Word parts
What it means
A drug given IV goes straight into the blood, so its bioavailability is 100%. A drug swallowed must be absorbed from the gut and pass through the liver first, where some of it is broken down (the first-pass effect), so less of it reaches the blood. That is why the oral dose of a drug is often bigger than the IV dose. Food, other drugs and the form of the tablet can change it.
For the nurse
Do not swap routes or forms (such as IV for oral, or one brand for another) without an order, because the amount that reaches the blood may differ.
Related terms
parenteral
Given by a route other than the digestive tract, usually by injection or into a vein.
therapeutic effect
The helpful effect a drug or treatment is given to produce.
prescription drug
A drug that can only be legally sold or given with an order from a licensed prescriber.