A new antibiotic developed for the treatment of infections caused by resistant gram-positive cocci has a volume of distribution of 11L. It is eliminated by first-order kinetics and has a half-life of 10 hours. If given by a continuous infusion, approximately how much time would it require for the drug to achieve a 95% plasma steady state concentration?

Question

A new antibiotic developed for the treatment of infections caused by resistant gram-positive cocci has a volume of distribution of 11L.  It is eliminated by first-order kinetics and has a half-life of 10 hours.  If given by a continuous infusion, approximately how much time would it require for the drug to achieve a 95% plasma steady state concentration?

Quizplus · Accepted Answer

During continuous infusion of a drug metabolized by first-order kinetics (i.e. a constant fraction of the drug is eliminated per unit time), the steady state concentration is reached in 4 to 5 half-lives. Thus, it would take approximately 40 hours, or four times the half-life of 10 hours, for the drug in question to reach approximately 95% steady-state concentration. Educational objective: During continuous infusion of a drug metabolized by first-order kinetics, the steady state concentration is reached in 4 to 5 half-lives.

A New Antibiotic Developed for the Treatment of Infections Caused