<prompt> A new antifungal medication is being tested in Phase I clinical trials. Examination of the pharmacokinetic propeies of the drug reveals that the half-life of the drug is 6 hours. If a continuous intravenous infusion of this drug were staed on a research subject, how long would it take to reach 75 of steady state?36912  <response>: 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. Ref: Buxton I.L., Benet L.Z. 2011. Chapter 2. Pharmacokinetics: The Dynamics of Drug Absorption, Distribution, Metabolism, and Elimination. In L.L. Brunton, B.A. Chabner, B.C. Knollmann Eds, Goodman Gilmans The Pharmacological Basis of Therapeutics, 12e. 