Pharmacokinetics Flashcards
It takes 5 half-lives to accomplish what two things?
- Reach Css (concentration steady state)
- Eliminate a drug
What is an example of a medication with a high first pass?
Morphine
What form of a weak acid can cross a membrane? Why?
Protonated form (HA) because it is non-ionized and readily absorbed
What form of a weak base can cross a membrane? Why?
Unprotonated form (B) because it is non-ionized and readily absorbed
If pKa is greater, what form dominates? What does this mean for weak acid versus weak base?
Protonated form dominates
- Acid will non-ionized (HA)
- Base will be ionized (BH+)
If pH is greater, what form dominates? What does this mean for weak acid versus weak base?
Unprotonated form dominates
- Acid will ionized (A-)
- Base will be non-ionized (B)
Where are drugs with a large Vd distributed in the body?
Tissues
Where are drugs with a small Vd distributed in the body?
Plasma
Does zero order or first order depend on plasma concentration of a drug?
First order
What three things is Css directly proportional to?
- Dose
- Bioavailability
- t1/2
What two things is Css indirectly proportional to?
- CL
- Vd
What is an example of zero order elimination? At what rate is it eliminated?
Alcohol
- 10 mg/hour
With maintenance dose, what can lead to an increase in Css (toxicity)?
- Increase dose only
- Decrease interval only
With maintenance dose, what can lead to an decrease in Css (ineffective dose)?
- Decrease dose only
- Increase interval only
In what gender/body type to drugs remain in the body longer? Why?
Obese women
- Adipose tissue acts as a reservoir, decreasing plasma levels and increasing half-life of a medication
