Oral bioavailability

Oral bioavailability (F%) is the fraction of an oral administered drug that reaches systemic circulation. After intravenous administration, a drug is directly and fully available in the bloodstream and can be distributed via systemic circulation to the point where a pharmacological effect takes place. If a drug is administered orally, it has to cross further barriers to reach the systemic circulation, which can significantly reduce the final extent of a drug in the bloodstream.