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+--- Thread: pharmac Q - wwjd (/showthread.php?tid=223527)
pharmac Q - wwjd - ArchivalUser - 09-25-2007
A new antifungal medication is being tested in Phase I clinical trials. Examination of the pharmacokinetic properties of the drug reveals that the half-life of the drug is 6 hours. If a continuous intravenous infusion of this drug were started on a research subject, how long would it take to reach 75% of steady state?
(A) 3 hours
(B) 6 hours
© 9 hours
(D) 12 hours
(E) 18 hours
(F) 24 hours
0 - ArchivalUser - 09-25-2007
(E) 18 hours
0 - ArchivalUser - 09-25-2007
okay i need break 2 1/2
(D) 12 hours
0 - ArchivalUser - 09-25-2007
dddddddd???
0 - ArchivalUser - 09-25-2007
the correct answer is D.
The rule of thumb is that the plasma concentration will reach 50% in one half-life, 75% in two half-lives, 87.5% in three half-lives, etc., so that the difference between the current drug level and 100% halves with each half-life. In this instance, it takes two half-lives to reach 75%. The half-live of this drug is 6 hours, so two half-lives is 12 hours.