Ceftriaxone is a third-generation cephalosporin that exhibits saturable plasma protein binding, which influences its pharmacokinetic parameters depending on the dose. Systemic clearance and volume of distribution of total drug show dependence on both concentration and time, whereas for unbound drug these parameters remain constant. The decrease in renal or non-renal clearance with age or in the presence of disease states is often compensated by the concurrent increase in free fraction, resulting in no apparent changes in half-life and no need for dose adjustment. Because of its unusually long plasma half-life, the availability of intramuscular administration and its high intrinsic activity against many organisms, ceftriaxone has become a popular agent in once-daily therapy of infections in paediatric patients, gonococcal infections and outpatient management of pneumonia and osteomyelitis.