The physiological availability of a given amount of a drug, as distinct from its chemical potency; proportion of the administered dose which is absorbed into the bloodstream.
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bio·avail·abil·i·ty -ə-.vā-lə-'bil-ət-ē n, pl -ties the degree and rate at which a substance (as a drug) is absorbed into a living system or is made available at the site of physiological activity
bio·avail·able -'vā-lə-bəl adj
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n.
the proportion of a drug that is delivered to its site of action in the body. This is usually the amount entering the circulation and may be low when the drugs are given by mouth.
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bio·avail·a·bil·i·ty (bi″o-ə-vāl″ə-bilґĭ-te) the degree to which a drug or other substance becomes available to the target tissue after administration.Medical dictionary. 2011.