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#1
06-13-2010
 USMLE Forums Master Steps History: 1 + CS Posts: 546 Threads: 91 Thanked 350 Times in 158 Posts Reputation: 396
Half-life Calculation Question

A new investigational drug is undergoing Phase I clinical trials. The half-life of this drug is 9 hours. A healthy volunteer has an adverse reaction and the drug is immediately discontinued. How long will it take until the plasma drug level is approximately 6% of the steady state level?
A. 9 hours
B. 18 hours
C. 27 hours
D. 36 hours
E. 45 hours
F. 54 hours
 The above post was thanked by: drortho (01-16-2012)

#2
06-13-2010
 USMLE Forums Guru Steps History: --- Posts: 487 Threads: 69 Thanked 341 Times in 163 Posts Reputation: 361
D??

is it D. 36 hours??
#3
06-13-2010
 USMLE Forums Scout Steps History: Not yet Posts: 14 Threads: 0 Thanked 6 Times in 5 Posts Reputation: 16

AGREE.
100---50----25-----12.5----6.26

4 HALF TIME = 36 h
 The above post was thanked by: savleem (01-08-2012)

#4
06-13-2010
 USMLE Forums Scout Steps History: 1+CK+CS Posts: 86 Threads: 3 Thanked 14 Times in 14 Posts Reputation: 24

totally agree, D
#5
06-14-2010
 USMLE Forums Master Steps History: 1 + CS Posts: 546 Threads: 91 Thanked 350 Times in 158 Posts Reputation: 396

Yes, the right answer is D. 36 hours
#6
06-21-2010
 USMLE Forums Scout Steps History: Not yet Posts: 18 Threads: 2 Thanked 5 Times in 3 Posts Reputation: 15

can some1 plz explain this,
#7
01-07-2012
 USMLE Forums Scout Steps History: Step 1 Only Posts: 26 Threads: 4 Thanked 9 Times in 8 Posts Reputation: 19

Quote:
 Originally Posted by usmle100 can some1 plz explain this,
If the 1/2 life =9hrs,it means that it will take 9hrs for 1/2 of the drug to disintegrate making only 50% available,another 9hrs to breakdown 50% of the 50,making it only 25% available,another 9hrs to break 1/2 of that down to 12.5% and then another 9hrs to break it to 6.something %.So,it takes 9hrs x 4 (36hrs) to get 6% of the drug in the system....hope that helps.Pray for me to pass my step 1 and goodluck
 The above post was thanked by: curiousmind (07-16-2012), Jorabim (06-28-2014)

 Tags Pharmacology-, Step-1-Questions

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