Pharmacokinetics Flashcards
What does ADME stand for?
Absorption
Distribution
Metabolism
Excretion
What is the main role of absorption?
Getting the drug into systemic circulation
What is bioavailability %?
Amount of drug in circulation/amount of drug administered
What does the area under a bioavailability curve represent?
The amount of drug in circulation (more area under the curve = better drug)
What four things can effect absorption?
- Route of administration (IV, PO, Nasal)
- Blood flow
- Surface area
- Contact time
What is the Y-axis on the bioavailability graph?
Plasma drug concentration (how much drug is in the blood)
-Drugs give IV will have a peak concentration immediately because it is going directly into the blood and it will decrease with time
What is the X-axis on the bioavailability graph?
Time
What is the goal of absorption?
Maximize drug into circulation
What is the First-Pass Effect?
Oral drugs go to the liver (through the portal vein) and the liver metabolizes it before it goes into system circulation
What is the issue with the First-Pass Effect?
An orally administered drug will most likely not have 100% bioavailability (oral drug considered good between 40-60% bioavailability)
(First-Pass Effect is the inverse of bioavailability. If bio is 60% then first pass is 40%)
Oral drugs must be stable at a ___ pH because of stomach acid
Low
Stomach acid can degrade certain drugs
Oral drugs are best if _____ soluble
Lipid (tablet vs capsule)
Why might the oral mucous membrane route (sublingual or intranasal) be better than PO?
- Faster absorption
- No first pass effect (bypasses portal vein)
- No exposure to GI HCl
- IN drugs good if unconscious pt bc they cannot swallow
- Sublingual drugs good if stomach acid would degrade the drug
What is the main role of distribution?
Move the drug from circulation (blood) to the target
Distribution is dependent on ______ to the organ
Blood flow/perfusion
What are 3 physical barriers to distribution?
- Blood brain barrier
- Placenta
- Testis and oocytes