 Welcome to Nursing School Explained and this video about bioavailability, which is a term that always comes into play when we talk about pharmacokinetics, which means how the medications are processed through the body. Pharmacokinetics happen in four different stages, which is absorption, distribution, metabolism and excretion. So check out my videos about these topics. And bioavailability is a term that always comes into play when we talk about the actual absorption of the medication. So bioavailability means how much of the medication is available or reaches the systemic circulation before it gets broken down by enzymes and other factors. And the IV route of medication allows for 100% of bioavailability because the medication reaches the systemic circulation as soon as we push the medication into the patient's IV. Other routes of administration may be decreased, but the degree we don't really know and factors that that depends on is whether the medication is lipid or water soluble because it has to pass through this phospholipid bilayer of the cell membrane. It depends on the pH of the medication. Medications with decreased pH have increased absorption. The concentration, the more concentrated the medication is, the higher its bioavailability is. If I give a medication that's twice as concentrated, then it's going to be more available in the body or more of it is going to reach that systemic circulation. The length of contact, so this pertains more to a like a sublingual administration route or maybe a lozenge that the patient is dissolving in their mouth. So that's why we instruct patients not to chew any kind of sublingual or buccal medications because the length of contact would be less and it would lessen the medication's bioavailability. Age always plays a role in pharmacokinetics and pharmacology in general and so for bioavailability in the pediatric and geriatric populations of the very young and the very old, we always have to think about decreased absorption through the topical route and then the presence of food, of course, has to do with the absorption and the bioavailability of medications that are given by the interval route through the GI tract. So please check out the other video specifically about absorption where I talk about the different routes of medication administration and what affects them and what inhibits them so that you have a better understanding of how bioavailability availability ties into this whole topic of pharmacokinetics. Thanks for watching. See you soon.