Iatrogenic disease: a disease caused by a physician usually due to the misdiagnosis and/or mistreatment of a particular disorder. See http://www.iatrogenic.org/index.html

IB- MECA: a potent and selective A₃ adenosine receptor agonist which is used as a pharmacological tool to investigate these receptors.
Klotz KN. Adenosine receptors and their ligands. Naunyn-Schmeid Arch Pharmacol (2000) 362: 382

IBAT: ileal bile acid transporter

Iberiotoxin: a 37 amino acid peptide toxin purified from the Indian red scorpion Buthus tamulus and which has 68% homology with charybdotoxin. It is a highly selective blocker of high conductance Ca²⁺-activated potassium channels and is used as a pharmacological tool to investigate these channels.

Ibogaine: a psychoactive indole alkaloid obtained from the rootbark of an African plant Tabernanthe iboga. It is being investigated for its effects in treating both drug and alcohol addiction. See http://www.ibogaine.org

Ibotenic acid: a neurotoxic isoxazole and an excitatory amino acid (a-amino-2,3-dihydro-3-oxa-5-isoxazole acetic acid). It is an amanita toxin obtainable from the mushroom fly agaric (Amanita muscaria). Ibotenic acid is a psychotropic compound, is weakly insecticidal and is structurally similar to kainic acid and muscimol (which is its decarboxylation product). As a drug of abuse it causes motor depression, ataxia, and changes in mood, perceptions and feelings. It is used as a pharmacological tool (it is an excitotoxin) to induce lesions in specific parts of the brain in animal models of Huntington's disease and other neurodegenerative diseases and epilepsy
Johnston GA, Curtis DR, De Groat WC, Duggan AW. Central actions of ibotenic acid and muscimol. Biochem Pharmacol (1968) 17 (12): 2488-2489



Ibuprofen: an arylpropionic acid derivative and non-steroidal anti-inflammatory compound (NSAID) (a-methyl-4-(2-methylpropyl)benzene acetic acid) used clinically to treat pain and inflammation. It acts by inhibiting cyclooxygenase. It is a component of many OTC analgesics. The arylpropionic acid moiety is shown in blue in the figure below.



IC₅₀: also known as the median inhibitory concentration, the amount of a compound which is necessary to inhibit the target molecule receptor or response elicited by an effector molecule by 50%.

ICI 118551: a selective β₂-adrenoceptor antagonist.

ICE: interleukin 1β-converting enzyme

ICSS: intracranial self-stimulation

Ictogenesis: the start and spread of a single epileptic seizure.

id: intraduodenally, a route of administration of a drug directly into the duodenum which avoids the strongly acidic conditions of the stomach.

Idiosyncratic drug response: a response to a drug which is not related to the pharmacological properties of the drug, which occurs only in a subset of patients being treated at therapeutic doses and which does not occur in the rest of the patients despite increasing the dose to otherwise toxic levels. Examples include the occurrence of hepatitis and malignant hyperthermia in response to the inhalational anaesthetic halothane.

Idazoxan: an analogue of yohimbine and selective α₂-adrenoceptor antagonist and imidazoline receptor ligand. It is used as a pharmacological tool in the study of this adrenoceptor subtype.
Dabire H. Idazoxan: a novel pharmacological tool for the study of α2-adrenoceptors. J Pharmacol (1986) 17; 113

Idoxuridine: an nucleoside antiviral drug which has been used clinically to treat skin infection of Herpes simplex but its toxicity particularly systemic and its weak efficacy have limited its use. It acts by interfering with viral replication. It is phosphorylated in the host cell by thymidine kinase to form the active triphosphate which inhibits DNA polymerase and this triphosphate is also incorporated into replicating DNA in place of thymidine. Defective viral protein is produced as a result and defective viral particles are produced.

IDPN: 3,3'-iminodiproprionitrile, a neurotoxin which appears to act by disrupting neurofilament- and intermediate filament-organelle association. It has been reported to disrupt learning and memory and has been used as a pharmacological tool to investigate neurone function.

IGER: Ihara's genetically epileptic rat

Ignarro, Louis J (1941-): American pharmacologist who shared the Nobel prize for Physiology or Medicine 1988 with Furchgott and Murad "for their discoveries concerning nitric oxide as a signaling molecule in the cardiovascular system".
http://nobelprize.org/nobel_prizes/medicine/laureates/1998/ignarro-autobio.html

Ihara's genetically epileptic rat (IGER): a mutant rat which exhibits circling seizures and generalized tonic-clonic convulsions. This behaviour develops from around 2 to 5 months after birth and this animal model has been used to investigate the effects of anti-epileptic drugs.

Ileal bile acid transporter (IBAT): sometimes referred to as the ileal apical sodium bile acid co-transporter, an energy-dependent bile acid pump mechanism which is located on the apical membrane of the enterocyte where it transports bile acids from the terminal ileum back to the gall bladder. It is important in the enterohepatic circulation of bile acids which ensures proper absorption of fat, cholesterol and fat-soluble vitamins from the intestine.

Ileal bile acid transporter inhibitors: compounds which inhibit the ileal apical sodium bile acid co-transporter to increase hepatic bile acid synthesis and reduce plasma LDL cholesterol levels. They are being developed for the treatment of hypercholesterolemia and examples include ezetimibe.

3-(1H-Imidazol-4- yl)propyl-di(4-fluorophenyl)-methyl ether hydrochloride: a potent H₃ histamine receptor antagonist.
Huls A et al. Novel histamine H₃ -receptor antagonists with benzyl ether structure or related moieties: synthesis and structure-activity relationships. Arch Pharm (Weinheim) (1996) 329; 379-385

Imidazole alkaloid: alkaloids comprising an imidazole ring. Examples include pilocarpine, a compound used clinically to treat glaucoma.

Imidazoles: a class of azole antifungal compound including clotrimazole, econazole, fenticonazole, sulconazole and tioconazole. They act by inhibiting cytochrome P-450 which catalyzes the 14 a-demethylation of lanosterol to ergosterol which is a mycosterol (fungal sterol) and essential component in mycelia and fungal cell walls. Imidazoles are used clinically for the treatment of vaginal candidiasis and dermatophyte infections.

Imidazolines: a class of drugs which includes clonidine, oxymetazoline, naphazoline, benazoline, tetrahydrozoline and tizanidine (used to treat spasticity). They all contain the imidazole moiety. Some examples are shown below.



Imidazoline receptors: receptors found in the nervous system and other tissues which bind imidazoline compounds such as agmatine and clonidine. They are divided into three subtypes, I₁, I₂.and I₃ and I₂ may be further divided into I_2A and I_2B. I₁ receptors are located in the brainstem notably the lateral reticular nucleus, in the bovine frontal cortex and the rat locus coeruleus and mediate the hypotensive effects of clonidine in the brainstem. I₂ Receptors are widely distributed throughout the brain and peripheral nervous system and are also located on mitochondrial membranes . In fact, brain I₂ receptor density changes in certain disease states such as Huntington's chorea and Alzheimer's disease. I₂ Receptors sites have many functions such as control of Na⁺ uptake in the renal tubule of rabbits, increased levels of mRNA for glial fibrillary acidic protein in cultured rat astrocytes and this may account for the neuroprotective effects of idazoxan (an α₂ adrenoceptor antagonist and I₂ antagonist.) I₃ Receptors (also referred to as an atypical imidazoline binding sites) appear to be present in the pancreas and may mediate type II diabetes. Although a number of compound are known to act as ligands at imidazoline receptor sites, their exact function in many cases is unclear.

Imidazoline receptor agonists: compounds which agonize I₁, I₂ and I₃ receptors. Examples of I₁ agonists include moxonidine, efaroxan, rilmenidine (a mixed α₂ adrenoceptor and I₁ agonist, cimetidine (an H₂ histamine receptor antagonist) and clonidine (which is a partial agonist at I₁ sites). I₂ Agonists include BU 224 (putative) and 2-BFI (putative) and I₃ agonists include efaroxan (putative).

Imidazoline receptor antagonists: compounds which block imidazoline receptors in the nervous system and other tissues. Examples of imidazoline receptor antagonists  include 'first generation' antagonists such as guanabenz, guanfacine, clonidine and lofexidine and 'second generation' antagonists such as rilmenidine and moxonidine (an SIRA, a selective imidazoline receptor antagonist). Not all of these compounds are chemically imidazolines.
I₁ Receptor antagonists include clonidine, I₂ antagonists include idazoxan and BU 224 and I₃ antagonists include KU14R (putative).

Imidazothiazoles: a class of drug used to treat helminthic, whipworm and hookworm infections in animals. Examples include levamisole (a nicotine-like nematocide used to treat ruminants and pigs) and butamisole (also a nicotine-like nematocide and a derivative of lavamisole).

Imiloxan: a moderately potent and selective a_2B-adrenoceptor antagonist. It has been investigated for its antidepressant effects.

3,3'- Iminodiproprionitrile (IDPN): a synthetic neurotoxin which targets motor neurones. It disrupts neurofilament- and intermediate filament-organelle association and cause axonal swelling and slow axonal transport. It has been used as a tool to investigate neurotoxicity.

Imipramine: a dibenzazepine derivative (10,11-dihydro-N,N-dimethyl-5H-bibenz[b,f]azepine-5-propanamine) tricyclic antidepressant. It is a noradrenaline and serotonin uptake inhibitor (more selective for 5-HT uptake inhibition) and increase brain levels of noradrenaline and 5-HT. It is used clinically to treat depressive illness and nocturnal enuresis in children. Its anti-muscarinic and cardiac side effects limits it use.



Immunoadjuvant: substance which augments, stimulates or activates cellular or humoral immune response.

Immunomer: a chemically modified immunostimulatory oligonucleotide. They are being developed as anticancers.

Immunomodulators: compounds which stimulate or suppress the immune system to be more or less active than normal.

Immunopharmacology: the branch of pharmacology that deals with the effects of compounds on the immune system particularly on the development of humoural and cellular immune responses.

Immunophilins: cytoplasmic receptors which bind immunosuppressants such as cyclosporin with high affinity. Examples include FK506 binding protein (FKBP).

Immunostimulants: compounds which enhance cellular and humoural immune responses.

Immunosuppressants: compounds which suppress cellular and humoural immune responses. They usually act in the induction phase of T cell stimulation and proliferation and fall into several classes according to their mechanism of action. The main classes are:

*  inhibitors of transcription for example cyclosporin and tacrolimus,

*  inhibitors of nucleotide synthesis for example azathioprine, mycophenolate mofetil, mizoribine and leflunomide,

*  inhibitors of growth factor signal transduction for example sirolimus and leflunomide,

*  inhibitors of cellular differentiation for example 15-deoxyspergualin, and

*  antilymphocyte antibodies including monoclonal antibodies directed at the T-cell antigen receptor complex for example OKT3 and TIOB9 and monoclonal antibodies directed at other cell surface antigens such as interleukin-2 receptor alpha.

Immunosuppressants are used clinically to treat autoimmune disease and to prevent the rejection of transplanted organs.

Immunotoxins: toxins which are produced by linking a bacterial toxin to a monoclonal antibody making them tissue-specific toxins.
Hertler AA, Frankel AE. Immunotoxins: a clinical review of their use in the treatment of malignancies. J Clin Oncol (1989) 7(12);1932-1942

IMRAD: the 'standard' format for the writing of scientific research reports, ie introduction, methods, results and discussion.

Inactivation theory: a theory proposed by Gosselin in 1970.
Gosselin RE. Drug receptor inactivation: a new kinetic model. Br J Pharmacol (1970) May;39(1); 215P

Inbreeding depression: a reduction in fitness and vigour of individual bred animals as a result of increased homozygosity due to inbreeding in a normally outbred population

Incapacitating agent: substances defined by the US Department of Defense as agents that produces temporary physiological or mental effects which will render individuals incapable of concerted effort in the performance of their assigned duties. Examples include psychadelic indoles such as lysergic acid diethylamide and anticholinergic agents such as 3-quinuclidinyl benzylate (sometimes referred to as BZ). They have been used at various times in warfare to incapacitate the enemy.

Incretins: a group of gastrointestinal hormones which cause an increase in the amount of insulin secreted from the β-cells of the Islets of Langerhans in the pancreas. The main two incretins are glucagon-like peptide 1 and glucose-dependent insulinotropic peptide. Because incretins decrease the blood levels of glucose, incretin mimetics are being developed for the treatment of diabetes.

Incretin mimetics: compounds which mimic the effects of incretin and so decrease blood glucose levels. Examples include exenatide.

Incretin modulators: compounds which modulate the effects of incretins and which are of use in the treatment of diabetes. Since the main incretins are degraded by the enzyme dipeptidyl peptidase 4, inhibitors of this enzyme such as vildagliptin and sitagliptin.

Incretion: the process of hormone uptake by cells and the opposite of secretion.

IND: investigational new drug, a term assigned to a new compounds that is being tested for its pharmacological properties with a view to its future clinical use.

Indirectly acting sympathomimetic amine: compounds which cause the release of catecholamines from the terminals of postganglionic sympathetic fibers . Examples include tyramine, ephedrine and amphetamine which are all structurally related to noradrenaline. Because of this resemblance, they are transported into nerve terminals by uptake 1.
   Tyramine is present is cheese, chocolate and red wines and is attributed to the headaches which sometimes occur after their consumption. After absorption from the gut the tyramine crosses the blood-brain barrier and causes release of noradrenaline in the brain causing vasodilation (see also cheese reaction).

Indole alkaloids: a very large family of over 600 alkaloids almost all of which are derived from tryptophan. Examples include harman alkaloids, physostigmine, ergot alkaloids and rauwolfia alkaloids.

Indomethacin: an arylacetic acid derivative and anti-inflammatory, antipyretic analgesic compound (1-(4-chlorobenzoyl)-5-methoxy-2-methyl-1H-indole-3-acetic acid). It is more potent than salicylates and is a potent inhibitor of cyclooxygenase showing some selectivity for COX-1.



Influx: the flow of ions or molecules into a cell.

Ingenol: an activator of protein kinase C.
Hasler C et al. Specific binding to protein kinase C by ingenol and its induction of biological responses. Cancer Res (1992) 52; 202-208

Inhibin: a dimeric glycopeptide (Mwt 31,000) produced in the testes and which acts in a feedback mechanism on the pituitary to regulate follicle-stimulating hormone without effects on leutenizing hormone secretion. It has been extensively investigated as a male chemical contraceptive since it is thought to be able to selectively block Sertoli cell function and disrupt spermatogenesis without a decrease in production of testosterone from the Leydig cells.

Inhibitory amino acids: amino acids present in the brain which function as inhibitory neurotransmitters. Examples include GABA and glycine.

Inhibitory postsynaptic potential (IPSP): a short-lived difference in potential in a postsynaptic membrane between a hyperpolarized area and the rest of the membrane caused by increased permeability of the synaptic membrane to cations such as Na⁺ and K⁺ (which cause localized hyperpolarization) following release of an inhibitory transmitter from the presynaptic nerve terminal.

INN: international nonproprietary name, a name selected The World Health Organization and given to drugs to help in their identification.
http://www.who.int/medicines/organization/qsm/activities/qualityassuran ce/inn/orginn.shtml

Inner salt: a salt formed within a molecule when two groups become oppositely charged. For example, in the presence of acids the amino group in amino acids is converted to NH³⁺ and bases will convert the carboxylic acid group to the carboxylate anion COO^-. At the isoelectric point for an amino acid, ie the pH at which both the amino and carboxylic groups are in their ionized state, an inner salt is formed.

Inodilation: the combination of drugs which have positive inotropic and vasodilating actions. Examples of inodilators include the phosphodiesterase 3 inhibitor enoximone, levosimendan (a calcium sensitizer and activator of potassium channels) and dobutamine (β₁-adrenoceptor antagonist).

Inositol phosphates: a class of plasma membrane components and phosphate esters of the cyclic alcohol myo-inositol. They are important intracellular second messengers in eukaryotic cells. One important member of this group of phosphates is inositol 1,4,5-trisphosphate (IP₃) which is released from phosphatidylinositol 4,5-bisphosphate  by the action of phospholipase C-β. IP₃ causes the release of calcium ions from intracellular stores in the endoplasmic reticulum and activation, for example, of  calcium-sensitive ion channels.
Irvine RF. Inositide evolution - towards turtle domination? J Physiol (2005) Jul 15;566(Pt 2); 295-300

Inotropes: compounds which alter the force of cardiac contraction. Positive inotropes increase the force of cardiac contraction.

Inotropic: relating to the actions of inotropes.

In situ: in a normal or natural location and a term used to describe the location where an action/reaction takes place.

Insecticides: compounds used to kill external parasites including mites, fleas, ticks and flies. Insecticides are important in veterinary pharmacology as these insects carry diseases. Examples of insecticides include organophosphates, carbamates and chlorinated hydrocarbons.

Insufflation: a form of drug administration where the drug is inhaled into the lungs.

Insulin: a 51 amino acid polypeptide dimeric hormone produced by the β-cells of the Islets of Langerhans in the pancreas and which promotes the biosynthesis of fatty acids and proteins and decreases blood glucose levels by activation of insulin receptors.

Insulin receptor: a tyrosine kinase class of transmembrane receptor comprising two á subunits and two β subunits which mediates the actions of its natural ligand insulin. Stimulation of insulin receptors causes and increase in glucose transporters in the membranes of adipocytes and muscle cells leading to an increase in uptake of glucose into these cells.

Insulin receptor agonists: compounds which stimulate insulin receptors thereby increasing uptake of glucose into tissues. They are being developed for the treatment of diabetes mellitus.
Bailey CJ. New pharmacologic agents for diabetes. Curr Diab Rep (2001) Oct 1(2); 119-26

Insulin sensitizers: compounds which sensitize tissues to the effects of insulin. Examples include peroxisome-proliferator-activated receptor agonists such as rosiglitazone (a PPAR γ agonist), S-15261, CLX-0901 and TLK-17411.

Insulinotropic: having insulin-like actions.

Integrases: a viral enzymes which facilitates the insertion of viral DNA into the DNA of the host and an enzyme essential for viral replication. See also HIV integrase.

Integrins: a large family of about 22 heterodimeric transmembrane glycoproteins which are responsible for the attachment of cells to extracellular matrix proteins of the basement membrane and the attachment of cells to cells such as platelets to platelets.

Intellectual property: a term used to describe the preparation and legal protection of trademarks, copyrights and inventions (described and protected by patents).

Intercalating agent: a compound which becomes inserted within the DNA double helix to disrupt its function by preventing polymerases and other DNA binding proteins from functioning properly. Intercalating agents are used in the treatment of cancer and examples include carboplatin and cisplatin.

Interceptive: another term for abortifacient.

Interferons (IFN): a family of proteins produced by the body in response to viral infections and which have immunomodulatory effects. They are broadly classified into IFNá, IFNβ and IFNγ. IFNá is used clinically to treat chronic hepatitis B and C, AIDS-related Kaposi's sarcoma, hairy cell leukaemia, renal carcinoma, T-cell lymphomas and other malignant diseases. IFNβ is used to treat multiple sclerosis and IFNγ is used as an adjunct to antibacterials in the treatment of infections associates with chronic granulomatous disease.

Interleukins (IL): a family of about 18 cytokines designated IL-1 to IL-18 produced by macrophages and activated T cells which act specifically as mediators between leucocytes and which mediate responses such as inflammation and immune responses, chemotaxis and stimulation of T cells and antigen-presenting cells.

Interleukin antagonists: compounds which inhibit the actions of interleukins by blocking their receptors.

Interleukin synthesis inhibitors: compound which prevent leukocytes from producing interleukins and so compounds with anti-inflammatory effects.

Interleukin 1β-converting enzyme (ICE): officially known as caspase 1, an enzyme (EC 3.4.22.36) which releases IL-1β and IL-18 from their precursor and an important enzyme in the production of both interleukins.

Interleukin 1β-converting enzyme inhibitors: compounds which inhibit interleukin 1β-converting enzyme and so inhibit the production of IL-1β. They are being developed for their anti-inflammatory activity and protective actions against joint damage.

Internalization: the transportation of a ligand-receptor complex to the interior of a cell following ligand binding.

Interstitial cell stimulating hormone: leutenizing hormone

Intracavernous: into the cavernous tissues of the penis and a route of administration of some drugs such as papaverine and prostaglandin E₁ in the treatment of erectile dysfunction.

Intracranial self-stimulation (ICSS): the self administration of drugs or electrical stimuli which cause largely pleasurable stimulation of the brain. ICSS is used to determine the function of reward systems and pleasure centres in the brain particularly pleasure-seeking behaviour.
Olds J, Milner PM. Positive reinforcement produced by electrical stimulation of septal area and other regions of rat brain. J Comp Phys Psych (1954) 47;419-427

Intrathecal: a route of drug administration in which a drug is directly injected into the cerebrospinal fluid.

Intravascular inactivation of active drug (IVIAD): the inactivation of a drug when it is present in the blood vessels by blood-borne enzymes or by the actions of  substances released by epithelial cells.

Intrinsic activity: the relative maximal response caused by a drug in a tissue preparation. A full agonist causes a maximal effect equal to that of the endogenous ligand so has high intrinsic activity and a partial agonist causes less than a maximal response so has lower intrinsic activity at that receptor site.

Intrinsic efficacy: the ability of a drug to affect a receptor and cause a biological response.

Intrinsic sympathomimetic activity (ISA): an activity observed in some adrenoceptor antagonists to weakly stimulate these receptors during their blockade (ie, they have agonist actions as well). Examples include the β-adrenoceptor antagonists  pindolol and carteolol.

in utero: within the uterus.

Inverse agonists: a type of agonist.

in vitro: within glass or in a test tube, Magnus bath (organ bath) or other laboratory container.

Ion channel: a transmembrane protein or protein complex which forms a hydrophobic pore in a membrane and which allows ions such as sodium, potassium and calcium ions to pass from the cell interior to exterior and back. See also sodium channels, potassium channels and calcium channels.

Ion channel blocker: compounds which block the flow of ions through ion channels. See also sodium channel blockers, potassium channel blockers and calcium channel blockers.

Ion trapping: the accumulation of molecules or ions in a compartment due to changes in its ionization state associated with a difference in the pH between compartments. Molecules are lipid soluble when they are unionized and can freely pass across membranes in this state. If they become ionized due to a difference in pH in the compartment into which the have diffused along a concentration gradient then they become less lipid soluble and become trapped in that compartment not being able to readily diffuse out of it. For example, ionized drugs can become trapped in breast milk by ion trapping due to the small difference in pH between blood and milk.

Ionophore: a lipophilic compound which forms charged or neutral complexes with ions allowing them to move across membranes more easily. Many ionophores have antimicrobial activity such as valinomycin. One of the most commonly used ionophores is A23187 which is used to move calcium ions across membranes. Antamanide acts as a sodium ionophore.

Ionophore antibiotics: polyether compounds which were developed as coccidiostats in poultry and have been used as growth promoters in cattle. They facilitate the transport of mono- and divalent cations across membranes and interfere with potassium ion transport across mitochondrial membranes. Examples include monensin, narasin, maduramicin and lasalocid.

Ionotropic receptors: also known as ligand-gated ion channels, receptors which are activated by ligands to allow the transmembrane conductance of ions (Na⁺, K⁺ and Cl^-). They are divided into two main groups, the nicotinic receptor family which includes nicotinic receptors, GABA_A, GABA_C, glycine and 5-HT₃ receptors and the glutamate receptor family which includes NMDA and non-NMDA receptors.

IP₃: inositol phosphates

Ipecacuanha: the root of a Brazilian rubiaceous herb (Cephaelis ipecacuanha) which is used in ethnopharmacology. It is a source of emetine which induces emesis.

Ipecacuanha alkaloids: a class of iridoid alkaloids which includes emetine, the main alkaloid is the emetic ipecac.

Ipratropium: an muscarinic receptor blocker used clinically to treat reversible airway obstruction. Ipratropium blocks the effects of a vagal reflex caused by mediators released from mast cells on receptors in the bronchial epithelial cells.

Iproniazid: a hydrazine-type monoamine oxidase inhibitor once used as an antidepressant. It is a derivative of the anti-tubercular drug isoniazid.

Ipsilateral: situated on or pertaining to the same side. The synonym is contralateral (on opposite sides).

IPSP: inhibitory postsynaptic potential

Irbesartan: a sartan and an angiotensin II receptor antagonist used clinically to treat hypertension and renal disease in type 2 (non-insulin-dependent) diabetes mellitus.

IRL-1038: an ET_B endothelin receptor antagonist.

IRL-1620: a selective ET_B endothelin receptor agonist and pharmacological tool used to study the function of ET_B receptors.

Irreversible competitive antagonism: a form of antagonism.

Irwin test: a test used to evaluate the effects of a new substance on behavior and physiological function.
Irwin S. Comprehensive observational assessment: 1a. A systematic, quantitative procedure for assessing the behavioral and physiological state of the mouse. Psychopharmacologia (Berl.) (1968) 13; 222-257

ISA: intrinsic sympathomimetic activity

Isoceptors: also known as isoreceptors.

Isoflurane: an inhalational halogenated ether-type anaesthetic and an isomer of enflurane with very similar anaesthetic actions although with a somewhat dissimilar toxicity profile. It is use in human and veterinary medicine to as a general anaesthetic for surgery.

Isolated perfused tubules: tubules from the kidneys of animals such as rabbits used to investigate the effects of drugs on the absorption of substances such as glucose and ions from the nephron.
Burg M, Grantham J, Abramow M, and Orloff J. Preparation and study of fragments of single rabbit nephrons. Am J Physiol (1966) 210; 1293-1298

Isomorphic animal model: also known as an analogue animal model, a type of animal experiment which mimics in an animal the effects a drug has in humans. This relies on intrinsic similarities in behaviour and biochemistry in animals and humans. Isomorphic animal models have been used in the investigation of hallucinogens.

Isoniazid: a synthetic bactericidal compound used clinically against Mycobacterium tuberculosis, the pathogen causing tuberculosis. Isoniazid was discovered in the 1950s and appears to act by inhibiting the synthesis of mycolic acids in the bacterial cell wall and disrupts cell metabolism possibly by interfering with the cellular electron transports system and the conversion of NAD⁺ to NADH.

Isoniazid-induced convulsions: convulsions induced by the anti-tuberculosis drug isoniazid. Typically, 200 mg/kg given subcutaneously to mice can induce convulsions and is used to investigate the effects of anticonvulsant drugs.

Isoprenaline: also known as isoproterenol and isopropylnoradrenaline, a potent b-adrenoceptor agonist. It has been used clinically as an inotropic sympathomimetic, ie used to treat shock because it stimulates cardiac b₂ adrenoceptors to increase heart output (and stimulates both β₁ and β₂ receptors more potently than adrenaline).

Isoquinoline alkaloids: a large group of alkaloids which occurs widely in plants. These alkaloids are mainly toxic and examples of plants which comprise them include Argemone species (prickly poppy), Chelidonium species (celandine poppy), Corydalis species (fitweed), Dicentra species (Dutchman's breeches), Papaver species (poppy) and Sanguinera species (bloodroot). Examples of isoquinoline alkaloids include papaverine, sanguinarine, protoverine, and chelidonine and are gastrointestinal irritants and CNS stimulants.

Isoreceptors: also known as isoceptors, a receptor subtype. Examples include β1 and β2 adrenoceptors.

Isosteres: chemical substituents or groups which have the same size or volume and which can be introduced or removed from a molecule in order to achieve the greatest biological activity.

Isosteric repalcement: a way of modifying a drug molecule by replacing single atoms or functional groups with chemical substituents which have similar size, shape and electromagnetic properties in order to develop molecules with more desirable properties or to eliminate undesirable properties while retaining its desirable pharmacological actions.

Isotonic: having an equal amount of dissolved solute in solution compared to the solutions around it which are typically separated from it by a membrane.

Isotopolog: a molecule which differs in its isotpoic composition from conventional molecules. Examples include deuterated form of conventional drugs where some or all of the hydrogen atoms have been substituted with deuterium. The incorporation of deuterium is stated to increase stability both to thermal and microbial degradation.

Isozymes: also known as isoenzymes, variant forms of an enzyme which have the same substrate specificity but which have differences in their primary (amino acid sequence) structures. These differences often mean that they are inhibited by different molecules which facilitates the development of structurally distinct inhibitor molecules. Isozymes are common and of vital importance in pharmacology particularly where selective inhibition and the lowering of unwanted side effects is desirable.

IUB: International Union of Biochemists, a governing organization in biochemistry and one which, amongst other activities, assigns EC numbers to enzymes.

IUPAC: International Union of Pure and Applied Chemistry, a governing organization in chemistry and one which, amongst other activities, set the guidelines for the naming of organic molecules.
http://www.iupac.org/dhtml_home.html

IUPHAR: International Union of Pharmacology, a non-governmental, non-profit organization founded in 1959 as part of the International Union of Physiological Sciences and has been independent since 1966. The main objectives of IUPHAR are to foster international co-operation in pharmacology, helping the development of pharmacology worldwide and promoting programmes of public awareness on pharmacological issues. They have an active and very useful publications section providing essential reading on matters relating to receptor nomenclature, characterization and functions.
http://www.iuphar.org/

Ivermectin: an antiparasitic compound derived from a group of naturally occurring fungal metabolites, the avermectins. Ivermectin is used in humans to treat river blindness (a worm infection caused by Onchocerca volvulus), is effective in the eradication of Wuchereria bancrofti which causes elephantiasis and is markedly effective against filaria in humans.
It is also widely used in veterinary pharmacology in all species to control infestations of ectoparasites especially mites, to treat all major gastrointestinal worms such as hookworms, heartworm, lungworm and whipworms in ruminants, pigs and dogs and in used in horses to treat bots, stomach worms, strongyles, pinworms and ascarids. Ivermectin is thought to paralyze worms by increasing chloride conductance after opening GABA_A-receptor-chloride channels and thus inhibit neurotransmission.

IVIAD: intravascular inactivation of active drug