RESUMO
Prescribers often face the challenge of predicting creatinine clearance (CrCl) in elderly patients who are 65 years or older and have serum creatinine (SCr) concentrations below 1 mg/dL. Studies have shown that utilizing rounded SCr would underestimate CrCl in this population, which could lead to the under-dosing of some medications like vancomycin. The current study aimed to compare the accuracy of vancomycin dosing using actual SCr versus rounded SCr to 1 mg/dL in elderly patients. A total of 245 patients were included. The therapeutic trough level (10-20 mg/L) was achieved in 138 (56.3%) patients using actual SCr. Sub-therapeutic (<10 mg/L) and supra-therapeutic (>20 mg/L) trough levels were observed in 32 (13.1%) and 75 (30.6%) patients, respectively. The predictive performance of different vancomycin doses based on actual SCr and rounded SCr compared to the targeted maintenance dose (TMD) showed a stronger correlation of dosing based on actual SCr with TMD (r = 0.55 vs. 0.31) compared to rounded SCr dosing; both doses showed similar precision, with ranges of ±552 mg/day for the dosing based on actual SCr and ±691 mg/day for the dosing based on rounded SCr. Furthermore, the dosing based on actual SCr showed a lower error percentage (69%) and a higher accuracy rate (57.6%) within ±10% of the TMD compared to the dosing based on rounded SCr, which had an error percentage of (92.3%) and an accuracy rate of (40%). The prevalence of vancomycin-associated nephrotoxicity (VAN) was seen in 44 (18%) patients. Patients between 75 and 84 years of age, those who were bedridden, and those with vancomycin trough concentrations greater than 20 mg/L had a higher risk of developing VAN. In conclusion, in elderly patients, estimating vancomycin dosing based on actual SCr was more accurate compared to rounded SCr to 1 mg/dL. The efficacy of vancomycin could be negatively affected by rounding up SCr, which could underestimate CrCl and result in the under-dosing of vancomycin.
RESUMO
The AUC0-24 is the most accurate way to track the vancomycin level while the Cmin is not an accurate surrogate. Most hospitals in Saudi Arabia are under-practicing the AUC-guided vancomycin dosing and monitoring. No previous work has been conducted to evaluate such practice in the whole kingdom. The current study objective is to calculate the AUC0-24 using the Bayesian dosing software (PrecisePK), identify the probability of patients who receive the optimum dose of vancomycin, and evaluate the accuracy and precision of the Bayesian platform. This retrospective study was conducted at King Abdulaziz medical city, Jeddah. All adult patients treated with vancomycin were included. Pediatric patients, critically ill patients requiring ICU admission, patients with acute renal failure or undergoing dialysis, and febrile neutropenic patients were excluded. The AUC0-24 was predicted using the PrecisePK platform based on the Bayesian principle. The two-compartmental model by Rodvold et al. in this platform and patients' dose data were utilized to calculate the AUC0-24 and trough level. Among 342 patients included in the present study, the mean of the estimated vancomycin AUC0-24 by the posterior model of PrecisePK was 573 ± 199.6 mg, and the model had a bias of 16.8%, whereas the precision was 2.85 mg/L. The target AUC0-24 (400 to 600 mg·h/L) and measured trough (10 to 20 mg/L) were documented in 127 (37.1%) and 185 (54%), respectively. Furthermore, the result demonstrated an increase in odds of AUC0-24 > 600 mg·h/L among trough level 15-20 mg/L group (OR = 13.2, p < 0.05) as compared with trough level 10-14.9 mg/L group. In conclusion, the discordance in the AUC0-24 ratio and measured trough concentration may jeopardize patient safety, and implantation of the Bayesian approach as a workable alternative to the traditional trough method should be considered.