USMLE Forums banner

Time to reach Drug Steady State

4K views 9 replies 7 participants last post by  medpack87 
#1 ·
A constant infusion of drug Y is begun. Drug Y has a Volume of Distribution of 5L, and a clearance of 0.05L/h.

Aproximately how long would it take drug Y to reach steady state?

a. 70
b. 100
c. 112
d. 280
e. 400

:confused:
 
#9 ·
corect answer is (D):

A constant infusion of drug Y is begun. Drug Y has a Volume of Distribution of 5L, and a clearance of 0.05L/h.

Aproximately how long would it take drug Y to reach steady state?

d. 280

t 1/2 = 0.7 x Vd / CL

t 1/2 = 0.7 x 5 / 0.05

t 1/2=3.5 / 0.05

t 1/2 = 70

clinical steady state = 4-5 x t 1/2

so

clinical steady state = 4 X 70 = 280
 
#10 ·
That question which I posted is a question from the Qmax question bank from FirstAid. The answer they give in their explanation is 70.

But I am also confused about this question, so I reported it, because it seems to me that they ask for steady state, and you need to multiply 70 x 4 to get 280 as most of you answered.

Also, in the explanation that comes with the question, they start by writing "First you need to calculate for half time", as if a second calculation would be needed to get to the answer, so even the explanation seems incomplete.

It is also known that FirstAid has some kinks, im 2 months away from the exam and im pretty sure the answer is 280, I hope I get a response from the FirstAid team.

Thanks for your feedback guys.
 
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top