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During an experiment 500mg of both drug X and Y are simultaneously administered IV, the serum concentration of both drugs after bolus administration is 5 mg and 2.5mg respectively. Assuming no drug interactions. Which of the finding regarding the drug Y is compared with drug X?

A. decreased clearance
B. decreased half life
C. decreased volume of distribution
D. increased clearance
E. increased half life
F. increased volume of distribution
 

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Yup - I agree - F...

If equivalent amounts of two drugs are introduced IV there's no bioavailability issue so this implies that if serum concentrations are different then more of drug x is not absorbed into tissues and such.

We define this as volume of distribution - ie: the Vd for X is lower than the Vd for y or the Vd for y is greater than the Vd for x

The formula that everyone is talking about is:

Vd = D / C where Vd= volume of distribution, D is dose (500mg here) and C is serum concentration (5 mg for x) and (2.5 mg for y)
 
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