E number: a number following the letter E and assigned to food and drug additives in the European Union countries. A list of E compounds can be found at the UK Food Standards Agency website. Some examples include E100 - curcumin, E110 - yellow orange S, E123 - amaranth, E140 - chlorophyll, E150 - caramel, E153 - carbon black, E163 - anthocynanins and E170 - calcium carbonate.

EAA: excitatory amino acid

Eadie-Hofstee plot: a graphical representation of the effects of enzyme inhibitors and a method to determine the Michaelis constant (Km) and the limiting velocity (Vmax) from a set of measurements of velocity at different substrate concentrations. Vo is plotted against Vo/[S], a straight line is obtained and the slope is equal to -Km and the y-intercept is equal to Vmax.

Ear oedema: a small animal model of inflammation usually carried out in mice, rats or rabbits in which oedema is induced on the external ear by treatment with a pro-inflammatory agent. Typically, 5mg TPA (12-O-tetradecanoylphorbol acetate) is dissolved in 20 μl of acetone and applied in 10 μl volumes to both inner and outer surfaces of one ear of mice from which fur has been removed before application. The other ear may be left untreated or vehicle only applied to act as a control. Oedema will form quite quickly, ie about 4 hrs after application and the ears can then be removed from the anaesthetized animal and weighed to determine the extent of oedema.
Carlson RP, O'Neill-Davis L, Chang J and Lewis AJ. Modulation of mouse ear edema by cyclooxygenase and lipoxygenase inhibitors and other pharmacologic agents. Agents Actions (1985) 17; 197-204

Easson-Stedman hypothesis: also known as the three-point attachment theory, a theory which proposes that three groups or moieties in a drug molecule must simultaneously interact with three complimentary sites on the receptor molecule. This theory is based on the knowledge that three points are required to define the absolute stereochemical configuration of an asymmetric carbon atom and that different enantiomers often have markedly different biological effects.

Ebselen: also known as PZ51, an organoselenium compound (2-phenyl-1,2-benzisoselenazol-3(2H)-one), a peroxynitrate scavenger, neuroprotectant, 15-lipoxygenase inhibitor, anti-oxidant, anti-inflammatory and nonselective cyclooxygenase inhibitor.

EC numbers: a unique number allocated to an enzyme by the Enzyme Commission which is part of The International Union of Biochemistry and Molecular Biology and a way to distinguish between the many thousands of known enzymes.The number is in the format EC x.xx.xx.xx . The first digits denote the class to which the enzyme belongs, the second number indicates the subclass, the third number indicates the sub-subclass and the fourth in the serial number.

The six classes of enzymes are;
1 - oxidoreductases which catalyze oxidation and reduction reactions,
2 - transferases which catalyze transfers of groups from donors to acceptors,
3 - hydrolases which catlayse the hydrolysis of various bonds,
4 - lyases which cleave bonds by both non-hydrolytic and non-oxidative bonds.
5 - isomerases which catalyze the conformational changes occurring within a molecule, and
6 - ligases which connect two molecules with the hydrolysis of ATP or other energy-providing triphosphates.
A full list of known enzymes can be found at http://us.expasy.org/enzyme/.

EC₅₀ (ED₅₀): the effective concentration (or effective dose) which yields 50% of the maximal obtainable effect.

Ecbolic agents: also known as oxytocics, drugs used to induce labour and bring on birth.

Eccles, John Carew (1903 - 1997): Australian physician and physiologist who shared the 1963 Nobel Prize for Physiology or Medicine with Huxley and Hodgkin "for their discoveries concerning the ionic mechanisms involved in excitation and inhibition in the peripheral and central portions of the nerve cell membrane". He modified Dales principle to state that a neuron releases the same transmitter at all of its processes.
Eccles JC. Prog. Chemical transmission and Dale's principle. Brain Res (1986) 68; 3-13
http://nobelprize.org/medicine/laureates/1963/eccles-bio.html

Ecgonine: a colourless, crystalline, nitrogenous compound and a breakdown product of cocaine (when cocaine is hydrolyzed with acids or alkalis). Its presence in blood is usually taken as evidence of cocaine consumption.

Echinomycin: a cytotoxic polypeptide quinoxaline antibiotic isolated from Streptomyces echinatus. It binds to DNA, inhibits RNA synthesis and has antitumour and antibacterial activity.

Ecstasy: also known as E, an amphetamine-like recreational drug (3,4-methylenedioxymethamphetamine, MDMA) first patented in 1914 for intended use as an appetite suppressant but which never entered use therapeutically. Ecstasy has become popular in some nightclubs but suffered bad publicity in the mid to late 1990s due to a series of deaths attributed to its use. It shows similar euphoric effects to amphetamine.
http://www.mdma.net/index.html#ecstasy

Ectoparasiticide: compounds used to kill ectoparasites, small animals such as ticks, flies and mites which infest the skin and fur of animals and fish. Examples include the synthetic pyrethroid cypermethrin which is used topically to treat flies in cattle and horses, blowfly larvae, biting lice, ticks, headflies of sheep, mites of poultry as well as scabies and mange mites in cattle, sheep and dogs. Cypermethrin acts on the sodium pump of parasite nerve axons initially causing excitement, then paralysis and death.

Edetate: an ethylenediaminetetraacetate salt.

Edisylate: a 1,2-ethanedisulphonate salt. Examples include chlormethiazole edisylate used to treat psychoses.

EDR: equi-effective dose ratio

EDRF: endothelin-derived relaxing factor

Edrophonium: a peripherally acting, quaternary ammonium, short-acting anticholinesterase that reversibly binds only to the anionic site of cholinesterase to enhance the effects of acetylcholine and to enhance neuromuscular transmission. Edrophonium is used mainly in the diagnosis of myasthenia gravis.

EDTA: ethylenediaminetetraacetic acid

EMR: equi-effective molar concentration ratio

Effect hysteresis: a tendency for a pharmacological effect to occur after the plasma concentration of that drug which gives rise to the effects is reached. There are several reasons for this which are often additive. They include a delay in transportation of drug from the plasma via the artery, veins and capillaries to cells where it exerts its effects, the slow rate at which some drugs bind to and dissociate from their target receptors and the time taken for drugs to elicit a measurable effect. The latter point is typified by selective serotonin uptake inhibitors (SSRI) and tricyclic antidepressants which can take days or weeks for their affects to appear.

Effectomer: the part or fragment of a polypeptide or subunit of an enzyme via which a response is elicited.

Efferent: a neuron which conduct impulses away from the CNS. They are also known as motor neurons.

Efficacy: the capacity or power of a drug to produce a desired effect in a cell, tissue or organ.

Efficacy theory: a modification by Stephenson of Clark's occupation theory.
Stephenson RPA. A modification of receptor theory. Br J Pharmacol (1956) 11;379-393

Efflux: the outflow molecules or ions from a cell or tissue.

Efflux pump: energy-consuming cell membrane pumps which mediate the outflow of molecules from cells often to protect the cell from toxic chemicals. One example is multidrug resistant bacteria which can eject antibiotic molecules leading to them becoming resistant to antibiotics. Some compounds such as alkylaminoquinolines are known to inhibit these efflux pumps and make bacteria more susceptible to antibiotics.

EGF: epidermal growth factor

Ehrlich, Paul (1854-1915): a German physician who carried out a lot of pioneering research on antibacterial compounds and who shared the 1908 Nobel prize for Physiology or Medicine with Mechnikov 'in recognition of their work on immunity'. Ehrlich is generally accredited as establishing chemotherapy as a branch of medicine.
http://nobelprize.org/medicine/laureates/1908/ehrlich-bio.html

Eicosanoids: a class of bioactive autacoids derived from polyunsaturated acids, eg arachidonic acid which is derived from membrane phospholipids. Eicosanoids include prostaglandins (PG), thromboxanes (TX) and leukotrienes (LT). Prostaglandins originate in the seminal vesicles and were thought to come from the prostate gland, thromboxanes are synthesized in thrombocytes and contain an oxane ring rather than a cyclopentane ring seen in prostaglandins and leukotrienes were first detected in leukocytes and contain 3 double bonds (triene) in their chain. Eicosanoids are all potent vasoactive compounds and cause contraction or relaxation of various smooth muscles, mediate inflammation and participate in chemotaxis. They are not stored in tissues but are synthesized de novo from membrane phospholipids as and when needed. They are derived from arachidonic acid via three pathways. The cyclooxygenase pathway yields prostaglandins and thromboxanes, the 5-lipoxygenase pathway produces leukotrienes and the cytochrome P450-dependent monooxygenase pathway synthesizes epoxides such as epoxyeicosatetraenoic acid.

EL mice: an animal model of reflex epilepsy with complex partial seizures. These mice exhibit seizures following vestibular stimuli such as tossing them into the air or altering their balance. Their seizures, which appear to originate in the hippocampus or deep structures in the temporal lobe, may be completely blocked by phenytoin and phenobarbitone.

Elapid neurotoxins: toxins obtained from snakes from the genus Elapidae, a group of snakes which include the mambas and commonly found in Australia. Examples include notexin, taipoxin, textilotoxin which can be isolated from Oxyuranus scutellatus and Notechis scutatus scutatus (Australian taipan snake). Most elapid neurotoxins are presynaptic phospholipase A₂ neurotoxins meaning that they have phospholipase A₂ activity and cause presynaptic neuromuscular blockade.

Elastases: an family of endopeptidase enzymes (EC 3.4.21.36 - pancreatic elastase and EC 3.4.21.37 - leukocyte elastase) which cleaves proteins within their structure. They are important as they can breakdown connective tissues and are implicated in the development of connective tissue inflammation such as hereditary emphysema, chronic obstructive pulmonary disease, cystic fibrosis, adult respiratory distress syndrome, ischemic-reperfusion injury and rheumatoid arthritis.

Elastase inhibitors: compounds which can inhibit elastases and so inhibit the breakdown of connective tissues. They are being developed for the treatment of a range of diseases including chronic pulmonary obstructive disease and examples include sivelestat and ONO-6818 which are both neutrophil elastase inhibitors.

Electrical battle test:
Tedeschi RE et al. Effects of various centrally acting drugs on fighting behavior of mice. J Pharmacol Exp Ther (1959) 125; 28-34

Electrophorus: a genus of cypriniod fish (related to carp) which includes the electric eel (Electrophorus electricus). They are used to study ion channels as they contain electric organs (electroplax).

Electroplax cells: large cells from the electric organs (electroplax) of electric fish such as the electric eel (Electrophorus electrics) and electric rays (commonly Torpedo marmorata). The electroplax generates a powerful electric shock and comprises highly modified muscle cells that operate under the control of the nervous system which is mediated by ACh.

Electroshock-induced convulsions:

Electuary: a drug mixed with sugar and water or honey to form a pasty material suitable for oral administration. Electuaries were once used to treat all manner of disorders and often contained plant extracts.

Eledoisin: a peptide extracted from the posterior salivary glands of certain small octopi or obtained by synthesis. Its pharmacological actions are similar to those of substance P and it is a potent vasodilator which increases capillary permeability.

Elevated plus-maze (EPM): a raised four-armed maze built in the shape of a + used to test the effects of anxiolytic compounds. Two of the arms are covered, ie dark and two are open, ie light. Test animals such as rats or mice tend to spend most time in the covered areas as they do not like heights or brightly-lit open spaces. If they have been treated with anxiolytic compounds, they spend more time in the open areas and the number of times they cross the threshold from the dark to light areas can be counted. Generally speaking, the more crossings, the greater the anxiolytic effects of the compounds being tested. Anxiogenics show the opposite effects and antidepressants and neuroleptics have no effects on animal behaviour in this test.

Elevated X-maze: a widely used test apparatus for anxiety and drugs to treat it and represents a test based on unconditioned responses to a potentially dangerous environment. The x or + maze comprises two closed and two open arms with open arms facing each other. The height, luminosity and open space in the open arms is assumed to induce fear or anxiety in the animal (usually a mouse) and extent of anxiety is assessed by measuring the time the animal spends in the open and closed arms and the number of entries made into each arm. When mice are placed in the centre of the maze they tend to spend most of their time in the closed arms and avoid the open arms but after they have been treated with anxiolytics their fears disappear and they spend more time in the open.
Lister RG. The use of a plus-maze to measure anxiety in the mouse. Psychopharmacology (1987) 92;180-185

Elimination: a process in which the body gets rid of drugs and their metabolites. Elimination can be via a number of routes the most common of which is in the urine but other include the faeces, breath and sweat.

Elion, Gertrude B (1918-1999): American chemist who shared the 1988 Nobel Prize for Physiology or Medicine with Black and Hitchings "for their discoveries of important principles for drug treatment".
http://nobelprize.org/medicine/laureates/1988/elion-autobio.html

ELISA: enzyme-linked immunosorbent assay

Elizabeth collar: nothing much to do with pharmacology but the funny lampshade-looking collar put around the necks of cats, dogs and other companion animals after they have had surgery or wound treatment to stop then biting or licking the dressing or wound.

E_max: the maximal effect that an agonist can induce. This value varies with experimental circumstances and according to receptor density.

Embonates: also known as pamoates, salts of embonic acid and a base. Embonate salts are used in pharmaceutical formulations because they show slow dissolution and are useful in formulations where extended duration of action is required. Example include chlorpromazine embonate, metformin embonate and pyrantel embonate (for hookworm infections in animals).

Emetic: a compound which induced emesis, ie vomiting and which include apomorphine, syrup of ipecac and inorganic salts such as zinc sulphate. Emesis is desirable in the event of accidental or intentional ingestion of poisons.

Emetine: an emetogenic and an alkaloid present in ipecacuanha which has been used in the treatment of amoebiasis.

Emodin: also known as franglula emodin, rheum emodin, archin and frangulic acid, a potent tyrosine kinase inhibitor (1,3,8-trihydroxy-6-methyl-9,10-anthracenedione) which is obtained from rhubarb root. It is a cathartic present in Cascara sagrada and was originally introduced as such in 1870s to irritate the bowel and increase peristalsis. It can suppress the proliferation of tumour cells and has been shown to induce apoptosis of some tumour cells in vitro.
Jayasuriya H et al. Emodin, a protein tyrosine kinase inhibitor from Polygonum cuspidatum. J Natural Products (1992) 55; 696-698

Emollients: substances which soften and lubricate the skin and mucous membranes and which are most often incorporated into an ointment or cream. Examples include anhydrous lanolin, dimethicone, hydrophilic petroleum jelly, polyethylene glycols and white wax.

Empiric therapy: also known as presumptive therapy, the use of antimicrobials to treat infections when the identity of causative pathogen is not known. The choice of antimicrobial is usually based on experience of similar clinical situations previously encountered and on the need to start therapy as early as possible.

Emetogenic: a compound which induces vomiting. This may be induced intentionally such as after the consumption of a drug overdose. Examples include emetine and ipecacuanha (which contains two active alkaloids; emetine and cephaeline).

Emmenagogue: a substance that promotes or assists the flow of menstrual fluid often causing the easing of menstrual discomfort. Various herbal remedies appear to have emmenagogic actions.

Empathogen: a term used by Ralph Metzner to denote chemical agents inducing feelings of empathy which is an awareness of the thoughts, feelings, or states of mind of others. Probably the best known empathogen is ecstasy (MDMA) which stimulates the brain to rapidly secrete large amounts of serotonin.

EMR: equi-effective molar concentration ratio

Emulsion: a suspension of particles in a liquid vehicle.

Emulsifier: a surface active agent which promotes the formation of an emulsion which is a colloid in which both phases are liquids, ie a liquid suspended in a liquid. Emulsifiers are important in the preparation of drug formulations and include mixtures of mono- and diglycerides of palmitic and stearic acid, synthetic spermaceti wax and esters of ethylene glycol with stearine.

Enalapril: an angiotensin-converting enzyme inhibitor used clinically to treat essential and renovascular hypertension, congestive heart failure and to prevent symptomatic heart failure and ischaemia in patients with left ventricular dysfunction.

Enantiomers: also known as optical isomers, molecules which are non-superimposable mirror images of each other which means that the molecules are not equivalent or identical. Each enantiomer exhibits optical activity and each can rotate the plane polarized light in opposite directions. The two isomers show exactly the same physical properties but their biological activities can be markedly different.
   One example of the differences in biological activity of enantiomers is thalidomide, which was responsible for thousands of birth defects in the 1960s. It is a glutamic acid derivative which was prescribed to treat morning sickness in pregnancy. The S form is a teratogen and caused phocomelia (a birth defect in which the limbs do not properly form) and the R form is an effective sedative. (Thalidomide is currently used clinically to treat refractory myeloma as it has immunomodulatory and anti-inflammatory effects.) The seemingly small difference between the structures of the R and S forms was not understood sufficiently at the time it was initially prescribed but the differences in biological activity were immense.



Other examples of enantiomers with differing biological activity include omeprazole and esomeprazole, citalopram and escitalopram, levocetirizine and cetirizine, and levobupivacaine and bupivacaine.

Enantioselective: in chemical synthesis, methods and reagents used for the purpose of producing a specific enantiomer in preference to any other isomer. Enantioselective synthesis and catalysts are important as enantiomers often differ markedly in biological activity.

Endectocides: compounds used for the treatment of both internal and external parasites in veterinary pharmacology. Examples include abamectin (a mixture of avermectins) which is used to treat tapeworms in horses and heartworms in dogs.

Endocannabinoids: endogenous ligands for cannabinoid receptors. Examples include anandamide and 2-arachidonoylglycerol.

Endocannabinoid system: a system within the body comprising cannabinoid receptors, their endogenous ligands (endocannabinoids) and enzymes involved in endocannabinoid biosynthesis and inactivation. The endocannabinoid system is involved in intracellular events controlling the proliferation and apoptosis of numerous types of cancer cells, plays a role in sensorimotor and motivational aspects of behaviour and modulates cardiovascular function.
Giuffrida A, Piomelli D. The endocannabinoid system: a physiological perspective on its role in psychomotor control. Chem Phys Lipids 2000 Nov;108(1-2);151-8
De Petrocellis L,  Cascio MG and Di Marzo V. The endocannabinoid system: a general view and latest additions. British Journal of Pharmacology (2004) 141; 765-774

Endocrine: relating to the function of the glands that secrete hormones and the (largely metabolic) actions of these hormones on tissues.

Endomorphins: endogenous opioid peptides and μ-opioid receptor agonists which show high affinity for these receptors. Two are currently known (endomorphin 1 and endomorphin 2) and both are implicated in the mechanism of pain.
Okada Y, Tsuda Y, Bryant SD, Lazarus LH. Endomorphins and related opioid peptides. Vitam Horm (2002) 65;257-79

Endopeptidase-24.11: also known as enkephalinase, common acute lymphoblastic leukaemia antigen and (correctly) neprilysin, a membrane-bound zinc metallopeptidase ectoenzyme (EC 3.4.24.11) which extracellularly degrades neuropeptides and hormones such as the enkephalins and atrial natriuretic peptide and, because it is present in the thymus and lymph nodes, may inactivate immune system mediators. It has broad specificity and generally cleaves peptides on the amino side of hydrophobic residues.

Endopeptidase-24.11 inhibitors: compounds which inhibit endopeptidase-24.11 and so inhibitors of the degradation of neuropeptides and hormones such as enkephalin and atrial natriuretic peptides. They are being developed for the treatment of heart failure. Examples include candoxatrilat which inhibits atrial natriuretic factor degradation and promotes diuresis in patients with mild heart failure and the neutral endopeptidase inhibitor SCH 34826.

Endorphins: a class of endogenous peptides with morphine-like effects and natural ligands for opiate receptors.

Endothelins: a group of three related isopeptides, ET-1, ET-2 and ET-3.
- Endothelin 1, discovered in 1988, is an endogenous 21 amino acid potent vasoconstrictor peptide which modulates vascular tone. ET-1 produced constitutively by vascular endothelia especially in the lungs and is a smooth muscle mitogen and a pro-inflammatory mediator with potent profibrotic effects. It is implicated in the pathogenesis of various cardiovascular, renal, pulmonary and central nervous system diseases. It also participates in a range of cancer-related process such as cell proliferation, inhibition of apoptosis, matrix remodeling, bone deposition and metastases. It exhibits selectivity for the ET-A receptor.
- Endothelin 2 is an endogenous peptide found mainly in the kidneys and intestine. It exhibits similar selectivity for both ET-A and ET-B receptors.
- Endothelin 3 is an endogenous neuropeptide and potent vasoconstrictor. It exhibits selectivity for the putative ET-C receptor.
Kedzierski RM and Yanagisawa M. Endothelin system: the double-edged sword in health and disease. Ann Rev Pharmacol Toxicol (2001) 41; 851-876
Schiffrin EL. Endothelin: role in hypertension. Biol Res (1998) 31(3); 199-208

Endothelin converting enzyme (ECE): a group of about seven metallopeptidases. Probably the most important is ECE-1 (EC 3.4.24.71), a phosphoramidon-sensitive enzyme which converts the precursor big endothelin to endothelin (ET-1) by endoproteolytic cleavage between Trp21 and Val22 and this is the final step in the production of this very potent vasoconstrictor which is secreted constitutively by endothelial cells.

Endothelin converting enzyme inhibitors: compounds which inhibit the actions of endothelin converting enzyme and so potentiate the vasoconstrictor effects of endothelin-1. ECE inhibitors have potential use in the treatment of hypertension, chronic heart failure, restenosis, atherosclerosis, renal failure and cerebral vasospasm. Examples of non-peptide ECE inhibitors include examples of non-peptide inhibitors include phosphoramidon, FR901533, PD-069185, CGS-35066, SM-19712, CGS-30084 and Ro 0677447.
http://www.biomedcentral.com/content/pdf/cd-505289.pdf

Endothelin receptors: receptors for endothelin which are divided into two subtypes, ie ET-A and ET-B. ET-A receptors are located on smooth muscle cells and endothelin binding to them causes vasoconstriction, whereas ET-B receptors are located on the vascular endothelium and ligand binding to them causes vasodilation via the production of nitric oxide. This effects of ET-B receptors is thought to protect against excessive vasoconstriction by removing endothelin from the circulation.
http://www.iuphar-db.org/GPCR/ChapterMenuForward?chapterID=1283

Endothelin receptor antagonists (ETRA): compounds which block the binding of endothelin to endothelin receptors and so inhibit the vasoconstrictor actions of this peptide. Endothelin receptor antagonists are being developed to treat pulmonary arterial hypertension especially selective ET-A receptor antagonists.

Endothelium-derived relaxing factor (EDRF):

Endotoxin shock: shock (an acute disruption of circulatory function) due to release of endotoxins by gram-negative bacteria in the blood. It can be caused by abdominal and pelvic infections as complications of trauma or surgery. These endotoxins cause cardiac preload and afterload to increased and myocardial contractility to decrease. Blood flow is poor and vital organs such as the brain, heart, kidneys and liver may fail leading to death.

Endotoxins: toxic proteins or lipopolysaccharides which are released when microbes comprising them are lysed by host immune cells. They have a variety of actions such as the induction of shock and their effects are often lethal.

Endplate: the end of a motor neuron which transmits neuronal impulses to a muscle cell.

Endplate potential: the electrical potential induced in an endplate by a chemical neurotransmitter.

Enflurane: a volatile liquid inhalational anaesthetic similar to halothane bus less potent than halothane. It is used clinically to induce and maintain general anaesthesia for surgery in humans and animals.

EDRF: endothelium-derived relaxing factor

Enkephalins: a family of pentapetides and endogenous opioid peptides which have analgesic actions.

Enkephalinase: a membrane-bound metalloendoprotease (EC 3.4.24.11) which catalyzes the hydrolysis of enkephalins and degrades many biologically active peptides in various tissues. It is present in the brain, airways, red blood cells, the kidneys and the gastrointestinal tract with the highest concentration being localized in the duodenum and jejunum.

Enkephalin convertase: also known officially as carboxypeptidase E, a carboxypeptidase enzyme (EC 3.4.17.10) which converts enkephalin precursors to enkephalin and which is localized in chromaffin granules in the adrenals and in neuroendocrine tissue.

Enkephalin convertase inhibitors: compounds which inhibit enkephalin convertase. Examples include the potent inhibitor guanidinoethylmercaptosuccinic acid (GEMSA), guanidinopropylsuccinic acid and the irreversible inhibitor bromoacetyl-D-arginine.

Enkephalinase inhibitors: inhibitors of enkephalinase and compounds with antinociceptive actions because they protect endogenous enkephalins from degradation. Examples include acetorphan and thiorphan.
Patel A, Smith HJ, Sewell RD. Inhibitors of enkephalin-degrading enzymes as potential therapeutic agents. Prog Med Chem (1993) 30; 327-378

Enkephalinergic: relating to the synthesis, storage and release of enkephalins.

Enniatins: a class of cyclodepsipeptides including enniatins B and B4 obtained from the entomopathogenic fungus Verticillium hemipterigenum and which have antimalarial and cytotoxic activities.

Entactogen: a 'distinct' class of psychoactive compounds having actions somewhere between those of stimulants and hallucinogens. Examples include 3,4-methylenedioxymethamphetamine (MDMA, ecstacy) and its alpha-ethyl homologue MBDB. They are often used recreationally.

Enterotoxigenic: relating to organisms which produce enterotoxins which are protein toxins released by a microorganism in the intestines. Examples of enterotoxigenic microorganisms include E. Coli O157, Vibrio cholera and Yersinia enterocolitica.

Enteric coating: a special coating usually made of a polymer which is applied to tablets or capsules to prevent them from releasing their active component and to control the absorption of active components until they reach specific areas of the intestines

Enterohepatic circulation: a system in which drug which has been absorbed from the gut is transported from to the liver by the hepatic portal vein, is then excreted into the bile, released back into the gut only to be reabsorbed and returned to the liver. Enterohepatic circulation creates a reservoir of circulating drug which may account for up to about 20% of total drug in the body and delays the elimination of the drug from the body. This form of circulation is important for morphine and ethinylestradiol.

Enterostatin (ENT): also known as VPDPR, a protein produced by the pancreas after food consumption which inhibits insulin secretion. Enterostatin may regulate fat intake and reduce body weight.

Enterotoxins: substances produced by bacteria and which have toxic effects on the gastrointestinal system usually inducing vomiting and diarrhoea. Examples include Staphylococcal enterotoxins which cause food poisoning.

Enthanate: a heptanoate salt. Examples include testosterone enthanate.

Entheogens: drugs which are taken in the search for divine inspiration. They are supposed to help in the search for 'eternal truths'. They are mainly hallucinogens. Entheogens include psilocybin, psilocin and ergonovine.

Entorhinal cortex: a cortex located in the ventromedial portion of the temporal lobe which has connections with the hippocampus and various other cortical and subcortical structures. It forms an integral part of the medial temporal lobe memory system and damage to the entorhinal cortex is observed in the early stages of Alzheimer's disease and in temporal lobe epilepsy.

Entry inhibitor (EI): also known as fusion inhibitors, a class of antiretroviral drugs and compounds which inhibit the entry of viruses usually HIV-1 into cells. The entry of this virus into cells is a multi-step process involving attachment, co-receptor binding and fusion and inhibitors of each step have been identified. For example, ibalizumab is a postattachment inhibitor, maraviroc and vicriviroc are both CCR5 antagonists which HIV uses as a coreceptor to bind and enter macrophages and enfuvirtide, a biomimetic peptide which binds to GP41 preventing the formation of an entry pore for the virus capsid.
Kuritzkes DR. HIV-1 entry inhibitors: an overview. Curr Opin HIV AIDS (2009) Mar; 4(2): 82-7

Enzyme induction: the process by which some compounds increase the catalytic activity of enzymes.

Enzyme inhibition: the process by which some compounds decrease the catalytic activity of enzymes reversibly or irreversibly and a major mechanism for the actions of a broad range of drugs in the body.

Enzyme-linked immunosorbent assay (ELISA): an enzyme immunoassay used to detect small amounts of specific proteins and some other biological substances. ELISA involves forming a complex of an enzyme-linked antibody which specifically binds to the analyte to be assayed. The resulting enzyme-antibody-specific substance complex is assayed and the amount of the specific substance can be determined. Variations of ELISA include capture ELISA, competitive ELISA and sandwiched ELISA.

Eotaxin: a family of three C-C chemokines (eotaxin-1, eotaxin-2 and eotaxin-3) which are potent eosinophil-specific chemoattractants purified from bronchioalveolar lavage fluid of sensitized animal. Eotaxins have been identified in rodent models of asthma and in host responses against tumours.

Eotaxin inhibitors: inhibitors of the chemokine eotaxin and which are being developed for the treatment of asthma. They are usually antagonists of the cysteine-cysteine chemokine receptor-3 (CCR3) and can selectively inhibit the recruitment of eosinophils into tissues.

EPHAR: Federation of European Pharmacological Societies, a 'non-profit voluntary association established to advance research and education in the science of pharmacology and to promote co-operation between national/regional pharmacological societies in Europe and surrounding countries'.
http://www.ephar.org/

Ephaptic transmission: the transmission of a nerve impulse across an ephapse which is a site where two or more nerve cell processes (which could be axons or dendrites) touch without forming a typical synaptic contact.

Ephedrine: an indirectly acting sympathomimetic compound (a-[1-(methylamino)ethyl]benzene-methanol) used as a bronchodilator, vasoconstrictor, mydriatic and CNS stimulant. Clinically it is used to treat reversible airways obstruction and in the form of drops to treat nasal obstruction.

Epibatidine: an alkaloid present in the skin of a common South American poisonous frog (Epipedobates triclor) and approximately 200-times more potent an analgesic than morphine (an effect is not blocked by naloxone). Both (+)- and (-)- epibatidine are potent nicotinic agonists showing selectivity towards neuronal and ganglionic receptor subtypes and are used as a tool to study these receptors.

Epidermal growth factor (EGF): a 53 amino acid mitogenic polypeptide which causes the growth of a number of epidermal and epithelial cell types in vitro and in vivo. It is involved in normal cell growth, oncogenesis and wound healing and stimulates a variety of epithelial cells to divide and is implicated in the aetiology of cancer.

Epidermal growth factor antagonists:

Epidermal growth factor receptors: also known as ErbB1 or HER1, a cell-surface receptor for epidermal growth factor and stimulation of these receptors by EGF causes cell division. They are present at unusually high levels on the surface of many types of cancer cells.

Epinephrine: US and worldwide term for adrenaline.

Epitope: the part of a immunogenic substance which elicits a response by the immune system.

EPM: elevated plus maze

EPMR: equi-potent molar ratio

Epothilones: naturally occurring, anticancer macrolides which have the same mechanism of action as paclitaxel.

Epoxidation: an important chemical reaction in metabolism. Epoxidation of some chemical substrates can yield toxic and carcinogenic products.

EPSP: excitatory postsynaptic potential

Equi-effective dose ratio (EDR): the ratio of the dose of both the reference and test compounds which produce identical biological responses.

Equi-effective molar ratio (EMR): equi-potent molar ratio.

Equi-potent molar ratio (EPMR): also known as equi-effective molar concentration ratio, a molar ratio of test and standard compound which elicit a certain response. EPMR has no units but the lower the value the more potent the compound.

ER: extraction ratio

Ergoline alkaloids: ergot alkaloids

Ergometrine: an oxytocic and active component obtained from the fungus ergot (Claviceps purpurea). It induces prolonged series of strong contractions in a quiescent uterus and has vasoconstrictor actions. Ergometrine is used clinically to treat postpartum haemorrhage.

Ergosterol: the most abundant fungal sterol and an essential component of fungal cell and mycelial membranes. It is not synthesized by all fungi but is present in many fungi of medicinal importance. Ergosterol synthesis in fungal cell walls is inhibited by azoles.

Ergot: a fungus (Claviceps purpura) which grows on rye and other grasses as a parasitic fungus. It produces many pharmacologically active compounds including  histamine, tyramine, acetylcholine and ergot alkaloids which include ergometrine.

Ergot alkaloids: also known as claviceps alkaloids and ergoline alkaloids, a group of over 30 indole alkaloids derived from the fungus ergot which all contain the ergoline ring system. Ergot alkaloids are divided into tow main classes, ie lysergic acid derivatives and clavine alkaloids. Lysergic acid derivatives include simple amides such as ergometrine and cyclic tripeptides such as ergotamine. A good example of a useful pharmacological application of ergot alkaloids is the dopamine agonist bromocriptine.

L-(+)-Ergothioneine: also known as ergothioneine dihydrate, an anti-oxidant, UV and γ-irradiation protectant and a peroxynitrate scavenger. It was originally isolated from ergot but is also present in mammalian blood, liver and kidneys.
Aruoma O et al. Antioxidant action of ergothioneine: Assessment of its ability to scavenge peroxynitrite. Biochem Biophys Res Commun (1997) 231; 389-391

Ergotism: also known as Saint Anthony's fire, poisoning due to the consumption of wheat and rye contaminated with ergot. Symptoms include convulsions, mental impairment, gangrene and sometimes death.

Error peptides: synthetic peptides which are variants of the synthesized peptides. These variants can be truncated forms, variants of the molecular conformation (but with normal primary structure) and blocked forms.

Erucic acid: a fatty acid which makes up 40 to 50% of the total fatty acid content of rapeseed, wallflower seed and mustard seed. Together with oleic acid it forms Lorenzo's oil which has been investigated clinically for its effects in the treatment of adrenoleukodystrophy and adrenomyeloneuropathy. Lorenzo's oil decreases the concentration of longer chain fatty acids in the body and may also reduces demyelination of neurons.

Erythromycins: macrolide antibiotics which inhibits translocation, ie protein synthesis in bacteria. Erythromycin is used clinically to treat campylobacter enteritis, pneumonia, legionnaire's disease, syphilis, non-gonococcal urethritis, chronic prostatitis, acne vulgaris, rosacea and in the prophylaxis of diphtheria and whooping cough. It is commonly used as an alternative to penicillin in hypersensitive patients. Erythromycin is also is a motilin agonist and acts as a gastroprokinetic, ie it increases gastric emptying rate.

Erythropoietin: a glycoprotein haemopoietic factor synthesized in the juxtaglomerular tissue of the kidney and which stimulates red blood cell formation. Recombinant human erythropoietin is used clinically to treat anaemia associated with end-stage renal failure.

Escin: also known as aescin, a saponin occurring in the seed of the horse chestnut tree used to increase the permeability of certain tissues. They inhibit oedema formation and decreases vascular fragility.

Eserine: also known as physostigmine.

Esylate: an ethanesulphonate salt.

Etabonate: ethyl carbonate salts. Examples include Loteprednol etabonate used to treat ocular inflammation.

Ethacrynic acid: a loop diuretic which forms a complex with cysteine and this complex is the active form of the drug. It acts mainly on the thick segment of the ascending loop of Henle inhibiting the transport of sodium chloride out of the tubule into the interstitial tissue. It inhibits the Na⁺/K⁺/2Cl^- carrier in the luminal membrane.

Ethambutol: a drug used to treat tuberculosis usually in combination with other drugs.

Ethnopharmacology: the branch of pharmacology dealing with the social, ethnic and cultural use of certain drugs which are used according to cultural and ethical rites and procedures as distinct from drug abuse. Ethnopharmacology has its origins in folk medicine. Drugs included here include ipecacuanha, kava, betel, khat, opium and soma.

Ethnoveterinary medicine: the branch of veterinary medicine that deals with the folk beliefs, knowledge, skills, methods and practices relating to the health care of animals and includes methods that livestock keepers use other than modern synthetic drugs.

Ethosuximide: a succinamide-type anti-epileptic compound used clinically to treat simple absence seizures, myoclonic seizures and atypical absence, atonic and tonic seizures. It inhibits T-type calcium channels

Ethyl carbamate: a small animal anaesthetic used prior to surgery. Typically, a dose of 1.5 mg/g given ip.

Ethylcholine aziridinium (AF64A): a selective for the cholinergic system and its effects are both dose- and site-dependent. AF64A treatment of rats will result in selective reductions in levels of ACh, AChE, ChAT, HAChT and K(+)- and ouabain-stimulated release of ACh in rat brains.

Ethylenediamines: a class of first generation antihistamines originally introduced clinically in 1942 with phenbenzamine. Other examples include antazoline, chlorpyramine, chlorothen, histapyrrodine, mepyramine and methapyrilen. Of these,  antazoline, for example, is used clinically to treat allergic conjunctivitis. The ethylenediamine moiety is shown in blue. 

Ethylenediaminetetraacetic acid (EDTA): a widely used chelating agent commonly present in physiological solutions to regulate metal ion concentrations.

Etidronate: disodium etidronate is a bisphosphonate which is absorbed into the hydroxyapatite crystals in bone slowing bone growth and its dissolution thereby reducing bone turnover. It is used clinically in the prevention and treatment of osteoporosis and corticosteroid-induce osteoporosis.

Etodolac: a non-steroidal anti-inflammatory drug with a similar pharmacological profile to naproxen and used clinically to treat pain and inflammation in rheumatoid arthritis and osteoarthritis.

Etomidate: an intravenous anaesthetic used as an anaesthesia inducing agent but is not used for maintenance of anaesthesia.

Etoposide: an anticancer drug which is particularly useful against small cell carcinoma of the bronchus, against lymphomas and testicular cancer.

Eudismic ratio (ER): the ratio between the activity of a eutomer (active enantiomer) divided by the activity of the distomer (inactive or poorly active enantiomer). The higher the ER, the more likely the compounds will be therapeutically efficacious and the more likely the adverse effects will be weak.
   An example of the importance of the ER is thalidomide. The (R) enantiomer possesses sedative properties and let to its clinically use in the 1960s as a sleep aid and for the treatment of morning sickness. The (S) enantiomer, however, has potent teratogenic effects and causes phocomelia in children whose mothers took thalidomide during pregnancy.

Eukaliuric diuresis: diuresis without increased loss of potassium in the urine. The opposite is kaliuretic diuresis where potassium is lost in the urine.

EACPT: European Association of Clinical Pharmacology and Therapeutics. An organization which aims to promote the use, teaching and understanding of clinical pharmacology throughout Europe.
http://www.sdu.dk/health/Homepages/EACPT/

Euthanaticum: a drug such as a barbiturate used to carry out euthanasia.

Euthanasia: the merciful killing of a human or animal for the purpose of ending pain and suffering.

Eutomer: more therapeutically useful molecule of an enantiomeric pair. The opposite is disotmer.

Evacuant: also known as a purgative, a substance causing evacuation of the bowels. Examples include senna.

Everted gut sac method: a method introduced in 1954 by Wilson and Wiseman to measure absorption of drug from the gut and a method which has been widely used to study intestinal drug transport.
Wilson T, Wiseman, G. The use of sacs of everted small intestine for the study of the transference of substances from the mucosal to the serosal surface. J Physiol (1954) 123; 116-125

Excipients: inert (ie therapeutically inactive) additives added to active drug compounds in the preparation of tablets, capsules and other dosage forms. They are added to modify the size, shape, colour, taste and dissolution profile of a drug and can make tablets easier to handle in manufacturing. Examples include, magnesium stearate (used as a lubricant) and lactose (a bulking agent to increase the size of tablets) and other compounds used as binders, solubilizers, coatings, glidants, pigments, lubricants and disintegrants.

Excitatory amino acids (EAA): amino acids which have excitatory actions in the nervous system. Examples include L-glutamate (the major excitatory neurotransmitter in the central nervous system), L-aspartate and L-homocysteate.

Excitatory amino acid receptors: receptors sensitive to excitatory amino acids such as L-glutamate, L-aspartate and L-homocysteate. These receptors can be grouped into ionotropic receptors (ie receptor activation is directly coupled to a membrane ion channel) and metabotropic receptors (ie receptor activation is coupled to an intracellular biochemical cascade).

Excitatory postsynaptic potential (EPSP): a short-lived difference in potential of a postsynaptic membrane between a depolarized area and the rest of the membrane caused by increases permeability of the synaptic membrane to cations such as Na⁺, K⁺ and Ca²⁺ (which cause localized depolarization) following release of an excitatory transmitter from the presynaptic nerve terminal.

Excitotoxins: compounds which have excitatory actions in the nervous system but which are toxic to them causing neuronal damage. Many of them are amino acids and include kainic acid, ibotenic acid, quinolinic acid (a glutamate analogue), cysteinesulphinic acid, homocysteic acid and folic acid. They are used as pharmacological tools.

Exocrine: relating to the excretion of substances from exocrine glands through ducts. Examples include the formation and release of digestive enzymes from the pancreas into the gut.

Exorphins: peptides with opiate activity which are produced by food during its digestion. Example include β-casomorphin which has only week opiate activity.

Exotoxins: also known as microbial toxins.

Expectorant: an agent which facilitates coughing where the cough is productive, ie produces sputum.

Extraction ratio (ER): the fraction of drug which is extracted from each unit of blood perfusing through an organ. If all the drug is extracted the ER value is 1, if 50% is extracted the value is 0.5 etc. Although the ER is a useful value, it does not indicate the overall efficacy of drug removal which may be affected by age of an individual and disease state. It is more important to know just how many millilitres of blood are affected and how often extraction is occurring. From this point of view ER can be used to calculate a more useful value for clearance.

Extraneuronal uptake: uptake of neurotransmitters by tissues other than neurones.

Extrapyramidal system: a neural network in the brain which is part of the motor system and is involves in the coordination of movements.

Extrapyramidal side effects: side effects of some drugs such as antipsychotic and neuroleptic drugs used to control psychoses and which include disorders of fine movement such as akinesia, dystonia and tardive dyskinesia. Extrapyramidal side effects are commonly seen with D₂ dopamine receptor antagonists (particularly first-generation antipsychotics) and are divided into acute dystonias (involuntary movements such as restlessness, muscle spasm and torticollis (neck spasm cause in the head to be turned)) and tardive dyskinesias (involuntary movements of the face, tongue, body and limbs which are slow in onset and which may become irreversible).

ex vivo: outside the body.

Eye wiping test: a test used to determine the pungency of a pro-inflammatory agent and to test the effects of analgesics.

Eyeblink conditioning: an animal model for predicting and understanding human learning and memory disorders.