View Full Version : [Nephrology] Factors determining the bioavailability

Wed 7th August '13, 10:35pm
Bioavailability is the percentage or fraction of the administered dose that reaches the systemic circulation of the patient. Factors that alter bioavailability include:

inherent dissolution
chemical form
dosage form (e.g., tablet, capsule)
route of administration
stability of the active ingredient in the GI tract
the extent of drug metabolism before reaching the system circulation.

Drugs which are administered as inactive precursors that must then be converted to an active product should be emphasized since some of the inactive precursor is eliminated from the body (renally excreted or metabolized to an inactive compound) before it can be converted to the active compund. It is complex.

Generally, for those drugs with nearly complete absorption (F >0.8), bioavailability is usually consistent. For those drugs with a low oral bioavailability (F <0.5), there is often a large variation in the extent of absorption.