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NBME 23 Answers

nbme23/Block 2/Question#15

A child with septicemia has an antibiotic clearance ...

28.8

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submitted by wired-in(28),

Maintenance dose formula is (CssCltau)/F where Css is steady-state target plasma conc. of drug, Cl is clearance, tau is dosage interval & F is bioavailability.

Neither dosage interval nor bioavailability is given, so ignoring those & plugging in the numbers (careful to convert units to mg/kg/day): (12 ug/mL * 1 mg/1000 ug) * (0.09 L/hr/kg * 1000 mL/1 L * 24 hr/1 day) = 25.92 mg/kg/day

...which isn't any of the answer choices listed. They must have rounded 0.09 L/hr/kg to 0.1 L/hr/kg, and doing so gives exactly 28.8 mg/kg/day (choice C)

lispectedwumbologist  That's so infuriating I stared at this question for 20 minutes thinking I did something wrong +19  
hyoid  ^^^^^ +2  
seagull  lol..my math never worked either. I also just chose the closest number. also, screw this question author for doing that. +2  
praderwilli  Big mad +4  
ht3  this is why you never waste 7 minutes on a question.... because of shit like this +5  
yotsubato  Why the FUCK did they not just give us a clearance of 0.1 if they're going to fuckin round it anyways... +6  
bigjimbo  JOKES +  
cr  in ur maths, why did u put 24h/1day and not 1day/24h? if the given Cl was 0.09L/hr/kg. I know it just is a math question, but i´d appreciate if someone could explain it. +  
d_holles  LMAO games NBME plays +  
hyperfukus  magic math!!!!! how TF r we supposed to know when they round and when they don't like wtf im so pissed someone please tell me step isn't like this...with such precise decimal answers and a calculator fxn you would assume they wanted an actual answer! +  
jean_young2019  OMG, I've got the 25.92 mg/kg/day, which isn't any of the answer choices listed. So I chose the D 51.8, because 51.8 is double of 25.9......I thought I must have make a mistake during the calculation ...... +  
atbangura  They purposely did that so if you made a mistake with your conversion like I did, you might end up with 2.5 which was one of the answer choices. SMH +  
titanesxvi  I did well, but I thought that my mistake was something to do with the conversion and end up choosing 2.5 because it is similar to 25.92 +  




so should we just skip these? cuz there's prob 10 more i couldve gotten write wasting my life on this one





Hey can someone please explain this! I am not sure how to do the math, I keep getting tripped up.

mousie  Equation is Maintenance dose = (concentration at steady state) * (Clearance) if you convert all the units to what it wanted them in (mg/kg/day) you'll get 25.92 like weird-in said above I didn't think to round 0.09 to 0.1 of course so I guessed 2.5 assuming I must have done a conversion wrong and was off by a tenth .... BOO bad Q +4  
hyperfukus  OMG ME TOO!!!!! +