Pharmacokinetics of Oral Dosing Review Flashcards
(16 cards)
What are examples of extravascular drug administration?
- Intramuscular injection
- Subcutaneous injection
- Nasal decongestants
- Topical agents (e.g. ointments, transdermal patches, lotions, creams)
- Rectal route
- Aerosol bronchodilators
- Sublingual
- Oral–> most common route of drug administration
basically anything not IV
What are the advantages of extravascular drug administration?
- Ease of administration
What are the disadvantages of extravascular drug administration?
- the source of variability in exposure/response
- takes time for drugs to enter systemic circulation following administration
- some drugs may be lost during the absorption process
What are examples of immediate release products for oral administration?
- Solids: tablets and capsules
- Liquids: Syrups, elixirs, suspensions, and emulsions
What are examples of modified release products for oral administration?
Extended-release
* Controlled-release: approximates zero order release, constant drug release over time
* Sustained-release: maintains drug release but not a constant rate
Delayed-release
* Common example is enteric-coated aspirin
Where is the major site of drug absorption?
the small intestine
What is the difference between ka and kel?
- ka= absorption rate constant
- kel= elimination rate constant
First order rate constants, units are time^-1
What is Cmax and Tmax?
- Cmax: maximum plasma concentration
- Tmax: time to reach Cmax
What are the two phases on the plasma drug conc curve?
(1) Absorption phase
(2) Post absorption phase (elimination phase)
What does F stand for? (other than my grade on this exam lol)
Bioavailibility
How does faster absorption change the tmax and cmax?
- Decreased tmax
- Increased cmax
What is tlag?
Delay between drug administration and the beginning of absorption
Describe bioavailability.
- It is the fraction of the administered dose that reaches systemic circulation (the heart)
- IV= absolute bioavailibility
- other dosage form= relative bioavailibility
- Bioavailibility has NO units
- Absolute bioavalibiity varies between 0 and 1
- F= (AUC/Dose)/(AUC/Dose)
- Estimation of F requires both oral and IV data
What does AUC mean in relation to bioavailibility?
AUC reflects the total amount of drug the body is exposed to. Larger AUC means the body is exposed to a larger amount of drug. AUC is proportional to dose in linear kinetics.
* Unless directed otherwise, bioavailibility is assumed to be absolute.
Is disposition rate-limiting?
Yes
How does the half-life of absorption and post absorption phase differ? What about the flip-flop phenomenon?
Generally, the half-life of the post-absorption phase corresponds to the elimination half-life. In the flip-flop phenomenon, the half-life of the “post-absorption phase” does NOT correspond to the elimination half-life. In this case, the half life of the post-absorption phase corresponds to the absorption half-life.
