Medicines and drugs

1. Medicines and drugs Option D Part 1

2. What is a drug? • What is the difference between a drug and a medicine? • List different types of medicines. • How are new drugs developed?

3. 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

4. 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.

5. 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.

6. How are drugs administered?

7. 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.

8. 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.

9. Discuss the following terms • Dosing regime • Tolerance • Side-effects • Therapeutic window

10. Terms • 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.

11. 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.

12. 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.

13. 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.