Application of Beta-lactam Therapeutic Drug Monitoring in Clinical Practice Using HPLC

Abstract

In beta-lactam therapy, investigation of the pharmacokinetic-pharmacodynamic (PK-PD) relationship has provided surrogate makers to predict clinical outcome. This study was designed to verify the therapeutic efficacy and clinical utility of beta-lactam therapeutic drug monitoring (TDM) in critically ill patients using high-performance liquid chromatography (HPLC). This cohort study included 13 patients who were intravenously administered ceftazidime (n = 6), cefepime (n = 1), imipenem (n = 1), meropenem (n = 1), or piperacillin (n = 4). Blood samples were collected at 3 time points fitted to a 1-compartment model, and concentrations were determined using HPLC. The PK-PD target was the percentage of the dosing interval during which the antibiotic concentration exceeded the minimum inhibitory concentration for the pathogens (%T > MIC), which is 50% for penicillins (piperacillin), 60% for cephalosporins (ceftazidime and cefepime), and 40% for carbapenems (imipenem and meropenem). Our process using HPLC enables the analytical results of TDM to be available within half a day. The results revealed significant inter-patient pharmacokinetic variability. During the initial regimen, beta-lactam concentrations reached the target %T > MIC in all patients, and dosage reduction was required for 5 patients (38%). Of the 13 evaluable patients, clinical improvement was observed in 11 (85%), and microbiological success was observed in 10 (77%). In summary, beta-lactam TDM achieved the treatment goals and might also allow for the personalization to prevent overdosing for variable pharmacokinetic changes in critically ill patients. These findings indicate that beta-lactam TDM using HPLC can be used in the standard pharmacy clinical practice for critically ill patients.