Drug profiles: glossary

Brief glossary of chemical and biochemical terms

A | B | C | D | E | F | G | H | I | K | L | M | N | O | P | R | S | T | U | V


α2-Adrenergic receptor

α2-Adrenergic receptors are the targets of catecholamine neurotransmitters such as noradrenaline. They are present in the central and peripheral nervous system and regulate, among others, the constriction or dilation of blood vessels and the motility of smooth muscle in gastrointestinal tract. Agonists of this receptor (e.g., clonidine) are often used to treat the symptoms of opioid withdrawal.

Active pharmaceutical ingredient

The substance in a pharmaceutical drug that is biologically active.


Often synonymous with cutting agent – a substance added as a diluent to a drug. It may be inert or pharmacologically active. Such diluents can be found in illicit powders as well as tablets, in which case the term might also include tablet binders.

Affinity constant

This is the equilibrium dissociation constant used in drug-receptor binding to describe how tightly a ligand (drug) binds to a particular receptor. Ligand-receptor affinities are measured in molar units (M), which correspond to the concentration of ligand at which the binding site of a particular receptor is half occupied. The smaller the constant, the more tightly bound the ligand is, and the higher the affinity between ligand and receptor.


A drug that mimics the effect of neurotransmitters or other endogenous molecules. It has the opposite effect to an antagonist.


Usually an inorganic base such as sodium hydroxide or sodium carbonate/bicarbonate. By combining with the chemically bound acid residue, an alkali is used, for example, to convert a salt into the free base.


A naturally occurring nitrogenous base, often with psychoactive properties and which may be active in very low doses (e.g. cocaine, morphine and certain other constituents of opium, dimethyltryptamine). Alkaloids are often regarded as end-products of plant metabolism, which may have evolved as protection against herbivores.

Aluminium foil method

A type of reductive amination that requires little equipment. A precursor ketone (e.g. P2P, PMK) is reacted in ethanol with aluminium metal pieces, an amine and a mercuric chloride catalyst. When the amine is methylamine and the ketone is PMK then the product is MDMA.


A chemical group comprising a nitrogen atom attached to one or more carbon atoms and one or more hydrogen atoms. Amines are typically bases, i.e. they react with acids to forms salts. Most psychoactive substances are either primary or secondary amines or, less commonly, tertiary or quaternary amines.


Also known as N-arachidonoylethanolamine, the endogenous ligand for cannabinoid receptors in the CNS and other organs.


An absence or near absence of oxygen.


An agent that opposes the action of another (compare agonist).

Anterograde amnesia

Loss of memory for experiences which occur after the use of a benzodiazepine, although the condition can also be caused by traumatic brain injury.


An antinociceptive substance is one that inhibits the perception of pain.



A nitrogenous substance, sometimes known as an alkaloid when derived from plant material, which reacts with acids to form a salt. Many bases are insoluble in water but soluble in organic solvents.


Indole alkaloid commonly found in skin (parotid) glands of Bufo alvarius: Colorado river toad and Bufo marinus: cane toad. Also present in the seeds and leaves of Piptadenia peregrina and Piptadenia macrocarpa (found in the Chinese preparation Yixin Wan, Kyushin and Lu-Shen Wan), as well as in the mushrooms Amanita citrina, Amanita porphyria and Amanita tomentella. It has serotonergic activity; also inhibits sodium, potassium and muscle ATP.



One of a group of compounds found only in Cannabis sativa including cannabidiol (CBD), cannabinol (CBN) and tetrahydrocannabinol (THC).


Chemical Abstracts Service. A body responsible for indexing the world’s chemistry-related literature and patents (http://www.cas.org/).

CB1 receptor

A cannabinoid receptor primarily located in the CNS. THC behaves as an agonist at the CB1 receptor, which is then responsible for the psychoactive effects. Other cannabinoid receptors, such as CB2, are found mainly in the immune system, and are partly involved in the perception of pain.


Cannabidiol (CBD) is one of several cannabinoids in Cannabis sativa. It behaves as an antagonist to THC and occurs at a higher concentration in cannabis resin than in cannabis.


Cannabinol (CBN) is a cannabinoid and an oxidation product of THC. It is normally only found in aged samples of cannabis and cannabis resin.

Cutting agent

A substance added as a diluent to a drug – often synonymous with adulterant. It may be inert or pharmacologically active. Such diluents can be found in illicit powders as well as tablets, in which case the term might also include tablet binders.

CYP2D6 enzyme

CYP2D6 is a member of the cytochrome P450 monooxygenase enzyme family in the liver catalysing the oxidative biotransformation of endogenous and exogenous substances, including many important drugs.



When a molecule contains two centres of asymmetry, it can form four diastereoisomers (i.e. two pairs of enantiomers). Thus, ephedrine, for example, exists as four diastereoisomers, two of which are known as pseudoephedrine.


A molecule consisting of two identical sub-units.


A group of natural products formally derived from four isoprene (C5) units to give a diterpene (C20). Some familiar diterpenoids are: the anti-cancer drug paclitaxel (taxol), the plant pigment component phytol, and the vitamins A and E. Notable psychoactive diterpenoids are salvinorin A and Δ9-tetrahydrocannabinol.


4-Bromo-2,5-dimethoxy-amphetamine (also known as brolamphetamine) is a synthetic amphetamine-type compound under international control according to the 1971 UN Convention on Psychotropic Substances. It is one of the most potent hallucinogens being active at 1–3 mg oral doses. DOB is a selective agonist of serotonin receptor subtypes, especially 5-HT2A, in the brain, but is also a strong vasoconstrictor at the periphery.


An example of a neurotransmitter, it is a naturally occurring substituted phenethylamine. Substances that interact with this receptor are said to be dopaminergic.



Originally used to describe MDMA, but since generalised to describe a wide range of substituted phenethylamines and, less precisely, certain unrelated substances.

Ehrlich’s reagent

A field test reagent consisting of 4-(dimethylamino)benzaldehyde, ethanol and hydrochloric acid. It is used for the detection of amines (cocaine, phencyclidine, etc.) and indole derivatives (psilocybin, LSD, yohimbine, etc). Its modified version contains 4-(dimethylamino)benzaldehyde, acetic acid and perchloric acid.


A substance that produces empathy with others, most often applied to MDMA and related drugs. See also entactogen.


One of a pair of stereoisomers arising from the presence in a molecule of an asymmetric carbon atom. The two enantiomers are mirror images of each other, with left- and right-handed forms denoted S (sinister) and R (rectus) respectively. Enantiomeric pairs were previously denoted by terms such as d (dextro) and l (laevo) or by the symbols (+) and (–).


The property of a naturally occurring substance that originates or produces within an organism, tissue, or cell.


A substance that produces a socialising effect and desire for contact, most often applied to MDMA and related drugs. See also empathogen.


First-pass metabolism

The effect whereby the concentration of an orally administered drug is reduced before it reaches the systemic circulation, often because of metabolism by the liver.


An unexpected, episodic recurrence of the effects of a hallucinogenic drug ong after its original use. In the fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) of the American Psychiatric Association, it is named ‘Hallucinogen Persisting Perception Disorder’.


Gamma-aminobutyric acid (GABA)

This is an abbreviation of Gamma-aminobutyric acid which is the chief inhibitory neurotransmitter in the CNS. GABA binds to any three classes of GABA receptors in brain cells. Drugs such as benzodiazepines, which also activate these receptors (agonists), typically have relaxing, anti-anxiety and anticonvulsant effects.

Gas chromatography-mass spectrometry (GCMS)

GCMS is a method to identify different substances within a test sample.

Grand mal seizure

Also known as a tonic-clonic seizure, it features a loss of consciousness and violent muscle contractions. It is caused by abnormal electrical activity throughout the brain, so signs and symptoms typically involve the entire body.


Kits consisting of all the requirements necessary to grow hallucinogenic mushrooms (e.g. Psilocybe cubensis, Psilocybe tampensis). They usually contain a box with colonised substrate, a bag with an air filter and paperclips. Depending on the species, a growkit can produce an average yield of several hundred grams in a few weeks (200–300 grams in 3 weeks).



The time required for the concentration of a drug in a tissue (e.g. blood) to fall to 50% of its initial value.


Apparent perception of an external object or person when no such object or person is present.


A substance that produces as a main effect perceptual distortions, especially visual and auditory. The effects can also extend beyond perceptions to changes of thought, mood and personality integration (self-awareness).The term is somewhat misleading as the hallucinogenic substances do not generally cause true hallucinations (i.e. sensory perceptions in the absence of external stimuli). However, the term is widely accepted by the scientific community.


When a series of chemical compounds differ only by a constant structural element, they are said to form a homologous series. Thus, MDA, MDMA and MDEA are homologues in which each successive member differs from the previous structure by a methylene moiety (CH2).

5-HT2A receptor

As subtype of serotonin (5-hydroxytryptamine, 5-HT) receptors, 5-HT2A receptors are present in the brain and the periphery and bind the endogenous neurotransmitter 5-HT. Classical hallucinogens, such as LSD, psilocin or DOB, are agonists of 5-HT2A receptors in the central nervous system. In the periphery, 5-HT2A receptors are involved in various cardiovascular functions, platelet aggregation and nociception.


Some salts contain water chemically bound within their crystalline structure: these are referred to as hydrates. An example is heroin (hydrate) hydrochloride, the molecular structure of which contains a water molecule.


Greater than the normal level of carbon dioxide in the blood.


An unusual and excessive rise in body temperature, over 42 °C or 107.6 °F.


Ibotenic acid

An excitotoxin, naturally occurring in the mushrooms Amanita muscaria and Amanita pantherina, among others. It is a powerful neurotoxin that is used as a ‘brain-lesioning agent’ in pharmacological and toxicological research and has shown to be highly neurotoxic when injected into the brain. It is 3 to 10 times as potent as glutamic acid and is used to study the excitatory mechanisms of glutamate neurotransmission.


The final and longest segment of the intestine having a large surface area. Readily available rodent ileum preparations are widely used in the pharmacological evaluation of opioid receptor agonists and antagonists.


A biochemical test that measures the presence or concentration of a substance in solutions that frequently contain a complex mixture of substances.

Impurity profiling

The separation of naturally occurring or synthetic by-products in a drug, often by chromatographic methods, to form a ‘fingerprint’ that may be characteristic of its origin or manufacturing route.

Infrared spectroscopy

Infrared (IR) spectroscopy is an analytical technique used to characterise atomic groups (e.g., CH, C=C, C=O, C(=O)NH2, OH) of organic compounds absorbing electromagnetic radiation particularly in the 4 000–400 cm-1 wavenumber (0.25–25 μm wavelength) range.

International Non-Proprietary Name (INN)

Defined by the World Health Organization (WHO) for substances that have or have had therapeutic value.


Described as difficulty falling asleep, frequent wakening during the night, early morning wakening and awaking un-refreshed.


International Union of Pure and Applied Chemistry. A body responsible for the systematic nomenclature of chemical entities (http://www.iupac.org /index_to.html).



The common name of both the tropical tree Mitragyna speciosa and the drug made from its leaves. The drug in small doses provides stimulant effects, while in large dosages it is sedative. Kratom preparations are used in folk medicine and also as opium substitutes.


Leuckart route

A popular method for converting ketones (e.g. P2P and PMK) to the corresponding amines using formic acid, ammonium formate or formamide/methylformamide as reagents. When the ketone is P2P, the result is amphetamine or methamphetamine, while MDA and MDMA arise from the ketone PMK.


A substance that is able to bind to another biomolecule (substrat/receptor) by means of intermolecular forces to form a complex by altering its chemical conformation (three-dimensional shape).


The property of a substance that gives it an affinity for fatty tissues/organic solvents and low aqueous solubility.


Marquis test

A field test using a reagent consisting of 10% formaldehyde in concentrated sulfuric acid. Various colours are produced by mixing the reagent with different drugs.

Mass spectrum

A pattern of charged molecular fragments produced by bombarding molecules with electrons. The fragmentation pattern is characteristic of the molecule.

Mescaline (3,4,5-trimethoxyphenethylamine)

An alkaloid derived from the Mexican peyote cactus; a hallucinogenic drug. In 1897, the German chemist Arthur Heffter was the first to isolate mescaline from the peyote cactus.


Chemical transformations occurring in an organism from the time a nutrient substance enters it until it has been utilised and the waste products eliminated. In animals and humans, digestion and absorption are primary steps, followed by a complicated series of degradations, syntheses, hydrolyses and oxidations, in which agents such as enzymes, bile acids and hydrochloric acid take part. These transformations are often localised with respect to the organs, tissues and types of cells involved.


An intermediate substance produced and used in the processes of a living cell or organism.

Miosis (myosis)

Constriction of the pupil of the eye is a normal response to light. Pinpoint pupils are one of the characteristic effect of opioids as well as sedative-hypnotics (e.g., barbiturates, benzodiazepines, and gamma-hydroxybutyrate) and cholinesterase inhibitors (e.g., organic phosphates or carbamate insecticides).


A psychoactive alkaloid with a complex structure present in the leaves of Mitragyna speciosa. Mitragynine and its 7-hydroxylated derivative are agonists at the μ-opioid receptor (MOR).


The major psychoactive alkaloid present in many mushrooms of the Amanita genus. Unlike psilocybin, muscimol is a potent, selective agonist of the GABAA receptor. Muscimol is similar in chemical structure and activity to ibotenic acid.


Muscle pain, most commonly caused by chronic fatigue, injury, metabolic disorders, certain infectious diseases or drugs (e.g., amphetamines, morphine, and phencyclidine).


Dilation of the pupil of the eye. It is a normal response to darkness. Light-insensitive mydriasis can be caused by anticholinergics (e.g., atropine), hallucinogens (e.g., psilocybin and mescaline) and, especially, stimulants (e.g., amphetamine) that elicit mydriasis by different mechanisms.



Naloxone is a semisynthetic opioid receptor antagonist developed in the 1960s. It is relatively short-acting and used clinically to reverse the effect of opioids (e.g. heroin) in overdose or postoperative sedation.


A condition characterized by abnormal sleepiness during daytime. It is often treated by administration of CNS stimulant drugs.

Narcotic analgesic

A type of analgesic acting on the central nervous system rather than on peripheral nerves. Many opioids (e.g. heroin/diamorphine) are typical narcotic analgesics.


Bitter, oxygenated cyclic diterpenoids (also called ent-clerodanes). Plants of the mint (Lamiaceae) family contain many biologically active neoclerodane derivatives (e.g. salvinorin A).


A chemical messenger involved in passing a signal from one neuron to adjacent neurons in the brain or spinal cord.

Nitrogenous base

A synthetic or naturally occurring substance containing one or more amine nitrogen atoms in its structure and acting as a base.


Also known as norepinephrine. An example of a neurotransmitter, it is a naturally occurring substituted phenethylamine.


Substances that interact with the noradrenaline receptor are said to be noradrenergic.

Nucleus accumbens

A collection of neurons forming the central part of the reward pathway of the brain. Its activation is responsible for the rewarding/reinforcing and addictive properties of a drug. Nearly all illicit drugs act upon the nucleus accumbens.


Rapid involuntary rhythmic movement of the eyes.


O-Desmethyltramadol (ODT)

O-Desmethyltramadol (ODT) is a major bioactive metabolite of tramadol, a synthetic opioid analgesic with low abuse potential. ODT has much higher opioid receptor affinity and greater analgesic activity than the parent drug.


See under tramadol.

μ-opioid receptor (MOR)

The μ-opioid receptor (MOR) is a type of opioid receptor that binds the endogenous opioid peptides enkephalins and endorphins. It is also the main target of synthetic opioid drugs.

κ-opioid receptor (KOR)

The κ-opioid receptor (KOR) is a type of opioid receptor which binds the opioid peptide dynorphin as the primary endogenous ligand.


One of a group of alkaloids isolated or chemically derived from opium. Often synonymous with opiate, but sometimes restricted to semisynthetic products (e.g. diamorphine) or chemically related synthetic substances (e.g. methadone).


The dried latex of the seed capsule of the opium poppy (Papaver somniferum L.).

Opium alkaloid

Often synonymous with opioid. See also alkaloid.



1-Phenyl-2-propanone: a ketone often used as a precursor to amphetamine and methamphetamine. P2P is listed in Table I of the United Nations 1988 Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.


Literally, to examine by pressing on the surface of the body to feel the organs or tissues underneath: in this context to squeeze and relax the contents of a plastic bag while inhaling and exhaling into it.


A chemical substance comprising a phenyl group attached to a linear chain of two carbon atoms and terminating in an amino group. The expanded name is 2-phenylethylamine. The phenethylamine family includes a range of substances that may be stimulants, entactogens or hallucinogens.


The study of evolutionary relationships among organisms using morphological characteristics and molecular (for example, genetic) sequencing data.


3,4-Methylenedioxyphenyl-2-propanone: a ketone often used as a precursor to MDMA. PMK is listed in Table I of the United Nations 1988 Convention Against Illicit Traffic in Narcotic Drugs and Psychotropic Substances.


A quantitative measure of the activity or strength of a drug: a different concept to purity, which is the proportion of active drug in a preparation.


Prevalence of drug use in the general population (adults or school children) is assessed through surveys, based on the self-reports of participants, in representative probabilistic samples of the whole population in most EU Member States and Norway.

Primary amine

A chemical group comprising a nitrogen atom attached to two hydrogen atoms and to a carbon atom.

Psychotropic drug

A generic term for substances that modify normal behaviour. Examples can be found in the 1971 UN Convention on Psychotropic Substances. Many are subclassified as stimulants or hallucinogens, but the term can also include sedatives, tranquillisers and hypnotics. Psychotropic drugs are differentiated from narcotics, which are more correctly known as narcotic analgesics.


The proportion (%) of active drug in a preparation: a different concept to potency, which is quantitative measure of the activity or strength of a drug. Most laboratories determine purities with respect to the base because in a sample sent for analysis the particular salt form cannot be determined without further, often unnecessary, investigation. So, for example, pure amphetamine base has a purity defined as 100%. When amphetamine base reacts with, for example, sulfuric acid to form the sulfate salt, then the purity of that salt, with respect to the base, is 79%; the remaining 21% is the sulfate residue. If the purity is expressed with respect to a specific salt form, then pure amphetamine sulfate has a purity of 100%.

Pyrrolidine ring

The central structure of the amino acids proline and hydroxyproline.



A 50:50 mixture of two enantiomers produced when a synthesis is not stereoselective.

Racemic mixture

See racemate.


A chemical process involving removal of oxygen atoms and/or addition of hydrogen atoms.

Reductive amination

A chemical process involving removal of oxygen atoms and addition of an amino group.


See enantiomer.


Rhinorrhea (‘runny nose’) is an excessive discharge of nasal fluid. It may be caused by common cold, allergies, and opioid withdrawal and can be treated with antihistamines and vasoconstrictors (e.g., amphetamine, phenylephrine).

Romberg’s test

A simple test used in neurological examination and also as an indicator for possible alcohol or drug impaired driving. It detects the inability to maintain a steady standing posture with the feet together and eyes closed. A loss of balance is interpreted as a positive Romberg sign (Rombergism).


Rubiaceae is a family of flowering plants that are concentrated in warmer and tropical climates around the world. The family includes Coffea of which seeds of several species are the source of the popular beverage coffee.


Salvinorin A

An extremely potent neoclerodane-type diterpenoid hallucinogen from the Salvia divinorum plant. It was once also called divinorin A.


The product of reacting a base with an acid. Many salts are soluble in water but insoluble in organic solvents.


See enantiomer.


The term S-DDD is a technical unit of measurement used in statistical analysis. This is not a recommended prescription dose, and can vary according to the condition being treated and medical practice in a particular country.

Secondary amine

A chemical group comprising a nitrogen atom attached to a hydrogen atom and two carbon atoms.


Also known as 5-hydroxytryptamine. An example of a neurotransmitter, it is a naturally occurring substance closely related to naturally occcurring and synthetic hallucinogenic tryptamines.

Simon test

A field test using a reagent consisting of sodium carbonate, acetaldehyde and sodium nitroprusside. Used for distinguishing primary amines from secondary amines.


A shop that specialises in psychoactive herbal substances that are legal in addition to a range of vitamins, mineral supplements and other health products.


Is the pure culture of mycelium which is already grown through a substrate. The substrate may consist of sterilised woodchips. From this, mushrooms will grow from microscopic spores, not seeds. A mature mushroom will drop as many as 16 billion spores. Spores must be collected in the nearly sterile environment of a laboratory and then used to inoculate grains or seeds. Mushroom spawn bags contain sterile hardwood chips with mushroom mycelium.


One of two or more forms of a molecule with the same sequence of atoms, which arises from the three-dimensional arrangement of those atoms.


A substance that increases psychomotor activity by increasing the production of certain neurotransmitters, especially in brain synapses.


Denoting neural action, endogenous chemical agents, or drugs that simulate the action of sympathetic postganglionic nerves or their transmitters. Synonymous with adrenergic.


A condition in which normally separate senses are fused, in which one type of stimulation evokes the sensation of another, as when the hearing of a sound produces the visualisation of a colour.



Excessive rapidity in the action of the heart; the term is usually applied to a heart rate above 100 beats per minute in an adult.


Tautomers are isomers of organic compounds that readily interconvert by a chemical reaction called tautomerism. This commonly results in the migration of a hydrogen atom, accompanied by a switch of a single bond and an adjacent double bond.

Tertiary amines

A chemical group comprising a nitrogen atom attached to three carbon atoms.


Δ9-Tetrahydrocannabinol, the major active principle in cannabis.

Therapeutic index

A measure of the relative safety of a drug expressed as the ratio of the lethal or toxic dose to the therapeutically effective dose.


Tramadol is a synthetic opioid analgesic with low abuse potential. Its major metabolite is O-desmethyltramadol (ODT) that has greater analgesic activity than the parent drug.


Group of biologically active compounds, including neurotransmitters (e.g. serotonin) and hallucinogens (e.g. LSD, psilocin and psilocybin). The chemical nucleus of these compounds is the monoamine alkaloid tryptamine that can be found in numerous plants and animals. Tryptamine is based around an indole ring structure, and is chemically related to the amino acid tryptophan.


Ultraviolet spectroscopy

Ultraviolet (UV) spectroscopy is an analytical technique for the characterisation of compounds that absorb electromagnetic radiation in the 200–700 nm wavelength range. Its use is largely limited to quantitative analysis.


Vapour phase infra-red spectrophotometry

The absorption of infra red radiation by a vapour that produces a spectrum that is characteristic of a particular compound.