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Old 07-20-2011
yasirsattar75's Avatar
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Calculator First Order Kinetics; How much of the drug will remain?

A patient was given a 160 mg of a drug IV and 80 mg was eliminated during the first 120 min. If the drug follows first order elimination kinetics how much of drug will remain 6 hours after its administration?
a. none
b. 10mg
c. 20 mg
d. 40mg
e. 60 mg
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Old 07-20-2011
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c) 20 mg
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Old 07-20-2011
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Quote:
Originally Posted by yasirsattar75 View Post
A patient was given a 160 mg of a drug IV and 80 mg was eliminated during the first 120 min. If the drug follows first order elimination kinetics how much of drug will remain 6 hours after its administration?
a. none
b. 10mg
c. 20 mg
d. 40mg
e. 60 mg
1 order kinetics
160 mg -> 80mg (50%) in 2h
t1/2 = 2h

then in 6 h = 3 t1/2
160 mg -> 80 mg -> 40 mg -> 20 mg
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Old 07-20-2011
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Yup
Its 20 mg!

First order kinetics = a constant fraction of drug is eliminated over a period of time. (Basically, half life)

First 2 hrs = 160 to 80
Next 2 hrs = 80 to 40
Next 2 hrs = 40 to 20

After 6 hrs, there is 20 mg of drug left.
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Old 07-21-2011
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c)20mg.In first order kinetics,fixed fraction of the drug is eliminated so after 6hrs it is 20mg
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