W32 SAQ Mock questions

Question 1

The HPV vaccine and the Johnson & Johnson/Janssen COVID-19 vaccine contain polysorbate 80 as a
stabiliser.
a. Explain why Polysorbate 80 is used in this injectable formulation. (3 marks)
b. Explain why this formulation needs to be stored in the fridge and in the original carton. (2
marks)

Answer 1

a.

Question 2

Describe the approaches you can take, according to the DLVO theory, to stabilise the emulsion as
shown below to prevent the drug particles from aggregation. (5 marks)

Question 3

A mother read about the news of a bad batch of cough syrup containing dextromethorphan that had
led to the hospitalisation and death of at least 16 children in India. She is about to buy a common
cough syrup OTC for her child, and she would like to find out from you a bit more about what
common excipients are in cough syrups? List at least FIVE excipients and state their function. (5 marks)

Question 4

Give a brief explanation as to how pH-partition theory suggests that the weak base chlordiazepoxide
(pKa 4.8) will be better absorbed from the small intestines than the stomach. (5 marks)

Question 5

Explain why the polysaccharide cellulose is insoluble in water. How might we be able to alter its molecular structure to develop polymers which have improved aqueous solubility and more pharmaceutical uses? (5 marks)

Answer 5

1. Cellulose has 3 hydroxyl groups on each monomer
2. This leads to extensive intermolecular attractions
3. Because the cellulose molecules are held together strongly, they cannot be separated which would allow them to enter solution
4. In methylcellulose, about a third of the hydroxyl groups have been etherised- methyl cellulose is slowly soluble in cold water

Question 6

Explain why the bioavailability of a drug administered orally is usually lower than the same drug
administered via the intravenous route. (5 marks)

Answer 6

1. When a drug is administered intravenously, it has 100% bioavailability
   Lower could be due to:
2. Drug broken down by stomach acid or enzymes
4. First pass metabolism- when the drug is successfully absorbed but then a proportion of it is metabolised on its ‘first-pass’ through the liver