stability

Degradation

Changes that adversely affect the properties of medicine

Microbial contamination

Expiry date

‘Use by’ date on label —> tells user the shelf life

Max shelf life of tablets

Up to 5 years

Aqueou based medicines expiry date

Less than 3 years

Degradation process types

Chemical, microbiological, physical

Stability ( USP definition)

The extent to which a medicine retains, within specified limits, and throughout its shelf life, the same properties and characteristics that it possessed at the time of its manufacture

USP

United States pharmacopeia

Label claim

A percentage of the original drug content placed during original manufacture

What percentage f drug loss does the BP ad USP allow

Up to 10% but 5% or 3% when there are toxic products

When are stability tests taken?

After storing the pack combination at internationally agreed temperatures and humidities —> provides scientific evidence for shelf life + storage conditions

Common storage Conditions

3 years when stored between 15-25 degrees Celsius (rtm)

Physical instabilities

Absorption

Diffusion/partition

Evaporation

Particle size changes(in suspensions, in emulsions)

Separation

Solubility changes

Chemical instabilities

Oxidation

Photolysis

Hydrolysis

Enzymes (from microbes)

Consequence of instability

• change in rate of drug release from a medicine

• Dose uniformity problems

• Changes in colour, smell and texture

• Changes that you can’t detect easily

• Microbial growth in medicines

• material adsorbs moisture

• Dissolve at surface and dry

What are changes due to instability that can’t be detected easily

Chemical degradation

Loss of potency & therapeutic effect

Increase in toxicity & adverse effect

Ostwald ripening

Process where smaller crystals or particles dissolve and redeposit their material on larger crystals

what can cause dose uniformity problems in emulsions and creams

• creaming & cracking

• Temp cycling

• Freezing - ice crystals cause separation

what can cause dose uniformity problems in Solutions

Precipitation due to solubility limit

Medicine stability in practice

• short shelf life

• Store as labelled on pack

• Expiry dates

What medicines are susceptible to caking

Suspensions

Bulk powders

Individually wrapped powders