Pharmacokinetics of Doripenem in Infected Patients Treated Within and Outside the Intensive Care Unit

A Systematic Review on Antimicrobial Pharmacokinetic Differences between Asian and Non-Asian Adult Populations

While the relevance of inter-ethnic differences to the pharmacokinetic variabilities of antimicrobials has been reported in studies recruiting healthy subjects, differences in antimicrobial pharmacokinetics between Asian and non-Asian patients with severe pathologic conditions require further investigation. For the purpose of describing the potential differences in antimicrobial pharmacokinetics between Asian and non-Asian populations, a systematic review was performed using six journal databases and six theses/dissertation databases (PROSPERO record CRD42018090054). The pharmacokinetic data of healthy volunteers and non-critically ill and critically ill patients were reviewed. Thirty studies on meropenem, imipenem, doripenem, linezolid, and vancomycin were included in the final descriptive summaries. In studies recruiting hospitalised patients, inconsistent differences in the volume of distribution (V_d) and drug clearance (CL) of the studied antimicrobials between Asian and non-Asian patients were observed. Additionally, factors other than ethnicity, such as demographic (e.g., age) or clinical (e.g., sepsis) factors, were suggested to better characterise these pharmacokinetic differences. Inconsistent differences in pharmacokinetic parameters between Asian and non-Asian subjects/patients may suggest that ethnicity is not an important predictor to characterise interindividual pharmacokinetic differences between meropenem, imipenem, doripenem, linezolid, and vancomycin. Therefore, the dosing regimens of these antimicrobials should be adjusted according to patients' demographic or clinical characteristics that can better describe pharmacokinetic differences.

Pharmacokinetics and Safety of Doripenem in Healthy Chinese Subjects and Monte Carlo Dosing Simulations

The aim of this study was to investigate the pharmacokinetics (PK) of doripenem in healthy Chinese subjects and evaluate the optimal dosage regimens of doripenem. A randomized, single-dose, three-period, self-crossover controlled extended-infusion clinical trial was conducted with 12 healthy Chinese subjects. Plasma and urine samples were collected to determine doripenem concentrations. Non-compartmental and population PK analysis were performed to characterize the PK of doripenem. The Monte Carlo simulation was employed to optimize dosing regimens based on the probability of target attainment of doripenem against pathogens with different minimum inhibitory concentrations (MIC). All 12 healthy Chinese subjects completed the study, and the doripenem was well tolerated. The study showed linearity relationships in the peak plasma concentration and the area under the concentration-time curve after intravenous infusion of doripenem from 0.25 g to 1.0 g. The cumulative urinary recovery rate of doripenem was 68.1–72.0% within 24 h. PPK modeling showed a two-compartmental model, with first-order elimination presenting the best fit for doripenem PK. Monte Carlo simulation results showed that 1.0 g q12h or 0.5 g q8h was an optimal regimen for pathogens susceptible to doripenem (MIC ≤ 1 mg/L); while high dose and extended infusion (1 g, q8h, 4 h infusion) was proposed for unsusceptible pathogens (2 ≤ MIC ≤ 8 mg/L). In the dose range of 0.25 to 1.0 g, doripenem showed linear pharmacokinetics. Doripenem at 1.0 g with a prolonged infusion time of 4 h was predicted to be effective against pathogens with MICs as high as 8 mg/L.

Pharmacokinetics of Doripenem in Healthy Koreans and Monte Carlo Simulations to Explore Optimal Dosage Regimens in Patients With Normal and Enhanced Renal Function

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Background:

Dose adjustment is often required in patients with normal or enhanced renal function. The aim of this study is to investigate the pharmacokinetic (PK) properties of doripenem and explore optimal dosing regimens in patients with normal or enhanced renal function according to various minimum inhibitory concentrations (MICs).

Methods:

The authors conducted a clinical trial and analyzed PK samples in 11 healthy Korean subjects applying noncompartmental analysis and a population approach. The population PK parameter estimates were used in Monte Carlo simulations to explore optimal dosing regimens for a probability of target attainment of 90% at 40% fT_MIC (free drug concentrations above MIC).

Results:

The time course of doripenem concentrations was well described by a 2-compartment model. The population typical values of clearance and steady-state volume were 22.9 L/h and 19.1 L, respectively, and were consistent with our noncompartmental analysis results. When the MIC was greater than 1 mcg/mL, at least increasing the dose or prolonging the infusion time was essential in patients with normal or enhanced renal function.

Conclusions:

These results suggest that dosage adjustment such as increasing the dose or lengthening the infusion time should be considered in patients with normal or enhanced renal function.

Impact of Real-Time Therapeutic Drug Monitoring on the Prescription of Antibiotics in Burn Patients Requiring Admission to the Intensive Care Unit

As pharmacokinetics after burn trauma are difficult to predict, we conducted a 3-year prospective, monocentric, randomized, controlled trial to determine the extent of under- and overdosing of antibiotics and further evaluate the impact of systematic therapeutic drug monitoring (TDM) with same-day real-time dose adaptation to reach and maintain antibiotic concentrations within the therapeutic range. Forty-five consecutive burn patients treated with antibiotics were prospectively screened. Forty fulfilled the inclusion criteria; after one patient refused to participate and one withdrew consent, 19 were randomly assigned to an intervention group (patients with real-time antibiotic concentration determination and subsequent adaptations) and 19 were randomly assigned to a standard-of-care group (patients with antibiotic administration at the physician's discretion without real-time TDM). Seventy-three infection episodes were analyzed. Before the intervention, only 46/82 (56%) initial trough concentrations fell within the range. There was no difference between groups in the initial trough concentrations (adjusted hazard ratio = 1.39 [95% confidence interval {CI}, 0.81 to 2.39], P = 0.227) or the time to reach the target. However, thanks to real-time dose adjustments, the trough concentrations of the intervention group remained more within the predefined range (57/77 [74.0%] versus 48/85 [56.5%]; adjusted odd ratio [OR] = 2.34 [95% CI, 1.17 to 4.81], P = 0.018), more days were spent within the target range (193 days/297 days on antibiotics [65.0%] versus 171 days/311 days in antibiotics [55.0%]; adjusted OR = 1.64 [95% CI, 1.16 to 2.32], P = 0.005), and fewer results were below the target trough concentrations (25/118 [21.2%] versus 44/126 [34.9%]; adjusted OR = 0.47 [95% CI, 0.26 to 0.87], P = 0.015). No difference in infection outcomes was observed between the study groups. Systematic TDM with same-day real-time dose adaptation was effective in reaching and maintaining therapeutic antibiotic concentrations in infected burn patients, which prevented both over- and underdosing. A larger multicentric study is needed to further evaluate the impact of this strategy on infection outcomes and the emergence of antibiotic resistance during long-term burn treatment. (This study was registered with the ClinicalTrials.gov platform under registration no. NCT01965340 on 27 September 2013.).

Population Pharmacokinetic Analysis of Doripenem after Intravenous Infusion in Korean Patients with Acute Infections

We investigated the population pharmacokinetics (PK) of doripenem in Korean patients with acute infections and determined an appropriate dosing regimen using a Monte Carlo simulation for predicting pharmacodynamics (PD). Patients (n = 37) with a creatinine clearance (CL_CR) of 20 to 50 ml/min or >50 ml/min who received a 250-mg or 500-mg dose of doripenem over the course of 1 h every 8 h, respectively, were included in this study. Blood samples were taken predosing and 0 h, 0.5 h, and 4 to 6 h after the fourth infusion. A nonlinear mixed-effect modeling tool was used for the PK analysis and pharmacodynamic simulation; doripenem PK were well described by a one-compartment model. The population mean values of the body weight (WT)-normalized clearance (CL/WT) and the body weight-normalized volume of distribution (V/WT) were 0.109 liter/h/kg of body weight (relative standard error, 9.197%) and 0.280 liter/kg (relative standard error, 9.56%), respectively. Doripenem CL was significantly influenced by CL_CR The proposed equation to estimate doripenem CL in Korean patients was CL/WT = 0.109 × WT × (CL_CR/57)^0.688, where CL/WT is in liters per hour per kilogram. CL in Korean patients was expected to be lower than that in Caucasian patients, regardless of renal function. The Monte Carlo simulation showed that 90% attainment of target PK/PD magnitudes could be achieved with the usual dosing regimens when the MIC was ≤1 mg/liter. However, prolonged infusions (4 h) should be considered, especially when patients have augmented renal function and for patients infected with pathogens with a high MIC. Our results provide an individualized doripenem dosing regimen for patients with various renal functions and for patients infected with bacteria with decreased susceptibility.

Pharmacokinetic and Pharmacodynamic Evaluation of Doripenem in Critically Ill Trauma Patients with Sepsis

BACKGROUND

Doripenem is approved by the Food and Drug Administration for the treatment of patients with complicated intra-abdominal infections and complicated urinary tract infections. While studies have described the pharmacokinetics/pharmacodynamics (PK/PD) of doripenem in the critically ill, no study has described the probability of target attainment profile among trauma patients with sepsis.

PATIENTS AND METHODS

This study was a prospective, open-label, pharmacokinetic study in the surgical intensive care unit (SICU) at Grady Health System. Thirty trauma patients with sepsis admitted to the SICU received doripenem 1 g infused over 4 hours every 8 hours for three doses. Blood samples were taken just before and after the third dose. A two-compartment model was fit to the data using non-parametric population PK modeling software. Embedded with the final PK model, a Monte Carlo Simulations (MCS) was performed to determine the PK/PD profile of doripenem 1 g, infused over 4 hours, every 8 hours after administration of the first and fourth doses.

RESULTS

Overall, the model fit the data well, and mean (standard deviation) clearance and volume of the central compartment were 16.9 (11.4) L/h and 28.5 (16.0) L, respectively. In the MCS analyses, doripenem 1 g, infused over 4 hours, administered every 8 hours, conferred >90% probabilities of achieving 30-50% time greater than the minimum inhibitory concentration (30-50% T>MIC) for MICs ≤2 mg/L after infusion of both the first and fourth doses. The MCS indicated that more intensive doripenem dosing schemes should be considered for organisms with MIC values in excess of 2 mg/L.

CONCLUSIONS

This is the first study to describe the doripenem PK/PD in critically ill patients with trauma. Among these patients, the MCS analyses suggest that current dosing strategies may be ineffective when the MIC value for the infecting pathogen is expected to be above 2 mg/L.

Population Pharmacokinetics and Pharmacodynamics of Doripenem in Obese, Hospitalized Patients

Background: Doripenem population pharmacokinetics and dosing recommendations are limited in obesity. Objective: To evaluate the population pharmacokinetics and pharmacodynamics of doripenem in obese patients. Methods: Hospitalized adults with a body mass index (BMI) ≥ 40 kg/m2 or total body weight (TBW) ≥45.5 kg over their ideal body weight received doripenem 500 mg every 8 hours, infused over 1 hour. Population pharmacokinetic analyses were performed using NONMEM, and Monte Carlo simulations were performed for 5 intermittent and prolonged infusion dosing regimens to calculate probability of target attainment (PTA) at 40% and 100% fT>MIC (free drug concentrations above the minimum inhibitory concentration). Results: A total of 20 patients were studied: 10 in an intensive care unit (ICU) and 10 in a non-ICU. A 2-compartment model with first-order elimination best described the serum concentration-time data. Doripenem clearance (CL) was significantly associated with creatinine CL (CRCL), volume of the central compartment with TBW and ICU residence, and volume of the peripheral compartment with TBW ( P < 0.05). Using 40% fT>MIC, PTA was >90% for all simulated dosing regimens at MICs ≤2 mg/L. Using 100% fT>MIC, prolonged infusions of 1 g every 6 hours and 2 g every 8 hours achieved >90% PTA at MICs ≤2 mg/L. Conclusions: CRCL, ICU residence, and TBW are significantly associated with doripenem pharmacokinetics. Currently approved dosing regimens provide adequate pharmacodynamic exposures at 40% fT>MIC for susceptible bacteria in obese patients. However, prolonged infusions of larger doses are needed if a higher pharmacodynamic target is desired.

Population Pharmacokinetics of Doripenem in Critically Ill Patients with Sepsis in a Malaysian Intensive Care Unit

Doripenem has been recently introduced in Malaysia and is used for severe infections in the intensive care unit. However, limited data currently exist to guide optimal dosing in this scenario. We aimed to describe the population pharmacokinetics of doripenem in Malaysian critically ill patients with sepsis and use Monte Carlo dosing simulations to develop clinically relevant dosing guidelines for these patients. In this pharmacokinetic study, 12 critically ill adult patients with sepsis receiving 500 mg of doripenem every 8 h as a 1-hour infusion were enrolled. Serial blood samples were collected on 2 different days, and population pharmacokinetic analysis was performed using a nonlinear mixed-effects modeling approach. A two-compartment linear model with between-subject and between-occasion variability on clearance was adequate in describing the data. The typical volume of distribution and clearance of doripenem in this cohort were 0.47 liters/kg and 0.14 liters/kg/h, respectively. Doripenem clearance was significantly influenced by patients' creatinine clearance (CL(CR)), such that a 30-ml/min increase in the estimated CL(CR) would increase doripenem CL by 52%. Monte Carlo dosing simulations suggested that, for pathogens with a MIC of 8 mg/liter, a dose of 1,000 mg every 8 h as a 4-h infusion is optimal for patients with a CL(CR) of 30 to 100 ml/min, while a dose of 2,000 mg every 8 h as a 4-h infusion is best for patients manifesting a CL(CR) of >100 ml/min. Findings from this study suggest that, for doripenem usage in Malaysian critically ill patients, an alternative dosing approach may be meritorious, particularly when multidrug resistance pathogens are involved.

Doripenem population pharmacokinetics and dosing requirements for critically ill patients receiving continuous venovenous haemodiafiltration

OBJECTIVES

Doripenem is a newer carbapenem with little data available to guide effective dosing during renal replacement therapy in critically ill patients. The objective of this study was to determine the population pharmacokinetics of doripenem in critically ill patients undergoing continuous venovenous haemodiafiltration (CVVHDF) for acute kidney injury (AKI).

METHODS

This was an observational pharmacokinetic study in 12 infected critically ill adult patients with AKI undergoing CVVHDF and receiving 500 mg of doripenem intravenously every 8 h as a 60 min infusion. Serial blood samples were taken on 2 days of treatment and used for population pharmacokinetic analysis with S-ADAPT.

RESULTS

The median (IQR) age was 62 (53-71) years, the median (IQR) weight was 77 (67-96) kg and the median (IQR) APACHE II score was 29 (19-32). The median blood, dialysate and replacement fluid rates were 200, 1000 and 1000 mL/h, respectively. A two-compartment linear model with doripenem clearance described by CVVHDF, renal or non-renal mechanisms was most appropriate. The mean value for total doripenem clearance was 4.46 L/h and volume of distribution was 38.0 L. Doripenem clearance by CVVHDF was significantly correlated with the replacement fluid flow rate and accounted for ∼30%-37% of total clearance. A dose of 500 mg intravenously every 8 h achieved favourable pharmacokinetic/pharmacodynamics for all patients up to an MIC of 4 mg/L.

CONCLUSIONS

This is the first paper describing the pharmacokinetics/pharmacodynamics of doripenem in critically ill patients with AKI receiving CVVHDF. A dose of 500 mg intravenously every 8 h was appropriate for our CVVHDF settings for infections caused by susceptible bacteria.