Therapeutic monitoring of Piperacillin in ICU patients

Background Infections remain one of the major causes of morbidity and mortality in patients admitted to intensive care units (ICUs). The rate of nosocomial infections among patients admitted to ICUs is 5-10 times higher than other general medicine and surgery wards. The most common nosocomial infections are pulmonary, urinary and blood stream infections that are often caused by P. aeruginosa, S. aureus, K. pneumoniae, S. marcescens, P. mirabilis and C. albicans (Trubiano & Padiglione 2015). The infection determines a large number of victims each year. Indeed, it has been estimated that in Europe about 25,000 people annually risk death due to the infections by MDR organisms (Blair et al. 2014). Strong evidence in literature endorses the benefits of penicillin TDM and suggests the existence, in the population of critically ill patients, of a correlation between the exposure of the target to the drug and the outcomes (Blondiaux et al. 2010; Sime et al. 2012; Hayashi et al. 2013). Therefore, this study was aimed at developing and validating a simple HPLC method for monitoring plasma level of piperacillin in ICU patients. Methods The HPLC-UV method was developed for piperacillin quantitation, starting from 200 μl of plasma samples treated with 200 μl of ACN+H3PO4 conc. 5 % (v/v) for protein precipitation. In plasma samples, ticarcillin was added as internal standard (IS). The stationary phase was HAISIL HL C18 250 mm  4.6 mm  5 μm (Higgins Analytical Inc., USA). Mobile phase was composed by 20 mM phosphate buffer (pH 2.5)/acetonitrile (73.5/26.5, v/v). The mobile phase was pumped within the HPLC system at a flow of 1 ml/min, while 30 μl of each sample were injected within the system. Absorbance of piperacillin and IS was measured at a wavelength of 220 nm. The method was validated according to the EMA 2015 guidelines, then it was applied to measure drug concentrations in 248 plasma samples from ICU patients (AbioKin project, Mario Negri, Bergamo, Italy). Results The chromatographic run time was 20 minutes, with retention times of ticarcillin and piperacillin of 13.4 and 18.0 min, respectively. Results of validation were as follows: linearity range, from 10 up to 400 μg/ml (r2=0.9994), accuracy and precision (< 8%), reproducibility (< 9%), limit of detection (9.57 μg/ml) and limit of quantitation (3.15 μg/ml) and average recovery (>90%). The method was applied to 248 plasma samples, resulting in a mean±SD concentration of 86.88±79.40 μg/ml, with a median concentration of 65.10 μg/ml (MIN-MAX range, 0-399.56 μg/ml). Of note, no interfering peaks were detected within the chromatogram despite the number of co-administered drugs. The method allows the preparation and analysis of 3 samples/h, but the availability of chromatographic systems equipped with autoinjectors does extend the analyses overnight, thus increasing the output. Conclusions In conclusion, a new chromatographic method for selective quantitation of piperacillin was developed and validated in plasma samples, with optimal performance to be applied to drug monitoring for ICU patients. Indeed, the application of the present HPLC-UV method may result in a more appropriate prescription of piperacillin with a subsequent improvement in clinical outcomes while the risk for the selection of resistant clones will be reduced. Bibliography Blair JMA, Webber MA, Baylay AJ, Ogbolu DO, Piddock LJ V. 2014. Molecular mechanisms of antibiotic resistance. Nat Publ Gr. 13:42–51. Blondiaux N, Wallet F, Favory R, Onimus T, Nseir S, Courcol RJ, Durocher A, Roussel-Delvallez M. 2010. Daily serum piperacillin monitoring is advisable in critically ill patients. Int J Antimicrob Agents. 35:500–503. Hayashi Y, Lipman J, Udy AA, Ng M, McWhinney B, Ungerer J, Lust K, Roberts JA. 2013. β-Lactam therapeutic drug monitoring in the critically ill: Optimising drug exposure in patients with fluctuating renal function and hypoalbuminaemia. Int J Antimicrob Agents. 41:162–166. Sime FB, Roberts MS, Peake SL, Lipman J, Roberts JA. 2012. Does beta-lactam pharmacokinetic variability in critically III patients justify therapeutic drug monitoring? A systematic review. Ann Intensive Care. 2:1–11. Trubiano JA, Padiglione AA. 2015. Nosocomial infections in the intensive care unit. Anaesth Intensive Care Med [Internet]. 16:598–602. Available from: http://dx.doi.org/10.1016/j.mpaic.2015.09.010