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#1
05-28-2010
 USMLE Forums Veteran Steps History: 1 + CK Posts: 234 Threads: 63 Thanked 127 Times in 63 Posts Reputation: 157
Pharmacokinetics of two IV drugs

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
 The above post was thanked by: hiratamkeen (10-06-2011)

#2
05-28-2010
 USMLE Forums Guru Steps History: --- Posts: 487 Threads: 69 Thanked 294 Times in 133 Posts Reputation: 314
F??

f.increased volume of distribution
#3
05-28-2010
 USMLE Forums Scout Steps History: Not yet Posts: 34 Threads: 1 Thanked 62 Times in 15 Posts Reputation: 72

f.increased volume of distribution
because serum conc is inversely related to Vd
#4
05-28-2010
 USMLE Forums Veteran Steps History: 1 + CS Posts: 209 Threads: 34 Thanked 92 Times in 30 Posts Reputation: 122

yup i will go with F

as amount given is same volume is inversely related to the concentration
#5
05-28-2010
 USMLE Forums Master Steps History: 1+CK+CS+3 Posts: 625 Threads: 19 Thanked 371 Times in 220 Posts Reputation: 391

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)
#6
05-28-2010
 USMLE Forums Veteran Steps History: 1 + CK Posts: 234 Threads: 63 Thanked 127 Times in 63 Posts Reputation: 157

yes the ans is F.Thanks for ur explanations
#7
05-30-2010
 USMLE Forums Scout Steps History: Not yet Posts: 83 Threads: 22 Thanked 30 Times in 16 Posts Reputation: 40
Yeah,

it's F the best Answer thanks Guys . .
#8
07-30-2011
 USMLE Forums Newbie Steps History: --- Posts: 4 Threads: 1 Thanked 0 Times in 0 Posts Reputation: 10

yep its f.

 Tags Pharmacology-, Step-1-Questions

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