Background and Importance Vancomycin clearance tends to be higher in patients with neutropenia¹; consequently, therapeutic drug monitoring (TDM) is highly recommended.²

Aim and Objectives To assess the achievement of a therapeutic pharmacokinetics/pharmacodynamics (PK/PD) target of vancomycin in oncologic and haematologic patients using trough-only TDM.

Material and Methods We conducted a retrospective and descriptive study that included oncological and haematological patients admitted to a second-level hospital, starting treatment with vancomycin and dosing adjustment guided by TDM at the Pharmacy service.

Demographic variables, Cockcroft-Gault creatinine clearance (CrCl), initial dosage, dose adjustments, the first trough level, duration of treatment, and reason for withdrawal were collected. Renal impairment was defined as CrCl < 60 ml/min. Dosages of 15-20 mg/kg/dose and trough levels between 10 and 20 µg/ml were considered optimal for intermittent infusion schedules. TDM used the PKS^® software.

Results Vancomycin trough levels were obtained in 49 patients; 12 were oncological, and 37 were haematological.

Dosage adjustment was necessary for 30 patients (61%), 25/30 due to subtherapeutic level (trough level <10 µg/ml) and 5/30 due to supratherapeutic level (through level >20 µg/ml with or without renal impairment).

The initial mean dosage was 13,7 ± 2,5 mg/kg/12h, except in three patients who started every 24 h due to renal impairment. After the dosage adjustment, the recommended mean dosage was 14 ± 3 mg/kg/8h in 18 patients and 13,6 ± 7,6 mg/kg/12h in 12 patients.

The mean duration of antibiotic treatment was 7 ± 4,2 days. The reasons for stopping the treatment were: clinical improvement (n=29), switch to a target treatment (n=10), clinical deterioration (n=9) and nephrotoxicity (n=1). Nine patients died.

Conclusion and Relevance More than half of the patients had subtherapeutic vancomycin levels and required antibiotic dose adjustment.

Most patients required shorter dosing intervals rather than increased doses to reduce the incidence of nephrotoxicity.

References

1. Bury D, et al. Eur J Clin Pharmacol 2019;75: 921–928

2. Rybak MJ, et al. Am J Health-Syst Pharm. 2020;77: 835–864

Conflict of Interest No conflict of interest