Medicines and drugs
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Medicines and drugs. Option D Part 1. What is a drug? What is the difference between a drug and a medicine? List different types of medicines. How are new drugs developed? .

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Medicines and drugs

Medicines and drugs

Option D

Part 1

Medicines and drugs

  • What is a drug?

  • What is the difference between a drug and a medicine?

  • List different types of medicines.

  • How are new drugs developed?

Pharmaceutical products

Pharmaceutical products

A medicine or drug is any chemical that does one or more of the following to the human body:

  • alters its physiological state (=how it functions), including consciousness, activity level or coordination

  • alters incoming sensory sensations

  • alters mood or emotions

Stages in development of a drug

Stages in development of a drug

  • Identify disease, could be new disease.

  • Identify target e.g. gene or enzyme which is necessary for disease to progress.

  • Identify ‘lead’ molecule which can act on gene/enzyme in the disease organism or host and isolate or manufacture it.

  • Preclinical trials: testing of ‘lead molecule’ in laboratory,

    • ‘in vitro’: the lead molecule is tested on animal/human cells and tissues which have been removed from the body and are kept in an artificial environment

    • ‘in vivo’: testing in live animals (usually 3 different species) to establish LD50 which is the amount which kills 50 % of animal population.

Stages in development of drug

Stages in development of drug

  • Clinical trials: on humans!!

    • Testing of its effectiveness and dose range on humans using the placebo effect. This is a ‘blind trial’ in which half of the people/patients involved are given the drug whilst the other half are given a similar substance which is not the drug but none of the patients know which half they are in. All patients should/could experience placebo.

    • Structural modifications likely to be made to, for instance, improve effectiveness or reduce side-effects.

  • Submission of reports ondrugand its trials to regulatory bodies.

  • Monitoring of the drug after it has been launched; molecule might need further structural changes.

Medicines and drugs

How are drugs administered?

Administering drugs 1

Administering drugs (1)

  • Oral: taken in by the mouth e.g. tablets, syrups, capsules.

  • Parenteral - by injection:

    • intravenous: into a vein of the blood stream – used for immediate impacts as its fastest method; drug is immediately pumped around the body by the blood.

    • intramuscular i.e. into the muscles, e.g. many vaccines, local anaesthetics, usually used when a large dose needs to be administered.

    • subcutaneous: in the layer of the skin directly below the cutis (dermis and epidermis) e.g. dental injections, morphine, insulin. Slow.

Administering drugs 2

Administering drugs (2)

  • Inhalation: e.g. medication for respiratory conditions such as asthma.

  • Rectal: inserted into the rectum e.g. treatment for digestive illnesses, drug absorbed into the blood stream.

  • Skin patches: e.g. hormone treatments.

Discuss the following terms

Discuss the following terms

  • Dosing regime

  • Tolerance

  • Side-effects

  • Therapeutic window



  • Dosing regime= the amount of drug used for each dose i.e. how much drug should be taken in to obtain desired therapeutic effect.

  • Tolerance

    Tolerance refers to the body’s reduced response to a drug i.e. its therapeutic effect is less than what it is intended, usually as a result of taking the drug over a long period of time. As a result more of the drug needs to be taken to achieve the same initial physiological effect with the danger of exceeding the lethal dose.

Therapeutic window 1

Therapeutic window (1)

  • The therapeutic window is the range of dosage over which a drug can be safely administered to a typical population. It is the range in concentration in the blood within which an administered drug must remain. The therapeutic window has a lowest and highest level.

  • The lowest level of concentration is called the effective level or ED50; below this level the drug loses its therapeutic effect.

  • The highest level is the toxic or LD50 level (= the dose needed to kill 50 % of (animal) population) above which adverse side-effects can occur.

Therapeutic window 2

Therapeutic window (2)

  • wide therapeutic window

    • small effective dose (ED50) and larger lethal dose (LD50) as a result there is a big difference between effective and lethal dose.

  • narrow therapeutic window

    • small difference between effective and lethal dose usually because lethal dose is small.

Terms 2

Terms (2)

  • Side-effects= physiological effects which are not intended and therefore undesired (intended = therapeutic effects); these could be:

    • beneficial e.g. protect against heart disease.

    • benign e.g. causing drowsiness, nausea constipation.

    • adverse i.e. causing damage to other organs.

  • Placebo effect

    • The placebo effect occurs when a person experiences a positive therapeutic effect although a substance which is not a drug has been administered; the human body is fooled into healing itself naturally.

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