Medicines and drugs

Option D

Part 1

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

medicine?• What is a pharmaceutical?• List different types of medicines.

• How are new drugs developed?

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

• Research– Identify disease, could be new disease.– Identify target e.g. gene or enzyme which is

necessary for disease to progress.• Development

– Identify ‘lead’ molecule which can act on gene/enzyme in the disease organism or host and isolate or manufacture it. May need to be modified for effectiveness.

Stages in development of a drug • Testing

– 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• Clinical trials: on humans!!

o 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 or even administrators know which half they are in. All patients should/could experience placebo.

o 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; new side-effects e.g. thalidomide.

Thalidomide

• Thalidomide was a drug used (in 50’s and 60’s) to treat morning sickness in pregnant women. The drug was not tested properly and resulted in birth defects in women who were treated with this drug.

Placebo effect• Placebo effect – inert substance that fools the body into curing

itself.• Occurs when a person experiences a positive therapeutic effect

because they believe they have been given a drug although the substance given in reality is not a medicine but a ‘placebo’. administered; the human body is fooled into healing itself. Often occurs with pain.

• How would you allow for the placebo effect when carrying out clinical trials?

• How would you analyze the results of clinical trials and make them reliable?

Administering drugs (1)• Oral: taken in by the mouth e.g. tablets, syrups, capsules -

advantages and disadvantages

• Parenteral - by injection:

o 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.

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

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

Parenteral administration

oralAdvantages Disadvantages

Easily taken No specialist equipment

needed

Can be destroyed by stomach acid

Slow to have an effect Can cause stomach

bleeding or vomiting Only small amount of drug

is absorbed Patient needs to be

conscious Kids????

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.

• Other ways:

– Skin patches: e.g. hormone treatments.– Topical, on the skin and in eyes/ears e.g. creams, eye drops

Discuss the following terms

• Therapeutic window• Tolerance• Side-effects

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. Value comes from LD50/ED50 (l=lethal e=effective d=dose)

• The lowest level of concentration is called the effective or therapeutic 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)

• 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.

Therapeutic Window

• High # - hard to overdose. This is because your LD50 is a very high number

• Low # - easy to overdose. This is because the LD50 will be a lower number closer to the ED50.

Vocabulary• 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.

• Side-effects physiological effects which are not intended and therefore undesired (unwanted physiological effects of a drug) (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.

Side Effects

• Morphine – strong analgesic – pain killer– Can make you constipated

• Aspirin – mild analgesic – (for headaches, etc)– Can cause stomach bleeding and thinning of the

blood

Terms • Dosing regime = the amount of drug used for

each dose i.e. how much drug should be taken (amount + frequency) to obtain desired therapeutic effect.