Dosing Regimen Design Flashcards
(10 cards)
Components of Dosing regimen
IV: Ro
bolus: dose + tau
Need to know
- target C
—- IV: Css
—- bolus: Cssmax, Cssmin or Cssavg
- Cl, V, t1/2 (need 2 )
—- oral : F
When to use loading dose
if want to rapidly increase concentration right away (acute)
+ long t1/2 (takes a while to get to Css)
To calculate need: target C, V , F (oral)
Constant IV
Only need CL + Css to get Ro
— changes to Ro directly changes Css if need to change dose
What PK parameter impacts LD
V
LD- Ctarget * V
T or F: LD is normally a single bolus dose
T- one big dose to increase C
- size depends on V
- if have drug in body before: take this into consideration when calculating loading dose
LD and Constant IV
- must start maintance dosing right away to keep C in desired range
Total C of drug in body: includes LD and IV
— as T increases, contribution of LD decreases; eventually only IV
Factors that impact selection of Dosing interval
-degree of fluctuation that is okay: depends on window of therapy
— wide TW: pt may be able to tolerate larger differences in C + still get good response
- fluctuation only impacted by t1/2
—- if dosing interval is double t1/2 : degree of change will be 4X (more fluctuation) - peak conc will bw 4x trough value
Factors for tau
- half life
- TW
- pt convenience
—- more frequent dosing: better C + consistent effects but less adherence
Guidelines for dosing intervals based on t1/2
tau = t1/2: degree of fluctuation is 2X
short 1/2: dose less often than t1/2 (t1/2> tau)
long t1/2 (> 24hrs): dose QD
How to calculate dosing regimen for bolus
- determine interval 1st
—— round down to number that makes sense : 4, 6, 8,12, 24 ( generally round down bc less fluctuation) - then dose; round to number that makes sense
— if know Cl: use Cssavg - then check: sub these values into Cssmax and Cssmin to see if within TW
