kaplan LN - samideb12

[ArchivalUser]

A drug achieves a plasma level of 16 mg /L shortly after the administration of the first oral dose.If the half-life and the dosing interval are both 6 hours ,what is the appropriate plasma level shortly before the adminstration of the fifth dose ?
A.15mg/L
B.24mg/L
C.28mg/L
D.30mg/L
E.31mg/L
Can someone explain this question please ?

[ArchivalUser]

i remember this question from maryam2009 explanation...!!! i can't seem to find it but if i remember correctly here how it goes:

1st = 16mg/L
2nd + 6 hours = 8 + 16 = 24
3rd + 6 hours = 12 + 16 = 28
4th + 6 hours = 14 + 16 = 30
5th + 6 hours = 15 + 16 = 31

so answer = AAA

because before the 5th dose the half life = 15.... thank you maryam!!!

[ArchivalUser]

but i did come across this just right now when i tried to look up again lol :

http://www.usmleforum.com/showthread.php?tid=637430

you'll find this interesting samideb, guess who posted the question lol thank you brother!

[ArchivalUser]

I posted it but got confused again .Zen ,thank you .I might be tired after a long working day.

[ArchivalUser]

oh no i wasnt trying to point that our sir... i was just saying wat a coincidence!!! your one of the hardest workers here!!! and we appreciate your efforts [especially I] thank you!!!

[ArchivalUser]

Samideb,

Can you figure out which part of the q is confusing to you?

[ArchivalUser]

I got it now.I understood it very well.

[ArchivalUser]

Very Good