Definition of Drug Stability
- Drug stability refers to the ability of a pharmaceutical product to maintain its physical, chemical, microbiological, therapeutic, and toxicological specifications throughout its shelf life.
- A drug degrades over time due to:
- Chemical reactions (e.g., hydrolysis, oxidation, photodegradation)
- Environmental factors (light, temperature, humidity)
- Interaction with excipients or container
Types of Stability:
- Chemical Stability: Ensures the drugs substance retains its chemical integrity and labeled potency.
- Physical Stability: Maintains the physical properties (appearance, palatability, dissolution, etc.).
- Microbiological Stability: Ensures sterility or resistance to microbial growth.
- Therapeutic Stability: Drugs continues to exert its intended therapeutic effect.
- Toxicological Stability: No increase in toxicity over time.
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Factors Affecting Drug Stability:
- Temperature: Higher temps can accelerate degradation.
- pH: Extreme pH can promote hydrolysis or oxidation.
- Light: Some drugs are photosensitive.
- Oxygen: Can lead to oxidative degradation.
- Moisture: Facilitates hydrolysis.
- Container and packaging: Interaction with packaging materials may destabilize the drug.
Stability Testing:
- Stability testing involves subjecting the drugs to different environmental conditions to determine its shelf life and proper storage conditions.
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