Solutions

Question 1

What are the advantages of using pharmaceutical liquids?

Answer 1

• ease of administration compared to solid dosage forms.
• increased rate of drug absorption - disintegration and dissolution processes do not have to occur.
• high bioavailability if adm via IV.
• taste of oral solution effectively masked by flavour, colour or syrup.

Question 2

What are the disadvantages of pharmaceutical liquids?

Answer 2

• difficult to formulate drugs with poor chemical stability
• difficult to formulate drugs which possess poor solubility (solubility enhancers can be added - these can be toxic - side effects to patient)
• may require specialist formulation strategies (taste masking, viscosity, appearance)

Question 3

What is meant by salvation?

Answer 3

Binding of solvent to solute.

Question 4

What is meant by hydration?

Answer 4

Binding of water to solute.

Question 5

What is isoelectric point?

Answer 5

The pH at which the net charge of the molecule is neutral.

Question 6

What is meant by amphoteric?

Answer 6

Possess acidic and basic properties.

Question 7

What is the purpose of solubilisation?

Answer 7

Makes the formulation water soluble or makes the formulation a uniform solution.

Question 8

In what ways can solubilization be achieved?

Answer 8

• water soluble drugs
• co-solvents
• surfactants
• complexation
• add hydrotrope
• chemical modification of drug - change structure as last resort

Question 9

What are co-solvents?

Answer 9

Co-solvents are substances added to a primary solvent (water) to increase the solubility of a poorly-water soluble drug.

Question 10

Give 3 examples of co-solvents.

Answer 10

Ethanol
Glycerol
Propylene glycol

Question 11

Explain how Kaletra oral solution (HIV treatment) for children is made.

Answer 11

Crush adult tablets into powder. Mix with 40% alcohol and 15% propylene glycol.

Question 12

What is meant by solubility parameter?

• SP is an analytical method for choosing co-solvents

Answer 12

Thermodynamic measure of the cohesive forces that exist in a substance.
Maximum solubility is achieved whenever the solubility parameters of the solvent and solute are identical.

Question 13

Describe dielectric constant.

• DC is an analytical method for choosing co-solvents

Answer 13

Maximum solubility is achieved in a particular solvent system at a defined dielectric constant.
The dielectric constant is equal to the capacitance of the condenser filled with some reference material (Cx) divided by the standard (Co).

Question 14

What are the 3 commonly used surfactants?

Answer 14

Spans, tweens, phospholipids.

- surfactant has similar structure to phospholipids - lipophilic drugs housed in the interior of micelles.

Question 15

What are hydrotropes?

Answer 15

Substances that solubilise hydrophobic compounds in water by means other than the surfactant/micelles mechanism.

Question 16

Give 3 examples of hydrotropes.

Answer 16

Sodium benzoate
Sodium p-toluenesulphonate
Sodium salicylate

Question 17

What are cyclodextrins?

Answer 17

Modified starches.

Question 18

Name the excipients found in a liquid formulation.

- disadv of pharm liquids = instability of API.

Answer 18

Vehicle, preservatives, sweetening agents, viscosity control, colours, flavours.

Question 19

What are some properties of a preservative?

Answer 19

• broad spectrum efficacy.
• physically, chemically and biologically stable over the shelf-life.
• non-toxic, physiologically and physiochemically inert.

Question 20

Name 5 preservatives commonly used in pharmaceutical liquid formulations.

Answer 20

Benzyl alcohol
Parabens
Benzoic acid
Sorbic acid
Syrups with 85% sugar

Question 21

What is the purpose of ethanol added to liquid formulations?

Answer 21

Offers protection from dilution as a result of condensation/evaporation.

Question 22

At what pH is sucrose stable in?

Answer 22

pH4-8

Question 23

Name two sweetening agents?

Answer 23

Saccharin

Aspartame

Question 24

How does menthol and chloroform affect taste? These are added as flavourings.

Answer 24

Desensitising agents - desensitise taste by blocking receptors in sensory system.
-have mild anaesthetic effect on sesnory receptors.

Question 25

What role does monosodium glutamate play in flavouring?

Answer 25

Enhances natural flavours.
Reduces bitter metallic taste of iron containing liuids.
Can generally reduce bitterness.

Question 26

How can liquids be stored?

Answer 26

Bottles, vials, IV bags, cartridges, pre-filled syringes, ampules.