L44 - IV Infusion Administration 2 Flashcards
How can you predict when Css will be achieved?
F = C/Css
ln(1-F) = -ktF
What is F?
Fraction of equilibrium attained at a given time of the infusion
What does the time to reach a fraction of ss depend on?
- t1/2
- (Cl and V)
What are the factors controlling the time to reach plateau?
- V anc Cl
- (t1/2)
What are advantages and disadvantages of getting and maintaining the required concentration in IV bolus?
Advantages
- Highest Cdrug observed upon injection C0
- gets Creq immediately
Disadvantages
- Cdrug declines from injection, as drug eliminated is not replaces
What are advantages and disadvantages of getting and maintaining the required concentration in IV infusion?
Disadvantages
- Cdrug starts at ), builds up to Css
- if Creq is Css, 4-5t1/2 required
Advantages
- once Css attained, maintained as infusion replaces drug eliminated
What can you do to get advantages from each administration method?
- IV bolus loading dose followed by IV infusion
- administer IV bolus dose to achieve Crequired without delay
- start IV infusion to maintain Crequired
What can you assume to IV bolus loading dose followed by IV infusion?
Drug in body resulting from IV bolus and IV infusion behave independently, total C will be sum of both fractions
What is the eqn to calculate concentration for IV bolus loading dose followed by IV infusion?
C = C0 x e^-kt x Css(1-e^-kt)
How and why can you change rate of infusion?
- infusion rate can be changed bc of toxicity or inadequate therapeutic response
- time to get new plateau only depends on t1/2 of drug
How can you predict the drug concentrations with IV bolus + IV infusion
First infusion with initial R is stopped, second infusion with new R started at time the first infusion was stopped
What will concentration be for 2 infusions?
The sum of the concentration remaining from 1st infusion + 2nd infusion
