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Old 03-28-2013
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Drug Calculating Drug Css (Steady State Concentration)

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
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Old 03-28-2013
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I think its b
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Old 03-28-2013
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Maintenance dose = CL X Css

Css = Maintenance dose / CL

= 0.1 mg/min / 60 L/Hr

Do the conversion: 1 Hr = 60 min

= 0.1 mg/min / 1 L/min

Css = 0.1 mg/L

My answer is B.
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Default 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
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Old 03-29-2013
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What happened to the dosing interval value? When you initially setup up the equation to figure out the Css. Because the equation is MD=Css x cl x dosing interval divide by bioavailability.
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Old 05-01-2014
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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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Old 05-01-2014
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Quote:
Originally Posted by Doctor Ali View Post
Maintenance dose = CL X Css

Css = Maintenance dose / CL

= 0.1 mg/min / 60 L/Hr

Do the conversion: 1 Hr = 60 min

= 0.1 mg/min / 1 L/min

Css = 0.1 mg/L

My answer is B.
its right calculation
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