard formulas for the creation of certain ‘drugs’ and ‘antidotes’ through Pharmacopoeias which first appeared in the form of a decree from Frederick II of Sicily in 1240 to use consistent and standard formulas; the first modern pharmacopoeias were the Florence Pharmacopoeia published in 1498, the Spanish Pharmacopoeia published in 1581 and the London Pharmacopoeia published in 1618. In the United States, regulation of drugs was a state right, as opposed to federal right.
But with the increase in fraudulent practices due to private incentives to maximize profits and poor enforcement of state laws, increased the need for stronger federal regulation. President Roosevelt signed the Federal Food and Drug Act in 1906 which established stricter standards. A 1911 Supreme Court decision, United States vs. Johnson, established that misleading statements were not covered under the FFDA; this directly led to Congress passing the Sherley Amendment which established a clearer definition of ‘misbranded’. Another key catalyst for advances in drug regulation were certain catastrophes that served as calls to the government to step in and impose regulations that would prevent repeats of those instances. One such instance occurred in 1937 when more than a hundred people died from using sulfanilamide elixir which had not gone through any safety testing; this directly led to the passing of the Federal, Food and Cosmetic Act in 1938. One other major catastrophe occurred in the late 1950s when Thalidomide, sold in Germany and sold around the world, led to 100,000 babies being born with various deformities.
The UK's Chief Medical Officer had established a group to look into safety of drugs on the market in 1959 prior to the crisis and was moving in the direction of address the problem of unregulated drugs entering the market. The crisis created a greater sense of emergency to establish safety and efficacy standards around the world; the UK started a temporary Committee on Safety of Drugs while they attempted to pass more comprehensive legislation. Though compliance and submission of drugs to the Committee on Safety of Drugs was not mandatory after, the pharmaceutical industry larger complied due to the thalidomide situation; the European Economic Commission passed a directive in 1965 in order to impose greater efficacy standards before marketing a drug. The United States congress passed the Drug Amendments Act of 1962 The Drug Amendments Act required the FDA to ensure that new drugs being introduced to the market had passed certain tests and standards. Both the EU and US acts introduced the requirements to ensure efficacy.
Of note, increased regulations and standards for testing led to greater innovation in pharm
A drug is any substance that, when inhaled, smoked, absorbed via a patch on the skin, or dissolved under the tongue causes a physiological change in the body. In pharmacology, a drug is a chemical substance of known structure, other than a nutrient of an essential dietary ingredient, when administered to a living organism, produces a biological effect. A pharmaceutical drug called a medication or medicine, is a chemical substance used to treat, prevent, or diagnose a disease or to promote well-being. Traditionally drugs were obtained through extraction from medicinal plants, but more also by organic synthesis. Pharmaceutical drugs may be used for a limited duration, or on a regular basis for chronic disorders. Pharmaceutical drugs are classified into drug classes—groups of related drugs that have similar chemical structures, the same mechanism of action, a related mode of action, that are used to treat the same disease; the Anatomical Therapeutic Chemical Classification System, the most used drug classification system, assigns drugs a unique ATC code, an alphanumeric code that assigns it to specific drug classes within the ATC system.
Another major classification system is the Biopharmaceutics Classification System. This classifies drugs according to their permeability or absorption properties. Psychoactive drugs are chemical substances that affect the function of the central nervous system, altering perception, mood or consciousness, they include alcohol, a depressant, the stimulants nicotine and caffeine. These three are the most consumed psychoactive drugs worldwide and are considered recreational drugs since they are used for pleasure rather than medicinal purposes. Other recreational drugs include hallucinogens and amphetamines and some of these are used in spiritual or religious settings; some drugs can cause addiction and all drugs can have side effects. Excessive use of stimulants can promote stimulant psychosis. Many recreational drugs are illicit and international treaties such as the Single Convention on Narcotic Drugs exist for the purpose of their prohibition. In English, the noun "drug" is thought to originate from Old French "drogue" deriving into "droge-vate" from Middle Dutch meaning "dry barrels", referring to medicinal plants preserved in them.
The transitive verb "to drug" arose and invokes the psychoactive rather than medicinal properties of a substance. A medication or medicine is a drug taken to cure or ameliorate any symptoms of an illness or medical condition; the use may be as preventive medicine that has future benefits but does not treat any existing or pre-existing diseases or symptoms. Dispensing of medication is regulated by governments into three categories—over-the-counter medications, which are available in pharmacies and supermarkets without special restrictions. In the United Kingdom, behind-the-counter medicines are called pharmacy medicines which can only be sold in registered pharmacies, by or under the supervision of a pharmacist; these medications are designated by the letter P on the label. The range of medicines available without a prescription varies from country to country. Medications are produced by pharmaceutical companies and are patented to give the developer exclusive rights to produce them; those that are not patented are called generic drugs since they can be produced by other companies without restrictions or licenses from the patent holder.
Pharmaceutical drugs are categorised into drug classes. A group of drugs will share a similar chemical structure, or have the same mechanism of action, the same related mode of action or target the same illness or related illnesses; the Anatomical Therapeutic Chemical Classification System, the most used drug classification system, assigns drugs a unique ATC code, an alphanumeric code that assigns it to specific drug classes within the ATC system. Another major classification system is the Biopharmaceutics Classification System; this groups drugs according to their permeability or absorption properties. Some religions ethnic religions are based on the use of certain drugs, known as entheogens, which are hallucinogens,—psychedelics, dissociatives, or deliriants; some drugs used as entheogens include kava which can act as a stimulant, a sedative, a euphoriant and an anesthetic. The roots of the kava plant are used to produce a drink, consumed throughout the cultures of the Pacific Ocean; some shamans from different cultures use entheogens, defined as "generating the divine within" to achieve religious ecstasy.
Amazonian shamans use ayahuasca a hallucinogenic brew for this purpose. Mazatec shamans have a long and continuous tradition of religious use of Salvia divinorum a psychoactive plant, its use is to facilitate visionary states of consciousness during spiritual healing sessions. Silene undulata is used as an entheogen, its root is traditionally used to induce vivid lucid dreams during the initiation process of shamans, classifying it a occurring oneirogen similar to the more well-known dream herb Calea ternifolia. Peyote a small spineless cactus has been a