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
Water soluble drugs _____
Fat soluble drugs ______
Stay in water (ex: UTI, want a water soluble drug because infection is in the bladder where liquid is)
Stay in fat (need a protein carrier in serum)
Why might a toe with gangrene need to be amputated?
There is no blood flow to the toe –> drug cannot get to tissue –> amputation
What is the process of altering a parent drug to different compounds?
Metabolism (biotransformation)
Drugs must be ____ to be eliminated ?????
Polar
What do phase I reactions do?
Convert the parent drug to a more polar metabolite (simple rxn, oxidation/reduction)
- Enhances water solubility
- May activate or inactivate
- Prepares molecule for phase II
What do phase II reactions do?
Adds a compound to the parent drug
- Enhances water solubility
- Almost always inactivates (failsafe way to inactive a drug)
- Prepares molecule for elimination
Which routes of drug administration have no first-pass effect?
- Transdermal
- IV
- Sublingual
- Rectal (very low first pass effect, if any)
Transdermal route has a slow or fast onset?
Slow
