Pharma MCQ 4

Question 1

by what mechanism do drugs cross the placenta?

Answer 1

down a concentration gradient

Question 2

how does fetal pH compare to mothers?

Answer 2

relatively acidic

Question 3

which of the following drugs are metabolised by esterases?

A. prilocaine
B. Esmolol
C. Aspirin
D. diamorphine
E. etomidate

Answer 3

all except prilocaine because it is an amide rather than an ester.

True. Metabolised rapidly by red cell esterases, esmolol has a short t1/2 of 10 minutes.

True. Aspirin is acetylsalicylic acid, metabolised by liver esterases to its components before undergoing further metabolism.

True. Diacetylmorphine, a pro-drug, requires to be broken down by esterases to 6-monoacetylmorphine and morphine in order to bind to opioid receptors.

True. Metabolism of etomidate is by non-specific liver esterases.

Question 4

Structure of diamorphine molecule?

Answer 4

is a 3,6 diacetylmorphine, a di-ester of one molecule of morphine and two molecules of acetic acid.

Question 5

How does diamorphine exert its activity at the opioid receptor?

Answer 5

It must first be broken down to 3- and 6-monoacetylmorphine, and on 6- is active. Then by a second ester hydrolysis to morphine.

Question 6

Where must the hydroxyl group be present for diamorphine activity?

Answer 6

at the 3- position.

Question 7

How do fentanyl and alfentanil compare in term of plasma clearance, initial volume of distribution and elimination half life.

Answer 7

Fentanyl
- initial volume of distribution,
and longer elimination half life.

But, also has a higher plasma clearance than alfentanil.

Question 8

Salicylate intoxication may trigger which abnormality in bleeding?

Answer 8

hypoprothrombinaemia

Question 9

Paracetamol bioavailability?

Answer 9

80% - extensively absorbed from small intestine.

Question 10

Paracetamol time to peak plasma level?

Answer 10

after one hour of oral administration.

Question 11

Side effect of giving Paracetamol IV?

Answer 11

Can cause hypotension.

Question 12

Ketamine:

mixture form?

Answer 12

It is presented as a racemic mixture, or as the S-enantiomer, which is more potent than the R-form and has fewer side-effects.

Question 13

Ketamine:

mode of action?

Answer 13

Ketamine is a non-competitive inhibitor of the excitatory NMDA receptor

Question 14

Ketamine:

active metabolites?

Answer 14

Norketamine (demethylated metabolite of ketamine) is one third as potent as ketamine)..

Question 15

Ketamine:

effect on blood flow?

Answer 15

increases cerebral blood flow, oxygen consumption and intracranial pressure.

Question 16

What poison can cause muscle weakness, lethargy and eventually paralysis and why?

Answer 16

Organophosphates - acetylcholinerase enzyme inhibitors.

Cause over stimulation at the NMJ.