ICT practice questions Flashcards
A buffering agent in oral liquid pharmaceutical solutions is also known as which ONE of the following?
a. Sweetening agent
b. Thickening agent
c. pH modifier
d. Wetting agent
e. Chelating agent
C. pH modifier
Which ONE of the following is NOT a mechanism for the separation of a physically unstable suspension of magnesium hydroxide in water?
a. Flocculation
b. Aggregation
c. Ostwald ripening
d. Hydrolysis
e. Sedimentation
= D
Only ONE of the following statements is CORRECT. Please select the CORRECT statement.
The pH of a solution containing 4 g of HCl (molar mass: 36.458 g/mol) in 100 mL of water is equal to which of the following (pH value rounded up):
a. pH= 0.041
b. pH= -0.041
c. pH= 3
d. pH= -3
e. None of the above.
=B
Only ONE of the following statements regarding an isothermal process is CORRECT. Please select the CORRECT statement.
a. Any heat transferred to the system is used to increase the system temperature.
b. Internal energy changes only for work done or received by the system.
c. No work is done on or by the system.
d. Any heat transferred to the system is used to do work.
e. q is equal to zero.
=D
Which ONE of the following statements is INCORRECT?
a. In a first-order reaction the plot of the natural log (ln) of the reactant concentration against time is a straight line.
b. In a pseudo-first order reaction, the concentration of one of the reactants is considered constant.
c. The rate of a second-order reaction is independent of the reactant concentration.
d. The half-life of the reactant in a zero-order reaction is proportional to the initial concentration.
e. In a complex reaction the overall rate equation cannot be directly written from the stoichiometric equation.
=C
Which ONE of the following Phase I and Phase II transformations CANNOT happen to ibuprofen?
a. Conjugation with amino acids.
b. Conjugation with glucuronic acid.
c. Oxidation of exposed alkyl group.
d. Oxidation of activated carbon centres next to sp and sp2 carbons.
e. Oxidative deamination
=E
Dextran is a branched polymer of α-d-glucose. Which ONE of the following is not a recognised use for this polymer?
a. Blood plasma expander
b. Anticoagulant
c. Ingredient in the enteric coating of tablets
d. Protectant in freeze drying
e. Bulking agent in freeze drying
=C
The Noyes-Whitney equation is used to describe which ONE of the following processes?
a. Settling of solid particles in a suspension.
b. Dissolution of drugs present as solid particles.
c. Flow of a viscous liquid with shear stress.
d. Ionisation of a weak acid with respect to pH and pKa.
e. Change in the reaction rate constant against temperature.
=B
A weakly acidic drug is known to have a pKa of 5.3. The aqueous solubility of the free acid is found to be 2.9 x 10-4 mol L-1. What is the minimum pH at which an aqueous solution containing 9.8 x 10-3 mol L-1 of the drug can be prepared?
a. 5.30
b. 2.90
c. 3.78
d. 6.82
e. 9.89
=D
Only ONE of the following statements regarding the impact of temperature on a process is CORRECT. Please select the CORRECT statement.
a. Viscosity increases with increasing temperature.
b. Solubility of a gas generally decreases with increasing temperature.
c. Saturation solubility of a solid decreases as temperature increase (assuming dissolution is an endothermic process).
d. Reaction rate constant increases with decreasing temperature (assuming an endothermic reaction).
e. Reaction rate constant decreases with increasing temperature (assuming an endothermic reaction).
=B
Which ONE of the options below would be the most appropriate way of expressing the concentration of a solid active ingredient in a solution to be applied externally?
a) mg per mL
b) mg per 5 mL
c) Parts
d) % v/v
e) % w/v
=E
Provide one characteristic which would enable you to distinguish a colloidal drug formulation from a solution. (1 mark)
Tyndall effect – light beam path through colloid is visible due to light scatter (1 mark) - also accept dialysis or electrophoresis as answers.
Give an example of one pharmaceutical suspension and one colloidal formulation. Choose two properties and briefly describe the differences between them. (4 marks)
Pharmaceutical suspension: paracetamol suspension, ibuprofen suspension, amoxicillin suspension, ciprofloxacin suspension, chloramphenicol palmitate suspension, phenytoin suspension, cholera vaccine etc. (1 mark)
Colloidal formulation: any creams or gels, Covid-19 vaccine etc. (1 mark)
Any two properties from below (2 marks)
Property:
Particle Size
1 nm to 1 µm (10-9 m to 10-6 m)
1 µm to 1 mm (10-6 m to 10-3 m)
Appearance
Cloudy, but uniform and homogeneous
Cloudy, heterogeneous, at least two substances visible
Separation
None Particles will eventually settle out
Filtration
Passes through filter Particles filtered out
Effect of light
Scatters light
Variable – generally cannot pass through
Visibility
Particles visible under microscope
Particles visible to naked eye
Briefly describe the major types of non-bonding intermolecular interactions. (5 marks)
There are three types of non-bonding intermolecular interactions: dipole-dipole interactions, van der Waals forces and hydrogen bonding (1 mark if all the three are mentioned).
Dipole-dipole interactions are interactions between the positive end of one dipole and the negative end of another dipole (1 mark). Dipole–dipole interactions arise when electrons are not equally shared in the covalent bonds because of the difference in electronegativity. (0.5 marks)
van der Waals forces are relatively weak forces of attraction that exist between non-polar molecules (1 mark). These forces are distance-dependent interactions between atoms or molecules (0.5 marks).
Hydrogen bonding is the attractive force between the hydrogen attached to an electronegative atom of one molecule (0.5 marks) and an electronegative atom of the same or a different molecule (0.5 marks).
Briefly explain why ethanol is often employed as a cosolvent in pharmaceutical solutions. (5 marks)
Cosolvents are added to aqueous formulations with the aim of improving the solubility of the active ingredient (1 mark).
Ethanol is a semi-polar solvent (1 mark) which means that it is typically able to dissolve polar and non-polar substances (1 mark).
The addition of ethanol as a cosolvent may mean that a pharmaceutical solution can be prepared when previously only an aqueous suspension was possible (1 mark). An example would be the use of ethanol in the production of paracetamol elixir – a solution (1 mark).
A prescription calls for the extemporaneous dispensing of 100 mL of “Primidone oral solution”. Based upon your knowledge of the bench-scale manufacture of medicines, suggest an appropriate method that could be followed to prepare primidone suspension according to the formula below. (5marks)
Formula:
* Primidone 250 mg tablets x 20
* Xanthan gum 0.4% to 100 mL
- Crush/grind around 10 bendroflumethiazide tablets in a pestle and mortar into a fine powder. (1 mark)
- Add a small amount of Xanthan gum 0.4% to the mortar and mix well with the pestle. (1 mark)
- Transfer the suspension to a tared (100 mL) bottle and then rinse the mortar with further portions of Xanthan gum solution (and add to the bottle). (2 marks)
- Make up to the final volume (shown by the tare mark) with Xanthan gum solution. (1 mark)
- Shake well. (1 mark)
Briefly describe the design and operation of a rotating viscometer and state the type of liquids with which it can be used. (5 marks)
A cylinder with a cone-shaped end (1 mark)
is rotated at a constant speed (1 mark)
in a second cylinder containing the liquid under investigation (1 mark).
The drag on the cone-shaped cylinder is measured and equated to the viscosity (1 mark).
Can be used for determining the viscosity of Newtonian and Non-Newtonian liquids (2 marks).
A patient has accidentally overdosed on a weakly basic drug. As part of their treatment, it is decided to give the patient ammonium chloride (a urine acidifier). Explain how this course of action may help the patient. (5 marks)
Renal excretion of drugs can be controlled by altering the pH of the urine with salt solutions (1 mark)
By acidifying the urine a weakly basic drug is more likely to be ionised in the urine (2 marks). This will lead to a decrease in re-absorption (1 mark) and an increase in excretion of the drug (1 mark). Increased excretion of the drug will therefore lower the plasma levels of the drug (1 mark).
Briefly explain the DLVO theory of colloidal stability. (5 marks)
0.5 marks for mentioning each point below and 0.5 marks for describing each term.
- Electrostatic repulsive forces (VR)
- Van der Waals forces of attraction (VA)
- Primary minimum
- Primary maximum
- Secondary minimum
- Arises from the interaction of ELECTRICAL DOUBLE LAYERS surrounding pairs of particles
- At large distances of separation, particles experience a minimal attraction. Forces of attraction are weak (flocculation) not coalescence i.e can redisperse upon shaking.
If a reaction is said to be a Zero order reaction, what will the rate of the reaction be?
. 0
b. 1
c. The value of k
d. Depends on the concentration of the reactants
e. None of the above
c
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)
Solvent: Purified water
Co-solvent: Ethanol, Glycerol
Viscosity-increasing agent: Carboxymethylcellulose sodium, hydroxymethcylcellulose
Antimicrobial preservative: Sodium benzoate, benzalkonium chloride Chelating/complexing agent: Disodium edetate/ EDTA
Sweetening agent: Maltitol, Sorbitol, Sodium cyclamate, Acesulfame, sucrose, fructose potassium
Antioxidant: Citric acid, ascorbic acid
Colourant: Amaranth, Caramel
Flavouring agent: Levomenthol, Cherry/Grenadine flavour
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)
a. Non-ionic surfactant (1 mark)
Contributes to steric stabilisation/entropic effects (1 mark)
The hydrophilic polymeric groups (polyoxyethylene groups) overlap which is thermodynamically unfavourable (a loss of entropy), causing them to separate (1 mark)
b. Store in the fridge to reduce rate of antibody degradation and microbial growth (1 mark)
Store in the original carton to protect from light (1 mark)
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 mark)
Van der Waals attraction causes drug particles to aggregate (1 mark)
At primary minimum, the particles coagulate irreversibly (1 mark)
The height of this repulsive force (Vmax) at primary maximum determines the stability of the system
(1 mark)
The height can be increased by electrostatic stabilisation using different surfactants and electrolyte
concentration (1 mark)
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)
- Explanation of pH-partition theory (1 mark)
- pH changes along the GI tract: in the stomach, the pH can be as low as 1.5, but it rises to pH 6 or higher in the small intestines (1 mark)
- Chlordiazepoxide is a weak base so it is more likely to be ionised at low pH values (at pH 2.8 it will be
99% ionised). (2 marks)
In the small intestines, the pH of >6 will mean that chlordiazepoxide is mostly (>90%) unionised and
therefore uncharged (1 mark) it is therefore more likely to cross the lipophilic gastro-intestinal
epithelium (1 mark)
Note: marks NOT awarded for information about small intestine surface area, long residence times
etc. The question asked for “how pH-partition theory suggests…
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)
Cellulose is a long straight-chain polymer made up of many beta-glucose monomers. Cellulose is insoluble as it is made up of many H bonds and this holds the microfibrils together strongly, this means that the bonds cannot be broken down when added to water.
To inc solubility, cellulose can be converted to HPMC or HEC which bother have a higher aqueous solubility than that of cellulose. (2)
* mention methylcellulose, structure of cellulose (OH groups),
MS:
Cellulose has three hydroxyl groups on each monomer (1 mark) and this leads to extensive intermolecular attractions – similar to the covalent crosslinks (1 mark)
Because the cellulose polymer molecules are held together strongly, they cannot be separated (or
“pulled apart”) which would allow them to enter solution (1 mark)
In methylcellulose about a third of the hydroxyl groups have been etherified – methyl cellulose is slowly soluble in cold water (1 mark)
HPMC is another cellulose ether derivative with an even better aqueous solubility (1 mark)
Some uses for methylcellulose /HPMC listed (1 mark)
Explain why the bioavailability of a drug administered orally is usually lower than the same drug administered via the intravenous route. (5 marks)
IV route= 100% bioavailability.
This is because drug is administered through the skeletal muscle and directly into bloodstream.
Whereas oral has several barriers before being absorbed through the phospholipid bilayer and then into the bloodstream. It also does not need to surpass digestion in the stomach and the first-pass metabolism in the liver, where some of the drug is metabolised and so does not enter the blood.
(3 marks)- need to mention solubility, molecular weight or log P (2 more marks)
MS:
When a drug is administered via the oral route there are several factors which can reduce the bioavailability, these could include:
1. Drug broken down by stomach acid or enzymes (1 mark)
2. Non-ideal physicochemical properties, e.g. low aqueous solubility (1 mark), log P too high/low (1 mark), molecular weight too high (1 mark)
3. First pass metabolism – this is when the drug is successfully absorbed but then a proportion of it is metabolised on its “first pass” through the liver (2 marks
What type of surfactant is polyoxyethylene (10) oleyl ether?
Non ionic
Cationic
Anionic
Zwitterionic
Co-surfactant
Non-ionic
(zwitterionic has 2 charges, cationic= positive charge, anionic= neg charge)
One-third of all drugs used in cancer therapy are hydrophobic. Which of the following is NOT a
reason for using drugs in a micellar form?
a. Micelles can be used to deliver water-insoluble drugs in their hydrophobic core
b. Micelles provide favourable changes in drug biodistribution for hydrophobic drugs
c. Micelles improve the permeability of drugs across the physiological barriers
d. Drug in a micellar form is protected from possible inactivation under the effect of biological surrounding
e. Drug in a micellar form provokes undesirable side effects on non-target organs and tissues
=E (opposite is correct)
