T1/2 in pharmacokinetics, i.e., elimination half-life, represents the time it takes to clear half of the compound’s concentration from systemic circulation during the log-linear elimination phase. Even as elimination half-life can be calculated for any dose route, it is best represented for a compound following an IV dose given the absorption component is bypassed with direct systemic administration. IV bolus curves for most drugs are biphasic, including a steep early phase representative of compound distribution to tissues, metabolism, and excretion. Once tissue distribution is equilibrated, the second phase of the curve represents metabolism and excretion. Points in this log-linear elimination phase are selected and used to determine the curve slope (m). The elimination rate constant (λz, k, or kel) is calculated from the slope as λz = 2.303 x m. Then, we calculate elimination half-life (t½) as 0.693 / λz. For reliability, the half-life calculation should be performed with a minimum of three terminal points in the λz range and have a determination coefficient (R2) of at least 0.85.