Ratio of the systemic exposure from extravascular (ev) exposure to that following intravenous (iv) exposure as described by the equation:

F = A_evD_iv / B_iv D_ev

where F (fraction of dose absorbed) is a measure of the bioavailability, A and B are the areas under the (plasma) concentration time curve following extravascular and intravenous administration respectively, and D_ev and D_iv are the administered extravascular and intravenous doses.