Advanced Higher Chemistry Unit 3(e) Medicines Advanced Higher Chemistry Unit 3(e)

DRUGS Substances which alter the biochemical processes in the body. Those with beneficial effects are called medicines.

HISTORY The first drugs came from plant brews. Pharmacologically active products in plant extracts were identified. These compounds (and derivatives of them) were synthesised where possible.

Aspirin

HOW MEDICINES FUNCTION Most work by bonding to receptors. Receptors are usually protein molecules that are on the surface of cells where they interact with small biological molecules. Alternatively, they are enzymes which catalyse chemical reactions (catalytic receptors).

PHARMACOPHORE The structural fragment of the molecule which gives it pharmocological activity. The shape of the pharmocophore complements that of the receptor site, allowing it to fit into the receptor. The functional groups on each (pharmocophore and receptor) are correctly positioned to interact and bind the receptor to the medicine. By comparing the structure of medicines with similar activity, the pharmocophore can be identified.

AGONISTS and ANTAGONISTS AGONISTS – enhance the body’s natural responses (produces a response like the body’s naturally active compound); ANTAGONISTS – block the body’s natural responses. (produces no response but prevents the body’s naturally active compound).

Salbutamol: agonist Used to treat acute asthma or prevent exercise-induced asthma. Can be injected intravenously to relax uterine smooth muscle and prevent premature labour. Has widely been replaced by nifidepine.

Nifidipine: antagonist A calcium channel blocker. Used in the long-term treatment of hypertension.

Propranolol: antagonist A beta blocker. Used to treat hypertension.

Sulphanilamides: antagonists Antibiotics.

Penicillin: antagonist Another antibiotic

Dopamine A neurotransmitter produced in the brain. Is greatly reduced in suffers of Parkinson’s disease. Can be given as a drug to increase heart rate or blood pressure. However, does not cross the blood-brain barrier so cannot be used to affect the central nervous system. Instead, precursors can be administered e.g. L-DOPA.

Dopamine L-DOPA

Apomorphine: agonist Issued via subcutaneous injection. Has a side-effect of a marked increase in problem gambling.

Deep brain stimulation