Mechanism of action

Question 1

Atropine

Answer 1

Block the effect of
acetylcholine on receptors
on parasympathetic and
sympathetic autonomic
ganglia

Question 2

Betamethasone

Answer 2

Diffuses into target cells and
binds to a cytoplasmic
glucocortoid receptor.
Activated receptor-
glucocortoid complex enters
the nucleus and binds to
steroid response elements
on target DNA molecules.
This either induces specific
mRNA synthesis or
represses genes by
inhibition of transcription
factors.

Question 3

Digoxin

Answer 3

Inhibits Na/K pump leading
to intracellular sodium
increase. Sodium calcium
exchanger activated to
extrude Na – leading to Ca
increase – promotes
activation of contractile
proteins

Question 4

Edrophonium

Answer 4

Reversible inhibition of
acetylcholinesterase
reduces breakdown of Ach
at cholinergic nerve endings.

Question 5

Ethanol

Answer 5

Binds to GABA receptors in
the brain, increasing the
effects of GABA, an
inhibitory neurotransmitter.
Alcohol is eventually
metabolised to Acetyl
Coenzyme A in the body.

Question 6

Ethinylestradiol

Answer 6

Suppresses the development of ovarian follicle by inhibiting
secretion of FSH. Suppress
ovulation by inhibiting LH
release.

Question 7

Ketaconazole

Answer 7

Inhibits cholesterol side-chain cleavage and enzymes
required for steroid
hormone synthesis

Question 8

Morphine

Answer 8

Activates µ opioid receptors
in brain & spinal cord to
inhibit pain transmission +
modify central perception of
pain

Question 9

Naloxone

Answer 9

Competitive antagonist of
opio6ids at µ, δ and κ
receptors

Question 10

Paracetamol

Answer 10

Inhibition of COX-1, COX-2 & COX-3

Question 11

Pyridostigmine

Answer 11

Reversible inhibition of
acetylcholinesterase
reduces breakdown of ACh
at cholinergic nerve endings.

Question 12

Rifampicin

Answer 12

Inhibits bacterial but not
human DNA-dependent
RNA polymerase leading to
reduced RNA synthesis in
the bacterial cell

Question 13

Suxamethonium

Answer 13

Mimics action of ACh at
neuromuscular junction.
Hydrolysis is slower than for
Ach, therefore results in
neuromuscular junction
blockage.

Question 14

Tamoxifen

Answer 14

Competes with the
endogenous oestrogen for
the oestrogen receptor, preventing cell activation +
proliferation

Question 15

Tubocurarine

Answer 15

Compete with acetylcholine
but do not initiate ion
channel opening. Reduce
the endplate depolarisations
produced by acetylcholine
to a size that is below the
threshold level for muscle
action potential generation