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Development and Classification of Medicine. Brenda McCartney 2 nd February 2011. Development of a Medicine. What is a drug?. Any biologically active chemical that does not occur naturally in the human body that can affect living processes

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Development and classification of medicine l.jpg

Development and Classification of Medicine

Brenda McCartney

2nd February 2011



What is a drug l.jpg
What is a drug?

  • Any biologically active chemical that does not occur naturally in the human body that can affect living processes

  • It is used for the treatment, prevention or alleviating the symptoms of disease.


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16th century Egypt

Ebers papyrus

poppy juniper berries

beer lead

swine teeth goose grease

lizard's blood donkey hooves

crushed precious stones

excreta from various animals

A little light history


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Where do drugs come from now?

  • Plants:

    Digoxin (foxglove)

    Belladonna (deadly nightshade)

    Diamorphine (opium poppy)

  • Animal tissue:

    Insulin, growth hormone

  • Synthetic manufacture:

    Most modern medicines


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The Pharmaceutical Industry

  • Develops, produces and markets drugs licensed for use as medicine.

  • Companies can deal in generic and / or brand medications.

  • Average cost to develop a successful new drug £145million - £1.2 billion

  • Subject to variety of laws and regulations.


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Stages in Drug Development

1 Drug discovery

Research & identification of compounds

2 Pre-clinical testing

Lab testing

3 Clinical trials

Testing on humans.


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1. Drug Discovery

  • From traditional remedies

    • Aspirin

    • Penicillin


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Aspirin – first synthetic drug

  • (460-377 BC) Hippocrates Pain relief treatments with powder made from the bark and leaves of the willow tree

  • (1829) Johann BüchnerIsolated pure salicin (salicylic acid (1838))

  • (1853) Charles Frederic Gerhardt first synthesised acetyl-salicylic acid (ASA)

  • (1898) Felix Hoffman Chemist at Bayer synthesized pure sample of ASA

  • (1899) Bayer receives patent for Aspirin®

  • Sales today exceed 50 billion pills per year


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Penicillin – the first antibiotic

  • Fleming was a researcher working in an untidy lab

  • After returning from holiday he noticed that bacterial plates had become contaminated with a fungus

  • Bacteria were not present near the fungus on the plate

  • He concluded that the fungus was secreting an antimicrobial agent

  • He extracted the agent and named it penicillin

    Fleming was presented the Nobel Prize

    for Medicine in 1945. He humbly said,

    "Nature makes penicillin; I just found it."


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2. Pre-clinical Testing.

  • In vitro testing

    • Test active compound against target cell

    • Provides evidence of beneficial / harmful effects

    • Very simplistic, target organs/tissues made up of multiple cell types

    • BUT lacks the homeostatic mechanisms and pathways found in animals / humans


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Pre-clinical animal testing

Pharmacology Testing

  • effects of drug on all major systems (absorption, metabolism, distribution, excretion, plasma levels, half life)

    Toxicology Testing

  • Acute toxicity (single dose)

  • Short term toxicity (daily dosing for 2 weeks – 3 months)


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Pre-clinical Testing

  • ED50 – Effective Dose 50

    the amount of the drug required to produce a specified effect in 50% of an animal population

  • LD50 Lethal Dose 50

    The amount of the drug required to cause death in 50% of an animal population


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But only human studies can tell use how useful and safe a drug is................

.....So clinical trials in human volunteers are needed.


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Clinical Trials. drug is................


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What are clinical trials? drug is................

  • Research studies involving humans

  • Used to determine if drug treatments are safe and effective

  • Are the safest and quickest way to find treatments that work


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Types of clinical trails. drug is................

  • Treatment trials

  • Prevention trials

  • Screening trials

  • Diagnostic trials

  • Quality of life studies

  • Genetics studies


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Clinical trial protocol drug is................

  • Strict scientific guidelines

    • Purpose of study

    • How many participants

    • Who is eligible

    • How study will be carried out

    • What information will be gathered

    • End points


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Clinical trials – phases drug is................

Stage 2

Preclinical

Stage 1

Drug Discovery

Stage 3

Clinical trials

Phase I

20-100 volunteers

Phase III

1000-5000 volunteers

10,000

compounds

250 compounds

5 compounds

1 approved drug

Phase II

100-500 volunteers

6.5 years

7 years

1.5 yrs

Adapted from Pharmaceutical Research and Manufacturers of America.


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Phases I trials drug is................

  • Use healthy volunteers

  • How does the drug affect the human body?

  • Drug absorption, metabolism and excretion

  • Preferred method of administration

  • What dosage is safe?


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Phase II trials drug is................

  • Use target patient group representative of those likely to benefit from the drug.

  • No pregnant women

  • Does the drug have a beneficial effect on the disease?

  • Determine therapeutic dose range.

  • Usually placebo controlled

  • Conducted by experts in the disease field


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Phase III trials drug is................

  • Obtains all data for regulatory agencies

  • Often multi-centered, multinational

  • Long term safety evaluated

  • Is new drug better than standard?


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Randomised controlled trial (RCT) drug is................

  • Volunteers randomly assigned to new treatment or best existing treatment

  • Doctors have no say in who goes in which group to reduce bias


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What is a placebo? drug is................

An inactive pill, identical in appearance to the treatment pill which is given to the control group.

Used to control for the placebo effect

Patient feels better due to belief in the treatment

Test pill Placebo


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Participants in Clinical Trials drug is................

  • Protocol sets out who can participate

  • Use inclusion / exclusion criteria

  • Factors that allow people in are inclusion criteria (study for males)

  • Factors used to reject are exclusion criteria (may have history of illness)


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Clinical trials – the results drug is................

  • Endpoint used to test trials success

  • Ideally use a hard endpoint – cure from disease

  • Statisticians analyse results – is A better than B?

  • Only after analysis do you tell which is A and B.


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Drug Licensing drug is................

  • Application submitted to Medicines and Healthcare products Regulatory Agency (MHRA)

  • MHRA carry out pre-marketing assessment of safety, quality and efficacy, examining all research and results in detail.


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Medicines and Healthcare products Regulatory Agency drug is................

  • An executive agency of the Department of Health

  • Enhance and safeguard the health of the public by ensuring that medicines and medical devices work and are acceptably safe. No product is risk free. 


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European Medicines Evaluation Agency (EMEA) drug is................

  • The EMEA co-ordinate drug licence applications within the European Union (EU).

  • Committee for Proprietary Medicinal Products (CPMP)


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Product Launch drug is................

  • When a drug has marketing authorisation, it is not available straight away. The company first have to apply to market their product. In the UK, they will apply to the MHRA. When this is done, the product is ‘launched’, and doctors can prescribe it.

  • The time it takes from marketing authorisation to launch in the UK is one of the fastest in the world.


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Black Triangle Drugs. drug is................

  • If the drug is an active substance which has been newly licensed for use in the UK.

  • If it contains a new combination of active substances.

  • If administration is via a new route or delivery system.

  • If the medicine is to be used in a new patient population.

  • If the drug is to be used for a new indication.


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MHRA monitoring of Black Triangle Drugs drug is................

  • confirm risk/benefit profiles established during the pre-marketing phase

  • increase understanding of the safety profiles of new medicines

  • ensure identification of previously unrecognised side effects as quickly as possible.

    Uses Yellow Card Scheme.


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Classification of a Medicine drug is................


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Names of drugs drug is................

  • Chemical name: describes the chemical structure: acetyl-p-amino-phenol

  • Generic name: a name that can be used by anyone: paracetamol

  • Trade name: owned by the manufacturer: Calpol


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Other ways to categorise drugs drug is................

  • What kind of molecule is it?

  • What organ system (or what disease) is it for? e.g., cardiac, psychotropic

  • What parts of cells are affected?


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What is the drug used for? drug is................

  • To cure e.g., infections, cancer

  • To suppress diseases or symptoms without attaining a cure e.g., hypertension, diabetes, pain control

  • To prevent disease (prophylactic) e.g., immunisation


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How does the drug act? drug is................

  • Replace a deficiency, e.g., vitamins, minerals, hormones

  • Interfere with cell function, e.g., block enzyme action

  • Kill / prevent growth of viruses, bacteria, fungi, protozoa, cancer


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Categories of drug drug is................

  • Anti-inflammatory

  • Analgesic

  • Antipyretic

  • Vaccine

  • Antihypertensive

  • Vitamin supplement

  • Antitussive

Anaesthetic

Surfactant

Laxative

Antiviral

Antifungal

Antibiotic


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How do drugs work? drug is................

  • Pharmacodynamics: study of how chemicals exert their effects

    The practical importance of this is enabling the design of new and better drugs


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receptor drug is................

Receptors

  • Receptors are proteins on the cell surface or inside the cell.

  • They bind the body’s own chemical messenger

  • Convert the binding event to a signal that the cell can recognize and respond to

signal


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“Lock & Key” drug is................

  • Interaction between a receptor and its signal molecule (ligand) is like “lock & key”.

  • Perfect fit depends on exact 3D shape and size of both molecules.


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drug drug is................

receptor

Receptors

  • Drugs also bring information to cells by fitting into the same receptor molecules.

  • The drug picks the lock and triggers a response by the cell.


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Agonists and Antagonists drug is................

  • Agonist: a drug that fits into a receptor and activates a response e.g., morphine, nicotine

  • Antagonist: a drug that fits into a receptor but blocks the receptor and does not activate a response e.g., beta-blockers


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Non-specific effects drug is................

  • Acidic or alkaline properties

  • Surfactant properties (amphotericin)

  • Osmotic properties (laxatives, diuretics)

  • Interactions with membrane lipids (anaesthetics)


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Side-effects and other effects drug is................

  • Not the “wanted” effect e.g. aspirin causes gastric ulcer

  • Diphenhydramine has a useful side-effect


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Side-effects and other effects drug is................

  • Hypersensitivity / allergy: exaggerated adverse reaction to drug

  • Toxic effects e.g., Thalidomide: teratogenic

  • Tolerance: increasing amounts are needed to produce the same effect


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Pharmacokinetics drug is................

How the body deals with the drug

We need to consider

  • Dose

  • Route of Administration

  • Absorption and distribution

  • Metabolism and excretion


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Dose drug is................amount of drug taken at any one time

  • Aim is to give the patient a dose of drug that achieves the desired effect without causing harmful side effects

  • Therapeutic Index(TI) is the ratio of the therapeutic dose to the toxic dose

  • Egs of drugs with low TI include digoxin lithium and methotrexate


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Administration drug is................

Route of administration depends on

  • how easy it is to use for patient

  • how quickly a drug needs toreach site of action

  • where it has to work in the body


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Routes of Administration drug is................

Intravenous

Inhaled

Oral

Transdermal

Subcutaneous

or intramuscular

injection

Topical

Rectal


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Oral drug is................ Route

  • Medications taken by mouth

  • Formulated in either a solid or liquid form

  • Absorbed from the GI tract mainly in the small intestine which is specialised for absorption (large surface area due to villi and microvilli).


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Disadvantages drug is................

  • Onset of action is relatively slow

  • Absorption may be irregular

  • Some drugs destroyed by enzymes or other secretions found in GI tract

  • Because blood from GItract passes through live it is subject to hepatic metabolism before reaching systemic circulation


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Buccal Route drug is................

Drug is formulated as a tablet or a spray and is absorbed from the buccal cavity

  • Sublingual absorption very fast onset of action but duration is short

  • Buccal absorption quick onset of action that is of longer duration than sublingual route


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Rectal Route drug is................

Drugs formulated as liquids ,solid dosages and semi solids.

The chosen preparation is inserted into the rectum where it is released to give local effect or absorbed to give a systemic effect


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Advantages drug is................

Can be used when oral route unsuitable

Useful when drug causes GI irritation

Can be used for local action

Disadvantages

Absorption irregular and unpredictable

Less convenient than oral route

Low patient acceptability

Rectal & Vaginal Route


Inhalation route l.jpg

Used predominately in the treatment of asthma drug is................

Drugs delivered directly to their site of action ie lungs

Advantages

Drugs inhaled through the nose or mouth to produce local or systemic effects

Drug dose required to produce desired effect is much smaller than oral route therefore reduction in side effects

Inhalation Route


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Topical Route drug is................

  • Skin used as site of administration

  • Lotions creams ointments powders

  • Skin has natural barrier function but specialised dosage forms have been developed that when applied they allow the drug to pass through and produce systemic effect


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Parenteral Route drug is................(drugs that are given by injection)

  • IV route -drugs injected directly into the systemic circulation (fast onset of action)

  • Subcutaneous route -drugs injected into the s/c layer of the skin (easiest and least painful)

  • Intramuscular route –drugs injected into muscle layers


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Examples in each category drug is................


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ADME drug is................

  • Absorption: the mechanism by which a drug enters the body

  • Distribution: the drug is transported throughout the body

  • Metabolism: the drug interacts with, and is processed by, the body

  • Elimination: the drug is removed from the body


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Absorption drug is................

  • Disintegration

  • Dissolution

  • Direct absorption at site of action, e.g., in the gut


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Steps in distribution drug is................

  • Drug must spread throughout blood volume

  • Drug must get out of the bloodstream between or through endothelial cells

  • Drug must cross the cell membraneinto cells


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Factors drug is................affecting distribution

  • Binding to plasma proteins: if a drug is bound to large plasma proteins, it will be unable to get out as the proteins are too large.

Arggh! I can’t fit through!


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Factors drug is................affecting distribution

  • Extent of blood supply. If a tissue is well perfused with blood, drugswill get there faster. Adipose tissue has low blood perfusion so drugs reach itslowly.


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Factors drug is................affecting distribution

  • pH. A drug will pass through membranes better if it is not ionised

  • Binding of drugs to other tissue components


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Lethal drug is................

Dose

Injected Dose

Drug Concentration

Therapeutic

Range

Oral Dose

Sub-

Therapeutic

Time

Metabolism: what happens to a drug


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F drug is................irst pass effect

  • All nutrients and drugs absorbed from the gut travel in the blood directly to the liver. The liver breaks down many drugs so they are inactivated before they ever enter the systemic circulation!

  • This can decrease drug delivery to target tissues

  • But some drugs are activated by the first pass effect


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Elimination drug is................

  • Mainly in the kidney. Also bile, gut, lung, breast milk.

  • Elimination of a drug is usually linked to renal function.


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Individual variation drug is................

  • Each person is unique how they respond to a drug

  • Age and sex (hormonal differences)

  • Weight: some drugs are stored in fat so less effective and longer lasting in obese people

  • Allergy

  • Kidney & liver function: how will they affect elimination?


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Pharmacodynamics is… drug is................

Pharmacokinetics is…

Receptor is like…

Ligand or drug is like…

First pass occurs in…

Many drugs are excreted by…

Liver

Lock

What the body does to the drug

Kidney

What the drug does to the body

Key

Memory work


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Pharmacodynamics is… drug is................

Pharmacokinetics is…

Receptor is like…

Ligand or drug is like…

First pass occurs in…

Many drugs are excreted by…

Liver

Lock

What the body does to the drug

Kidney

What the drug does to the body

Key

Memory work


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