Estimating a drug's elimination rate-constant or half-life from a single blood sample: A practical approach with particular benefits for critically ill/vulnerable patients.

•Focus is on a pharmacokinetic parameter of practical utility to clinicians: the elimination rate-constant k of a drug in the blood plasma.•The motivation is that multiple blood measurements are impracticable/impossible in vulnerable patients.•For 3 scenarios of drug administration, we derive k from a single measurement of drug concentration.•The results may be of practical benefit to critically ill patients and allow a personalised approach to drug monitoring.