Mechanisms of action

Question 1

5a-reductase inhibitors

Answer 1

Reduce the size of the prostate
Inhibits 5a-reductase which converts testosterone to dihydrotestosterone.
Dihydrotestosterone stimulates prostatic growth
Improve urinary flow
Usually additive therapy

Question 2

Alpha blockers

Answer 2

Usually highly selective for a1-adrenoceptor in smooth muscle, particularly in bladder and prostate
Induces relaxation and vasodilation

Question 3

Acetylcholinesterase inhibitors

Answer 3

Inhibit cholinesterase enzymes that breakdown acetylcholinesterase
Increase availability of acetylcholine for neurotransmission
Improve cognitive function and reduce the rate of cognitive decline

Question 4

Acetylcysteine

Answer 4

Replenishes the body’s supply of glutathione

Breaks disulphide bonds when in contact with mucus, reducing its viscosity

Question 5

Activated charcoal

Answer 5

Molecules adsorbed onto charcoal surface, reducing absorption into the systemic circulation
Increase elimination of poisons which is useful for molecules that are readily reabsorbed into gut by creating a steep concentration gradient encouraging diffusion

Question 6

Adenosine

Answer 6

Reduces frequency of spontaneous depoloarisation and increases resistance to depolarisation
Increases atrioventricualr node refractoriness

Question 7

Adrenaline

Answer 7

potent agonist of alpha 1 and 2, beta 1 and 2
Vasodilatory effects
Restore blood flow to heart in cardiac arrest
Bronchodilation and suppression of inflammatory mediators from mast cells in anaphylaxis

Question 8

Aldosterone antagonists

Answer 8

Increases activity of luminal epithelial sodium channels

Increases excretion of sodium and water, increasing potassium retention.

Question 9

Antaacids

Answer 9

Buffer stomach acids

alginates increase viscosity of stomach contents which Reduces reflux into oesophagus

Question 10

Allopurinol

Answer 10

Xanthine oxidase inhibitor
prevent metabolism of xanthine to uric acid
Reduces precipitation of uric acid in joints

Question 11

Aminoglycosides

Answer 11

Bind irreversibly to bacterial ribosomes and inhibit protein synthesis
Resistance by reduced cell membrane permeability to aminoglycosides
Acquisition of enzymes that prevent them from reaching ribosomes

Question 12

Aminosalicylates

Answer 12

Unknown

Antiinflammatory and immunosuppressive properties

Question 13

Amiodarone

Answer 13

Blockade of sodium, calcium and potassium channels
Antagonism of alpha and beta-adrenergic receptors
Reduce spontaneous depolarisation, slow conduction and increase resistance to depolarisation
Reduces ventricular rate in AF
Prevention of VT and defibrilition in refractory VT

Question 14

ACE inhibitors

Answer 14

Prevent conversion of angiotensin 1 to angiotensin II
Angiotensin II vasoconstrictive and stimulates aldosterone secretion
Blocking its action reduces vascular resistance and dilates, particularly efferent arteriole
Lowers BP by promoting sodium and water excretion

Question 15

ARBS

Answer 15

Block action of angiotensin II on angiotensin type 1 receptor
reduces peripheral vascular afterload
dilates efferent glomerular arteriole
promotes sodium and water excretion
reduces venous return