CC17 – Drug elimination half-life
CC17. Drug elimination half-life (t 1⁄2) is the time taken for the drug plasma concentration to decrease by 50% and is calculated during the elimination phase.
17.1. Drug elimination half-life is constant when drug elimination follows first-order kinetics.
17.2. Drug elimination half-life is proportional to volume of distribution when clearance is constant.
17.3. Drug elimination half-life is inversely proportional to clearance when volume of distribution is constant.
17.4. Drug elimination half-life can vary between patients, as patient, drug and environmental factors (e.g., disease state and age-related physiological changes) can alter drug clearance or volume of distribution.
17.5. Drug elimination half-life is used to estimate the time at which steady state is achieved following repeated administration of a drug that follows first-order kinetics.
