Solutions Flashcards
What are the advantages of using pharmaceutical liquids?
- 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.
What are the disadvantages of pharmaceutical liquids?
- 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)
What is meant by salvation?
Binding of solvent to solute.
What is meant by hydration?
Binding of water to solute.
What is isoelectric point?
The pH at which the net charge of the molecule is neutral.
What is meant by amphoteric?
Possess acidic and basic properties.
What is the purpose of solubilisation?
Makes the formulation water soluble or makes the formulation a uniform solution.
In what ways can solubilization be achieved?
- water soluble drugs
- co-solvents
- surfactants
- complexation
- add hydrotrope
- chemical modification of drug - change structure as last resort
What are co-solvents?
Co-solvents are substances added to a primary solvent (water) to increase the solubility of a poorly-water soluble drug.
Give 3 examples of co-solvents.
Ethanol
Glycerol
Propylene glycol
Explain how Kaletra oral solution (HIV treatment) for children is made.
Crush adult tablets into powder. Mix with 40% alcohol and 15% propylene glycol.
What is meant by solubility parameter?
- SP is an analytical method for choosing co-solvents
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.
Describe dielectric constant.
- DC is an analytical method for choosing co-solvents
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).
What are the 3 commonly used surfactants?
Spans, tweens, phospholipids.
- surfactant has similar structure to phospholipids - lipophilic drugs housed in the interior of micelles.
What are hydrotropes?
Substances that solubilise hydrophobic compounds in water by means other than the surfactant/micelles mechanism.
Give 3 examples of hydrotropes.
Sodium benzoate
Sodium p-toluenesulphonate
Sodium salicylate
What are cyclodextrins?
Modified starches.
Name the excipients found in a liquid formulation.
- disadv of pharm liquids = instability of API.
Vehicle, preservatives, sweetening agents, viscosity control, colours, flavours.
What are some properties of a preservative?
- broad spectrum efficacy.
- physically, chemically and biologically stable over the shelf-life.
- non-toxic, physiologically and physiochemically inert.
Name 5 preservatives commonly used in pharmaceutical liquid formulations.
Benzyl alcohol Parabens Benzoic acid Sorbic acid Syrups with 85% sugar
What is the purpose of ethanol added to liquid formulations?
Offers protection from dilution as a result of condensation/evaporation.
At what pH is sucrose stable in?
pH4-8
Name two sweetening agents?
Saccharin
Aspartame
How does menthol and chloroform affect taste? These are added as flavourings.
Desensitising agents - desensitise taste by blocking receptors in sensory system.
-have mild anaesthetic effect on sesnory receptors.
What role does monosodium glutamate play in flavouring?
Enhances natural flavours.
Reduces bitter metallic taste of iron containing liuids.
Can generally reduce bitterness.
How can liquids be stored?
Bottles, vials, IV bags, cartridges, pre-filled syringes, ampules.
