[Translated article] Therapeutic Drug Monitoring of antibiotic and antifungical drugs in paediatric and newborn patients. Consensus Guidelines of the Spanish Society of Hospital Pharmacy (SEFH) and the Spanish Society of Paediatric Infectious Diseases (SEIP).

Therapeutic monitoring of antibiotics and antifungals based on pharmacokinetic and pharmacodynamic (PK/PD) parameters is a strategy increasingly used for the optimization of therapy to improve efficacy, reduce the occurrence of toxicities, and prevent the selection of antimicrobial resistance, particularly in vulnerable patients including neonates and the critical or immunocompromised paediatric host. In neonates and children, infections account for a high percentage of hospital admissions, and anti-infectives are the most used drugs. However, paediatric PK/PD studies and the evidence regarding the efficacy and safety of some newly marketed antibiotics and antifungals-usually used off-label in paediatrics-to determine the optimal drug dosage regimens are limited. It is widely known that this population presents important differences in the PK parameters (especially in drug clearance and volume of distribution) in comparison with adults that may alter antimicrobial exposure and, therefore, compromise treatment success. In addition, paediatric patients are more susceptible to potential adverse drug effects and they need closer monitoring. The aim of this document, developed jointly by the Spanish Society of Hospital Pharmacy and the Spanish Society of Paediatric Infectious Diseases, is to describe the available evidence on the indications for therapeutic drug monitoring (TDM) of antibiotics and antifungals in newborn and paediatric patients, and to provide practical recommendations for TDM in routine clinical practice to optimise their dosing, efficacy and safety. Of antibiotics and antifungals in the paediatric population.

Spanish Society of Hospital Pharmacy and the Spanish Society of Pediatric Infectious Diseases (SEFH-SEIP) National Consensus Guidelines for therapeutic drug monitoring of antibiotic and antifungal drugs in pediatric and newborn patients. / Documento nacional de consenso de monitorización terapéutica de antibióticos y antifúngicos en el paciente pediátrico y neonatal de la Sociedad Española de Farmacia Hospitalaria (SEFH) y la Sociedad Española de Infectología Pediátrica (SEIP).

Therapeutic monitoring of antibiotics and antifungals based on pharmacokinetic and pharmacodynamic parameters, is a strategy increasingly used for the optimization of therapy to improve efficacy, reduce the occurrence of toxicities, and prevent the selection of antimicrobial resistance, particularly in vulnerable patients including neonates and the critical or immunocompromised host. In neonates and children, infections account for a high percentage of hospital admissions and anti-infectives are the most used drugs. However, pediatric pharmacokinetic and pharmacodynamic studies and the evidence regarding the efficacy and safety of some newly marketed antibiotics and antifungals -usually used off-label in pediatrics- to determine the optimal drug dosage regimens are limited. It is widely known that this population presents important differences in the pharmacokinetic parameters (especially in drug clearance and volume of distribution) in comparison with adults that may alter antimicrobial exposure and, therefore, compromise treatment success. In addition, pediatric patients are more susceptible to potential adverse drug effects and they need closer monitoring. The aim of this document, developed jointly between the Spanish Society of Hospital Pharmacy (SEFH) and the Spanish Society of Pediatric Infectious Diseases (SEIP), is to describe the available evidence on the indications for therapeutic drug monitoring of antibiotics and antifungals in newborn and pediatric patients and to provide practical recommendations for therapeutic drug monitoring in routine clinical practice to optimize pharmacokinetic and pharmacodynamic parameters, efficacy and safety of antibiotics and antifungals in the pediatric population.

Therapeutic Drug Monitoring of antibiotic and antifungical drugs in paediatric and newborn patients. Consensus Guidelines of the Spanish Society of Hospital Pharmacy (SEFH) and the Spanish Society of Paediatric Infectious Diseases (SEIP).

Therapeutic monitoring of antibiotics and antifungals based on pharmacokinetic and pharmacodynamic (PK/PD) parameters is a strategy increasingly used for the optimization of therapy to improve efficacy, reduce the occurrence of toxicities, and prevent the selection of antimicrobial resistance, particularly in vulnerable patients including neonates and the critical or immunocompromised paediatric host. In neonates and children, infections account for a high percentage of hospital admissions, and anti-infectives are the most used drugs. However, paediatric PK/PD studies and the evidence regarding the efficacy and safety of some newly marketed antibiotics and antifungals-usually used off-label in paediatrics-to determine the optimal drug dosage regimens are limited. It is widely known that this population presents important differences in the PK parameters (especially in drug clearance and volume of distribution) in comparison with adults that may alter antimicrobial exposure and, therefore, compromise treatment success. In addition, paediatric patients are more susceptible to potential adverse drug effects and they need closer monitoring. The aim of this document, developed jointly by the Spanish Society of Hospital Pharmacy and the Spanish Society of Paediatric Infectious Diseases, is to describe the available evidence on the indications for therapeutic drug monitoring (TDM) of antibiotics and antifungals in newborn and paediatric patients, and to provide practical recommendations for TDM in routine clinical practice to optimise their dosing, efficacy and safety. Of antibiotics and antifungals in the paediatric population.

Efficacy and safety of colistin plus beta-lactams for bone and joint infection caused by fluoroquinolone-resistant gram-negative bacilli: a prospective multicenter study.

OBJECTIVES: The prognosis of bone and joint infections (BJI) caused by Gram-negative bacilli (GNB) worsens significantly in the face of fluoroquinolone-resistance. In this setting, scarce pre-clinical and clinical reports suggest that intravenous beta-lactams plus colistin may improve outcome. Our aim was to assess the efficacy and safety of this treatment in a well-characterized prospective cohort. METHODS: Observational, prospective, non-comparative, multicenter (14 hospitals) study of adults with BJI caused by fluoroquinolone-resistant GNB treated with surgery and intravenous beta-lactams plus colistin for ≥ 21 days. The primary endpoint was the cure rate. RESULTS: Of the 44 cases included (median age 72 years [IQR 50-81], 22 [50%] women), 32 (73%) had an orthopedic device-related infection, including 17 (39%) prosthetic joints. Enterobacterales were responsible for 27 (61%) episodes, and Pseudomonas spp for 17 (39%), with an overall rate of MDR/XDR GNB infections of 27/44 (61%). Patients were treated with colistin plus intravenous beta-lactam for 28 days (IQR 22-37), followed by intravenous beta-lactam alone for 19 days (IQR 5-35). The cure rate (intention-to-treat analysis; median follow-up = 24 months, IQR 19-30) was 82% (95% CI 68%-90%) and particularly, 80% (95% CI 55%-93%) among patients managed with implant retention. Adverse events (AEs) leading to antimicrobial withdrawal occurred in 10 (23%) cases, all of which were reversible. Colistin AEs were associated with higher plasma drug concentrations (2.8 mg/L vs. 0.9 mg/L, p = 0.0001). CONCLUSIONS: Combination therapy with intravenous beta-lactams plus colistin is an effective regimen for BJI caused by fluoroquinolone-resistant GNB. AEs were reversible and potentially preventable by close therapeutic drug monitoring.

Synergistic efficacy of ceftazidime/avibactam and aztreonam against carbapenemase-producing Pseudomonas aeruginosa: insights from the hollow-fiber infection model.

BACKGROUND: Combination therapy is an attractive therapeutic option for extensively drug-resistant (XDR) Pseudomonas aeruginosa infections. Existing data support the combination of aztreonam and ceftazidime/avibactam (CZA) against class serine-ß-lactamase (SBL)- and metallo-ß-lactamase (MBL) - producing Enterobacterales. However, data about that combination against SBL- and MBL-producing P. aeruginosa are scarce. The objective of the study was to assess the in vitro activity of CZA and aztreonam alone and in combination against SBL- and MBL-producing XDR P. aeruginosa isolates. METHODS: The combination was analyzed by means of the hollow-fiber infection model in three selected carbapenemase-producing P. aeruginosa isolates that were representative of the three most common XDRP. aeruginosa high-risk clones (ST175, ST111, ST235) responsible for global nosocomial infection outbreaks. RESULTS: The three isolates were nonsusceptible to CZA and nonsusceptible to aztreonam. In the dynamic hollow-fiber infection model, the combination of CZA plus aztreonam exerts a bactericidal effect on the isolates, regardless of their resistance mechanism and demonstrates synergistic interactions against three isolates, achieving a bacterial reduction of 5.07 log10 CFU/ml, 5.2 log10 CFU/ml and 4 log10 CFU/ml, respectively. CONCLUSION: The combination of CZA and aztreonam significantly enhanced the in vitro efficacy against XDR P. aeruginosa isolates compared to each monotherapy. This improvement suggests that the combination could serve as a feasible treatment alternative for infections caused by carbapenemase-producing XDR P. aeruginosa, especially in scenarios where no other treatment options are available.

New Predictive Equation for the Estimation of Plasma Concentrations of Formed Colistin in Patients Treated With Colistimethate Sodium for Multidrug-Resistant Gram-Negative Bacterial Infections.

BACKGROUND: The clinical use of colistin methanesulphonate (CMS) is limited by potential nephrotoxicity. The selection of an efficient and safe CMS dose for individual patients is complicated by the narrow therapeutic window and high interpatient pharmacokinetic variability. In this study, a simple predictive equation for estimating the plasma concentration of formed colistin in patients with multidrug and extremely drug-resistant gram-negative bacterial infections was developed. METHODS: The equation was derived from the largest clinical cohort of patients undergoing therapeutic drug monitoring (TDM) of colistin for over 8 years in a tertiary Spanish hospital. All variables associated with C ss,avg were selected in a multiple linear regression model that was validated in a second cohort of 40 patients. Measured C ss,avg values were compared with those predicted by our model and a previous published algorithm for critically ill patients. RESULTS: In total, 276 patients were enrolled [the mean age was 67.2 (13.7) years, 203 (73.6%)] were male, and the mean (SD) C ss,avg was 1.12 (0.98) mg/L. Age, gender, estimated glomerular filtration rate, CMS dose and frequency, and concomitant drugs were included in the model. In the external validation, the previous algorithm appeared to yield more optimized colistin plasma concentrations when all types of C ss,avg values (high and low) were considered, while our equation yielded a more optimized prediction in the subgroup of patients with low colistin plasma concentrations (C ss,avg <1.5 mg/L). CONCLUSIONS: The proposed equation may help clinicians to better use CMS among a wide variety of patients, to maximize efficacy and prevent nephrotoxicity. A further prospective PK study is warranted to externally validate this algorithm.

Complementary and alternative medicine in HIV care: frequency of consumption, risks and interactions with antiretroviral therapy.

OBJECTIVES: People living with HIV (PLWH) are common users of complementary and alternative medicine (CAM). The main objective of this study was to study the frequency and patterns of CAM natural products use in a large cohort of PLWH and to identify potential drug-drug interactions (DDIs) and the impact on their antiretroviral treatment (ART) adherence and efficacy. METHODS: This was a cross-sectional multicenter survey including 420 PLWH from different Spanish hospitals. Participants completed a face-to-face questionnaire on CAM consumption and different sociodemographic and clinical data were collected. DDIs between CAM and ART were identified and classified according to the Liverpool University Database and patient factors related to CAM consumption were assessed. RESULTS: 420 participants were included (82.6% male, mean age 47 years); 209 patients (49.8%) were taking at least one CAM. The most consumed CAM were green, black and red tea (n=146, 25.4%), ginger (n=26, 4.5%), fish oil (n=25, 4.4%) and cannabis (n=24, 4.2%). An ART based on integrase inhibitors was the only factor independently associated with CAM consumption (OR 1.54, 95% CI 1.04 to 2.26). 50 potential CAM-ART interactions in 43 (20.6%) patients taking CAM were identified, being clinically significant in 80% of the cases. CAM products most frequently involved with a potential significant DDI were supplements containing divalent cations (n=11) and garlic (n=7). No differences in ART efficacy and adherence were observed between patients with and without CAM consumption. CONCLUSIONS: Almost 50% of patients were taking at least one CAM product and its use was associated with an integrase inhibitor based ART. One out of every six patients was at risk of presenting with an interaction between a CAM and their ART, confirming the need to review continuously the use of CAM as part of the medication review process.

Outcomes of Drug Interactions Between Antiretrovirals and Co-Medications, Including Over-the-Counter Drugs: A Real-World Study.

INTRODUCTION: The objective was to characterize real-world outcomes of drug-drug interactions (DDIs) between antiretrovirals (ARVs) and other drugs, including over-the-counter medications (OTC), and treatment outcomes in clinical practice. METHODS: www.clinicalcasesDDIs.com is an open-access website for healthcare providers to consult and briefly describe real-world clinical cases on DDI with ARVs. We reviewed all the clinical cases reported to the website between March 2019 and May 2023. RESULTS: A total of 139 cases were reported, mostly involving ritonavir or cobicistat (boosters; 74 cases), unboosted integrase inhibitors (InSTI; 29 cases), and non-nucleoside reverse transcriptase inhibitors (NNRTI; 23 cases). Central nervous system drugs (29 cases) and cardiovascular drugs (19 cases) were the most frequently described co-medications. Notably, OTC medications were implicated in 27 cases, including mineral supplements (11 cases), herbals (8 cases), weight loss drugs (4 cases), anabolic steroids (3 cases), and recreational drugs (1 case). OTC acted as the perpetrator drug in 21 cases, leading to loss of ARV efficacy in 17 instances (mineral supplements in 10 cases, weight loss drugs in 4 cases, herbals in 3 cases). Additionally, toxicity was reported in 4 out of 6 cases where OTC was considered the victim drug of the DDI (anabolic steroids in 3 cases, MDMA in 1 case). CONCLUSIONS: Frequent unwanted outcomes resulting from DDIs between ARVs and OTC medications underscore the importance of integrating non-prescription drugs into medication reconciliation. The real-world data available through www.clinicalcasesDDIs.com serves as a valuable resource for assessing the clinical relevance of DDIs.

Stability Studies of Antipseudomonal Beta Lactam Agents for Outpatient Therapy.

Outpatient parenteral antimicrobial therapy (OPAT) is a useful treatment strategy against Pseudomonas aeruginosa and other multidrug-resistant bacteria. However, it is hindered by the lack of stability data for the administration of antibiotics under OPAT conditions. Our objective was to investigate the stability of nine antipseudomonal and broad-spectrum beta lactam antibiotics (aztreonam, cefepime, cefiderocol, ceftazidime, ceftazidime/avibactam, ceftolozane/tazobactam, meropenem, meropenem/vaborbactam, and piperacillin/tazobactam) to allow the spread of OPAT programs. All the antibiotics were diluted in 500 mL 0.9% sodium chloride and stored at 4, 25, 32, and 37 °C for 72 h in two different devices (infusion bags and elastomeric pumps). The solutions were considered stable if the color, clearness, and pH remained unchanged and if the percentage of intact drug was ≥90%. All the antimicrobials remained stable 72 h under refrigerated conditions and at least 30 h at 25 °C. At 32 °C, all the antibiotics except for meropenem and meropenem/vaborbactam remained stable for 24 h or more. At 37 °C, only aztreonam, piperacillin/tazobactam, cefepime, cefiderocol, and ceftolozane/tazobactam were stable for at least 24 h. The stability results were the same in the two devices tested. All the antibiotics studied are actual alternatives for the treatment of antipseudomonal or multidrug-resistant infections in OPAT programs, although the temperature of the devices is crucial to ensure antibiotic stability.

Agreement between pharmacists and physicians on the assessment of appropriateness of antimicrobial prescribing.

INTRODUCTION: Audits for monitoring the quality of antimicrobial prescribing are a main tool in antimicrobial stewardship programs; however, interobserver reliability has not been conclusively assessed. Our objective was to measure the level of agreement between pharmacists and physicians on the appropriateness of antimicrobials prescribing in hospitals. METHODS: A national multicenter, cross-sectional study was conducted of patients who were receiving antimicrobials one day of April 2021. Hospital participation was voluntary, and the study population was randomly selected. Pharmacists and physicians performed a simultaneous, independent assessment of the quality of antimicrobial prescriptions. The observers used an assessment method by which all indicators of the quality of antimicrobial use were considered. Finally, an algorithm was used to rate overall antimicrobial prescribing as appropriate, suboptimal, inappropriate, or not assessable. Gwet's AC1 coefficient was used to assess interobserver agreement. RESULTS: In total, 101 hospitals participated, and 411 hospital antimicrobial prescriptions were reviewed. The strength of agreement was moderate regarding the overall quality of prescribing (AC1=0.51; 95%CI=[0.44-0.58]). A very good level of agreement (AC1>0.80) was observed between pharmacists and physicians in all indicators of the quality, except for duration of treatment, rated as good (AC1=0.79; 95%CI=[0.75-0.83]), and registration on the medical record, rated as fair (AC1=0.34; 95%CI=[0.26-0.43]). The agreement was greater in critical care, onco-hematology, and pediatric units than in medical and surgery units. CONCLUSIONS: In this point prevalence study, a moderate level of agreement was observed between pharmacists and physicians in the evaluation of the appropriateness of antimicrobials prescribing in hospitals.

Colistin plasma concentrations are not associated with better clinical outcomes in patients with pneumonia caused by extremely drug-resistant Pseudomonas aeruginosa.

IMPORTANCE: In some cases, colistin is the only treatment option for infections caused by the very drug-resistant Pseudomonas aeruginosa. However, in the past decade, there have been questions concerning its pharmacokinetics and concentration at the site of infection. In this scenario, its use in a difficult-to-treat infection like pneumonia is currently debatable. This is a clinical pharmacokinetic study of colistin in patients with multidrug-resistant P. aeruginosa pneumonia. Our findings demonstrate that colistin exposure is associated with worse clinical outcomes rather than better clinical outcomes, implying that other therapeutic options should be explored in this clinical setting.

Clinical, Microbiological and Treatment Characteristics of Severe Postoperative Respiratory Infections: An Observational Cohort Study.

Respiratory infections are frequent and life-threatening complications of surgery. This study aimed to evaluate the clinical, microbiological and treatment characteristics of severe postoperative pneumonia (POP) and tracheobronchitis (POT) in a large series of patients. This single-center, prospective observational cohort study included patients with POP or POT requiring intensive care unit admission in the past 10 years. We recorded demographic, clinical, microbiological and therapeutic data. A total of 207 patients were included, and 152 (73%) were men. The mean (SD) age was 70 (13) years and the mean (SD) ARISCAT score was 46 (19). Ventilator-associated pneumonia was reported in 21 patients (10%), hospital-acquired pneumonia was reported in 132 (64%) and tracheobronchitis was reported in 54 (26%). The mean (SD) number of days from surgery to POP/POT diagnosis was 6 (4). The mean (SD) SOFA score was 5 (3). Respiratory microbiological sampling was performed in 201 patients (97%). A total of 177 organisms were cultured in 130 (63%) patients, with a high proportion of Gram-negative and multi-drug resistant (MDR) bacteria (20%). The most common empirical antibiotic therapy was a triple-drug regimen covering MDR Gram-negative bacteria and MRSA. In conclusion, surgical patients are a high-risk population with a high proportion of early onset severe POP/POT and nosocomial bacteria isolation.

Real-world experience of therapeutic drug monitoring and PK/PD achievement of ceftaroline administered by different infusion regimens in patients with confirmed infections caused by Gram-positive bacteria.

BACKGROUND: Ceftaroline is a novel cephalosporin active against MDR Gram-positive (GP) bacteria. For ß-lactam antibiotics, such as ceftaroline, prolonged infusions and therapeutic drug monitoring (TDM) are used for dosage optimization based on their pharmacokinetics/pharmacodynamics (PK/PD). OBJECTIVES: To describe our experience with TDM and PK/PD target attainment of ceftaroline administered by intermittent and prolonged infusion in a cohort of patients with MDR-GP bacterial infections. METHODS: Patients treated with ceftaroline administered by continuous (24 h), extended (3 h/6 h) and intermittent infusion (1 h) and undergoing TDM of plasma concentrations were included. A 100%fT>4×MIC was the pre-specified PK/PD target and 100%fT>10×MIC was considered overexposure. Dose recommendations were made based on TDM results and each patient's clinical condition. RESULTS: Twelve patients [83.3% male, median age of 73 (38-83) years] were included. Nine patients (75%) achieved 100%fT>4×MIC, all under prolonged infusions. In one patient, the 100%fT was >10×MIC but no toxicity was observed. Based on TDM results, initial doses were recommended to be maintained in eight patients, decreased in three and increased in one. CONCLUSIONS: The administration of ceftaroline by prolonged infusion together with TDM may be a useful strategy for achieving the desired PK/PD target in these patients. However, more studies evaluating the relationship between PK/PD attainment and clinical outcomes are needed.

Development and Validation of a Risk Score for Predicting Non-Adherence to Antiretroviral Therapy.

Several patient-related factors that influence adherence to antiretroviral therapy (ART) have been described. However, studies that propose a practical and simple tool to predict nonadherence after ART initiation are still scarce. In this study, we develop and validate a score to predict the risk of nonadherence in people starting ART. The model/score was developed and validated using a cohort of people living with HIV starting ART at the Hospital del Mar, Barcelona, between 2012 and 2015 (derivation cohort) and between 2016 and 2018 (validation cohort),. Adherence was evaluated every 2 months using both pharmacy refills and patient self-reports. Nonadherence was defined as taking <90% of the prescribed dose and/or ART interruption for more than 1 week. Predictive factors for nonadherence were identified by logistic regression. Beta coefficients were used to develop a predictive score. Optimal cutoffs were identified using the bootstrapping methodology, and performance was evaluated with the C statistic. Our study is based on 574 patients: 349 in the derivation cohort and 225 in the validation cohort. A total of 104 patients (29.8%) of the derivation cohort were nonadherent. Nonadherence predictors were patient prejudgment; previous medical appointment failures; cultural and/or idiomatic barriers; heavy alcohol use; substance abuse; unstable housing; and severe mental illness. The cutoff point (receiver operating characteristic curve) for nonadherence was 26.3 (sensitivity 0.87 and specificity 0.86). The C statistic (95% confidence interval) was 0.91 (0.87-0.94). These results were consistent with those predicted by the score in the validation cohort. This easy-to-use, highly sensitive, and specific tool could be easily used to identify patients at highest risk for nonadherence, thus allowing resource optimization and achieving optimal treatment goals.

Therapeutic Drug Monitoring of Vancomycin Concentrations for the Management of Bone and Joint Infections: An Urgent Need.

Vancomycin is used for the treatment of bone and joint infections (BJI), but scarce information is available about its pharmacokinetic/pharmacodynamic (PK/PD) characteristics. We aimed to identify the risk factors associated with the non-achievement of an optimal PK/PD target in the first therapeutic drug monitoring (TDM). Methods: A retrospective study was conducted in a tertiary hospital from January 2020 to January 2022. Patients with BJI and TDM of vancomycin on day 2 of treatment were included. Initial vancomycin fixed doses (1 g every 8 h or 12 h) was decided by the responsible doctors. According to TDM results, dosage adjustments were performed. An AUC24h/MIC < 400 mg × h/L, between 400 and 600 mg × h/L and >600 mg × h/L, were defined as suboptimal, optimal and supratherapeutic, respectively. Patients were grouped into these three categories. Demographic, clinical and PK characteristics were compared between groups. Nephrotoxicity at the end of treatment was assessed. Results: A total of 94 patients were included: 22 (23.4%), 42 (44.7%) and 30 (31.9%) presented an infratherapeutic, optimal and supratherapeutic PK/PD targets, respectively. A younger age and initial vancomycin dose <40 mg/kg/day were predictive factors for achieving a suboptimal PK/PD target, while older age, higher serum-creatinine and dose >40 mg/kg/day were associated with overexposure. The nephrotoxicity rate was 22.7%. More than 50% of patients did not achieve an optimal PK/PD. Considering age, baseline serum-creatinine and body weight, TDM is required to readily achieve an optimal and safe exposure.

Primary care electronic medication record discrepancies in patients starting treatment at a hospital-based ambulatory care pharmacy and impact on prevalence of potential drug-drug interactions.

OBJECTIVE: Our objective was to evaluate the prevalence of discrepancies between primary care electronic medication records (EMR) and patient reported medication (PRM) in ambulatory patients starting a hospital dispensing treatment (HDT) at a hospital-based ambulatory care pharmacy (HACPh). Our secondary aims were to analyse factors associated with the presence of discrepancies and their impact on the prevalence of potential drug-drug interactions (DDIs) with the HDT. METHODS: Retrospective study including 230 patients starting a HDT at the HACPh. Pharmacists interviewed patients and PRM was compared with EMR. Discrepancies were classified as omissions (medication in the PRM not present in the EMR) and commissions (medication active in the EMR that the patients were not taking). Potential DDIs with the HDT were screened, and univariate and multivariate analyses were performed to detect factors associated with the presence of discrepancies. RESULTS: We identified 221 discrepancies in 116 (50.4%) patients. Being visited by three or more medical specialties (OR 1.93, 95% CI 1.11 to 3.37) and attending private healthcare (OR 4.36, 95% CI 1.14 to 16.72) in the 12 months before the study inclusion were the factors independently associated with the presence of discrepancies. Among patients with commissions (n=91), 15.4% had a potential DDI between the HDT and one medication from the EMR that they were not taking at that moment. Among patients with omissions (n=45), 11.1% had a potential DDI between the HDT and a medication in the PRM not present in the EMR. CONCLUSIONS: About 40% of patients had one or more medications in the EMR which they were not taking and one fifth used medications that were not listed in the EMR. EMR should not be used as the only source of information when screening for DDIs, especially in patients followed by different medical specialties or combining private and public healthcare.

Suboptimal Concentrations of Ceftazidime/Avibactam (CAZ-AVI) May Select for CAZ-AVI Resistance in Extensively Drug-Resistant Pseudomonas aeruginosa: In Vivo and In Vitro Evidence.

This study correlates in vivo findings in a patient with an extensively drug-resistant (XDR) P. aeruginosa infection who developed resistance to ceftazidime-avibactam (CAZ-AVI) with in vitro results of a 7-day hollow-fiber infection model (HFIM) testing the same bacterial strain. The patient was critically ill with ventilator-associated pneumonia caused by XDR P. aeruginosa ST175 with CAZ-AVI MIC of 6 mg/L and was treated with CAZ-AVI in continuous infusion at doses adjusted for renal function. Plasma concentrations of CAZ-AVI were analyzed on days 3, 7, and 10. In the HIFM, the efficacy of different steady-state concentrations (Css) of CAZ-AVI (12, 18, 30 and 48 mg/L) was evaluated. In both models, a correlation was observed between the decreasing plasma levels of CAZ-AVI and the emergence of resistance. In the HIFM, a Css of 30 and 48 mg/L (corresponding to 5× and 8× MIC) had a bactericidal effect without selecting resistant mutants, whereas a Css of 12 and 18 mg/L (corresponding to 2× and 3× MIC) failed to prevent the emergence of resistance. CAZ/AVI resistance development was caused by the selection of a single ampC mutation in both patient and HFIM. Until further data are available, strategies to achieve plasma CAZ-AVI levels at least 4× MIC could be of interest, particularly in severe and high-inoculum infections caused by XDR P. aeruginosa with high CAZ-AVI MICs.

Therapeutic Drug Monitoring and Prolonged Infusions of Ceftolozane/Tazobactam for MDR/XDR Pseudomonas aeruginosa Infections: An Observational Study.

BACKGROUND AND OBJECTIVE: Prolonged infusion of ceftolozane/tazobactam (C/T) is a strategy used to increase achievement of pharmacokinetic/pharmacodynamic targets for the treatment of multi- or extensively drug-resistant MDR/XDR Gram-negative microorganisms. The objective of this study was to describe our therapeutic drug monitoring (TDM) experience of C/T administered by prolonged infusion or intermittent infusion to patients with MDR/XDR Pseudomonas aeruginosa infections. Our outcomes of interest were pharmacokinetic/pharmacodynamic target achievement and clinical cure. METHODS: Patients with MDR/XDR P. aeruginosa infections treated with C/T were enrolled between February 2018 and February 2020. Blood samples were obtained as part of a TDM program. The pharmacokinetic/pharmacodynamic therapeutic target of C/T was defined as 100% of the duration of the dosing interval that free concentrations are above the minimum inhibitory concentration (MIC) (100 %ƒT ≥ MIC) of the causative pathogen. Dose changes were performed according to TDM results. RESULTS: Forty patients were included: 13 (32.5%) with a proven MDR and 27 (67.5%) with a XDR P. aeruginosa infection. C/T was administered by prolonged infusion in 32 (80%) patients and by intermittent infusion in 8 (20%) patients. Lower doses were administered in the prolonged infusion compared to the intermittent infusion group [3 (9.4%) vs. 5 (62.5%] patients received a dose of 9 g/day (ceftolozane 2 g + tazobactam 1 g, every 8 h; p = 0.004). All patients achieved the pharmacokinetic/pharmacodynamic target and C/T concentrations exceeded 10 × MIC in > 50% of patients in both groups. TDM-recommended dose reductions occurred in 19 (47.5%) patients, being 16 (84.2%) in the prolonged infusion group. A high proportion of patients achieved clinical cure (82.5%). CONCLUSIONS: The administration of C/T by prolonged infusion with TDM-guided dosing allowed the achievement of a pharmacokinetic/pharmacodynamic target even at lower doses. C/T showed a high efficacy for treating MDR/XDR P. aeruginosa infections.