Background In patients with normal renal function (NRF) amikacin is commonly prescribed at standard doses of 15–20 mg/kg/day assuming that there is no drug accumulation. In general, NRF is defined by glomerular filtration rate (GFR) ≥60 mL/min. Optimal amikacin trough serum levels (ATSL) should be ≤1 mg/L.
Purpose The aim of this study was to evaluate if amikacin standard dosing of 15–20 mg/kg/day is appropriate to achieve the serum level trough target for preventing drug accumulation in patients with NRF.
Material and methods Retrospective observational study of adult hospitalised patients treated with amikacin and GFR ≥60 mL/min selected from our therapeutic drug monitoring (TDM) database from January 2007 to June 2015. GFR values were estimated by the formula from the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI). Critically ill patients and haemodialysis patients were excluded. Variables collected: age, sex, GFR, weight, height, body surface area (BSA), dose regimen and ATSL. ATSL were considered supratherapeutic if >1 mg/L. Patients were also divided into two groups according to GFR values: 60–90 mL/min (A) and >90 mL/min (B).
Results 53 patiens (40 men) with 69 determinations of amikacin were selected. Median age was 71 years (28–86) and median BSA was 1.83 m2 (1.37 to 2.28). 30 (43.5%) ATSL were classified in the GFR group A and 39 (56.5%) in the GFR group B. 30 (43%) ATSL were >1 mg/L (median 1.74 mg/L, range 1.1–10 mg/L), 21 of which were classified as group A. Amikacin dose was reduced in 26 of 30 (87%) cases, while maintained in four cases with serum levels closer to the target (between 1.1 and 1.2 mg/L). According to GFR amikacin dose was reduced in 66% of cases (20 of 30) in group A while in only 15% of cases (6 of 39) in group B.
Conclusion In adult patients with NRF, amikacin once daily dosing may cause drug accumulation on the basis of accepted trough targets, especially in patients with GFR between 60 and 90 mL/min. TDM of amikacin should be performed despite NRF to avoid drug accumulation.
No conflict of interest.
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