What is bioavailability? Significance of bioavailability. Factors modifying bioavailability.

Bioavailability: The rate at which and the extent to which the unchanged drugs become available for systemic action at the site of action, following administration is called bioavailabilty.

Significance of Bioavailability: 

• For comparing different formulation of same drug.
• For comparing different formulation of same drug produced by different companies.

Factors modifying bioavailability:

• Pharmaceutical factors
• Physical state of drug and particles size.
• Formulation properties.
• Manufacturing variability.
• Presystemic elimination.
• Enterohepatic circulation of drug.
• Biological factors.