Absorption of Drugs Flashcards
What is passive diffusion?
Does not involve a carrier. The med moves down the concentration gradient.
What is facilitated diffusion?
Meds enter the cell via specialized transmembrane carrier proteins. Meds move down the concentration gradient. Does not equine energy.
What is active transport?
Energy dependent transport that involves the use of carrier proteins. Moves meds against the concentration gradient.
Endocytosis vs. Exocytosis
Endocytosis: engulfment of a drug by the cell membrane and transpire into the cell by pinching off the drug filled vesicle.
Exocytosis: release of meds from vesicles.
How does pH effect absorption?
Most meds are either weak acids or weak bases. A drug passes through membranes more readily if it is uncharged. For a weak acid, the uncharged/protonated HA can permeate & A- can’t. For a weak base, the uncharged form B can penetrate but the protonated form BH+ can’t. LIKE IN LIKE: acidic meds like acidic environment and vice versa.
What is pKa?
Ionization constant. It is the measure of the strength of the interaction of a compound with a proton. The lower the pKa of a drug, the more acidic it is.
What is bioavailability?
It is the fraction of administered drug that reaches the systemic circulation. It is determined by comparing plasma levels of a drug after a particular route of admin. with plasma drug elves achieved by IV injection. IV bioavailability is 100%.
