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The entry of a drug substance into the bloodstream from the site of administration.

A neurotransmitter in the central and peripheral nerves. Acetylcholine was the first neurotransmitter to be discovered, first described by Sir Henry Dale and colleagues in the UK in the 1930s.

Active substance
A chemical which has been shown to have pharmacological activity.

A purine neurotransmitter and/or neuromodulator that is found in both the peripheral and central nervous system.

A subtype of adenosine receptor which is believed to be important in Parkinson's disease, depression and anxiety.

A substance which interacts with a receptor to cause a biological response.

A "lack of movement" which is a symptom of Parkinson's disease.

A substance which reduces or eliminates pain.

A compound whose chemical structure is similar to another.

Drugs or other substances which reduce appetite.

A substance which reduces or prevents the effect of an agonist at a receptor site.

Substances which block the activity of acetylcholine. These agents are modestly effective in Parkinson's disease.

The long projections from nerves which transmit electrical impulses to the nerve terminals. Axons are covered in an insulating material (myelin) which is composed of fatty substances and looks white to the naked eye (hence the term white matter).

A measure of the amount of drug which is absorbed into the body and is available to exert its biological action.

Blind study
A double-blind clinical study is one in which neither patient nor the investigator knows which drug is being administered during the study. In a single-blind study the investigator but not the patient will know which drug is being taken.

The Body Mass Index (BMI) is a measure of a person's "fatness". This is derived by measuring height and weight as follows:
BMI = weight in kg/height in metres2 .

Slow movement which is often a problem for Parkinson's disease patients.

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Pertaining to the heart.

Pertaining to the heart and blood vessels.

A substance that accelerates a chemical change.

Pertaining to the brain.

A condition which results from long term liver damage (whether by infection, alcohol, drugs or certain inflammatory diseases) and describes a situation in which the liver becomes scarred and functions poorly. If the damage persists the liver goes on to fail, in which case transplantation is the only option.

Clinical data
Usually refers to information obtained during a clinical trial but could be applied to any information obtained from a patient in the course of treatment or examination.

Clinical study
The administration of a drug to healthy volunteers or patients to assess the safety, tolerability, pharmacokinetics and/or efficacy of that drug.

Clinical trial application
An application made to a regulatory authority to seek approval to conduct a clinical study in patients.

Chemistry, Manufacturing and Control (CMC) data are the chemical and pharmaceutical data which are included in an IND or an NDA.

Contract Manufacturing Organisation.

Drugs which block the metabolic breakdown of dopamine by the enzyme catechol-o-methyl-transferase (COMT) also help to relieve symptoms of Parkinson's disease to some extent.

Computational Chemistry
A computer method used to design molecules.

The treatment with which the drug being tested is compared – often placebo or a marketed drug.

Coronary artery
The blood vessel which supplies blood to the heart.

A hormone which is essential to a number of processes in the body including energy provision (mobilisation and storage of glucose), salt balance and the body's responses to stress. The 5-HT1A receptor has a role in the regulation of cortisol levels.

Contract Research Organisation.

Cross-over study
A clinical study in which subjects receive two or more different medications with a drug-free period between them.

A chemical which acts as a cellular messenger, typically of the immune system.

Destructive to cells.

Data sheet
A summary of the information about a drug that is provided to doctors and pharmacists in the UK to enable the drug to be prescribed appropriately. It contains the uses, doses, contraindications, warnings and precautions that must be taken into account.

An amine neurotransmitter. The reduced level of dopamine in the "substantia nigra" brain region is one of the primary deficits in Parkinson's disease patients.

The abnormal movements of the face and body that Parkinson's disease patients suffer when given L-DOPA treatment for a number of years. This is a side effect of treatment rather than a symptom of the disease.

The therapeutic effect of a drug.

Vomiting - a common problem when treating cancer patients with chemotherapy or radiotherapy.

Group of peptide hormones produced by the vascular epithelium (walls of the blood vessels). When released it acts directly on the walls of blood vessels to cause vasoconstriction. It is the most potent vasoconstrictor known.

The study of a disease as it affects groups of people.

US Food and Drug Administration.

5-hydroxytryptamine (serotonin), an amine neurotransmitter substance found in the body.

The dosage form of a drug such as tablet, capsule, fluid for injection, which is made to deliver the drug substance to the body.

(Gamma-Aminobutyric Acid) - an inhibitory amino acid neurotransmitter in brain and spinal cord.

The total gene complement of a set of chromosomes.

Good Laboratory Practice. Set of regulations and guidelines controlling the conduct of pre-clinical studies aimed at ensuring the quality and integrity of data generated during development of a new drug.

An excitatory amino acid neurotransmitter in brain and spinal cord.

Good Manufacturing Practice. Set of regulations and guidelines controlling the quality of manufacturing operations aimed at ensuring consistency of product quality in order to ensure patient safety.

Grey Matter
Parts of the brain rich in nerve cell bodies, hence appearing grey to the naked eye.

The iron-containing protein in red blood cells which transports oxygen.

Bleeding from a ruptured blood vessel.

High blood sugar.

Hypothalamic 5-HT1A receptors
The 5-HT1A receptors that are present in the hypothalamic region of the brain.

Immune Response Modifier
A compound which enhances the body's immune response to combat infectious agents.

Substances which reduce the immune response.

Investigational New Drug. The notification of data relating to a new drug, which must be made to the FDA before it may be administered to man.

A disease target for a drug.

The transfer of a licence by agreement from another organisation in order to develop or market the particular product which is licensed.

One of a number of chemicals released into the blood and tissues as part of the body's defense to damage by infection or inflammation. Interferons are used to treat a number of conditions including Multiple Sclerosis.

In vitro
Carried out in an artificial system outside the body (literally – "in glass").

In vivo
Carried out in a living biological system, either animals or humans (literally - "in life").

A substance derived from the ipecacuanha plant root and used to induce vomiting.

A situation of oxygen deprivation. Prolonged oxygen deprivation in the brain results in permanent damage, commonly described as a stroke. The usual cause is a blood clot in an artery supplying the brain tissue.

A group of lipids which act as chemical messengers within the body.

The standard treatment for Parkinson's disease. This substance is the building block for the manufacture of dopamine by nerve cells, which is the primary deficit in Parkinson's disease. Long term L-DOPA treatment results in dyskinesia.

A general term to describe substances (such as drugs) which bind to receptors.

One of the leukotrienes.

Marketing Authorisation Application – an application to a drug regulatory authority in Europe for approval to market a drug.

MAO-B inhibitors
Drugs which slow the metabolic breakdown of dopamine by the enzyme monoamine oxidase (MAO), which can help relieve the symptoms of Parkinson's disease.

The effect of the body on an administered compound which results in its transformation into other compounds prior to excretion.

New Chemical Entity. A newly identified molecule with a novel structure.

New Drug Application. An application to the FDA for approval to market a drug.

Caused by the nervous system.

Relating to the nervous system.

A term to describe a particular form of pain which is caused by damage to nerves. Burns, viral infections (eg shingles), diabetes, cancer, disc problems, amputation (phantom limb) and certain chemicals can give rise to neuropathic pain which is difficult to treat with currently available medicines.

Toxicity to the nervous system.

A chemical mediator released from nerve terminals in response to nerve stimulation and which binds to receptors which are on the surface of other nerve cells. There are a number of different classes of neurotransmitters as well as many different receptor types and subtypes.

N-methyl, D-aspartate - a subtype of glutamate receptor.

Describes the sensation of pain. Nociceptive stimuli are painful stimuli.

Nonsteroidal Anti-Inflammatory Drugs, used to treat pain. Examples include Brufen, Voltarol etc.

Drugs derived from opium, such as codeine and morphine.

The absorption, distribution, metabolism and excretion of a drug by the body, studied over a period of time.

The determination of the economic value that a treatment regime provides – often compared with other established therapies.

The study of the interaction of pharmacologically active compounds at their sites of action and their biological effects.

Phase I
First stage of testing in human subjects. Studies in healthy subjects to determine biological properties including, pharmacological activity, pharmacokinetics and tolerability of a new drug.

Phase IIa
First stage of testing in patients. Studies in a small number of patients to make a preliminary determination of efficacy and safety of a new drug to provide proof of the concept.

Phase IIb
Studies in a larger number of patients to determine the range of doses to be used in the Phase III clinical trials.

Phase III
Full scale clinical trials to determine efficacy and safety of a drug prior to seeking marketing approval.

Phase IV
Large scale clinical trials carried out after regulatory approval designed to expand experience of the efficacy and safety of the drug, often in comparison with other treatments. Sometimes referred to as marketing support trials.

An inactive substance used as a comparison with an active drug.

This describes what is left in blood once the cells (red cells, white cells) have been removed.

Post Herpetic Neuralgia
A form of neuropathic pain that results from infection with Herpes Virus (the common term is shingles).

Pre-clinical studies
In vitro or in vivo non-clinical studies performed to determine safety, pharmacological activity and product quality.

Designed to prevent, as opposed to treat, a disease or condition.

A protein located on a cell membrane or within the cell with which a hormone, neurotransmitter or drug interacts to produce or prevent a biological response.

Pertaining to the kidney.

Serotonin (5-hydroxytryptamine or 5-HT)
An amine neurotransmitter involved in eating, mood, headache and sexual behaviour.

The study of the integrity of a drug substance or finished product over time under various, well defined and controlled storage conditions.

Cerebral ischaemia (lack of oxygen to the brain) is usually the result of blockage or rupture of a blood vessel in the brain giving rise to the risk to permanent brain damage. The type of disability the patient suffers is determined by the position and the extent of the damaged area. About 30% of strokes are fatal.

Subarachnoid space
Space between the arachnoid membrane of the brain and another membrane (piamater) which is in direct contact with the central nervous system.

Substantia Nigra
A group of nerve cell bodies in the mid-brain that contain dopamine. It is this part of the brain that degenerates in Parkinson's disease. The levels of the neurotransmitter dopamine are unusually low in Parkinson's patients. Replacement of dopamine is one strategy to relieve symptoms.

The preparation of a substance by chemical means as opposed to its extraction from a natural source.

Causing an undesired or adverse effect. Most substances will cause adverse effects if high enough doses are given.

The study of the undesired or adverse effects of a substance on the body.

All marketed drugs have an internationally approved name for the compound (drug substance), as distinct from the trade name. The system of naming employs a common “stem” for each member of a class of compounds sharing the same mechanism of action. “Triptan” (as in frovatriptan) is the stem adopted for drugs that act on 5-HT1 receptors and which share a similar mechanism of action in relieving migraine attacks.

An induced narrowing of blood vessels.

An induced expansion of blood vessels.

Prolonged and profound constriction of blood vessels leading to inadequate blood supply to a tissue or organ.

White Matter
Areas of the brain rich in axons. The white appearance occurs due to the high density of myelin, the fatty insulation which covers the axons (like insulation on electrical cable).

A molecular structure found in many common drugs and products (eg caffeine).