Evaluation of a new vancomycin dosing method

A simple method for administering vancomycin in the spinal cord injured population

OBJECTIVE

To examine the applicability in patients with spinal cord injury (SCI) of a modified version of the commonly used Lake and Peterson dosing regimen for vancomycin.

DESIGN

Nonrandomized, prospective clinical trial with a historical control.

SETTING

Spinal cord injury unit at a Veterans Affairs Medical Center.

PATIENTS

Hospitalized patients with a history of SCI at least 6 months earlier and an estimated creatinine clearance of > or = 15 mL/min who required vancomycin therapy. The experimental group consisted of 15 evaluable patients, 8 with tetraplegia and 7 with paraplegia.

INTERVENTION

Vancomycin regimens were initiated using a modified version of the guidelines of Lake and Peterson.

MAIN OUTCOME MEASURE

After 4 to 8 doses, peak vancomycin concentrations in serum were obtained 15 minutes after a 1-hour infusion, and trough concentrations were drawn within 30 minutes of the next scheduled dose.

RESULTS

Only 3 of 15 (20%) patients in the experimental group required a single adjustment in the dosing interval to achieve the targeted serum vancomycin concentrations. The proportion of patients who required dosing modification was significantly lower in the experimental group than in a group of 16 SCI control patients who received vancomycin according to the dosing recommendations in the drug insert (20% vs 75%, respectively; p = .002).

CONCLUSION

These results support the need for tailored vancomycin dosing in the SCI population and the efficacy of this simple method of administering vancomycin in achieving desirable concentrations of vancomycin in the serum of SCI patients.

Evaluation of a method for initiating vancomycin therapy: experience in 205 patients

This study evaluated a dosing method for initiating vancomycin therapy in a large population based on patients' age, weight, and renal function. The aims were to determine the method's efficacy in achieving predetermined peak and trough serum concentrations, and to calculate the cost savings incurred by individualizing therapy. Average doses +/- 1 SD of 7.93 +/- 0.29 mg/kg corrected body weight (lean body weight + 40% excess weight) were administered at intervals predicted by the patients' estimated creatinine clearances (range 22-130 ml/min). The calculated mean dose +/- SD was 558 +/- 83 mg (range 350-750 mg) and the calculated median interval was 12 hours (range 6-24 hr). Peak and trough concentrations +/- SD measured at steady state averaged 26.0 +/- 5.4 and 7.3 +/- 2.3 micrograms/ml, respectively. Peak and trough serum concentrations fell within the predetermined therapeutic range in 311 (76%) of 410 samples. Peak concentrations were in the range of 20-30 micrograms/ml in 145 (71%) of 205 samples. Trough concentrations were in the range of 5-10 micrograms/ml in 166 (81%) of the 205 samples. This simplified dosing method successfully individualized therapy in most patients, and produced a significant savings to the pharmacy in reduced drug acquisition costs and to patients in reduced drug charges.