L43 - IV Infusion Administration 1 Flashcards
What is continuous infusion?
- drug added to a large volume of parenteral fluid
- solution slowly and continurously administered into a vein
What are advantages of continuous infusion?
- drug plasma levels easily controlled by changing infusion rate (R)
- constant drug plasma levels can be achieved
- less problems of irritation/toxicity
What are disadvantages of continuous infusion?
- continuous monitoring
- solubility and stability of some drugs
- fluid restricted patients
How do you calculate the constant rate of infusion?
R = mass of drug infused/ unit time
What are assumption of the one compartment open model for IV infusion?
- elimination - first order process (k elim rate const)
- drug input - zero order process (R zero-order const rate)
- linear kinetics
What is the variation of A in the body with time the balance resulting from?
The input rate into the body (infusion rate) and the rate out of the body (elim rate)
What is input rate?
- R - mass of drug entering circulation per unit time
- zero order, constant value
- adds drug to the body
What is rate out?
- elim rate k x A
- decreases amount of drug in the body
What is the one compartment open model for IV infusion eqn?
Eqn2 - A = R/k (1-e^-kt)
Eqn3 - C = R/kV(1-e^-kt) ~ R/Cl
What can we apply the IV infusion model to?
Drug administration in which input of drug into body corresponds to zero-order process // transdermal patches, oral forms
What does eqn 3 predict?
Drug concentration during IV infusino
What are the different phases in IV infusion plasma drug profile?
- accumulation phase
- plateau (steady state)
- exponential decline
What is accumulation phase like?
- input rate: R (mass/time) = constant
- elimination rate: dA/dt = A.k = Cl x C
- elim rate < input rate
- drug accumulates into body, plasma conc increases
What is the plateau (ss) of an IV infusion?
- input rate R remains constant
- elim rate dA/dt = A.k = Cl x C inc with time as A in body increases
- elim rate = input rate
- ss has been reached, drug conc becomes constant Css
What eqn can u use to predict values during ss?
R = Css x Cl
What is input, elim rate and conc like once infusion is stopped?
- input rate = 0
- dA/dt = A.k - Cl x C
- C = C0 x e^-kt
How can you get k and t1/2 from post-infusion data?
lnCpostinf = lnC0 - k x tpost inf
