Calculation skills: Understanding the plasma half-life

Abstract

The plasma half-life (t1/2) of a drug refers to the time it takes for the plasma concentration of a drug to decrease to half of its initial value (Greenstein, 2008). The concentration of a drug in the plasma falls as it is metabolized and excreted (Alder et al, 2015). Knowing a drug's half-life is important in determining the dose of a drug needed to achieve and maintain a therapeutic effect and to avoid toxicity (Alder et al, 2015). The accumulated dose of the drug reduces with each dose.