Mechanism of Action

Question 1

Adrenaline

Answer 1

Stimulates alpha and beta receptors, predominantly at the alpha 1 and beta 1 and 2 receptors.
Alpha 1 stimulation causes smooth muscle contraction, vasoconstriction, and stimulation of glycogenolysis and gluconeogenesis.
Beta 1 stimulation causes an increase in cardiac contractility (inotropy), an increase in heart rate (chronotropy) and increase in the speed of electrical conduction within the heart (dromotropy).
Beta 2 stimulation causes smooth muscle relaxation, skeletal muscle vasodilation, bronchodilation, and stabilisation of mast cell membranes, reducing histamine release.

Question 2

Aspirin

Answer 2

Antiplatelet, antipyretic, anti-inflammatory, and analgesic effects, but only used for antiplatelet effects out-of-hospital.
Aspirin inhibits the enzyme cyclooxygenase which results in a reduction in the formation of prostaglandins and thromboxane.

Question 3

Glucagon

Answer 3

Glucagon increases the blood glucose level by stimulating glycogenolysis (the breakdown of glycogen into glucose), predominantly within the liver.

Question 4

Glyceryl trinitrate

Answer 4

GTN is a vasodilator, acting on vascular smooth muscle to cause venous and arterial vasodilation, with the predominant effect being on veins.
The mechanism of action is not clear, but it appears that GTN results in the formation of nitric oxide which is a vasodilator.
It causes:
A reduction in venous return (preload) to the heart, reducing ventricular filling and cardiac output and therefore reducing myocardial oxygen demand;
Arterial dilation which reduces peripheral resistance (afterload), reducing the force the left ventricle must overcome to eject blood into the arteries, therefore reducing myocardial oxygen demand;
Dilation of the coronary arteries which may increase coronary blood supply, although this is not usually clinically significant.

Question 5

Ibuprofen

Answer 5

A non-steroidal anti-inflammatory drug (NSAID) that is predominantly used for treating pain.
Ibuprofen inhibits the activity of the enzyme prostaglandin synthetase, reducing prostaglandin production and causing a reduction in inflammation, pain, and fever.

Question 6

Ipratropium

Answer 6

Ipratropium is a bronchodilator and an anticholinergic agent with predominantly antimuscarinic activity. It antagonises acetylcholine receptors, causing vagal inhibition resulting in bronchodilation.

Question 7

Loratadine

Answer 7

Loratadine is a non-sedating antihistamine that antagonises peripheral histamine receptors, blocking the action of histamine and reducing itching and redness.

Question 8

Methoxyflurane

Answer 8

An inhaled analgesic with an unknown mechanism of action.

Question 9

Ondansetron

Answer 9

Ondansetron is an antiemetic that antagonises serotonin receptors centrally in the brain and peripherally in the gastrointestinal tract, resulting in a reduction in nausea and vomiting.

Question 10

Paracetamol

Answer 10

Paracetamol inhibits the reduction of prostaglandins resulting in a reduction in pain and fever.

Question 11

Prednisolone/prednisone

Answer 11

Prednisone is a prodrug that is metabolised to prednisolone in the liver.
Prednisolone is a corticosteroid with anti-inflammatory and immunosuppressant actions. It inhibits the production of inflammatory mediators, including prostaglandin and leukotrienes, resulting in a reduction in the inflammatory and immune response.

Question 12

Salbutamol

Answer 12

Salbutamol is a bronchodilator that agonises beta-2 receptors.

Question 13

Tramadol

Answer 13

Tramadol is an analgesic that has multiple action within the central nervous system, including opiate receptor stimulation and the inhibition of the re-uptake of noradrenaline and serotonin.