Define Absorption
The process of drug uptake from the site of administration and transfer into the blood stream
What dictates the rate and efficiency of absorption
Site of administration
Name which sites of administration have TOTAL absorption
Intravenous (IV)
Name which sites of administration have PARTIAL absorption
Oral
Intramuscular
Transmucosal/transdermal
Define Bioavailability
A measure of how much drug reaches the circulatory system and is available at the site of action
What 6 things affect the bioavailability of a drug
- Route of administration
- Degradation of drug prior to absorption
- Gastrointestinal (GI) absorption mechanisms (active transport vs. passive diffusion)
- Solubility (hydrophilic drugs vs hydrophobic drugs)
- Hepatic first pass effect
- Drug chemistry (presence of binders or dispersing agents, particle size, etc.)
Define Drug Distribution
The ability of a drug to move from the circulatory system into the interstitium and tissues
Factors affecting Drug Distribution
- Blood flow
- Protein binding
- Permeability (ability to cross capillary barriers and specific types of capillary barriers that are largely impermeable such as the blood brain barrier)
Define Volume of Distribution (Vd)
A theoretical amount of fluid the drug is dispersed in after administration
Vd = total amount of drug in body/blood concentration of drug
Define a Phase I reaction of drug metabolism
Convert molecules into often still active slightly polar, water-soluble metabolites through oxidation, reduction, or hydrolysis reactions (e.g., cytochrome P-450 system)
Define a Phase II reaction of drug metabolism
Convert molecules into inactive polar metabolites via acetylation, glucouronidation, or sulfating that are then excreted by the kidneys
