The expiry date printed on your medicines isn’t arbitrary—it’s carefully determined through rigorous stability studies to ensure the drug remains safe and effective throughout its shelf life.
Here’s a breakdown of how it’s done:
—Step 1: Stability Studies
Pharmaceutical companies test drugs under controlled conditions to monitor:Potency: The active ingredient should remain within 90–110% of its labeled content.Degradation: Impurities must stay below specified limits.Physical Stability: The product should maintain its appearance, hardness, and dissolution profile.Microbial Limits: The drug must not develop harmful microbial contamination.These studies are performed using samples stored under specific temperature and humidity conditions for months or years.
Here’s a breakdown of how it’s done:
Step 1: Stability Studies
Pharmaceutical companies test drugs under controlled conditions to monitor:
Potency: The active ingredient should remain within 90–110% of its labeled content.
Degradation: Impurities must stay below specified limits.
Physical Stability: The product should maintain its appearance, hardness, and dissolution profile.
Microbial Limits: The drug must not develop harmful microbial contamination.
These studies are performed using samples stored under specific temperature and humidity conditions for months or years.
Step 2: Testing Conditions
The testing conditions depend on the market’s climatic zone. For example:
Zone I (21°C/45% RH): Cooler regions like the UK or Russia.
Zone II (25°C/60% RH): Temperate regions like the USA, Europe, and Japan.
Zone IVa (30°C/65% RH): Hot and moderately humid regions like India and Brazil.
Zone IVb (30°C/75% RH): Hot and very humid regions like ASEAN countries and Gulf states.
In addition, accelerated stability studies at 40°C/75% RH simulate long-term stability in just 6 months.
Step 3: Data Analysis and Shelf Life Prediction
After testing, the degradation rate is analyzed. If a drug’s potency drops below 90% or impurities exceed the limit within a given time frame, that becomes the shelf life.
For instance:
A drug stored at 30°C/65% RH retains its potency for 36 months.
After 36 months, its active ingredient dips below 90%, so the shelf life is set as 3 years from the manufacturing date.
Step 4: Why Accelerated Testing Matters
Accelerated stability studies allow companies to predict shelf life faster. For example, storing a drug at 40°C/75% RH for 6 months gives an indication of how it will perform under real-time conditions for 2-3 years.
If accelerated testing shows significant changes, intermediate conditions (like 30°C/65% RH) are used for further evaluation.
Why This Is Important
Drugs sold in different countries need tailored stability data based on the region’s climate.
Proper storage conditions, like keeping medicines in a cool, dry place, ensure they remain effective throughout their shelf life.
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