Fast and Sensitive Analysis of Fosfomycin in Human Plasma Microsamples Using Liquid Chromatography-Tandem Mass Spectrometry for Therapeutic Drug Monitoring

BACKGROUND

Fosfomycin is an antibiotic recently repurposed as a potential combination treatment for difficult-to-treat Gram-negative bacterial infections. The pharmacokinetic features of fosfomycin have demonstrated that different pathophysiologic alterations may affect its exposure. Therapeutic drug monitoring may improve real-time management of fosfomycin therapy in different clinical scenarios.

OBJECTIVES

To develop and validate a fast and sensitive liquid chromatography - tandem mass spectrometry method for measuring fosfomycin in human plasma microsamples (3 µL).

METHODS

Analysis was preceded by a user-friendly pre-analytical single-step process performed via a rapid chromatographic run of 2.5 minutes, followed by negative electrospray ionization and detection on a high-sensitivity triple quadrupole tandem mass spectrometer operated in the multiple reaction monitoring mode. European Medicines Agency guidelines were used to validate the specificity, sensitivity, linearity, precision, accuracy, matrix effects, extraction recovery, limits of quantification, and stability of the analytical method.

RESULTS

The new assay produced accurate (BIAS%: 0.9-9.1) and precise (coefficient of variation [CV]%: 8.1-9.5) measurements of fosfomycin over a concentration range of 1-1000 mg/L. Overall, analyte recovery was consistent (mean values: 91.2%-97.2%) at all tested concentration levels. The analyte was also stable in human plasma and the final extract under various storage conditions. The clinical applicability of the assay was confirmed through quantitation of plasma samples obtained from patients.

CONCLUSIONS

A sensitive liquid chromatography - tandem mass spectrometry method for measuring fosfomycin in plasma was developed and validated according to the European Medicines Agency criteria. Quantitation of fosfomycin in clinical plasma samples confirmed that the assay is suitable for therapeutic drug monitoring in clinical scenarios.

Impact of attaining aggressive vs. conservative PK/PD target on the clinical efficacy of beta-lactams for the treatment of Gram-negative infections in the critically ill patients: a systematic review and meta-analysis

BACKGROUND

To perform a systematic review with meta-analysis with the dual intent of assessing the impact of attaining aggressive vs. conservative beta-lactams PK/PD target on the clinical efficacy for treating Gram-negative infections in critical patients, and of identifying predictive factors of failure in attaining aggressive PK/PD targets.

METHODS

Two authors independently searched PubMed-MEDLINE and Scopus database from inception to 23rd December 2023, to retrieve studies comparing the impact of attaining aggressive vs. conservative PK/PD targets on clinical efficacy of beta-lactams. Independent predictive factors of failure in attaining aggressive PK/PD targets were also assessed. Aggressive PK/PD target was considered a100%fT>4xMIC, and clinical cure rate was selected as primary outcome. Meta-analysis was performed by pooling odds ratios (ORs) extrapolated from studies providing adjustment for confounders using a random-effects model with inverse variance method.

RESULTS

A total of 20,364 articles were screened, and 21 observational studies were included in the meta-analysis (N = 4833; 2193 aggressive vs. 2640 conservative PK/PD target). Attaining aggressive PK/PD target was significantly associated with higher clinical cure rate (OR 1.69; 95% CI 1.15-2.49) and lower risk of beta-lactam resistance development (OR 0.06; 95% CI 0.01-0.29). Male gender, body mass index > 30 kg/m2, augmented renal clearance and MIC above the clinical breakpoint emerged as significant independent predictors of failure in attaining aggressive PK/PD targets, whereas prolonged/continuous infusion administration of beta-lactams resulted as protective factor. The risk of bias was moderate in 19 studies and severe in the other 2.

CONCLUSIONS

Attaining aggressive beta-lactams PK/PD targets provided significant clinical benefits in critical patients. Our analysis could be useful to stratify patients at high-risk of failure in attaining aggressive PK/PD targets.

Balancing the scales: achieving the optimal beta-lactam to beta-lactamase inhibitor ratio with continuous infusion piperacillin/tazobactam against extended spectrum beta-lactamase producing Enterobacterales

Piperacillin/tazobactam (TZP) is administered intravenously in a fixed ratio (8:1) with the potential for inadequate tazobactam exposure to ensure piperacillin activity against Enterobacterales. Adult patients receiving continuous infusion (CI) of TZP and therapeutic drug monitoring (TDM) of both agents were evaluated. Demographic variables and other pertinent laboratory data were collected retrospectively. A population pharmacokinetic approach was used to select the best kidney function model predictive of TZP clearance (CL). The probability of target attainment (PTA), cumulative fraction of response (CFR) and the ratio between piperacillin and tazobactam were computed to identify optimal dosage regimens by continuous infusion across kidney function. This study included 257 critically ill patients (79.3% male) with intra-abdominal, bloodstream, and hospital-acquired pneumonia infections in 89.5% as the primary indication. The median (min-max range) age, body weight, and estimated glomerular filtration rate (eGFR) were 66 (23-93) years, 75 (39-310) kg, and 79.2 (6.4-234) mL/min, respectively. Doses of up to 22.5 g/day were used to optimize TZP based on TDM. The 2021 chronic kidney disease epidemiology equation in mL/min best modeled TZP CL. The ratio of piperacillin:tazobactam increased from 6:1 to 10:1 between an eGFR of <20 mL/min and >120 mL/min. At conventional doses, the PTA is below 90% when eGFR is ≥100 mL/min. Daily doses of 18 g/day and 22.5 g/day by CI are expected to achieve a >80% CFR when eGFR is 100-120 mL/min and >120-160 mL/min, respectively. Inadequate piperacillin and tazobactam exposure is likely in patients with eGFR ≥ 100 mL/min. Dose regimen adjustments informed by TDM should be evaluated in this specific population.

Implementation and validation of a Bayesian method for accurately forecasting duration of optimal pharmacodynamic target attainment with dalbavancin during long-term use for subacute and chronic staphylococcal infections

Dalbavancin is increasingly being used for long-term treatment of subacute and chronic staphylococcal infections. In this study, a new Bayesian model was implemented and validated using MwPharm software for accurately forecasting the duration of pharmacodynamic target attainment above the efficacy thresholds of 4.02 mg/L or 8.04 mg/L against staphylococci. Forecasting accuracy improved substantially with the a posteriori approach compared with the a priori approach, particularly when two measured concentrations were used. This strategy may help clinicians to estimate the duration of optimal exposure with dalbavancin in the context of long-term treatment.

Population Pharmacokinetic and Pharmacodynamic Analysis for Maximizing the Effectiveness of Ceftobiprole in the Treatment of Severe Methicillin-Resistant Staphylococcal Infections

Ceftobiprole is a fifth-generation cephalosporin used for different Gram-positive bacterial infections. A population pharmacokinetic analysis was conducted in real-life clinical patients to assess the adequacy of current dosages. Population pharmacokinetics was conducted using non-linear mixed effect modeling. Monte Carlo simulations were performed to determine the probability of target attainment (PTA) of free trough or steady-state concentration over MIC (fCtrough/MIC or fCss/MIC) ≥ 1 or ≥4 associated with both the standard and intensified dosing regimens adjusted for renal function. Cumulative fraction of response (CFR) against methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus epidermidis (MRSE) were also calculated. A total of 132 patients with 503 concentrations were included. Most of them (107/132, 81.1%) had hospital- or community-acquired pneumonia, endocarditis, and bacteremia. A three-compartment model adequately fitted ceftobiprole concentration-time data. Estimated glomerular filtration rate significantly affected drug clearance. Monte Carlo simulations showed that the optimal target of fCtrough/MIC or fCss/MIC ≥ 4 is achieved only with the use of the standard dosages administered by continuous infusion (CI) against MRSA infections in patients with preserved renal function. Intensified dosages administered by CI are needed in patients with impaired renal function and/or augmented renal clearance against MRSA and in patients with preserved renal functions against MRSE.

Impact of a newly established expert clinical pharmacological advice program based on TDM results in tailoring antimicrobial therapies hospital-wide in a tertiary university hospital: findings after the first-year of implementation

BACKGROUND

Therapeutic drug monitoring (TDM) may be helpful in tailoring treatment with antimicrobials, and expert interpretation of the results may make it more clinically useful.

METHOD

The study aim was to assess retrospectively the first-year impact (July 2021-June 2022) of a newly established expert clinical pharmacological advice program (ECPA) based on TDM results in tailoring therapy with 18 antimicrobials hospital-wide in a tertiary university hospital. All patients having ≥1 ECPA were grouped in five cohorts [hematology, intensive care unit (ICU), pediatrics, medical- and surgical- wards]. Four indicators of performance were identified [total ECPAs; total ECPA recommending dosing adjustments/total ECPAs both at first and at subsequent assessments; turnaround time (TAT) of ECPAs, defined as optimal (<12h), quasi-optimal (12-24h), acceptable (24-48h), suboptimal (>48h)].

RESULTS

A total of 8484 ECPAs were provided for tailoring treatment in 2961 patients, mostly admitted in the ICU (33.8%) and in the medical wards (29.4%). The proportions of ECPAs recommending dosing adjustments were >40% at first assessment (40.9% in hematology; 62.8% in ICU; 53.9% in pediatrics; 59.1% in medical wards; 59.7% in surgical wards), and decreased consistently at subsequent TDM assessments (20.7% in hematology; 40.6% in ICU; 37.4% in pediatrics; 32.9% in medical wards; 29.2% in surgical wards). The overall median TAT of the ECPAs was optimal (8.11h).

CONCLUSIONS

The TDM-guided ECPA program was successful in tailoring treatment with a wide panel of antimicrobials hospital-wide. Expert interpretation by MD clinical pharmacologists, short TATs and strict interaction with ID consultants and clinicians were crucial in attaining this.

Fast and Sensitive Method for Simultaneous Quantification of Meropenem and Vaborbactam in Human Plasma Microsamples by Liquid Chromatography-Tandem Mass Spectrometry for Therapeutic Drug Monitoring

Meropenem (MRP)-Vaborbactam (VBR) is a novel beta-lactam/beta-lactamase inhibitor used for the management of difficult-to-treat Gram-negative infections. Among critically ill patients, MRP-VBR shows remarkable inter-individual variability in pharmacokinetic behavior, thus justifying the implementation of therapeutic drug monitoring (TDM) for improving real-time management in different challenging scenarios. In this study, we developed and validated a fast and sensitive Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS) method for the simultaneous quantification of MRP and VBR in human plasma microsamples of 3 microliters. The analysis required only a single-step sample preparation and was performed by means of a fast chromatographic run of 4 min, followed by positive electrospray ionization and detection on a high-sensitivity triple quadrupole tandem mass spectrometer operated in multiple reaction monitoring modes. The straightforward analytical procedure was successfully validated, based on the EMA guidelines, in terms of specificity, sensitivity, linearity, precision, accuracy, matrix effect, extraction recovery, the limit of quantification, and stability. The novel method was successfully applied for simultaneously measuring MRP and VBR concentrations in more than 42 plasma samples collected from critically ill patients affected by carbapenem-resistant Gram-negative bacteria infections.

A novel method to evaluate ceftazidime/avibactam therapy in patients with carbapenemase-producing Enterobactericeae (CPE) bloodstream infections

INTRODUCTION

This study reports experience managing eight patients with bloodstream infections treated with a continuous infusion of ceftazidime-avibactam.

METHODS

Patients who were treated for documented CPE BSIs susceptible to CAZ-AVI and who underwent real-time therapeutic drug monitoring were retrospectively assessed. Ceftazidime MICs were assessed in presence of increasing concentrations of avibactam by the broth microdilution method. An inhibitory sigmoid Emax model was used to characterize ceftazidime MIC reduction as a function of avibactam concentration, and the MICi was derived by conditioning the best-fit model using steady-state avibactam concentrations (Css). Ceftazidime fCss/MICi ratio was calculated for each patient and correlated to microbiological outcome.

RESULTS

By adopting the innovative concept of effective MIC with an inhibitor (MICi), a trend towards higher microbiological failure and resistance development was found in patients with a lower ceftazidime fCss/MICi ratio (2/3 vs. 0/5).

CONCLUSION

Assessment of changes in the ceftazidime MIC in relation to increasing avibactam concentration could represent a more robust pharmacokinetic/pharmacodynamic method for predicting microbiological failure given beta-lactam/beta-lactamase inhibitor combinations.

Successful and Safe Real-Time TDM-Guided Treatment of Invasive Pulmonary and Cerebral Aspergillosis Using Low-Dose Isavuconazole in a Patient with Primary Biliary Cirrhosis: Grand Round/A Case Study

BACKGROUND

The authors present a case of a 67-year-old woman with primary biliary cirrhosis (Child-Pugh class B) who was treated with isavuconazole for invasive pulmonary and cerebral aspergillosis. Isavuconazole treatment was initiated with the standard maintenance dose of 200 mg daily. Therapeutic drug monitoring (TDM) was performed to target trough concentrations within the desired range of 1.0-5.13 mg/L.

METHODS

Real-time TDM and pharmacokinetic analyses were used to determine the dose adjustments. Liver transaminases (alanine aminotransferase and gamma-glutamyl transferase) were assessed to monitor hepatotoxicity.

RESULTS

The trough plasma levels gradually increased over time up to 17.8 mg/L. TDM-guided clinical pharmacological advice was helpful to initially reduce the dose, then to temporarily suspend drug administration, and finally to calculate the correct dose that allowed for long-term treatment up to day 258. No major signs and/or symptoms of drug-related toxicity occurred, apart from a transient increase in gamma-glutamyl transferases that normalized after the drop in isavuconazole trough levels within the desired range.

CONCLUSIONS

TDM-guided clinical pharmacological advice was essential for the successful and safe management of isavuconazole treatment in this patient with moderate liver dysfunction.

Does Cytokine-Release Syndrome Induced by CAR T-Cell Treatment Have an Impact on the Pharmacokinetics of Meropenem and Piperacillin/Tazobactam in Patients with Hematological Malignancies? Findings from an Observational Case-Control Study

Chimeric antigen receptor (CAR) T-cell therapy is a promising approach for some relapse/refractory hematological B-cell malignancies; however, in most patients, cytokine release syndrome (CRS) may occur. CRS is associated with acute kidney injury (AKI) that may affect the pharmacokinetics of some beta-lactams. The aim of this study was to assess whether the pharmacokinetics of meropenem and piperacillin may be affected by CAR T-cell treatment. The study included CAR T-cell treated patients (cases) and oncohematological patients (controls), who were administered 24-h continuous infusion (CI) meropenem or piperacillin/tazobactam, optimized by therapeutic drug monitoring, over a 2-year period. Patient data were retrospectively retrieved and matched on a 1:2 ratio. Beta-lactam clearance (CL) was calculated as CL = daily dose/infusion rate. A total of 38 cases (of whom 14 and 24 were treated with meropenem and piperacillin/tazobactam, respectively) was matched with 76 controls. CRS occurred in 85.7% (12/14) and 95.8% (23/24) of patients treated with meropenem and piperacillin/tazobactam, respectively. CRS-induced AKI was observed in only 1 patient. CL did not differ between cases and controls for both meropenem (11.1 vs. 11.7 L/h, p = 0.835) and piperacillin (14.0 vs. 10.4 L/h, p = 0.074). Our findings suggest that 24-h CI meropenem and piperacillin dosages should not be reduced a priori in CAR T-cell patients experiencing CRS.

Population Pharmacokinetic and Pharmacodynamic Analysis of Valganciclovir for Optimizing Preemptive Therapy of Cytomegalovirus Infections in Kidney Transplant Recipients

This study aimed to develop a population pharmacokinetic/pharmacodynamic (PK/PD) model of valganciclovir for preemptive therapy of cytomegalovirus (CMV) infection in kidney transplant patients. A population PK/PD model was developed with Monolix. Ganciclovir concentrations and CMV viral loads were obtained retrospectively from kidney transplant patients receiving routine clinical care. Ten thousand Monte Carlo simulations were performed with the licensed dosages adjusted for renal function to assess the probability of attaining a viral load target of ≤290 and ≤137 IU/mL. Fifty-seven patients provided 343 ganciclovir concentrations and 328 CMV viral loads for PK/PD modeling. A one-compartment pharmacokinetic model coupled with an indirect viral turnover growth model with stimulation of viral degradation pharmacodynamic model was devised. Simulations showed that 1- and 2-log10 reduction of CMV viral load mostly occurred between a median of 5 to 6 and 12 to 16 days, respectively. The licensed dosages achieved a probability of reaching the viral load target ≥90% at days 35 to 49 and 42 to 56 for the thresholds of ≤290 and ≤137 IU/mL, respectively. Simulations indicate that in patients with an estimated glomerular filtration rate of 10 to 24 mL/min/1.73m2, a dose increase to 450 mg every 36 h may reduce time to optimal viral load target to days 42 and 49 from a previous time of 49 and 56 days for the thresholds of ≤290 and ≤137 IU/mL, respectively. Currently licensed dosages of valganciclovir for preemptive therapy of CMV infection may achieve a viral load reduction within the first 2 weeks, but treatment should continue for ≥35 days to ensure viral load suppression.

Measuring Creatinine Clearance Is the Most Accurate Way for Calculating the Proper Continuous Infusion Meropenem Dose for Empirical Treatment of Severe Gram-Negative Infections among Critically Ill Patients

Assessment of glomerular filtration rate (GFR) is necessary for dose adjustments of beta-lactam that are excreted by the kidneys, such as meropenem. The aim of this study was to compare the daily dose of 24 h-continuous infusion (CI) meropenem when GFR was calculated by means of measured creatinine clearance (mCL_CR) or estimated by the CKDEPI (eGFR_CKDEPI), Cockcroft-Gault (eGFR_CG), and MDRD (eGFR_MDRD) equations. Adult critically ill patients who underwent therapeutic drug monitoring (TDM) for the assessment of 24 h-CI meropenem steady state concentration (Css) and for whom a 24 h-urine collection was performed were retrospectively enrolled. Meropenem clearance (CL_M) was regressed against mCL_CR, and meropenem daily dose was calculated based on the equation infusion rate = daily dose/CL_M. eGFR_CKDEPI, eGFR_CG, and eGFR_CKDEPI were regressed against mCL_CR in order to estimate CL_M. Forty-six patients who provided 133 meropenem Css were included. eGFR_CKDEPI overestimated mCL_CR up to 90 mL/min, then mCL_CR was underestimated. eGFR_CG and eGFR_MDRD overestimated mCL_CR across the entire range of GFR. In critically ill patients, dose adjustments of 24 h-CI meropenem should be based on mCL_CR. Equations for estimation of GFR may lead to gross under/overestimates of meropenem dosages. TDM may be highly beneficial, especially for critically ill patients with augmented renal clearance.

A descriptive pharmacokinetic/pharmacodynamic analysis of continuous infusion ceftazidime-avibactam in a case series of critically ill renal patients treated for documented carbapenem-resistant Gram-negative bloodstream infections and/or ventilator-associated pneumonia

OBJECTIVES

To describe the pharmacokinetic/pharmacodynamic (PK/PD) behaviour of continuous infusion (CI) ceftazidime-avibactam and the microbiological outcome in a case series of critically ill renal patients treated for documented carbapenem-resistant Gram-negative (CR-GN) bloodstream infections (BSI) and/or ventilator-associated pneumonia (VAP).

METHODS

Critically ill patients with different degrees of renal function who were treated with CI ceftazidime-avibactam for documented CR-GN infections, and who underwent therapeutic drug monitoring from April 2021 to March 2022, were retrospectively assessed. Ceftazidime and avibactam concentrations were determined at steady-state, and the free fraction (fC_ss) was calculated. The joint PK/PD target of ceftazidime-avibactam was considered as optimal when both C_ss/MIC ratio for ceftazidime ≥4 (equivalent to 100%fT>_4xMIC) and C_ss/C_T ratio for avibactam >1 (equivalent to 100% fT>C_T of 4.0 mg/L) were simultaneously achieved (quasi-optimal if only one of the two was achieved, and suboptimal if neither of the two was achieved). The relationship between ceftazidime-avibactam PK/PD targets and microbiological outcome was assessed.

RESULTS

Ten patients with documented CR-GN infections (5 BSIs, 4 VAP, 1 BSI+VAP) were retrieved. The joint PK/PD targets of ceftazidime-avibactam were optimal and quasi-optimal in eight and two cases, respectively. Microbiological failure occurred in two patients (one with VAP, one with BSI+VAP), one of whom developed ceftazidime-avibactam resistance. Both underwent renal replacement therapy, and failed despite attaining optimal joint PK/PD target and receiving fosfomycin co-treatment.

CONCLUSION

CI administration may enable optimal joint PK/PD targets of ceftazidime-avibactam to be achieved in most critical renal patients with CR-GN infections, and may help to minimize the risk of microbiological failure.

618. Pharmacokinetic/pharmacodynamic analysis of combination therapy with continuous infusion (CI) fosfomycin plus extended-infusion (EI) or CI beta-lactams for treating documented carbapenem-resistant Gram-negative bloodstream infections and/or hospital-acquired pneumonia: a case series

Background

To describe the pharmacokinetic/pharmacodynamic (PK/PD) behaviour and the microbiological outcome of combination therapy with continuous infusion (CI) fosfomycin plus extended-infusion (EI) or CI beta-lactams for treating severe carbapenem-resistant Gram-negative (CR-GN) infections.

Methods

Single-center retrospective study of patients who were treated with CI fosfomycin plus EI or CI beta-lactams for severe CR-GN infections and who underwent therapeutic drug monitoring (TDM), from 01 April 2021 to 31 January 2022. Concentrations of CI fosfomycin, meropenem and ceftazidime-avibactam were determined at steady-state (Css), while those of EI cefiderocol were measured at trough (Cmin). The desired joint PK/PD targets of combination therapy were considered as optimal when simultaneously the area-under-the curve to minimum inhibitory concentration (AUC/MIC) ratio for fosfomycin was &gt; 83 and the Css/MIC for meropenem or for ceftazidime-avibactam or the Cmin/MIC ratio for cefiderocol was &gt; 4 (quasi-optimal if only one of the two was achieved, and suboptimal if none of the two was achieved). Relationship between the joint PK/PD targets and microbiological failure (MF) defined as isolation of the same pathogens from follow-up blood cultures or BAL and assessed within 30 days of treatment onset, was investigated.

Results

Among the 16 retrieved patients with documented CR-GN infections, 12 underwent TDM of both fosfomycin and beta-lactams, and seven out of these (3 HAP, 3 BSI+HAP, and one BSI) had determination of fosfomycin MIC determined by agar-dilution (see Table). The joint PK/PD targets were optimal in 4 cases and quasi-optimal in the other 3y. MF occurred in two patients (29%) who were affected by HAP, received combination therapy with ceftazidime-avibactam, and achieved only quasi-optimal joint PK/PD targets (with fosfomycin AUC/MIC &lt; 83). No MF occurred in patients with optimal joint PK/PD targets.

Summary of the relationship between PK/PD targets and microbiological failure in patients receiving combination therapy with CI fosfomycin plus EI/CI beta-lactams

Conclusion

CI fosfomycin in combination with EI/CI beta-lactams may allow for the achievement of optimal joint PK/PD targets in most patients with CR-GN infections, and may represent a potential strategy for minimizing the risk of MF.

Disclosures

All Authors: No reported disclosures.

The knowledge and attitudes of pharmacists related to the use of dietary supplements: An observational study in northeastern Italy

Inappropriate use of dietary supplements can be potentially harmful to patients, especially given the uncontrolled information on the Internet and social media. The role that pharmacists play in advising citizens and purchasing these products can help improve their safer use, but the knowledge, attitudes, and practices of these professionals on this topic are still largely unknown.

Pharmacists in the Italian Region of Friuli-Venezia Giulia (FVG) were surveyed from September 2020 to February 2021 using a 54-item online questionnaire. The questions were related to knowledge, attitudes, and practice. Data on gender, age, work experience, degree, and function in pharmacy were also collected.

232 questionnaires were completed, predominantly by women (71 %). The majority of respondents had a degree in Pharmacy (77 %) and were employed in a pharmacy (66 %) where they had worked for at least 10 years (61 %). Pharmacists’ knowledge was rated as low, with one-third of participants above the median; knowledge was higher among more experienced pharmacists. Larger knowledge gaps were noted regarding the potential carcinogenicity of multivitamin misuse and the undesirable presence of unlabeled ingredients in dietary supplements. Employees were more likely than owners to report purchasing dietary supplements at the direct request of patients (p < 0.05).

The low level of pharmacists’ knowledge about the use of dietary supplements is unsatisfactory, with concerning impact on patient safety. Young professionals in particular would benefit from continuous education to better advise patients. Nevertheless, the European regulatory framework for the manufacture, sale and post-marketing surveillance of dietary supplements needs to be strengthened.

Linezolid Population Pharmacokinetics to Improve Dosing in Cardiosurgical Patients: Factoring a New Drug-Drug Interaction Pathway

Background

Linezolid-induced myelosuppression limits optimal therapy in cardiosurgical patients with deep-seated infections at current doses.

Methods

Adult patients who received a cardiac surgery intervention and linezolid for a documented or presumed serious Gram-positive infection were evaluated. Therapeutic monitoring data, dosing, concomitant medications, and other pertinent laboratory data were collected retrospectively. A population pharmacokinetic model was constructed to identify covariates and test potential drug-drug interactions that may account for interpatient variability. Simulations from the final model identified doses that achieve a target therapeutic trough concentration of 2-8 mg/L.

Results

This study included 150 patients (79.3% male) with sepsis and hospital acquired pneumonia in 71.7% as the primary indication. The population had a median (min-max) age, body weight and estimated glomerular filtration rate (eGFR) of 66 (30–85) years, 76 (45–130) kg and 46.8 (4.9–153.7) mL/min, respectively. The standard linezolid dosage regimen achieved the therapeutic range in only 54.7% of patients. Lower than standard doses were necessary in the majority of patients (77%). A two-compartment Michaellis-Menten clearance model with weight, kidney function, and the number of interacting drugs were identified as covariates that best fit the concentration-time data. Cyclosporine had the greatest effect on lowering the maximum elimination rate (Vmax) of linezolid. Empiric linezolid doses of 300 to 450 mg every 12 hours based on eGFR and the number of interacting medications is suggested by this analysis.

Conclusions

Lower empiric linezolid doses in cardiosurgical patients may avoid toxicities. Confirmatory studies are necessary to verify these potential drug interactions.

Real-World Comparison of Isavuconazole and Voriconazole in Terms of the Need for Dosage Adjustments Guided by Clinical Pharmacological Advice During Primary Prophylaxis of Invasive Fungal Infections in Pediatric Patients with Hemato-Oncological Malignancies

BACKGROUND

Limited evidence concerning optimal azole dosing regimens currently exists for antifungal prophylaxis in hemato-oncological pediatric patients.

METHODS

Hemato-oncological children receiving intravenous or oral isavuconazole or voriconazole for primary antifungal prophylaxis at IRCCS Azienda Ospedaliero-Universitaria of Bologna during November 2020 to October 2021 and undergoing CPA programs based on real-time therapeutic drug monitoring (TDM) were retrospectively analyzed. CPAs for isavuconazole and voriconazole and the number of dosage adjustments were collected. Normalized trough concentrations [(C min )/dose/kg] were calculated for both drugs at each TDM assessment, and the coefficient of variation was determined. The efficacy and safety of the drugs were evaluated.

RESULTS

Sixteen hemato-oncological pediatric patients received azole prophylaxis (mean age and weight: 9.1 ± 4.9 years and 32.6 ± 16.0 kg; 6 isavuconazole and 10 voriconazole). Sixty and 89 CPAs were delivered as isavuconazole and voriconazole, respectively. Dosage adjustments were needed in 3.3% of cases for isavuconazole and 53.9% of cases for voriconazole ( P < 0.001). At first TDM, achievement of the desired target during standard dosing regimens was higher for isavuconazole (83.3%) than for voriconazole (10.0%; P = 0.008). Dispersion of normalized concentrations was higher for voriconazole (CV = 139.1% vs. CV = 79.4%). Elevation of ALT and aspartate aminotransferase levels between baseline and the third month was higher in patients receiving voriconazole (median, 28 vs. 90 U/L; P = 0.038, and 19 vs. 65.5 U/L; P = 0.002).

CONCLUSIONS

Our findings suggest that there is limited variability in isavuconazole exposure in hemato-oncological pediatric patients receiving azole prophylaxis , resulting in a low need for CPA-guided dosage adjustments.

Expert clinical pharmacological advice may make an antimicrobial TDM program for emerging candidates more clinically useful in tailoring therapy of critically ill patients

Background

Therapeutic drug monitoring (TDM) may represent an invaluable tool for optimizing antimicrobial therapy in septic patients, but extensive use is burdened by barriers. The aim of this study was to assess the impact of a newly established expert clinical pharmacological advice (ECPA) program in improving the clinical usefulness of an already existing TDM program for emerging candidates in tailoring antimicrobial therapy among critically ill patients.

Methods

This retrospective observational study included an organizational phase (OP) and an assessment phase (AP). During the OP (January–June 2021), specific actions were organized by MD clinical pharmacologists together with bioanalytical experts, clinical engineers, and ICU clinicians. During the AP (July–December 2021), the impact of these actions in optimizing antimicrobial treatment of the critically ill patients was assessed. Four indicators of performance of the TDM-guided real-time ECPA program were identified [total TDM-guided ECPAs July–December 2021/total TDM results July–December 2020; total ECPA dosing adjustments/total delivered ECPAs both at first assessment and overall; and turnaround time (TAT) of ECPAs, defined as optimal (< 12 h), quasi-optimal (12–24 h), acceptable (24–48 h), suboptimal (> 48 h)].

Results

The OP allowed to implement new organizational procedures, to create a dedicated pathway in the intranet system, to offer educational webinars on clinical pharmacology of antimicrobials, and to establish a multidisciplinary team at the morning bedside ICU meeting. In the AP, a total of 640 ECPAs were provided for optimizing 261 courses of antimicrobial therapy in 166 critically ill patients. ECPAs concerned mainly piperacillin–tazobactam (41.8%) and meropenem (24.9%), and also other antimicrobials had ≥ 10 ECPAs (ceftazidime, ciprofloxacin, fluconazole, ganciclovir, levofloxacin, and linezolid). Overall, the pre–post-increase in TDM activity was of 13.3-fold. TDM-guided dosing adjustments were recommended at first assessment in 61.7% of ECPAs (10.7% increases and 51.0% decreases), and overall in 45.0% of ECPAs (10.0% increases and 35.0% decreases). The overall median TAT was optimal (7.7 h) and that of each single agent was always optimal or quasi-optimal.

Conclusions

Multidisciplinary approach and timely expert interpretation of TDM results by MD Clinical Pharmacologists could represent cornerstones in improving the cost-effectiveness of an antimicrobial TDM program for emerging TDM candidates.

Successful Treatment of Bacteremia and Ventilator-Associated Pneumonia Caused by KPC/OXA-48-like Klebsiella pneumoniae Co-Producer with a Continuous Infusion of High-Dose Meropenem Plus Fosfomycin Guided by Real-Time Therapeutic Drug Monitoring

Bacteremia and ventilator-associated pneumonia due to a pan-resistant Klebsiella pneumoniae strain co-producing KPC and OXA-48 carbapenemases was successfully treated in a COVID-19 critically ill patient with a combination therapy of a high-dose continuous infusion of meropenem (up to 3 g every 6 h, daily) plus fosfomycin (up to 24 g/daily) that was guided by real-time therapeutic drug monitoring. Clinical pharmacological advice was helpful in maximizing, over time, the pharmacodynamic target attainment of both antibiotics.

Real-Time Optimization of Pharmacodynamic Target Attainment at Infection Site during Treatment of Post-Neurosurgical Ventriculitis Caused by Carbapenem-Resistant Gram Negatives with Ceftazidime-Avibactam-Based Regimens: A Report of Two Cases

We present two cases of post-neurosurgical ventriculitis caused by carbapenem-resistant Gram-negative pathogens successfully treated with high-dose ceftazidime/avibactam. The existence of a real-time clinical pharmacological advice program, by enabling the optimization of the PK/PD targets over time at the infection site, turned out to be very helpful.

Impact of Maximizing Css/MIC Ratio on Efficacy of Continuous Infusion Meropenem Against Documented Gram-Negative Infections in Critically Ill Patients and Population Pharmacokinetic/Pharmacodynamic Analysis to Support Treatment Optimization

Introduction: optimal treatment of Gram-negative infections in critically ill patients is challenged by changing pathophysiological conditions, reduced antimicrobial susceptibility and limited therapeutic options. The aim of this study was to assess the impact of maximizing Css/MIC ratio on efficacy of continuous infusion (CI) meropenem in treating documented Gram-negative infections in critically ill patients and to perform a population pharmacokinetic/pharmacodynamic analysis to support treatment optimization.

Materials and Methods: Classification and regression tree (CART) analysis was used to identify whether a cutoff of steady-state meropenem concentration (Css)-to-minimum inhibitory concentration (MIC) (Css/MIC) ratio correlated with favorable clinical outcome. A non-parametric approach with Pmetrics was used for pharmacokinetic analysis and covariate evaluation. The probability of target attainment (PTA) of the identified Css/MIC ratio was calculated by means of Monte Carlo simulations. Cumulative fraction of response (CFRs) were calculated against common Enterobacterales, P. aeruginosa and A. baumannii as well.

Results: a total of 74 patients with 183 meropenem Css were included. CART analysis identified a Css/MIC ratio ≥4.63 as cutoff value significantly associated with favorable clinical outcomes. Multivariate regression analysis confirmed the association [OR (95%CI): 20.440 (2.063–202.522); p < 0.01]. Creatinine clearance (CL_CR) was the only covariate associated with meropenem clearance. Monte Carlo simulations showed that, across different classes of renal function, dosages of meropenem ranging between 0.5 and 2 g q6h over 6 h (namely by CI) may grant PTAs of Css/MIC ratios ≥4.63 against susceptible pathogens with an MIC up to the EUCAST clinical breakpoint of 2 mg/L. The CFRs achievable with these dosages were very high (>90%) against Enterobacterales across all the classes of renal function and against P. aeruginosa among patients with CL_CR < 30 ml/min/1.73 m², and quite lower against A. baumannii.

Discussion: our findings suggest that Css/MIC ratio ≥4.63 may be considered the pharmacodynamic target useful at maximizing the efficacy of CI meropenem in the treatment of Gram-negative infections in critically ill patients. Dosages ranging between 0.5 g q6h and 2 g q6h by CI may maximize the probability of favorable clinical outcome against meropenem-susceptible Gram-negative pathogens among critically ill patients having different degrees of renal function.

A descriptive case series of pharmacokinetic/pharmacodynamic target attainment and microbiological outcome in critically ill patients with documented severe extensively drug-resistant Acinetobacter baumannii bloodstream infection and/or ventilator-associated pneumonia treated with cefiderocol

OBJECTIVES

The aim of this study was to explore the relationship between cefiderocol pharmacokinetic/pharmacodynamic (PK/PD) target attainment and microbiological outcome in critically ill patients affected by extensively drug-resistant Acinetobacter baumannii (XDR-AB) bloodstream infection (BSI) and/or ventilator-associated pneumonia (VAP).

METHODS

Patients who received compassionate use of cefiderocol to treat documented XDR-AB infections at the intensive care unit of the IRCCS Azienda Ospedaliero-Universitaria of Bologna and who underwent therapeutic drug monitoring (TDM) from 15 March 2021 to 30 April 2021 were retrospectively assessed. Cefiderocol trough concentration (Cmin) was determined at steady-state, and the free fraction (fCmin) was calculated according to a plasma protein binding of 58%. The fCmin/MIC ratio was selected as a pharmacodynamic parameter of cefiderocol efficacy and was defined as optimal if ≥4, quasi-optimal if between 1 and 4, and suboptimal if <1. The association between fCmin/MIC and microbiological outcome was assessed.

RESULTS

A total of 13 patients treated with cefiderocol for the management of XDR-AB infections (6 BSI plus VAP, 5 VAP and 2 BSI) were retrieved. fCmin/MIC ratios were suboptimal in 3 cases (23%) and quasi-optimal or optimal in 5 cases each (38%). Microbiological failure occurred in seven cases (54%; six with VAP and one with VAP plus BSI). Microbiological failure occurred in 80% of patients with suboptimal fCmin/MIC compared with 29% of those achieving optimal or quasi-optimal fCmin/MIC ratio.

CONCLUSION

Suboptimal attainment of PK/PD targets of cefiderocol may lead to microbiological failure of treatment with cefiderocol of critically ill patients affected by XDR-AB VAP.

Real-Life Population Pharmacokinetics of Recombinant Factor XIII and Dosing Considerations for Preventing the Risk of Bleeding in Patients with FXIII Congenital Deficiency

BACKGROUND AND OBJECTIVE

Recombinant factor XIII (rFXIII) at the recommended dosage of 35 IU/kg every 4 weeks is currently used for prophylaxis of bleeding in patients affected by FXIII deficiency. The aim of this study was to describe the population pharmacokinetics of rFXIII in patients with FXIII deficiency being treated with rFXIII in real-life and to assess, using Monte Carlo simulations, the attainment of defined FXIII concentration thresholds associated with prevention of the risk of bleeding over time.

METHODS

A nonlinear mixed-effects model approach was used for population analysis. Monte Carlo simulations were used to generate 10,000 FXIII concentration-time profiles associated with incremental doses of 25, 30, 35, 40, 45 and 50 IU/kg of rFXIII. The probability of target attainment (PTA) of FXIII concentrations at thresholds of > 0.05, > 0.10 and > 0.15 IU/mL were calculated weekly, from days 7 to 49.

RESULTS

A total of 18 patients provided 99 FXIII concentrations; most patients (77.8%, 14/18) had severe FXIII deficiency. A two-compartment pharmacokinetic model with linear elimination from the central compartment best described rFXIII data. No covariates were associated with rFXIII disposition. Pharmacokinetic parameter estimates were 0.16 mL/h/kg for clearance, 57.35 mL/kg for volume of distribution at steady-state, and 11.72 days for elimination half-life. The standard 35 IU/kg dose resulted in PTAs of the pharmacodynamic thresholds of FXIII concentrations of > 0.05, > 0.10 and > 0.15 IU/mL at day 28 that were equal to 89.9%, 68.9% and 47.8%, respectively.

CONCLUSIONS

Intensive FXIII monitoring from day 14, and/or shortening the dosing interval between rFXIII administrations, should be considered to minimise the risk of bleeding.

A Proof of Concept of the Role of TDM-Based Clinical Pharmacological Advices in Optimizing Antimicrobial Therapy on Real-Time in Different Paediatric Settings

Introduction: Antimicrobial treatment is quite common among hospitalized children. The dynamic age-associated physiological variations coupled with the pathophysiological alterations caused by underlying illness and potential drug-drug interactions makes the implementation of appropriate antimicrobial dosing extremely challenging among paediatrics. Therapeutic drug monitoring (TDM) may represent a valuable tool for assisting clinicians in optimizing antimicrobial exposure. Clinical pharmacological advice (CPA) is an approach based on the correct interpretation of the TDM result by the MD Clinical Pharmacologist in relation to specific underlying conditions, namely the antimicrobial susceptibility of the clinical isolate, the site of infection, the pathophysiological characteristics of the patient and/or the drug-drug interactions of cotreatments. The aim of this study was to assess the role of TDM-based CPAs in providing useful recommendations for the real-time personalization of antimicrobial dosing regimens in various paediatric settings. Materials and methods: Paediatric patients who were admitted to different settings of the IRCCS Azienda Ospedaliero-Universitaria of Bologna, Italy (paediatric intensive care unit [ICU], paediatric onco-haematology, neonatology, and emergency paediatric ward), between January 2021 and June 2021 and who received TDM-based CPAs on real-time for personalization of antimicrobial therapy were retrospectively assessed. Demographic and clinical features, CPAs delivered in relation to different settings and antimicrobials, and type of dosing adjustments were extracted. Two indicators of performance were identified. The number of dosing adjustments provided over the total number of delivered CPAs. The turnaround time (TAT) of CPAs according to a predefined scale (optimal, <12 h; quasi-optimal, between 12-24 h; acceptable, between 24-48 h; suboptimal, >48 h). Results: Overall, 247 CPAs were delivered to 53 paediatric patients (mean 4.7 ± 3.7 CPAs/patient). Most were delivered to onco-haematological patients (39.6%) and to ICU patients (35.8%), and concerned mainly isavuconazole (19.0%) and voriconazole (17.8%). Overall, CPAs suggested dosing adjustments in 37.7% of cases (24.3% increases and 13.4% decreases). Median TAT was 7.5 h (IQR 6.1-8.8 h). Overall, CPAs TAT was optimal in 91.5% of cases, and suboptimal in only 0.8% of cases. Discussion: Our study provides a proof of concept of the helpful role that TDM-based real-time CPAs may have in optimizing antimicrobial exposure in different challenging paediatric scenarios.

Population pharmacokinetics of continuous infusion of piperacillin/tazobactam in very elderly hospitalized patients and considerations for target attainment against Enterobacterales and Pseudomonas aeruginosa

Continuous infusion (CI) piperacillin/tazobactam is frequently used to treat infections in very elderly patients. This study aimed to conduct a population pharmacokinetic analysis of CI piperacillin/tazobactam, and to identify optimal dosages for safe and effective probability of target attainment (PTA) against Enterobacterales and Pseudomonas aeruginosa. Non-linear mixed-effects modelling was performed with Pmetrics. Monte Carlo simulations assessed the steady-state concentration (Css) of increasing piperacillin/tazobactam regimens (from 2.25 to 18 g daily by continuous infusion). Permissible doses were defined as those associated with <10% probability of Css >157.2 mg/L. PTA at the pharmacodynamic targets of free plasma steady-state concentration (fCss)/minimum inhibitory concentration (MIC) ≥1 and ≥4 and cumulative fraction of response (CFR) against EUCAST MIC distribution were also calculated. A total of 141 patients (median age 85 years) provided 217 plasma piperacillin Css. Most patients (55.2%) had hospital-acquired pneumonia and intra-abdominal infections. A one-compartment pharmacokinetic model with parallel linear and Michaelis-Menten elimination best described piperacillin data. Creatinine clearance (CL_CR) was the covariate retained by the model. Pharmacokinetic estimates were 6.05 L/h for clearance and 3.39 mg/L for the Michaelis-Menten constant. Permissible doses were up to 4.5, 9, 11.25 and 13.5 g daily by continuous infusion for patients with CL_CR of 0-19, 20-39, 40-59 and 60-79 mL/min/1.73 m², respectively. At the clinical breakpoint of 8 mg/L, the permissible doses only achieved optimal PTA for fCss/MIC ≥1 in patients with CL_CR 20-79 mL/min/1.73 m². Optimal CFRs with the permissible doses were only attained against Escherichia coli and Proteus mirabilis. Permissible dosages and CL_CR should be considered for prescribing CI piperacillin/tazobactam in very elderly patients.

Real-time TDM-based optimization of continuous-infusion meropenem for improving treatment outcome of febrile neutropenia in oncohaematological patients: results from a prospective, monocentric, interventional study

Objectives

To assess the role that real-time therapeutic drug monitoring (TDM)-guided optimization of continuous-infusion (CI) meropenem may have in maximizing empirical treatment and in preventing breakthrough infection and/or colonization with carbapenem-resistant Enterobacteriaceae (CRE) among oncohaematological patients with febrile neutropenia (FN).

Methods

A monocentric, interventional, prospective study was conducted. The pharmacodynamic (PD) target was a steady-state meropenem concentration-to-MIC ratio (C_ss/MIC) of 4–8. The primary endpoint was 14 day all-cause mortality. The secondary endpoint was the prevalence of CRE colonization in rectal swabs of patients rehospitalized within 3 months.

Results

Among the 75 patients enrolled, most (56%) had AML, almost half (37/75, 49.3%) underwent HSCT and one-third (32%) received meropenem as monotherapy. Meropenem dosages were adjusted in 30.1% of TDM reassessments. Gram-negative infections were microbiologically documented in 20.0% of patients. All of the 12 patients having infections caused by in vitro meropenem-susceptible pathogens attained the desired PD target and were cured. Three patients had infections caused by in vitro meropenem-resistant pathogens. Two of these achieved a C_ss/MIC target of 1 and were cured; the other one achieved a suboptimal PD target (0.59) and died. The 14 day all-cause mortality (10.7%) was significantly associated, at multivariate regression, with HSCT (OR 0.086, 95% CI 0.008–0.936, P = 0.044) and with augmented renal clearance (OR 10.846, 95% CI 1.534–76.672, P = 0.017). None of the patients who had hospital readmissions in the 3 month follow-up (63/75) had CRE colonization in rectal swabs.

Conclusions

Real-time TDM-guided CI meropenem may be a useful approach for attaining adequate exposure and preventing CRE emergence in FN oncohaematological patients.

Comparative Population Pharmacokinetics of Darunavir in SARS-CoV-2 Patients vs. HIV Patients: The Role of Interleukin-6

Background

Darunavir is an anti-HIV protease inhibitor repurposed for SARS-CoV-2 treatment.

Objective

The aim of this study was to assess the population pharmacokinetics of darunavir in SARS-CoV-2 patients compared with HIV patients.

Methods

Two separate models were created by means of a nonlinear mixed-effect approach. The influence of clinical covariates on each basic model was tested and the association of significant covariates with darunavir parameters was assessed at multivariate regression and classification and regression tree (CART) analyses. Monte Carlo simulation assessed the influence of covariates on the darunavir concentration versus time profile.

Results

A one-compartment model well-described darunavir concentrations in both groups. In SARS-CoV-2 patients (n = 30), interleukin (IL)-6 and body surface area were covariates associated with darunavir oral clearance (CL/F) and volume of distribution (V_d), respectively; no covariates were identified in HIV patients (n = 25). Darunavir CL/F was significantly lower in SARS-CoV-2 patients compared with HIV patients (4.1 vs. 10.3 L/h; p < 0.001). CART analysis found that an IL-6 level of 18 pg/mL may split the SARS-CoV-2 population in patients with low versus high darunavir CL/F (mean ± standard deviation 3.47 ± 1.90 vs. 8.03 ± 3.24 L/h; proportion of reduction in error = 0.46). Median (interquartile range) darunavir CL/F was significantly lower in SARS-CoV-2 patients with IL-6 levels ≥ 18 pg/mL than in SARS-CoV-2 patients with IL-6 levels < 18 pg/mL or HIV patients (2.78 [2.16–4.47] vs. 7.24 [5.88–10.38] vs. 9.75 [8.45–13.79] L/h, respectively; p < 0.0001). Increasing IL-6 levels affected darunavir concentration versus time simulated profiles. We hypothesized that increases in IL-6 levels associated with severe SARS-CoV-2 disease may downregulate the cytochrome P450 (CYP) 3A4-mediated metabolism of darunavir.

Conclusions

This is a proof-of-concept of SARS-CoV-2 disease–drug interactions, and may support the need for optimal dose selection of sensitive CYP3A4 substrates in severe SARS-CoV-2 patients.

Electronic supplementary material

The online version of this article (10.1007/s40262-020-00933-8) contains supplementary material, which is available to authorized users.

Proactive therapeutic drug monitoring (TDM) may be helpful in managing long-term treatment with linezolid safely: findings from a monocentric, prospective, open-label, interventional study

BACKGROUND

Thrombocytopenia may be a dose-dependent adverse effect of linezolid therapy.

OBJECTIVES

To assess whether proactive therapeutic drug monitoring (TDM) could be helpful in preventing and/or in recovering from the occurrence of linezolid-induced thrombocytopenia during long-term treatment.

METHODS

This was a monocentric, prospective, open-label, interventional study conducted between June 2015 and December 2017 among adult patients receiving >10 days of linezolid therapy and undergoing proactive TDM (desired trough level 2-8 mg/L) and platelet count assessment at day 3-5 and then once weekly up to the end of treatment.

RESULTS

Sixty-one patients were included. Twenty-eight (45.9%) always had desired trough level (group A) and 33 (54.1%) experienced linezolid overexposure (group B) [29/33 transiently (subgroup B1) and 4/33 persistently (subgroup B2)]. No patient experienced linezolid underexposure. Median duration of treatment for the different groups ranged between 19 and 54 days. Thrombocytopenia occurred overall in 14.8% of cases (9/61). The incidence rate of thrombocytopenia was significantly lower (P=0.012) in both group A (10.7%; 3/28) and subgroup B1 (10.3%; 3/29) than in subgroup B2 (75.0%; 3/4). Thrombocytopenic patients belonging to both group A and group B1 recovered from thrombocytopenia without the need for discontinuing therapy. Multivariate linear regression analysis revealed that thrombocytopenia was independently associated with baseline platelet count and with median linezolid trough concentrations.

CONCLUSIONS

Proactive TDM of linezolid may be beneficial either in preventing or in recovering from dose-dependent thrombocytopenia, even when treatment lasts for more than 28 days. Larger prospective studies are warranted to confirm our findings.

Covid-19 and the role of smoking: the protocol of the multicentric prospective study COSMO-IT (COvid19 and SMOking in ITaly)

The emergency caused by Covid-19 pandemic raised interest in studying lifestyles and comorbidities as important determinants of poor Covid-19 prognosis. Data on tobacco smoking, alcohol consumption and obesity are still limited, while no data are available on the role of e-cigarettes and heated tobacco products (HTP). To clarify the role of tobacco smoking and other lifestyle habits on COVID-19 severity and progression, we designed a longitudinal observational study titled COvid19 and SMOking in ITaly (COSMO-IT). About 30 Italian hospitals in North, Centre and South of Italy joined the study. Its main aims are: 1) to quantify the role of tobacco smoking and smoking cessation on the severity and progression of COVID-19 in hospitalized patients; 2) to compare smoking prevalence and severity of the disease in relation to smoking in hospitalized COVID-19 patients versus patients treated at home; 3) to quantify the association between other lifestyle factors, such as e-cigarette and HTP use, alcohol and obesity and the risk of unfavourable COVID-19 outcomes. Socio-demographic, lifestyle and medical history information will be gathered for around 3000 hospitalized and 700-1000 home-isolated, laboratory-confirmed, COVID-19 patients. Given the current absence of a vaccine against SARS-COV-2 and the lack of a specific treatment for COVID-19, prevention strategies are of extreme importance. This project, designed to highly contribute to the international scientific debate on the role of avoidable lifestyle habits on COVID-19 severity, will provide valuable epidemiological data in order to support important recommendations to prevent COVID-19 incidence, progression and mortality.

Population Pharmacokinetics of Continuous-Infusion Meropenem in Febrile Neutropenic Patients with Hematologic Malignancies: Dosing Strategies for Optimizing Empirical Treatment against Enterobacterales and P. aeruginosa

A population pharmacokinetic analysis of continuous infusion (CI) meropenem was conducted in a prospective cohort of febrile neutropenic (FN) patients with hematologic malignancies. A non-parametric approach with Pmetrics was used for pharmacokinetic analysis and covariate evaluation. Monte Carlo simulations were performed for identifying the most appropriate dosages for empirical treatment against common Enterobacterales and P. aeruginosa. The probability of target attainment (PTA) of steady-state meropenem concentration (Css)-to-minimum inhibitory concentration (MIC) ratio (Css/MIC) ≥1 and ≥4 at the European Committee on Antimicrobial Susceptibility Testing (EUCAST) clinical breakpoint of 2 mg/L were calculated. Cumulative fraction of response (CFR) against Enterobacterales and P. aeruginosa were assessed as well. PTAs and CFRs ≥ 90% were considered optimal. A total of 61 patients with 178 meropenem Css were included. Creatinine clearance (CL_CR) was the only covariate associated with meropenem clearance. Monte Carlo simulations showed that dosages of meropenem ranging between 1 g q8h and 1.25 g q6h by CI may grant optimal PTAs of Css/MIC ≥4 at the EUCAST clinical breakpoint. Optimal CFRs may be granted with these dosages against the Enterobacterales at Css/MIC ≥ 4 and against P. aeruginosa at Css/MIC ≥ 1. When dealing against P. aeruginosa at Css/MIC ≥ 4, only a dosage of 1.5 g q6h by CI may grant quasi-optimal CFR (around 80–87%). In conclusion, our findings suggest that dosages of meropenem ranging between 1 g q8h and 1.25 g q6h by CI may maximize empirical treatment against Enterobacterales and P. aeruginosa among FN patients with hematologic malignancies having different degree of renal function.

Population pharmacokinetics of continuous-infusion ceftazidime in febrile neutropenic children undergoing HSCT: implications for target attainment for empirical treatment against Pseudomonas aeruginosa

OBJECTIVES

To conduct a population pharmacokinetic analysis of continuous-infusion ceftazidime in a retrospective cohort of paediatric HSCT patients who were empirically treated for febrile neutropenia (FN) and who underwent therapeutic drug monitoring of ceftazidime steady-state plasma concentrations (Css) for optimization of drug exposure.

METHODS

A non-parametric approach with Pmetrics was used for pharmacokinetic analysis and covariate evaluation. Monte Carlo simulations were performed to calculate the PTA of the pharmacodynamic determinant of efficacy (Css/MIC ≥4) against Pseudomonas aeruginosa with continuous-infusion ceftazidime dosages of 1-6 g daily. The Css safety threshold was arbitrarily placed at 100 mg/L and advisable dosages were used.

RESULTS

A total of 46 patients with 70 ceftazidime Css values were included. Estimated glomerular filtration rate (eGFR) and body surface area were the covariates associated with drug clearance. At the EUCAST clinical breakpoint of 8 mg/L, simulations showed that continuous-infusion ceftazidime dosages of 4-6 g daily attained optimal PTAs (>90%) across most of 16 different clinical scenarios based on four classes of eGFR (50-145, 145.1-200, 200.1-286 and 286.1-422 mL/min/1.73 m2) and body surface area (0.30-0.64, 0.65-0.88, 0.89-1.34 and 1.35-1.84 m2). In patients with body surface area 0.30-0.64 m2 and eGFR ≤200 mL/min/1.73 m2 the advisable dose of 3 g daily allowed only suboptimal PTAs (<75%). The cumulative fraction of response against MIC distribution of P. aeruginosa was >87%.

CONCLUSIONS

Continuous-infusion ceftazidime dosages ranging from 3 to 6 g daily according to different classes of eGFR and body surface area may allow optimized empirical treatment of P. aeruginosa infections in paediatric HSCT patients with FN.

Successful and safe long-term treatment of cerebral aspergillosis with high-dose voriconazole guided by therapeutic drug monitoring

We report the case of a patient who had cerebral aspergillosis after otorhinolaryngologic surgery and who was successfully and safely treated with high-dose voriconazole (200 mg q6h) for more than 1 year thanks to a TDM-guided approach coupled with pharmacological review and with genotyping of CYP2C19 polymorphisms. The findings support the idea that personalized medicine based on TDM coupled with the need of avoiding drug-drug interactions may be helpful for maximizing the net benefit (probability of efficacy vs. probability of adverse events) of voriconazole in the management of long-term treatment of cerebral aspergillosis.

Co-administration of proton pump inhibitors and/or of steroids may be a risk factor for low trough concentrations of posaconazole delayed-released tablets in adult patients with haematological malignancies

AIMS

The aim of this study was to determine clinical variables associated with posaconazole exposure among adult patients with haematological malignancies who received posaconazole tablets for prophylaxis of invasive fungal infections (IFIs).

METHODS

The study population included adult patients with haematological malignancies who received posaconazole delayed-release tablets for prophylaxis of IFIs after induction chemotherapy for acute leukaemia or graft-versus-host-disease (GVHD) complicating hematopoietic stem cell transplantation (HSCT) in the period January 2016-December 2017.

RESULTS

Sixty-six consecutive patients with 176 posaconazole C_min were included for evaluation in the study. Subtherapeutic posaconazole concentrations (< 0.7 mg l^-1 ) were observed at least once in 33.3% of patients (22/66), and overall in 17.0% of therapeutic drug monitoring (TDM) episodes (30/176). At multilevel linear regression, use of PPIs (P = 0.008), use of intermediate or high dose steroids (>0.7 mg kg^-1 daily) (P = 0.022) and male gender (P = 0.025) were significantly associated with decreased C_min , whereas time from starting therapy (P = 0.032) was associated with increased C_min in our patient population.

CONCLUSION

Posaconazole exposure during treatment with delayed-released tablet formulation may be affected by the use of PPIs and/or of intermediate or high dose steroids.

Population pharmacokinetics of fluconazole in liver transplantation: implications for target attainment for infections with Candida albicans and non-albicans spp

OBJECTIVES

The study aims to assess the population pharmacokinetics of fluconazole and the adequacy of current dosages and breakpoints against Candida albicans and non-albicans spp. in liver transplant (LT) patients.

PATIENTS AND METHODS

Patients initiated i.v. fluconazole within 1 month from liver transplantation (LTx) for prevention or treatment of Candida spp. infections. Multiple assessments of trough and peak plasma concentrations of fluconazole were undertaken in each patient by means of therapeutic drug monitoring. Monte Carlo simulations were performed to define the probability of target attainment (PTA) with a loading dose (LD) of 400, 600, and 800 mg at day 1, 7, 14, and 28 from LTx, followed by a maintenance dose (MD) of 100, 200, and 300 mg daily of the pharmacokinetic/pharmacodynamic target of AUC_24h/MIC ratio ≥ 55.2.

RESULTS

Nineteen patients were recruited. A two-compartment model with first-order intravenous input and first-order elimination was developed. Patient's age and time elapsed from LTx were the covariates included in the final model. At an MIC of 2 mg/L, a LD of 600 mg was required for optimal PTAs between days 1 and 20 from LTx, while 400 mg was sufficient from days 21 on. A MD of 200 mg was required for patients aged 40-49 years old, while a dose of 100 mg was sufficient for patients aged ≥ 50 years.

CONCLUSIONS

Fluconazole dosages of 100-200 mg daily may ensure optimal PTA against C. albicans, C. parapsilosis, and C. tropicalis. Higher dosages are required against C. glabrata. Estimated creatinine clearance is not a reliable predictor of fluconazole clearance in LT patients.

Population pharmacokinetics and dosing considerations for the use of daptomycin in adult patients with haematological malignancies

Objectives

To assess the population pharmacokinetics (popPK) of daptomycin at the conventional dose of 6 mg/kg/day in a cohort of oncohaematological patients.

Methods

Patients underwent serial blood sampling on day 3 of therapy (before dosing and at 0, 0.5, 1, 2, 3, 5, 7, 9 and 12 h after dosing) to assess the pharmacokinetic profile of daptomycin. PopPK and Monte Carlo simulation were performed to define the probability of target attainment (PTA) with 6, 8, 10 and 12 mg/kg/day of the pharmacokinetic/pharmacodynamic target of AUC 24 /MIC >1081.

Results

Thirty patients were recruited. A two-compartment open model with first-order intravenous input and first-order elimination was developed. Estimated creatinine clearance (CL CR ), serum albumin concentration (Alb) and presence of AML were covariates included in the final model. Monte Carlo simulation showed that the conventional 6 mg/kg/day dose resulted in optimal PTAs (≥80%) in the presence of pathogens with an MIC up to 0.5 mg/L only in patients with CL CR 50-100 mL/min/1.73 m 2 , Alb 26-45 g/L and a haematological diagnosis other than AML. Conversely, higher dosages, up to 12 mg/kg/day, were needed to achieve this goal in the presence of pathogens with an MIC of 0.25-0.5 mg/L in all of the other tested scenarios. In patients with CL CR 101-150 mL/min/1.73 m 2 and Alb 15-25 g/L, suboptimal PTAs (<60%) were predicted even with 12 mg/kg/day dosing .

Conclusions

Our study provides a strong rationale for considering daptomycin dosages of ≥ 8 mg/kg/day in several clinical scenarios for oncohaematological patients. In some of these scenarios therapeutic drug monitoring could be a useful adjunct for optimized care.

[Pharmacogenetics of immunosuppressants]

Individualized drug therapy with immunosuppressants is an hot topic in transplantation. Therapeutic drug monitoring (TDM) is currently utilized to guide therapy, but toxic or subtherapeutic concentrations can only be identified after the drug is administered. Pharmacogenetics, by studying the relationship between a human genetic difference and drug response, holds great promises in optimizing immunosuppressive drug prescribing for solid organ transplantation.Nevertheless, a complete translation in the clinic has lagged behind,due to the overall complexity of the genetic approach, and the lack of sound evidence of identified genetic polymorphisms in ultimately explaining drug exposure. However, for tacrolimus it is likely that a genotype-based drug dosage can benefit patient outcome, while for cyclosporine data appear less convincing. Mycophenolic acid undergoes a complex metabolic pathway and various genes affecting drug disposition are under investigations, with promising results for some of them of being of value in aiding clinicians in decision making. Finally, for sirolimus and everolimus the lack of data and the absence of large prospective studies do not allow to draw any conclusion.