liquid medicines

What are the three main types of liquid medicines?

Solutions, suspensions, emulsions

What is a solution?

A liquid medicine where all ingredients are completely dissolved and present as a single molecule

What is a suspension?

A liquid medicine containing insoluble solid particles dispersed in a liquid

What is an emulsion?

A liquid medicine containing insoluble liquid droplets dispersed in another liquid

What is a vehicle in a liquid medicine?

The main liquid ingredient that carries the drug

What is the most common vehicle used in liquid medicines?

Water (BP quality)

Why are syrups, glycerol, and sorbitol used as vehicles?

They improve palatability and are easier to pour

Which vehicles are mainly used for external medicines?

Alcohol, ether, propylene glycol

Why are preservatives added to liquid medicines?

To inhibit microbial growth and prevent contamination and degradation

Give examples of preservatives used in oral liquids

Sorbates, benzoates, benzyl alcohol, parabens

Examples of preservatives used in external preparations

benzalkonium chloride, thiomersal, chlorbutanol

Why can preservatives be problematic?

many patients may react to them

Role of antioxidants

prevent oxidation by reacting with oxygen or free radicals

Give examples of water-soluble antioxidants

ascorbic acid, sulphites, sulphur dioxide

Give examples of oil-soluble antioxidants

Vitamin E, BHA,BHT

What is a chelating agent?

A substance that binds metal ions to prevent oxidation

Example of a chelating agent

EDTA

Safety issues associated with synthetic colours

Bronchoconstriction in asthmatics, hyperactivity in children

Which colouring is being withdrawn in the EU?

Titanium dioxide (E171)

Role of solubility enhancers

improve drug dissolution

Two common solubility enhancement strategies

Cosolvents and surfactants

How do surfactants improve solubility?

form micelles in water

Why are suspensions physically unstable?

Particles settle due to gravity

Common thickening agents

Hypromellose, xanthan gum, alginate, starch,PEG

How can wetting of particles be improved?

by adding a surfactant