Establishing a clinical pharmacokinetic service for gentamicin in a community hospital

To assess the feasibility and acceptability of a pharmacy-based clinical pharmacokinetic service for gentamicin, serum gentamicin levels were measured by radioimmunoassay in 44 patients hospitalized during a three-month period in an acute-care general hospital. Serum levels measured pre- and post-infusion were used to estimate pharmacokinetic parameters and optimum dosage regimens for individual patients. Based on serum level measurements of gentamicin, 30% of patients required no dosage adjustment, 23% an increase in dose and 47% a decrease in dose. Of the 30 changes recommended, 83% were implemented by physicians. Monitoring serum levels and adjusting dosage reduced the number of patients with sub-therapeutic and toxic serum levels. Adjusting dosage with the aid of serum levels appeared to be most useful for the elderly patient or the patient with impaired kidney function. Initial choice of dosage regimens for patients would be improved by appropriate use of the Hull and Sarubbi dosing nomogram (with certain modifications) or method of estimating pharmacokinetic parameters. The Hull and Sarubbi method was considered preferable to the dosing recommendation of 1.1 mg/kg at an interval of eight times the serum creatinine value. Excellent physician acceptance of a gentamicin serum level monitoring service was demonstrated in terms of the physician's usage of the service and implementation of the pharmacist's recommendations. A multidisciplinary approach involving medicine, pharmacy, nursing and laboratory staff was essential for successful operation of the pharmacokinetic service. However, the responsibility for the development and overall coordination of the pharmacokinetic service should remain with the pharmacist.