CP-207 Analysis of frequency of underdosing in obese patients treated with vancomycin

BackgroundObese patients with normal serum creatinine have increased renal clearance, and consequently the dose of some drugs, such as vancomycin, should be dosed based on actual body weight (ABW). According to the American Society of Health-System Pharmacists (ASHP) guidelines, the recommended dosing regimen is 15–20 mg/kg ABW/12 hours intravenously, with subsequent dosage adjustment based on serum vancomycin concentrations. Nevertheless, in our hospital, vancomycin is often used as a fixed dose regimen regardless of patient weight, based on the manufacturer´s labelling recommendation.PurposeTo determine the frequency of underdosing of vancomycin in obese patients and possible risk factors.Material and methodsA single centre, retrospective, observational study from January 2014 to September 2016 was carried out. Morbidly obese adult patients, defined as a body mass index (BMI) ≥ 30 according to the WHO classification, with at least one trough level obtained at steady state, were included. Patients were excluded if they had a creatinine clearance (CrCl) 65 years (OR 0.206, 95% CI 0.04–0.98; p< 0.05) and initial dosing regimen of 1000 mg/12 hours (OR 0.008, 95% CI 0.0–0.55; p< 0.05) compared with 1000 mg/24 hours.ConclusionIt is important to monitor levels of vancomycin in obese patients, especially in those aged