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#1
03-30-2012
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Dose needed to achieve steady state?

Pharmacokinetic characteristics of propranolol include Vd — 300 L/70 kg, CI = 700 mL/min, oral bioavailability f = 0.25. What is the dose needed to achieve a plasma level equivalent to a steady-state level of 20 g/L?

A. 4mg
B. 8mg
C. 12 mg
D. 24 mg
E. 48 mg

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#2
03-30-2012
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Check units in calculation?

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#3
03-30-2012
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wow...

So:

LD=(Vd x Css)/f

( 300L/70kg x 20g/L ) / 1/4

( 6L / 70kg ) x 4

0.34 L/kg

......
wtf
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#4
03-31-2012
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Quote:
 Originally Posted by DocSikorski wow... So: LD=(Vd x Css)/f ( 300L/70kg x 20g/L ) / 1/4 ( 6L / 70kg ) x 4 0.34 L/kg ...... wtf
Two concepts you can take
1) Vd is volume and dont not a ratio of volume/wt so take just 300
2)Cp is taken not Css

Correct if i m wrong

Still the answer wont be same

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 The above post was thanked by: DocSikorski (03-31-2012), doxy (03-31-2012)
#5
04-03-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,039 Threads: 189 Thanked 570 Times in 323 Posts Reputation: 580
g-> mg?

I think there's a typo and in the stem it should say

"a plasma level equivalent to a steady-state level of 20 mg/L" NOT "20 g/L".
That's the only explanation that makes sense to me.

Assuming that it is 20mg/L and using loading dose formula I would calculate this as follows:

(Vd x Cp) / f = 300L x 20 mg/L / 0.25 = 24000 mg = 24 g -> the answer D

Please correct me if I'm wrong.
#6
04-04-2012
 USMLE Forums Guru Steps History: Not yet Posts: 414 Threads: 30 Thanked 87 Times in 70 Posts Reputation: 97

Quote:
 Originally Posted by Casandra I think there's a typo and in the stem it should say "a plasma level equivalent to a steady-state level of 20 mg/L" NOT "20 g/L". That's the only explanation that makes sense to me. Assuming that it is 20mg/L and using loading dose formula I would calculate this as follows: (Vd x Cp) / f = 300L x 20 mg/L / 0.25 = 24000 mg = 24 g -> the answer D Please correct me if I'm wrong.
Yes considering its typo its correct but that is 6 typos in one unit of kaplan pharm 😡

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#7
04-04-2012
 USMLE Forums Master Steps History: 1+CK+CS Posts: 1,039 Threads: 189 Thanked 570 Times in 323 Posts Reputation: 580

Quote:
 Originally Posted by Kabutar111 Yes considering its typo its correct but that is 6 typos in one unit of kaplan pharm 😡 Sent from my iPad using Tapatalk HD

Yeah, I know how you feel...it's frustrating for me too... so I thank again for this forum where we can discuss and brainstorm!!!
I've reached out for the older version of Kaplan (2006/2007 p.31 if anyone is using it too) and in the same question they say that the steady level is 20microg/L and the answer is also 24 mg. So I really do think it's a typo and it just should keep us more alert!
 The above post was thanked by: Kabutar111 (04-04-2012)

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