Calculating drug doses Flashcards
what is is dose
amount of drug to be given
what is doage
amount of drug to be given per time
2 ways to determine dose
- follow guidelines taking PT into account
2. look up drug properties and then use formulas
how to deterimine the target [C] (2)
- look up in monograph
2. use Sx as surrogate
what is caveat to [c] rules
the [c] does not always correspond to the effect - eg THC
2 issues in calcualting dose
- form/route
2. speed of delivery (need loading dose?)
dose formula
dose = (target [c])xVd
what is dose formula is not paraenteral
dose = (CxVd)/(bioavailability (F))
what is bioequivalence
comparapable plasma [c]
what is therapeutic equivalence
comparable clinical effectiveness
what are 2 assumptions for single dose
- all dose distributed into this volume quickly
2. use calculation of initial [c]
how long until reach steady state
4-5 half lives
how to get to steady state faster
loading dose
what is clearance rate
rate of elim./plasma drug [c]
what is differential [c] formula
C=C0e -kt
what is t.5 forlmula
ln2/ke
what is formula for ke from log graph
(2.303)(-slope)
what is clearance rate formula
Cl = Ke x Vd
what is Ke
constant for rate of elimination
what is steady state formula
rate of infusion/rate of elimination
what is formula for using a loading dose to get to steady state [c]
dose = Css * Vd
if giving repeated dosing, where should doses be kept
between [C]toxic and [c]therapeutic
what is loading dose formula for oral drugs
(Ctarget * Vd)/F
what does % mean
1g/100ml
