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Calculating Drug Css (Steady State Concentration)

9K views 6 replies 6 participants last post by  asma aqib08 
#1 ·
29 years female brought to ER after accident. Morphine continuous at dose of 0.1 mg/min, t 1/2 = 1.9 hour , clearance = 60L/hr , Vd= 230 L, then which Css (steady state concentration) will be attained??


a) 0.016 mg/L
b) 0.1 mg/L
c) 0.026 mg/L
d) 0.0016 mg/L
 
#4 ·
corect answer:B)

29 years female brought to ER after accident. Morphine continuous at dose of 0.1 mg/min, t 1/2 = 1.9 hour , clearance = 60L/hr , Vd= 230 L, then which Css (steady state concentration) will be attained??

b) 0.1 mg/L

for Css = Dosing rate "drug in" must be equal to rate of elimination "drug out'

MD = CL X Css / f
Css = dose / CL

dose = 0.1 mg/min
units should be same for other measure hence,
CL = 60L/hr then
CL = 1L / min

now

Css= 0.1 / 1 = 0.1 mg / L

Css= 0.1 mg/ L

formulas:
MD = CL X Css / f
Ko = CL X Css
 
#6 ·
Shouldn't the answer be D, the question mentions the infusion rate not the maintenance dose so using the formula for infusion rate,
infusion rate = clearance * steady state plasma concentration...
hence .1 = 60 * steady state plasma concentration
steady state plasma concentration= .1/60
steady state plasma concentration= .0016(D)
 
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