A PROSPECTIVE LABORATORY-BASED AUDIT OF GENTAMICIN USE AND THERAPEUTIC MONITORING

We report a study investigating the proportion of patients in whom the rapeutic serum concentrations of gentamicin are achieved in the early phase of treatment and to determine the underlying reasons for sub-opt imal therapy. A laboratory based prospective study of 83 courses of ge ntamicin was performed (excluding patients receiving renal replacement therapy of with bacterial endocarditis) in a London teaching hospital . Of 83 monitored courses 74 had paired levels tested. Initial trough concentrations were >2mg/L in nine (12%) and were <1mg/L in 51 (69%) i ndicating levels were seldom in the toxic range. The first monitored p eaks were sub-therapeutic in 58 (78%) courses using a cut-off of 5mg/L and only seven (9%) were greater than 6mg/L. Of these seven patients, six had trough levels of greater than 2mg/L. Of those with initial le vels below 5mg/L, 33 had further serum levels tested, of which 26 (79% ) remained below 5mg/L. Of those for whom dosing information was avail able 73% received 80mg tds and the mean dose for those for which body weight was known was 3.3mg/kg/day (SD=0.7). Most patients continued to receive 8-hourly dosing with 80mg of gentamicin, leading to subtherap eutic peak levels in the majority of cases. In those patients with sat isfactory peaks, such dosing frequency leads to elevated troughs. This suggests that such dosing practices should be abandoned and replaced with dosing based on body weight and divided into no more than two dai ly doses.