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

In this paper we present a mathematical solution that allows the elimination rate-constant or half life of a drug to be estimated from a single blood drug measurement. This is of great utility in clinical areas involving care of criticallly ill or vulnerable patients, where providing more than one blood sample can involve significant risks. The calculations used in our approach, based solely on a single sample, do not require complex pharmacokinetic software, but instead can be simply performed at the patient’s bedside using standard personal computing tools. The proposed method allows a personalised estimate of the drug’s half life, which is preferable to using population averages, or using estimates based on proxy markers of lagging organ function, which are both indirect and generally inaccurate for a patient with confounding factors.