- In pharmacology, bioavailability (BA) is a subcategory of absorption and is the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. By definition, when a medication is administered intravenously, its bioavailability is 100%.
Source: Griffin, J.P. The Textbook of Pharmaceutical Medicine (6th Ed.). New Jersey: BMJ Books. ISBN 978-1-4051-8035-1