is the degree to which, or the rate at which, a medication or other substance is absorbed or becomes available at the targeted place in the body. Bioavailability can be influenced by inactive ingredients (see Excipients
) in the drug such as additives that prevent the medication from dissolving in the stomach. If a medication that is intended to be taken on an empty stomach is taken instead with food, this can also change the absorption rate and affect the bioavailability of the active ingredient(s).
Grapefruit juice inhibits the enzymes that break down certain medications. This can increase the bioavailability of a drug such as BuSpar by as much as 400%, which could be toxic.