How Expiry Dates Are Determined for Medicines?

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.

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 III (30°C /35% RH): Temperate regions like Egypt, Jordan.
• 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.

Read also:

• What Do 30°C/65% RH and 30°C/75% RH Represent?
• Different Types of Stability Studies in Pharmaceutical Industry

Resource Person: Dev Soni