Unit 2 - Pharmacokinetics - Part 2 Flashcards
Which administration route will use the first pass metabolism?
The enteral route (i.e. oral ingestion)
Which organ is involved, primarily, in first pass metabolism?
The liver
Describe the hepatic portal system.
1 - The small intestine, and digestive organs absorb products of digestion.
2 - Nutrient molecules travel in the hepatic portal vein to the liver
3 - Liver monitors blood content.
4 - Blood enters the general circulation by way of the hepatic vein.
Why does most absorption in the GI tract occur in the small intestine?
High surface area.
Drugs and nutrients travel from the digestive organs to where? By what means?
From the digestive organs, nutrients and drugs are absorbed and travel through the hepatic portal vein to the liver.
First-pass metabolism:
- Happens to all _____ dosage that are absorbed from the GI tract, enter the ______ vein, and then reach the liver
- Dosage that is delivered via _________ and _____ or other routes of administration are ____ subjected to first-pass metabolism
oral
hepatic
sublingual, rectal, not
What is first pass metabolism? (Defn)
A phenomenon of drug metabolism whereby the concentration of a drug is greatly reduced before it reaches the systemic circulation.
What is bioavailability?
The fraction of unchanged drug found in the systemic circulation
What would the bioavailability value be for IV?
1
Drug delivered to vascular system directly
What is the bioavailability a function of for an oral dosage form?
F (bioavailability) = fg * fh
fg - fraction of the drug absorbed
fh - fraction of the drug left after first-pass elimination
What is reabsorption?
The process of re-incorporation of drug into the bloodstream from excreting organs
Where does reabsorption occur?
- What are the excreting organs?
GI tract:
- gallbladder
- Large intestine
- kidney
- mammary gland
What is the main way of re-transfering a drug back into the circulation system?
Through passive diffusion
What does it mean when a drug has a long half life?
Stays in the body for prolonged periods.
The more a drug reabsorbs, the longer it remains in the body.
What are qualities of a good over the counter drug?
Safe:
- high therapeutic index: gap between therapeutic dose and toxic dose is huge
Easy to take:
- convenient dosage form for example
