Clinical experience with a method for adjusting gentamicin dose from measured drug clearance

Gentamicin clearance was measured in 26 patients by a method which requires four blood samples. Clearance was used to calculate mean steady state serum concentrations [Css] with the aim of maintaining Css within the range 2.5-3.0 mg/l. All of the patients who failed to respond to antibiotic treatment had adequate Css and peak levels; all of these patients had serious underlying problems to explain their poor response. In contrast some patients responded satisfactorily despite being apparently underdosed. In two patients poor clinical response was associated with low Css levels despite adequate doses and peak levels; both patients responded to increased doses. In patients with stable renal function doses calculated from initial clearance measurements did result in Css within the desired range. In patients with unstable renal function measurement of clearance gave a better indication of the severity of renal impairment than measurement of serum creatinine or peak and trough levels but the bioassay used was too slow to allow adequate dose adjustment.