Pharma MCQ 5

Question 1

How is atracurium metabolised?

Answer 1

Metabolism of atracurium occurs by enzymatic (non-specific esterases) and non-enzymatic mechanisms (spontaneous hydrolysis, or Hoffmann degradation).

Question 2

What is atracurium broken down into? what is its clinical significance?

Answer 2

Laudanosine - often mentioned because it may cause seizures.

Question 3

How much protein bound is atracurium?

Answer 3

15%

Question 4

Lidocaine:

1. inhibits which pump?
2. ester or amide?
3. does it affect cardiac action potential?
4. can cause drowsiness or sedation?

Answer 4

1. binds to internal surface of sodium channel, preventing its opening.
2. amide
3. yes, SHORTENS repolarisation phase 3.
4. can cause drowsiness/ sedation as a late effect.

Question 5

How is alcohol metabolised?

Answer 5

Alcohol is metabolised in cytoplasm by alcohol dehydrogenase to acetaldehyde,

then by acetaldehyde dehydrogenase to acetate.

Question 6

Alcohol is eliminated by what order kinetics?

Answer 6

first order kinetics - because there are a fixed number of enzymes, and rate of elimination is proportional to substrate concentration until all the enzymes are saturated.

Then amount eliminated remains constant despite substrate concentration increase (zero-order)

Question 7

What hormone dose alcohol effect?

Answer 7

Inhibits ADH (also known as arginine vasopressin) release - therefore causing unregulated diuresis.

Question 8

Alcohol is the treatment of choice in what type of poisoning?

Answer 8

Methanol poisoning.

Question 9

Temazepam is the metabolite of what drug?

Answer 9

Diazepam (minor metabolite)

Question 10

Benzodiazepine mechanism of action?

Answer 10

exert effect at alpha unit of GABAa receptors, a ligand gated ion channel. Enhances the chloride conductance leading to membrane hyperpolarisation.

Question 11

Elimination half life of temazepam?

Answer 11

8 hours, can lead to ‘hangover’ effect.

Question 12

What order of kinetics is phenytoin eliminated?

Answer 12

Hydroxylation in the liver is saturable just above therapeutic levels (first order),

following which metabolism is zero order or constant rate, when plasma levels may rise considerably.

Phenytoin has a narrow therapeutic index and it is important to check plasma levels in order to avoid toxicity.

Question 13

How does Phenytoin affect a fetus?

Answer 13

It may cause fetal hydantoin syndrome:

• with craniofacial abnormalities
• growth retardation
• cardiac defects
• mental retardation

Question 14

Phenytoin percentage protein binding?

Answer 14

90%

Question 15

How does phenytoin affect cardiac conduction?

Answer 15

Phenytoin is a class 1b antiarrhythmic drug which enhances AV nodal conduction.

Question 16

How does Digoxin produce ionotropic effect?

Answer 16

It increases intracellular calcium levels - positive iontropy.

Question 17

Site of action of digoxin?

Answer 17

Digoxin inhibits the Na+/K+-ATPase

Question 18

Why is Digoxin used in treatment of AF?

Answer 18

in atrial fibrillation, slows conduction in the AV node,

this helps to control the ventricular rate in AF

Question 19

How is Digoxin metabolised/ eliminated from the body?

Answer 19

Digoxin is excreted primarily unchanged via the kidney by glomerular filtration and tubular secretion, hence the necessity for dose adjustment in renal impairment.

Less than 10% undergoes metabolism in the liver.

Question 20

Digoxin elimination half life?

Answer 20

Digoxin has a long elimination half-life of 35 hours, which is increased by renal impairment

Question 21

How do the following drugs exert their positive ionotropic effect? What mechanism/ site of action?

1. isoprenaline
2. dopamine
3. glucagon
4. dobutamine

Answer 21

1. Isoprenaline - action at beta-1 (somewhat offset by the beta2 effects which reduce SVR)
2. Dopamine - Beta1 effects predominate at 0-10 µ g.kg-1.min-1
3. Glucagon receptors initiate the resulting increase in intracellular cAMP.
4. Dobutamine is a directly acting drug with predominantly Beta1 effects.

Question 22

Clonidine:

• site of action
• mechanism of analgaesic effect

Answer 22

• Clonidine stimulates presynaptic alpha2 receptors, decreasing nor-adrenaline release from sympathetic nerve terminals, leading to a reduction in sympathetic tone.
• analgaesic effects mediated by activation of alpha2 receptors in the dorsal horn of the spinal cord.

Question 23

Lidocaine: Inhibits Na/K pump mechanism.

True/ False

Answer 23

False.

Local anaesthetic agents bind to the internal surface of the sodium channel, preventing its activation.

Question 24

Which part of cardiac action potential can Lidocaine effect?

Answer 24

Repolarisation phase 3 is shortened.

Question 25

How is Temazepam produced?

Answer 25

Hydroxylation of diazepam produces its minor metabolite temazepam.