option d part 1. what is a drug? what is the difference between a drug and a medicine? list...
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MEDICINES AND DRUGS
Option D
Part 1
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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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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 sensationsalters mood or emotions
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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.
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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 on drug and its trials to regulatory bodies.
Monitoring of the drug after it has been launched; molecule might need further structural changes.
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How are drugs administered?
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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.
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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.
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Discuss the following terms
Dosing regime Tolerance Side-effects Therapeutic window
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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.
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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.
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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.
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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.