PK of IV Infusion Flashcards
1 mg/hr to mg/min
0.0167 mg/min
1 mg/hr to mcg/min
16.7 mcg/min
1 mg/L to mcg/ml
1 mcg/ml
1 L/hr to ml/min
16.7 ml/min
steady-state
rate in = rate out
Rate in
R
Rate out
Cl * C
when infusion starts
R > Cl * C
What happens to elimination rate when you increase concentration?
Increases
When you increase the infusion rate, what happens to Css?
Increases
If you increase the R, what happens to tss?
it doesn’t change because tss is only impacted by half-life
when is Css achieved?
3.3 t1/2
Which formula do you use when choosing the bigger R method for reaching the targeted Css?
R=Cl* C / (1-e^-kt)
Continuous infusion before s-s
Two concepts/formulas
1) rate in > rate out
2) C = Css (1-e^-kt)
At s-s, which formula do we use?
1) rate in = rate out
2) R=Cl*Css
Stopped infusion
concept/formulas
1) rate in = 0
2) C = Css * e^-kt
3) DL=Css * V
1t1/2
50% Css
2 t1/2
75% Css
3 t1/2
87.5% Css
3.3 t1/2
90% Css
What does being at steady-state mean?
rate of drug infused is equal to rate of drug eliminated
what are the units of R?
mg/hr
Why do we say that drug input is independent?
the concentration of the drug in the body does not affect the rate of administration
formula for the time required to reach fraction x
tx = -1.44 * t1/2 * ln(1-x)
