Accumulation of the solvent vehicle sulphobutylether beta cyclodextrin sodium in critically ill patients treated with intravenous voriconazole under renal replacement therapy

Management of Invasive Infections in Diabetes Mellitus: A Comprehensive Review

Patients with diabetes often have more invasive infections, which may lead to an increase in morbidity. The hyperglycaemic environment promotes immune dysfunction (such as the deterioration of neutrophil activity, antioxidant system suppression, and compromised innate immunity), micro- and microangiopathies, and neuropathy. A greater number of medical interventions leads to a higher frequency of infections in diabetic patients. Diabetic individuals are susceptible to certain conditions, such as rhino-cerebral mucormycosis or aspergillosis infection. Infections may either be the primary symptom of diabetes mellitus or act as triggers in the intrinsic effects of the disease, such as diabetic ketoacidosis and hypoglycaemia, in addition to increasing morbidity. A thorough diagnosis of the severity and origin of the infection is necessary for effective treatment, which often entails surgery and extensive antibiotic use. Examining the significant issue of infection in individuals with diabetes is crucial. Comprehensive research should examine why infections are more common amongst diabetics and what the preventive treatment strategies could be.

COVID-19-associated pulmonary aspergillosis in hemodialysis patients

Background

Coronavirus disease 2019 (COVID-19)-associated pulmonary aspergillosis (CAPA) is a fatal complication in the general population. However, there are few reports on CAPA in patients undergoing hemodialysis (HD).

Methods

This retrospective observational cohort study was conducted at a single center between December 2020 and June 2021. We enrolled 21 HD patients with COVID-19 undergoing treatment and divided them into two groups, CAPA and non-CAPA (COVID-19 with and without pulmonary aspergillosis), and evaluated their characteristics, clinical outcomes and comorbidities.

Results

The log-rank test revealed that the 90-day survival rate after the initiation of treatment for COVID-19 was significantly lower in the CAPA (n = 6) than in the non-CAPA group (n = 15) (P = 0.0002), and the 90-day mortality rates were 66.6% and 0% in the CAPA and non-CAPA groups, respectively. In the CAPA group, four patients died due to respiratory failure (on Days 6 and 20), gastrointestinal bleeding (Day 8) and sepsis (Day 33); the reverse transcription-polymerase chain reaction (RT-PCR) for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remained positive when they died. The remaining two patients survived and the negative conversion of RT-PCR for SARS-CoV-2 was confirmed on Days 10 and 15. The negative conversion of serum (1, 3)-β-d-glucan (BDG) was confirmed on Day 15 in one patient; the BDG remained positive on Day 64 in the other.

Conclusions

CAPA is a fatal complication in HD patients and the general population. Therefore, clinicians should consider the possibility of testing for CAPA in patients undergoing HD. Mycological workups may be helpful for the early detection of CAPA.

Liposomal remdesivir inhalation solution for targeted lung delivery as a novel therapeutic approach for COVID-19

Strong infectivity enables coronavirus disease 2019 (COVID-19) to rage throughout the world. Moreover, the lack of drugs with definite therapeutic effects further aggravates the spread of the pandemic. Remdesivir is one of the most promising anti-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) drugs. However, the limited clinical effects make its therapeutic effect controversial, which may result from the poor accumulation and activation of remdesivir in the lung. Therefore, we developed lyophilized remdesivir liposomes (Rdv-lips) which can be reconstituted as liposomal aerosol for pulmonary delivery to improve the in vivo behavior of existing remdesivir cyclodextrin conclusion compound (Rdv-cyc) injections. Liposome encapsulation endowed remdesivir with much higher solubility and better biocompatibility. The in vitro liposomal aerosol characterization demonstrated that Rdv-lips possessed a mass median aerodynamic diameter of 4.118 µm and fine particle fraction (<5 µm) higher than 50%, indicating good pulmonary delivery properties. Compared to the Rdv-cyc intravenous injection group, the Rdv-lips inhalation group displayed a nearly 100-fold increase in the remdesivir-active metabolite nucleotide triphosphate (NTP) concentration and better NTP accumulation in the lung than the Rdv-cyc inhalation group. A faster transition from remdesivir to NTP of Rdv-lips (inhalation) could also be observed due to better cell uptake. Compared to other preparations, the superiority of Rdv-lips was further evidenced by the results of an in vivo safety study, with little possibility of inducing inflammation. In conclusion, Rdv-lips for pulmonary delivery will be a potent formulation to improve the in vivo behavior of remdesivir and exert better therapeutic effects in COVID-19 treatment.

The Safe Administration of Remdesivir in a Patient with Acute Kidney Injury Requiring Hemodialysis

Remdesivir is a nucleoside analog prodrug with broad-spectrum antiviral activity, including against coronaviruses. This has prioritized the inclusion of remdesivir in coronavirus disease 2019 (COVID-19) clinical trials. The United States Food and Drug Administration has granted emergency use authorization for remdesivir. This emergency use authorization does not recommend the use of remdesivir in patients with estimated glomerular filtration rate (eGFR) less than 30 mL/min unless the benefits outweigh the risks. To date, there are no studies and scant information in the literature evaluating remdesivir utilization in patients with eGFR less than 30 mL/min or receiving hemodialysis. With little utilization data for patients with acute or chronic kidney injury, remdesivir may not be considered, leaving this patient population without the opportunity of a potentially beneficial treatment option. We present a case of one patient with eGFR less than 30 mL/min that required hemodialysis in which remdesivir was safely initiated, with therapy completed without any serious adverse events.

Kolliphor® HS 15-cyclodextrin Complex for the Delivery of Voriconazole: Preparation, Characterization, and Antifungal Activity

BACKGROUND

This study aimed to reduce the amount of sulfobutylether-β-cyclodextrin (SBECD) used in the marketed voriconazole injections to meet the clinical needs of patients with moderate-to-severe renal impairment (creatinine clearance rate <50 mL/min).

OBJECTIVE

This study found that the surfactant Kolliphor® HS 15 (HS 15) and SBECD had significant synergistic effects on solubilizing voriconazole, and a novel voriconazole complex delivery system (VRC-CD/HS 15) was established.

METHODS

The complex system was characterized, and its antifungal activity was studied by dynamic light scattering, dialysis bag method, disk diffusion, and broth microdilution.

RESULTS

Compared with the control, its encapsulation efficiency (90.07±0.48%), drug loading (7.37±0.25%) and zeta potential (-4.36±1.37 mV) were increased by 1.54%, 41.19%, and 296.36%, respectively; its average particle size (13.92±0.00 nm) was reduced by 15.69%, so the complex system had better stability. Simultaneously, its drug release behavior was similar to that of the control, and it was a first-order kinetic model. Antifungal studies indicated that the complex system had noticeable antifungal effects. With the increase of drug concentration, the inhibition zone increased. The minimum inhibitory concentrations of the complex system against Cryptococcus neoformans, Aspergillus niger and Candida albicans were 0.0313 μg/mL, 1 μg/mL and 128 μg/mL, respectively.

CONCLUSION

It showed a significant inhibitory effect on C. neoformans and had a visible therapeutic effect on Kunming mice infected with C. neoformans. Consequently, VRC-CD/HS 15 had better physicochemical properties and still had an apparent antifungal effect, and was promising as a potential alternative drug for clinical application.

Pharmacokinetics and Pharmacodynamics of Anti-infective Agents during Continuous Veno-venous Hemofiltration in Critically Ill Patients: Lessons Learned from an Ancillary Study of the IVOIRE Trial

BACKGROUND

Hemofiltration rate, changes in blood and ultrafiltration flow, and discrepancies between the prescribed and administered doses strongly influence pharmacokinetics (PK) and pharmacodynamics (PD) of antimicrobial agents during continuous veno-venous hemofiltration (CVVH) in critically ill patients.

METHODS

Ancillary data were from the prospective multicenter IVOIRE (hIgh VOlume in Intensive caRE) study. High volume (HV, 70 mL/kg/h) was at random compared with standard volume (SV, 35 mL/kg/h) CVVH in septic shock patients with acute kidney injury (AKI). PK/PD parameters for all antimicrobial agents used in each patient were studied during five days.

RESULTS

Antimicrobial treatment met efficacy targets for both percentage of time above the minimal inhibitory concentration and inhibitory quotient. A significant correlation was observed between the ultrafiltration flow and total systemic clearance (Spearman test: P < 0.005) and between CVVH clearance and drug elimination half-life (Spearman test: P < 0.005). All agents were easily filtered. Mean sieving coefficient ranged from 38.7% to 96.7%. Mean elimination half-life of all agents was significantly shorter during HV-CVVH (from 1.29 to 28.54 h) than during SV-CVVH (from 1.51 to 33.85 h) (P < 0.05).

CONCLUSIONS

This study confirms that CVVH influences the PK/PD behavior of most antimicrobial agents. Antimicrobial elimination was directly correlated with convection rate. Current antimicrobial dose recommendations will expose patients to underdosing and increase the risk for treatment failure and development of resistance. Dose recommendations are proposed for some major antibiotic and antifungal treatments in patients receiving at least 25 mL/kg/h CVVH.

Interpersonal Factors in the Pharmacokinetics and Pharmacodynamics of Voriconazole: Are CYP2C19 Genotypes Enough for Us to Make a Clinical Decision?

Background:

Invasive mycoses are serious infections with high mortality and increasing inci-dence. Voriconazole, an important drug to treat invasive mycosis, is metabolized mainly by the cytochrome P450 family 2 subfamily C member 19 enzyme (CYP2C19) and is affected by the genotypes of CYP2C19.

Objective:

We reviewed studies on how genotypes affect the pharmacokinetics and pharmacodynamics of voriconazole, and attempted to determine a method to decide on dosage adjustments based on genotypes, after which, the main characteristic of voriconazole was clarified in details. The pharmacokinetics of voriconazole are influenced by various inter and intrapersonal factors, and for certain populations, such as geriatric patients and pediatric patients, these influences must be considered. CYP2C19 genotype represents the main part of the interpersonal variability related to voriconazole blood concentrations. Thus monitoring the concentration of voriconazole is needed in clinical scenarios to minimize the negative influences of inter and intrapersonal factors. Several studies provided evidence on the stable trough concentration range from 1-2 to 4-6 mg/L, which was combined to consider the efficacy and toxicity. However, the therapeutic drug concentration needs to be narrowed down and evaluated by large-scale clinical trials.

Conclusion:

Though there is insufficient evidence on the relationship between CYP2C19 genotypes and clinical outcomes, there is a great potential for the initial voriconazole dose selection to be guided by the CYP2C19 genotype. Finally, voriconazole therapeutic drug monitoring is essential to provide patient-specific dosing recommendations, leading to more effective anti-fungal regimens to increase clinical effica-cy and reduce adverse drug reactions.

Invasive Aspergillosis in solid-organ transplant recipients: Guidelines from the American Society of Transplantation Infectious Diseases Community of Practice

These updated AST-IDCOP guidelines provide information on epidemiology, diagnosis, and management of Aspergillus after organ transplantation. Aspergillus is the most common invasive mold infection in solid-organ transplant (SOT) recipients, and it is the most common invasive fungal infection among lung transplant recipients. Time from transplant to diagnosis of invasive aspergillosis (IA) is variable, but most cases present within the first year post-transplant, with shortest time to onset among liver and heart transplant recipients. The overall 12-week mortality of IA in SOT exceeds 20%; prognosis is worse among those with central nervous system involvement or disseminated disease. Bronchoalveolar lavage galactomannan is preferred for the diagnosis of IA in lung and non-lung transplant recipients, in combination with other diagnostic modalities (eg, chest CT scan, culture). Voriconazole remains the drug of choice to treat IA, with isavuconazole and lipid formulations of amphotericin B regarded as alternative agents. The role of combination antifungals for primary therapy of IA remains controversial. Either universal prophylaxis or preemptive therapy is recommended in lung transplant recipients, whereas targeted prophylaxis is favored in liver and heart transplant recipients. In these guidelines, we also discuss newer antifungals and diagnostic tests, antifungal susceptibility testing, and special patient populations.

A case of Phaeohyphomycosis caused by Corynespora cassiicola infection

BACKGROUND

Corynespora cassiicola infection is common in plants, but the human Corynespora cassiicola infection in our report is rare according to the literature.

CASE PRESENTATION

We report a case of subcutaneous phaeohyphomycosis caused by a plant pathogen in a patient with acute heart failure. The organism was isolated and identified as Corynespora cassiicola according to its morphological characteristics and gene analysis. The patient was treated successfully with systemic voriconazole.

CONCLUSIONS

This is the third reported case of subcutaneous infection caused by Corynespora cassiicola and the first reported case with accompanied renal impairment, which was associated with acute heart failure. Our case also suggests the importance of renal function monitoring in patients receiving intravenous voriconazole treatment.

Clinical Pharmacokinetics of Sulfobutylether-β-Cyclodextrin in Patients With Varying Degrees of Renal Impairment

Delafloxacin, a fluoroquinolone, has activity against Gram-positive organisms including methicillin-resistant S aureus and fluoroquinolone-susceptible and -resistant Gram-negative organisms. The intravenous formulation of delafloxacin contains the excipient sulfobutylether-β-cyclodextrin (SBECD), which is eliminated by renal filtration. This study examined the pharmacokinetics and safety of SBECD after single intravenous (IV) infusions in subjects with renal impairment. The study was an open-label, parallel-group, crossover study in subjects with normal renal function or mild, moderate, or severe renal impairment, and those with end-stage renal disease undergoing hemodialysis. Subjects received 300 mg delafloxacin IV or placebo IV, containing 2400 mg SBECD, in 2 periods separated by ≥14-day washouts. SBECD total clearance decreased with decreasing renal function, with a corresponding increase in area under the concentration-time curve (AUC_0-∞ ). After IV delafloxacin 300 mg administration, SBECD mean total clearance was 6.28 and 1.24 L/h, mean AUC_0-∞ was 387 and 2130 h·μg/mL, and mean renal clearance was 5.36 and 1.14 L/h in normal and severe renal subjects, respectively. Similar values were obtained after IV placebo administration. In subjects with end-stage renal disease, delafloxacin 300 mg IV produced mean SBECD AUC_0-48 values of 2715 and 7861 h·μg/mL when dosed before and after hemodialysis, respectively. Total SBECD clearance exhibited linear relationships to estimated glomerular filtration rate and creatinine clearance. Single doses of IV delafloxacin 300 mg and IV placebo were well tolerated in all groups. In conclusion, decreasing renal function causes reduced SBECD clearance and increased exposures, but SBECD continues to exhibit a good safety and tolerability profile in IV formulations.

Pharmacokinetics of antifungal drugs: practical implications for optimized treatment of patients

Introduction

Because of the high mortality of invasive fungal infections (IFIs), appropriate exposure to antifungals appears to be crucial for therapeutic efficacy and safety.

Materials and methods

This review summarises published pharmacokinetic data on systemically administered antifungals focusing on co-morbidities, target-site penetration, and combination antifungal therapy.

Conclusions and discussion

Amphotericin B is eliminated unchanged via urine and faeces. Flucytosine and fluconazole display low protein binding and are eliminated by the kidney. Itraconazole, voriconazole, posaconazole and isavuconazole are metabolised in the liver. Azoles are substrates and inhibitors of cytochrome P450 (CYP) isoenzymes and are therefore involved in numerous drug–drug interactions. Anidulafungin is spontaneously degraded in the plasma. Caspofungin and micafungin undergo enzymatic metabolism in the liver, which is independent of CYP. Although several drug–drug interactions occur during caspofungin and micafungin treatment, echinocandins display a lower potential for drug–drug interactions. Flucytosine and azoles penetrate into most of relevant tissues. Amphotericin B accumulates in the liver and in the spleen. Its concentrations in lung and kidney are intermediate and relatively low myocardium and brain. Tissue distribution of echinocandins is similar to that of amphotericin. Combination antifungal therapy is established for cryptococcosis but controversial in other IFIs such as invasive aspergillosis and mucormycosis.

Phase I trial to investigate the effect of renal impairment on isavuconazole pharmacokinetics

Purpose

The purpose of the study is to evaluate the effect of renal impairment (RI) and end-stage renal disease (ESRD) on the pharmacokinetics (PK) of isavuconazole and the inactive cleavage product, BAL8728.

Methods

A single intravenous dose of the prodrug isavuconazonium sulfate (372 mg, equivalent to 200 mg isavuconazole and 75 mg of BAL8728 cleavage product) was administered to healthy controls (parts 1 and 2) and participants with mild, moderate, or severe RI (part 2) or ESRD (part 1); ESRD participants received two doses of 200 mg isavuconazole, 1 h post-dialysis (day 1) and prior to dialysis (day 15). Plasma PK parameters for isavuconazole included maximum concentration (C_max), area under the concentration–time curve (AUC) from time of dose to 72 h (AUC₇₂), AUC extrapolated to infinity (AUC_∞), AUC to last measurable concentration (AUC_last), half-life (t_½ h), volume of distribution (V_z), and total clearance (CL), for the healthy control group versus those with mild, moderate, or severe RI or ESRD.

Results

Isavuconazole C_max values were 4% higher in mild RI and 7, 14, and 21% lower in participants with moderate RI, severe RI, or ESRD versus the healthy control group, respectively. When hemodialysis occurred post-dose (day 15), participants with ESRD had a 30% increase in AUC₇₂ for isavuconazole in parallel with reduction of extracellular volume induced by dialysis. Exposure (AUC_∞ and AUC_last) was not significantly different for participants with mild, moderate, or severe RI versus healthy controls although there was considerable variability. The t_1/2 (day 1) was 125.5 ± 63.6 h (healthy control group), 204.5 ± 82.6 h (ESRD group) in part 1, and 140.5 ± 77.7 h (healthy control group), 117.0 ± 66.2 h (mild RI), 158.5 ± 56.4 h (moderate RI), and 145.8 ± 65.8 L/h (severe RI) in part 2. CL was 2.4 ± 0.8 L/h (healthy control group) and 2.9 ± 1.3 L/h (ESRD group) in part 1 and 2.4 ± 1.2 L/h (healthy control group), 2.5 ± 1.0 L/h (mild RI), 2.2 ± 0.8 L/h (moderate RI), and 2.4 ± 0.8 L/h (severe RI) in part 2. The V_z was 382.6 ± 150.6 L in the healthy control group and 735.6 ± 277.3 L in ESRD patients on day 1 in part 1 of the study. In part 2 of the study, V_z was 410.8 ± 89.7 L in the healthy control group, 341.6 ± 72.3 L in mild RI, 509.1 ± 262.2 L in moderate RI, and 439.4 L in severe RI.

Conclusions

Based on the findings of this study, dose adjustments of isavuconazole are unlikely to be required in individuals with RI or in those with ESRD who receive hemodialysis.

Electronic supplementary material

The online version of this article (doi:10.1007/s00228-017-2213-7) contains supplementary material, which is available to authorized users.

Adverse Effects of Voriconazole: Analysis of the French Pharmacovigilance Database

Background:

The most common adverse effects of voriconazole reported during clinical trials were disturbances of vision (30% of pts.), skin rashes (17.3%), and elevations in hepatic enzymes level (~10% of pts.; varying with enzymes). However, postmarketing data concerning safety of voriconazole are limited.

Objective:

To describe voriconazole adverse drug effects (ADEs) after 4 years of the drug's availability in France and determine their occurrence.

Methods:

All cases of ADEs including voriconazole reported to the French Pharmacovigilance Database between 2002 and 2005 were analyzed. For each case, the following data were recorded; age, sex, indication, concomitant disease, concomitant medications, and ADE description. Causality link between voriconazole and ADEs was performed using the Naranjo probability scale.

Results:

A total of 227 ADE cases were reported in 178 adults and 9 children (<12 y), with 66% occurring in males. The patients' median age was 49.6 (2–80) years. ADEs included liver function test abnormalities (23%), visual disturbances (18%), skin rashes (17%), neurologic disturbances (14%), cardiovascular events (10%), hematologic disorders (8%), and renal disturbances (4%). Other less commonly identified ADEs included headache, nausea, vomiting, and diarrhea. Drug–drug interactions were observed in 7 cases. According to the Naranjo criteria, 84% of ADEs were classified as possible, 7% as probable, 5% as highly probable, and 4% as doubtful.

Conclusions:

Most AOEs found in this study are well documented in the literature, except for cardiac complications, which are rarely reported. Few ADEs related to drug interactions were observed; however, due to the extensive metabolism of voriconazole by cytochrome P450 isoenzymes, clinicians should be aware of potential interactions between voriconazole and other drugs metabolized through this pathway.

Effective treatment of invasive Aspergillus fumigatus infection using combinations of topical and systemic antifungals in a severely burned patient

The authors describe an invasive Aspergillus fumigatus deep-burn wound infection in a severely burned patient that was successfully treated with a combination of topical terbinafine and systemic voriconazole antifungal therapy. To our knowledge, this is the first case report describing the effective control of an invasive deep-burn wound infection using this combination.

Role of New Antifungal Agents in the Treatment of Invasive Fungal Infections in Transplant Recipients: Isavuconazole and New Posaconazole Formulations

Invasive fungal infections are a major cause of morbidity and mortality among solid organ transplant (SOT) and hematopoietic stem cell transplant (HSCT) recipients. Transplant patients are at risk for such invasive fungal infections. The most common invasive fungal infections are invasive candidiasis in the SOT and invasive aspergillosis in the HSCT. In this article, we will discuss the epidemiology of invasive fungal infections in the transplant recipients and susceptibility patterns of the fungi associated with these infections. Additionally, the pharmacology and clinical efficacy of the new antifungal, isavuconazole, and the new posaconazole formulations will be reviewed. Isavuconazole is a new extended-spectrum triazole that was recently approved for the treatment of invasive aspergillosis and mucormycosis. Advantages of this triazole include the availability of a water-soluble intravenous formulation, excellent bioavailability of the oral formulation, and predictable pharmacokinetics in adults. Posaconazole, a broad-spectrum triazole antifungal agent, is approved for the prevention of invasive aspergillosis and candidiasis in addition to the treatment of oropharyngeal candidiasis. Posaconazole oral suspension solution has shown some limitations in the setting of fasting state absorption, elevated gastrointestinal pH, and increased motility. The newly approved delayed-release oral tablet and intravenous solution formulations provide additional treatment options by reducing interpatient variability and providing flexibility in these set of critically ill patients. This review will detail these most recent studies.

A pharmacokinetic comparison of two voriconazole formulations and the effect of CYP2C19 polymorphism on their pharmacokinetic profiles

Purpose

SYP-1018 is a lyophilized polymeric nanoparticle formulation of voriconazole that is under development for intravenous dosing. This study compared the pharmacokinetic and tolerability profiles of SYP-1018 with those of Vfend^®, the marketed formulation of voriconazole. The effect of CYP2C19 polymorphism on the voriconazole pharmacokinetics was also evaluated.

Methods

An open-label, two-treatment, two-period, two-sequence crossover study was conducted in 52 healthy male volunteers, who randomly received a single intravenous infusion of either of the two voriconazole formulations at 200 mg. Blood samples were collected up to 24 hours after drug administration for pharmacokinetic analysis. The plasma concentrations of voriconazole were determined using liquid chromatography with tandem mass spectrometry, and the pharmacokinetic parameters were estimated using a noncompartmental method. CYP2C19 genotype was identified in 51 subjects.

Results

The geometric mean ratio (90% confidence interval) of SYP-1018 to Vfend^® was 0.99 (0.93–1.04) for the maximum plasma concentrations (C_max) and 0.97 (0.92–1.01) for the area under the concentration–time curve (AUC) from dosing to the last quantifiable concentration (AUC_last). Nineteen homozygous extensive metabolizers (EMs, *1/*1), 19 intermediate metabolizers (IMs, *1/*2 or *1/*3), and ten poor metabolizers (PMs, *2/*2, *2/*3, or *3/*3) were identified, and the pharmacokinetic comparability between SYP-1018 and Vfend^® was also noted when analyzed separately by genotype. The systemic exposure to voriconazole was greatest in the PM group, followed by the IM, and then the EM groups. Furthermore, the intrasubject variability for C_max and AUC_last was greater in IMs and PMs than in EMs. No serious adverse event occurred, and both treatments were well tolerated.

Conclusion

SYP-1018 had comparable pharmacokinetic and tolerability profiles to Vfend^® after a single intravenous infusion. CYP2C19 genotype affected not only the pharmacokinetics of voriconazole, but its intrasubject variability. SYP-1018 can be further developed as a clinically effective alternative to Vfend^®.

Evaluation of sulfobutylether-β-cyclodextrin (SBECD) accumulation and voriconazole pharmacokinetics in critically ill patients undergoing continuous renal replacement therapy

Introduction

Intravenous (IV) voriconazole is not recommended in patients with creatinine clearance <50 ml/min to avoid potentially toxic accumulation of sulfobutylether-β-cyclodextrin (SBECD). The purpose of this study was to evaluate the pharmacokinetics of SBECD, voriconazole, and voriconazole N-oxide in critically ill patients undergoing continuous renal replacement therapy (CRRT) and to determine if CRRT removes SBECD sufficiently to allow for the use of IV voriconazole without significant risk of SBECD accumulation.

Methods

This prospective, open-label pharmacokinetic study enrolled patients >18 years old receiving IV voriconazole for a known or suspected invasive fungal infection while undergoing CRRT. Serial blood and effluent samples were collected on days 1, 3, 5, 7, and every 3 to 5 days thereafter. SBECD, voriconazole, and voriconazole N-oxide plasma and effluent concentrations were measured by liquid chromatography-tandem mass spectrometry. Pharmacokinetic, pharmacodynamic, and pharmacogenetic analyses were conducted.

Results

Ten patients (mean ± standard deviation (SD)) 53 ± 11 years old, 50% male, 81 ± 14 kg, with Acute Physiologic and Chronic Health Evaluation II (APACHE II) scores of 31.5 ± 3.8 were evaluated. All patients underwent continuous venovenous hemofiltration (CVVH) with a median predilution replacement fluid rate of 36 (interquartile range (IQR) 32 to 37) ml/kg/hr and total ultrafiltration rate of 38 (IQR 34 to 39) ml/kg/hr. Mean ± SD voriconazole and SBECD dosages administered were 8.1 ± 2.1 mg/kg/day and 129 ± 33 mg/kg/day, respectively. Voriconazole plasma trough concentrations were >1 mg/L in all patients with CVVH accounting for only 15% of the total body clearance. CVVH accounted for 86% of the total body clearance of SBECD with the majority of the dose being recovered in the effluent. Minimal increases in dose normalized SBECD area under the concentration-time curve from 0 to 12 hours (AUC0-12) (4,484 ± 4,368 to 4,553 ± 2,880 mg*hr/L; P = 0.97) were observed after study day 1.

Conclusions

CVVH effectively removed SBECD at a rate similar to the ultrafiltration rate. Voriconazole clearance by CVVH was not clinically significant. Standard dosages of IV voriconazole can be utilized in patients undergoing CVVH without significant risk of SBECD accumulation.

Trial registration

ClinicalTrials.gov NCT01101386. Registered 6 April 2010.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0753-8) contains supplementary material, which is available to authorized users.

The effects of methylphenidate on cognitive control in active methamphetamine dependence using functional magnetic resonance imaging

Methamphetamine (MA) dependence is associated with cognitive deficits. Methylphenidate (MPH) has been shown to improve inhibitory control in healthy and cocaine-dependent subjects. This study aimed to understand the neurophysiological effects before and after acute MPH administration in active MA-dependent and control subjects. Fifteen MA-dependent and 18 control subjects aged 18-46 years were scanned using functional magnetic resonance imaging before and after either a single oral dose of MPH (18 mg) or placebo while performing a color-word Stroop task. Baseline accuracy was lower (p = 0.026) and response time (RT) was longer (p < 0.0001) for the incongruent compared to congruent condition, demonstrating the task probed cognitive control. Increased activation of the dorsolateral prefrontal cortex (DLPFC) and parietal cortex during the incongruent and Stroop effect conditions, respectively was observed in MA-dependent compared to control subjects (p < 0.05), suggesting the need to recruit neural resources within these regions for conflict resolution. Post- compared to pre-MPH treatment, increased RT and DLPFC activation for the Stroop effect were observed in MA-dependent subjects (p < 0.05). In comparison to MPH-treated controls and placebo-treated MA-dependent subjects, MPH-treated MA-dependent subjects showed decreased activation of parietal and occipital regions during the incongruent and Stroop effect conditions (p < 0.05). These findings suggest that in MA-dependent subjects, MPH facilitated increased recruitment of the DLPFC for Stroop conflict resolution, and a decreased need for recruitment of neural resources in parietal and occipital regions compared to the other groups, while maintaining a comparable level of task performance to that achieved pre-drug administration. Due to the small sample size, the results from this study are preliminary; however, they inform us about the effects of MPH on the neural correlates of cognitive control in active MA-dependent subjects.

Treatment of invasive candidiasis in the elderly: a review

Fungi are major causes of infections among immunocompromised or hospitalized patients with serious underlying diseases and comorbidities. Candida species remain the most important cause of opportunistic infections worldwide, affecting predominantly patients over 65 years old, while they are considered to be the fourth most common cause of nosocomial bloodstream infections. The rapidly growing elderly population has specific physiological characteristics, which makes it susceptible to colonization and subsequent infection due to Candida species. Comorbidities and multidrug use should be taken into account any time the therapeutic regimen is under consideration. Different classes of antifungal drugs are available for the treatment of invasive fungal infections but echinocandins, apart from their activity against resistant strains (Candida glabrata and Candida krusei), seem to be safe, with limited adverse events and minimal drug-drug interactions in comparison to the other regimens. Therefore, these agents are strongly recommended when dealing with elderly patients suffering from an invasive form of Candida infection.

Optimizing antifungal choice and administration

BACKGROUND

The antifungal armamentarium includes a number of drug classes and agents within each class. Successful IFI management depends on optimal matching of drug choice with the individual patient and causative pathogen, and maximizing effectiveness of the selected drug through appropriate dosing and toxicity management.

OBJECTIVE

This review is intended to provide a brief overview of key factors involved in optimizing antifungal choice and administration for patients with invasive fungal infections (IFIs).

FINDINGS

Antifungals differ in spectrum of activity, and these differences are critical when selecting the antifungal most likely to provide success for a patient with an IFI. When the species has not yet been identified, an analysis of regional epidemiology and risk factors can provide clues as to the most likely pathogen. For severely immunocompromised patients, a fungicidal agent may be preferred over a fungistatic agent, although more research is needed in this area. Triazoles, particularly itraconazole and posaconazole, exhibit great interpatient pharmacokinetic variability related to absorption. Steps can be taken to maximize absorption when using these agents. Voriconazole concentration is affected by polymorphisms in the major metabolic enzyme, cytochrome P450 2C19. Triazoles, and to a lesser extent other antifungals, are also subject to drug-drug interactions, which needs to be considered when selecting a particular antifungal agent for use in a severely ill patient on polypharmacy. Therapeutic drug monitoring may be a useful adjunct for patients receiving itraconazole, voriconazole, or posaconazole. When the IFI involves a pharmacologically protected site, such as the central nervous system (CNS) or eye, 5-fluorocytosine, fluconazole, or voriconazole are generally preferred. Echinocandin penetration is typically inadequate for IFIs of the CNS or eye. Antifungal agents also differ in their toxicity profiles, and these issues also need to be considered and managed when making an antifungal choice.

CONCLUSION

Successful management of IFIs relies in part on the accurate selection of an antifungal agent for the infection. Drug characteristics can help in the selection of drug therapy. These characteristics include the drug's spectrum of activity, pharmacokinetics, pharmacodynamics, toxicity profile, and distribution to the infection site. Matching the drug profile to the patient and fungal species contribute to optimal management of infection.

Evaluation of intravenous voriconazole in patients with compromised renal function

Background

Incorporation of the solubilizing excipient, sulfobutylether-β-cyclodextrin (SBECD), in the intravenous (IV) formulation of voriconazole has resulted in the recommendation that this formulation be used with caution in patients with creatinine clearances (Cl_cr) < 50 mL/min. This study evaluated the safety of IV voriconazole compared with two other IV antifungals not containing SBECD in patients with compromised renal function.

Methods

A total of 128 patients aged 11–93 years who had a baseline Cl_cr < 50 mL/min between January 1, 2007 and December 31, 2010 were identified from a database of a university-affiliated inpatient healthcare system; of these, 55 patients received caspofungin, 54 patients received fluconazole, and 19 patients received voriconazole. Changes in serum creatinine (S_cr) and Cl_cr levels while on therapy were compared with baseline values and between groups.

Results

The groups had similar characteristics apart from the larger proportion of females that received fluconazole. Baseline S_cr was higher in those receiving caspofungin, but maximal increases of S_cr and decreases in Cl_cr were greatest for the fluconazole group. Acute kidney injury (AKI), assessed by RIFLE criteria, was more frequent in the fluconazole vs. the caspofungin group (p < 0.01); incidence of AKI in the voriconazole group was not significantly different than found in the other two groups. The infecting organism was a predictor of AKI and formulation with SBECD was not.

Conclusions

Treatment of fungal infections in patients with compromised renal function with an SBECD-containing antifungal agent was not associated with AKI in clinical practice. Since the infecting organism was associated with AKI, decision on which antifungal to use should be determined by susceptibilities to the organism and not the incorporation of SBECD in the IV formulation.

Safety and tolerability of voriconazole in patients with baseline renal insufficiency and candidemia

Acutely ill patients with candidemia frequently suffer from renal insufficiency. Voriconazole's intravenous formulation with sulfobutylether beta-cyclodextrin (SBECD) is restricted in patients with renal insufficiency. We evaluated the use of intravenous voriconazole formulated with SBECD in candidemic patients with renal insufficiency and compared treatment outcome and safety to those who received a short course of amphotericin B deoxycholate followed by fluconazole. We reviewed data on treatment outcome, survival, safety, and tolerability from the subset of patients with moderate (creatinine clearance [CrCl], 30 to 50 ml/min) or severe (CrCl, <30 ml/min) renal insufficiency enrolled in a trial of voriconazole compared to amphotericin B deoxycholate followed by fluconazole for treatment of candidemia in 370 patients. Fifty-eight patients with renal impairment were identified: 41 patients on voriconazole and 17 on amphotericin B/fluconazole. The median duration of treatment was 14 days for voriconazole (median, 7 days intravenous) and 11 days for amphotericin B/fluconazole, 3 days of which were for amphotericin B. Despite the short duration of exposure, worsening of renal function or newly emerged renal adverse events were reported in 53% of amphotericin B-treated patients compared to 39% of voriconazole-treated patients. During treatment, median serum creatinine decreased in the voriconazole arm, whereas creatinine increased in the amphotericin B/fluconazole arm, before return to baseline at week 3. All-cause mortality at 14 weeks was 49% in the voriconazole arm compared to 65% in the amphotericin B/fluconazole arm. Intravenous voriconazole formulated with SBECD was effective in patients with moderate or severe renal insufficiency and candidemia and was associated with less acute renal toxicity than amphotericin B/fluconazole.

Administration of voriconazole in patients with renal dysfunction

BACKGROUND

The intravenous use of voriconazole requires coadministration with sulphobutylether-β-cyclodextrin, which may accumulate in patients with impaired renal function.

METHODS

All adult patients treated with the same formulation of voriconazole for a minimum of 3 consecutive days were included. Renal function was assessed based on the creatinine level and the calculated creatinine clearance (CrCl). Change in renal function was calculated on days 3, 7, and end of treatment (EOT) and was defined based on the RIFLE criteria.

RESULTS

Among 166 patients in whom baseline renal function was assessed, 42 (25.3%) had a CrCl <50 mL/min and received intravenous voriconazole, 77 (46.4%) had a CrCl ≥50 mL/min and received intravenous voriconazole, and 47 (28.3%) had a CrCl <50 mL/min and were treated with oral voriconazole. Renal function changed on days 3, 7, and EOT in 19 (11.4%), 14 (8.4%), and 28 (16.9%) patients, respectively. Multivariate analyses identified significant predictors of renal dysfunction: (1) day 3, hematologic malignancy (odds ratio [OR], 5.09, P = .01), fluconazole use within 30 days prior to voriconazole (OR, 6.21; P = .008), coadministration of penicillins (OR, 6.12; P = .03), and immunosuppressants (OR, 7.00; P = .002); (2) day 7, baseline liver impairment (OR, 5.30; P value = .004); (3) EOT, administration of penicillins (OR, 2.39; P = .04).

CONCLUSIONS

Voriconazole route of administration and baseline renal function were not predictors of worsening renal dysfunction on days 3, 7, and EOT. Underlying disease, baseline liver impairment, and concomitant administration of other drugs (eg, penicillins, fluoroquinolones, immunosuppressants) were the strongest predictors of renal dysfunction.

Pharmacokinetic evaluation of voriconazole treatment in critically ill patients undergoing continuous venovenous hemofiltration

INTRODUCTION

Voriconazole represents an essential part of antimicrobial therapy in critically ill patients. The aim of this study was to exclude a significant alteration in voriconazole pharmacokinetics in critically ill patients undergoing continuous venovenous hemofiltration (CVVH).

METHODS

Six patients dependent on CVVH with evidence of an invasive mycotic infection treated with intravenous voriconazole at the standard dosing regimen were investigated. The total serum concentration of voriconazole in arterial blood and the concentration in ultrafiltrate were measured by reverse-phase high-performance liquid chromatography with ultraviolet detection. The authors profiled a 5-point pharmacokinetic concentration-time curve during the 12-hour standard maintenance dosing interval and derived the basic pharmacokinetic parameters.

RESULTS

The serum voriconazole concentration did not decrease <1.0 mg/L at any time point, and the mean was 4.3 ± 2.6 mg/L and the median (range) 3.6 (9.0) mg/L. The sieving coefficient of the drug did not exceed 0.30 in any patient (0.22 ± 0.08). The mean serum AUC0-12, the mean total clearance, and the mean clearance via CVVH were 53.52 ± 29.97 mg·h/L [the median (range) of 57.74 (62.34) mg·h/L], 0.11 ± 0.07 L·h-1·kg-1, and 0.007 ± 0.003 L·h-1·kg-1, respectively. The clearance by the CVVH method ranged from 4% to 20% of the total drug clearance. The disposition of voriconazole was not compromised. The mean elimination half-life was 27.58 ± 35.82 hours [the median of 13.10 (92.21) hours], and the mean distribution volume value was 3.28 ± 3.10 L/kg [the median of 2.01 (8.10) L/kg]. Marked variability in serum concentrations, elimination half-life, distribution volume, and total clearance was seen. Half of the patients showed some drug accumulation.

CONCLUSIONS

The clearance of voriconazole by CVVH is not clinically significant. In view of this finding, voriconazole dose adjustment in patients undergoing the standard method of CVVH is not required. However, the observed potential for an unpredictable voriconazole accumulation suggests the usefulness for monitoring its levels in critically ill patients.

Italian guidelines for diagnosis, prevention, and treatment of invasive fungal infections in solid organ transplant recipients

Use of various induction regimens, of novel immunosuppressive agents, and of newer prophylactic strategies continues to change the pattern of infections among solid organ transplant (SOT) recipients. Although invasive fungal infections (IFIs) occur at a lower incidence than bacterial and viral infections in this population, they remain a major cause of morbidity and mortality worldwide. In March 2008, a panel of Italian experts on fungal infections and organ transplantation convened in Castel Gandolfo (Rome) to develop consensus guidelines for the diagnosis, prevention, and treatment of IFIs among SOT recipients. We discussed the definitions, microbiological and radiological diagnoses, prophylaxis, empirical treatment, and therapy of established disease. Throughout the consensus document, recommendations as clinical guidelines were rated according to the standard scoring system of the Infectious Diseases Society of America and the United Stated Public Health Service.

When and how to cover for fungal infections in patients with severe sepsis and septic shock

Candida species remain the most frequently isolated fungi in intensive care unit (ICU) patients with severe sepsis or septic shock. Delayed antifungal therapy in these patients is a recognized risk factor for mortality. However, the diagnosis of invasive candidiasis remains difficult and is frequently delayed. Clinical scores have been proposed to assess the risk of development of invasive candidiasis or candidemia. Laboratory tools for early diagnosis are disappointing or still under development. Triazoles, polyenes, and echinocandins are the key drugs used to treat invasive candidiasis in ICU patients with similar efficacy, but very variable tolerability. The increasing incidence of fluconazole-resistant and susceptible-dose dependent strains and the safety profile of antifungal agents must be taken into account when selecting empiric therapy, frequently leading to the initial use of echinocandins in ICU patients with severe sepsis or septic shock.

Using pharmacokinetics and pharmacodynamics to optimise dosing of antifungal agents in critically ill patients: a systematic review

The prevalence of invasive fungal infections (IFIs) caused by Candida spp. is increasing in critically ill patients. Recent development of new antifungal agents has significantly contributed to the successful treatment of IFIs. However, the pharmacokinetics of antifungal agents can be altered in a number of disease states, including critical illness. Therefore, doses established in healthy volunteers and other patient groups may not be appropriate for the critically ill. Moreover, inadequate dosing may contribute to treatment failure and the emergence of resistance. This systematic review provides a critical analysis of the pharmacokinetics of antifungal agents in the critically ill and their relevance to dosing requirements in clinical practice. Based on the limited data available, dosing of some antifungal agents may have to be adjusted in critically ill patients with conserved renal function as well as in those requiring renal replacement therapy. Further research to confirm the appropriateness of current dosing strategies to attain the appropriate pharmacodynamic targets is recommended.

Update on the optimal use of voriconazole for invasive fungal infections

Voriconazole is an extended-spectrum triazole with excellent bioavailability that has now become the treatment of choice for aspergillosis. It has a unique side effect profile compared with other azoles, as well as a number of clinically important drug-drug interactions. These factors, along with a correlation between increased serum levels and improved outcomes, have prompted an interest in therapeutic drug monitoring of this agent. The pharmacology and clinical outcomes data of voriconazole are presented in this review.

Review of the basic and clinical pharmacology of sulfobutylether-beta-cyclodextrin (SBECD)

Despite its use in commercially available drugs such as intravenous voriconazole, there is little known in the medical literature about the clinical pharmacology of the solubilizing agent, sulfobutylether-beta-cyclodextrin (SBECD). This paper summarizes all known data on SBECD pharmacokinetics and safety. In animals, volume of distribution approximates extracellular water volume and clearance is determined by the glomerular filtration rate. SBECD does not have any apparent effects on cardiovascular or respiratory systems, nor on autonomic and somatic functions in animals. In 1- and 6-month studies in rats and dogs, the most noteworthy findings were renal tubular vacuolation and foamy macrophages in the liver and lungs. Mild toxicity in the kidney and liver as a consequence of vacuolation occurred in rats at the maximum dose of 3000 mg/kg, which is approximately 50-fold greater than the SBECD dose typically administered in man. Doses up to 1500 mg/kg produced no histopathological evidence of toxicity in dog kidneys. SBECD has also been studied in healthy volunteers and subjects with renal dysfunction. Whereas plasma SBECD levels accumulate in those with renal compromise, there were no deleterious effects on renal function. Nonetheless, serum creatinine levels should be monitored in subjects with renal compromise receiving multiple doses of SBECD.

Pharmacokinetics of sulfobutylether-beta-cyclodextrin and voriconazole in patients with end-stage renal failure during treatment with two hemodialysis systems and hemodiafiltration

Sulfobutylether-beta-cyclodextrin (SBECD), a large cyclic oligosaccharide that is used to solubilize voriconazole (VRC) for intravenous administration, is eliminated mainly by renal excretion. The pharmacokinetics of SBECD and voriconazole in patients undergoing extracorporeal renal replacement therapies are not well defined. We performed a three-period randomized crossover study of 15 patients with end-stage renal failure during 6-hour treatment with Genius dialysis, standard hemodialysis, or hemodiafiltration using a high-flux polysulfone membrane. At the start of renal replacement therapy, the patients received a single 2-h infusion of voriconazole (4 mg per kg of body weight) solubilized with SBECD. SBECD, voriconazole, and voriconazole-N-oxide concentrations were quantified in plasma and dialysate samples by high-performance liquid chromatography (HPLC) and by HPLC coupled to tandem mass spectrometry (LC-MS-MS) and analyzed by noncompartmental methods. Nonparametric repeated-measures analysis of variance (ANOVA) was used to analyze differences between treatment phases. SBECD and voriconazole recoveries in dialysate samples were 67% and 10% of the administered doses. SBECD concentrations declined with a half-life ranging from 2.6 +/- 0.6 h (Genius dialysis) to 2.4 +/- 0.9 h (hemodialysis) and 2.0 +/- 0.6 h (hemodiafiltration) (P < 0.01 for Genius dialysis versus hemodiafiltration). Prediction of steady-state conditions indicated that even with daily hemodialysis, SBECD will still exceed SBECD exposure of patients with normal renal function by a factor of 6.2. SBECD was effectively eliminated during 6 h of renal replacement therapy by all methods, using high-flux polysulfone membranes, whereas elimination of voriconazole was quantitatively insignificant. The SBECD half-life during renal replacement therapy was nearly normalized, but the average SBECD exposure during repeated administration is expected to be still increased.

Pharmacokinetics and safety of 14 days intravenous voriconazole in allogeneic haematopoietic stem cell transplant recipients

BACKGROUND

Voriconazole is used to manage invasive fungal diseases in recipients of an allogeneic haematopoietic stem cell transplant (HSCT) after myeloablative treatment. Little is known about the pharmacokinetics (PK) of voriconazole in this population, who also receive cyclosporine A.

METHODS

Patients admitted for an allogeneic HSCT were eligible for the study. Voriconazole was given intravenously at 6 mg/kg twice daily on day 1, then 4 mg/kg twice daily until the day of transplant to reach steady-state conditions and then continued for a further week during which cyclosporine A was administered. Blood samples were drawn on the day of HSCT and daily for the next 14 days. PK curves were determined on days 7 and 14. PK parameters were calculated using non-compartmental analysis. CYP2C19*2 and CYP2C19*3 polymorphisms were also determined.

RESULTS

Ten patients were fully evaluable. Median AUC(0-12) of voriconazole on the day of HSCT was 33.81 mg.h/L [interquartile range (IQR) 20.59-39.39] and 25.61 mg.h/L (IQR 22.48-38.65) 1 week later. AUC(0-12) of voriconazole on both days was similar to data reported for healthy volunteers. Trough levels were <1.0 mg/L for 3 of 10 patients on the day of HSCT and for 4 of 10 patients 1 week later. No difference in clearance of voriconazole was found between CYP2C19 extensive metabolizers (n = 4) and carriers of one non-functional allele (n = 6).

CONCLUSIONS

Exposure and clearance of voriconazole in recipients of an allogeneic HSCT are similar to those of healthy volunteers though there was high intra- and inter-individual variation in drug exposures which may have implications for similar patient populations.

Monitoring plasma voriconazole levels following intravenous administration in critically ill patients: an observational study

Data relating to the pharmacokinetics of voriconazole in critically ill patients are lacking. A prospective observational study was conducted on 18 non-consecutive critically ill patients aged 24-97 years, comprising 12 patients with normal renal function (NRF) [creatinine clearance (CL(Cr)) > or = 60 mL/min] and 6 patients with moderate renal impairment (MRI) (CL(Cr) 40-55 mL/min), administered voriconazole intravenously (6 mg/kg loading dose and 3-4 mg/kg twice daily thereafter) in order to determine the suitability of these doses in this patient population. Steady-state blood levels were monitored and liver and renal function were recorded throughout treatment. Large variability in patient plasma levels was observed, ranging from 37% at < or = 1 mg/L (minimum inhibitory concentration at which, for most fungal pathogens, 90% of isolates are susceptible) to 19% at >5.5mg/L. Moreover, maintaining trough concentrations above clinical breakpoints was not consistently achieved because 16/30 (53%) were < or = 1 mg/L. In a few MRI patients, average concentrations were found to be significantly different compared with those of NRF patients administered the same dose, however this difference was not noted in pharmacokinetic parameters following dose normalisation. None of the patients experienced deterioration in renal or liver function. Recommended voriconazole doses are inadequate to achieve drug concentrations >1 microg/mL over the entire dosing interval in some critically ill patients.

Therapeutic drug monitoring of voriconazole in a child with invasive aspergillosis requiring extracorporeal membrane oxygenation

We describe a patient with invasive pulmonary aspergillosis on extracorporeal membrane oxygenation therapy in which therapeutic drug monitoring and individualization of therapy by measuring voriconazole plasma concentrations were performed.

Clinical practice guidelines for the management of candidiasis: 2009 update by the Infectious Diseases Society of America

Guidelines for the management of patients with invasive candidiasis and mucosal candidiasis were prepared by an Expert Panel of the Infectious Diseases Society of America. These updated guidelines replace the previous guidelines published in the 15 January 2004 issue of Clinical Infectious Diseases and are intended for use by health care providers who care for patients who either have or are at risk of these infections. Since 2004, several new antifungal agents have become available, and several new studies have been published relating to the treatment of candidemia, other forms of invasive candidiasis, and mucosal disease, including oropharyngeal and esophageal candidiasis. There are also recent prospective data on the prevention of invasive candidiasis in high-risk neonates and adults and on the empiric treatment of suspected invasive candidiasis in adults. This new information is incorporated into this revised document.

Pharmacokinetics of antibiotics or antifungal drugs in intensive care units

Intensive care unit (ICU) patients present several unusual pharmacokinetic (PK) characteristics compared with less seriously ill patients, including increased distribution volume and variable clearance. Interpatient PK variability is often considerable and can produce a wide range of values for PK parameters and major differences in drug exposure. These analyses have led to the development of simulation techniques and population PK models to assess dosing regimens in specific patient subsets. Plasma concentrations may frequently overestimate target-site concentrations and therefore clinical efficacy. The unbound drug concentration at the infection site should be preferred. Although renal replacement therapy techniques are commonly used in ICU patients, data concerning antibiotic dosing in this setting remain limited. Administration of antibacterial agents by continuous infusion is becoming a common technique to avoid undesirable high peak concentrations and low trough concentrations and to optimize PK-pharmacodynamic indices.