A new antifungal medication is being tested in clinical trials in Chennai. 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?

The rule of thumb is that the plasma concentration will reach 50% in one half-life, 75% in two half-lives and 87.5% in three half-lives. 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.