Therapeutic drug monitoring of gentamicin: a 6-year follow-up audit

Background and objective : In 1984 a therapeutic drug monitoring (TDM) service was established in Hospital Universiti Sains Malaysia (HUSM) and gentamicin concentrations were measured and used to design optimal regimens for the antibiotic. In this study we report on a 6-year follow-up audit since our first assessment of the service.Method: Records of 733 requests for gentamicin monitoring were reviewed.Results: Of the 592 patients involved, 39% were neonates and 42% were adults. Peak gentamicin concentrations were within the therapeutic range in 65% of the patients at first monitoring and 79% of the corresponding trough concentrations were within the non-toxic range. After dosage adjustment, 81% of the peak concentrations were within the therapeutic range and trough concentrations rose to levels regarded as toxic in 7% of patients. In patients with therapeutic peak concentrations at the first monitoring point, the average duration of gentamicin therapy was statistically shorter than in those patients who failed to achieve a therapeutic peak concentration. The distribution of gentamicin peak and trough concentrations in terms of therapeutic ranges were also better than those found in 1990.Conclusion: TDM for gentamicin is well accepted in HUSM and its application has contributed to improved gentamicin administration. Furthermore, our physicians are now able to choose more appropriate dosage regimens for their patients because the majority of gentamicin concentrations attained even at the first monitoring were within the therapeutic range.