Pharmacokinetics/pharmacodynamics of echinocandins

Updated antimicrobial dosing recommendations for obese patients

The prevalence of obesity has increased considerably in the last few decades. Pathophysiological changes in obese patients lead to pharmacokinetic (PK) and pharmacodynamic (PD) alterations that can condition the correct exposure to antimicrobials if standard dosages are used. Inadequate dosing in obese patients can lead to toxicity or therapeutic failure. In recent years, additional antimicrobial PK/PD data, extended infusion strategies, and studies in critically ill patients have made it possible to obtain data to provide a better dosage in obese patients. Despite this, it is usually difficult to find information on drug dosing in this population, which is sometimes contradictory. This is a comprehensive review of the dosing of different types of antimicrobials (antibiotics, antifungals, antivirals, and antituberculosis drugs) in obese patients, where the literature on PK and possible dosing strategies in obese adults was critically assessed.

Therapeutic Drug Monitoring of Antifungal Agents in Critically Ill Patients: Is There a Need for Dose Optimisation?

Invasive fungal infections are an important cause of morbidity and mortality, especially in critically ill patients. Increasing resistance rates and inadequate antifungal exposure have been documented in these patients, due to clinically relevant pharmacokinetic (PK) and pharmacodynamic (PD) alterations, leading to treatment failure. Physiological changes such as third spacing (movement of fluid from the intravascular compartment to the interstitial space), hypoalbuminemia, renal failure and hepatic failure, as well as common interventions in the intensive care unit, such as renal replacement therapy and extracorporeal membrane oxygenation, can lead to these PK and PD alterations. Consequently, a therapeutic target concentration that may be useful for one patient may not be appropriate for another. Regular doses do not take into account the important PK variations in the critically ill, and the need to select an effective dose while minimising toxicity advocates for the use of therapeutic drug monitoring (TDM). This review aims to describe the current evidence regarding optimal PK/PD indices associated with the clinical efficacy of the most commonly used antifungal agents in critically ill patients (azoles, echinocandins, lipid complexes of amphotericin B, and flucytosine), provide a comprehensive understanding of the factors affecting the PK of each agent, document the PK parameters of critically ill patients compared to healthy volunteers, and, finally, make recommendations for therapeutic drug monitoring (TDM) of antifungals in critically ill patients.

Therapeutic Drug Monitoring of the Echinocandin Antifungal Agents: Is There a Role in Clinical Practice? A Position Statement of the Anti-Infective Drugs Committee of the International Association of Therapeutic Drug Monitoring and Clinical Toxicology

PURPOSE

Reduced exposure to echinocandins has been reported in specific patient populations, such as critically ill patients; however, fixed dosing strategies are still used. The present review examines the accumulated evidence supporting echinocandin therapeutic drug monitoring (TDM) and summarizes available assays and sampling strategies.

METHODS

A literature search was conducted using PubMed in December 2020, with search terms such as echinocandins, anidulafungin, caspofungin, micafungin, or rezafungin with pharmacology, pharmacokinetics (PKs), pharmacodynamics (PDs), drug-drug interactions, TDM, resistance, drug susceptibility testing, toxicity, adverse drug reactions, bioanalysis, chromatography, and mass spectrometry. Data on PD/PD (PK/PD) outcome markers, drug resistance, PK variability, drug-drug interactions, assays, and TDM sampling strategies were summarized.

RESULTS

Echinocandins demonstrate drug exposure-efficacy relationships, and maximum concentration/minimal inhibitory concentration ratio (Cmax/MIC) and area under the concentration-time curve/MIC ratio (AUC/MIC) are proposed PK/PD markers for clinical response. The relationship between drug exposure and toxicity remains poorly clarified. TDM could be valuable in patients at risk of low drug exposure, such as those with critical illness and/or obesity. TDM of echinocandins may also be useful in patients with moderate liver impairment, drug-drug interactions, hypoalbuminemia, and those undergoing extracorporeal membrane oxygenation, as these conditions are associated with altered exposure to caspofungin and/or micafungin. Assays are available to measure anidulafungin, micafungin, and caspofungin concentrations. A limited-sampling strategy for anidulafungin has been reported.

CONCLUSIONS

Echinocandin TDM should be considered in patients at known risk of suboptimal drug exposure. However, for implementing TDM, clinical validation of PK/PD targets is needed.

Precision Therapy for Invasive Fungal Diseases

Invasive fungal infections (IFI) are a common infection-related cause of death in immunocompromised patients. Approximately 10 million people are at risk of developing invasive aspergillosis annually. Detailed study of the pharmacokinetics (PK) and pharmacodynamics (PD) of antifungal drugs has resulted in a better understanding of optimal regimens for populations, drug exposure targets for therapeutic drug monitoring, and establishing in vitro susceptibility breakpoints. Importantly, however, each is an example of a “one size fits all strategy”, where complex systems are reduced to a singularity that ensures antifungal therapy is administered safely and effectively at the level of a population. Clearly, such a notion serves most patients adequately but is completely counter to the covenant at the centre of the clinician–patient relationship, where each patient should know whether they are well-positioned to maximally benefit from an antifungal drug. This review discusses the current therapy of fungal infections and areas of future research to maximise the effectiveness of antifungal therapy at an individual level.

Assessment of Micafungin Dosage Regimens in Patients with Cancer Using Pharmacokinetic/Pharmacodynamic Modeling and Monte Carlo Simulation

Micafungin is widely used for invasive candidiasis, especially in critically ill patients and those with cancer, and for empirical antifungal therapy in patients with neutropenic fever. This is the first study to investigate the pharmacokinetics and disposition parameters of micafungin in patients with cancer. In this observational pharmacokinetic study, blood samples were collected and analyzed using high-performance liquid chromatography. Pharmacokinetic parameters were estimated using Monolix 4.4 software. The plasma micafungin concentrations were measured in a total of 133 samples from 19 patients. In the final two-compartment model with linear elimination, the estimated micafungin clearance (CL) was significantly higher in patients with cancer than in those without cancer (1.2 vs. 0.6 L/h, p = 0.012), whereas other parameters did not significantly differ between the two groups. Aspartate and alanine transaminases and body weight significantly influenced micafungin CL in patients, with and without cancer. Overall, the probability of target attainment increased with increasing doses and decreased with higher MICs in both groups. In simulations, the patients without cancer achieved higher pharmacokinetic/pharmacodynamic targets with a 90% probability for all simulated doses, compared to the patients with cancer. Micafungin demonstrated dose-proportional linear pharmacokinetics in both the patients with and those without cancer. The estimated micafungin CL was significantly higher in patients with cancer, suggesting a need for increased dosage, especially for Candida spp. with high MICs, in these patients. Further studies should assess the efficacy and optimum dosage of micafungin for the treatment and prevention of febrile neutropenia (FN) in patients with cancer.

Pharmacokinetics/Pharmacodynamics of caspofungin in plasma and peritoneal fluid of liver transplant recipients

Background: The weaker diffusion of echinocandins in the peritoneal fluid (PF) could promote Candida resistant isolates. The aim of this study was to analyse the pharmacokinetics/pharmacodynamics (PK/PD) of caspofungin in plasma and PF of liver transplant recipients.Methods: Liver transplant patients received caspofungin as postoperative prophylaxis. Caspofungin concentrations were quantified in plasma and in PF on Days 1, 3 and 8. Data were analysed using non-linear mixed-effect modelling and Monte Carlo simulations. Area under curve (AUC) in plasma and PF were simulated under three dosing regimens. Probabilities of target attainment (PTA) were calculated using fAUC_0-24/minimal inhibitory concentration (MIC) ratios with MICs ranging from 0.008 to 8 mg/litre. All the patients included were monitored weekly for Candida colonisation and for Candida infections.Results: Twenty patients were included. Median daily dose of caspofungin was 0.81 mg/kg. Plasma (n=395) and peritoneal (n=50) concentrations at steady state were available. A two-compartment model with first-order absorption and elimination was described. Our two-compartment model with first-order absorption and elimination model produced an effective PK/PD relationship in plasma, achieving a PTA ≥90% and MIC ranging from 0.008 to 0.12 mg/L for C. albicans and glabrata. In PF, PTAs at D8 were only optimal for a MIC of 0.008 in patients weighing 60 kg under the three dosing regimens. Among the 16 patients colonized, all MIC values were below the maximal concentration (Cmax) in plasma but not in PF.Conclusion: Peritoneal concentrations of caspofungin were low. Simulations showed that the PTA for Candida spp. in PF were not optimal, that might suggesting a potential risk of resistance.

Antifungal drugs: An updated review of central nervous system pharmacokinetics

Invasive fungal infections (IFIs) in the central nervous system (CNS) are particularly hard to treat and are associated with high morbidity and mortality rates. Four chemical classes of systemic antifungal agents are used for the treatment of IFIs (eg meningitis), including polyenes, triazoles, pyrimidine analogues and echinocandins. This review will address all of these classes and discuss their penetration and accumulation in the CNS. Treatment of fungal meningitis is based on the antifungal that shows good penetration and accumulation in the CNS. Pharmacokinetic data concerning the entry of antifungal agents into the intracranial compartments are faulty. This review will provide an overview of the ability of systemic antifungals to penetrate the CNS, based on previously published drug physicochemical properties and pharmacokinetic data, for evaluation of the most promising antifungal drugs for the treatment of fungal CNS infections. The studies selected and discussed in this review are from 1990 to 2019.

Synthesis, Optimization, Antifungal Activity, Selectivity, and CYP51 Binding of New 2-Aryl-3-azolyl-1-indolyl-propan-2-ols

A series of 2-aryl-3-azolyl-1-indolyl-propan-2-ols was designed as new analogs of fluconazole (FLC) by replacing one of its two triazole moieties by an indole scaffold. Two different chemical approaches were then developed. The first one, in seven steps, involved the synthesis of the key intermediate 1-(1H-benzotriazol-1-yl)methyl-1H-indole and the final opening of oxiranes by imidazole or 1H-1,2,4-triazole. The second route allowed access to the target compounds in only three steps, this time with the ring opening by indole and analogs. Twenty azole derivatives were tested against Candida albicans and other Candida species. The enantiomers of the best anti-Candida compound, 2-(2,4-dichlorophenyl)-3-(1H-indol-1-yl)-1-(1H-1,2,4-triazol-1-yl)-propan-2-ol (8g), were analyzed by X-ray diffraction to determine their absolute configuration. The (−)-8g enantiomer (Minimum inhibitory concentration (MIC) = IC₈₀ = 0.000256 µg/mL on C. albicans CA98001) was found with the S-absolute configuration. In contrast the (+)-8g enantiomer was found with the R-absolute configuration (MIC = 0.023 µg/mL on C. albicans CA98001). By comparison, the MIC value for FLC was determined as 0.020 µg/mL for the same clinical isolate. Additionally, molecular docking calculations and molecular dynamics simulations were carried out using a crystal structure of Candida albicans lanosterol 14α-demethylase (CaCYP51). The (−)-(S)-8g enantiomer aligned with the positioning of posaconazole within both the heme and access channel binding sites, which was consistent with its biological results. All target compounds have been also studied against human fetal lung fibroblast (MRC-5) cells. Finally, the selectivity of four compounds on a panel of human P450-dependent enzymes (CYP19, CYP17, CYP26A1, CYP11B1, and CYP11B2) was investigated.

Therapeutic drug monitoring of systemic antifungal agents: a pragmatic approach for adult and pediatric patients

Introduction: Therapeutic drug monitoring (TDM) has been shown to optimize the management of invasive fungal infections (IFIs), particularly for select antifungal agents with a well-defined exposure-response relationship and an unpredictable pharmacokinetic profile or a narrow therapeutic index. Select triazoles (itraconazole, voriconazole, and posaconazole) and flucytosine fulfill these criteria, while the echinocandins, fluconazole, isavuconazole, and amphotericin B generally do not do so. Given the morbidity and mortality associated with IFIs and the challenges surrounding the use of currently available antifungal agents, TDM plays an important role in therapy.Areas covered: This review seeks to describe the rationale for TDM of antifungal agents, summarize their pharmacokinetic and pharmacodynamic properties, identify treatment goals for efficacy and safety, and provide recommendations for optimal dosing and therapeutic monitoring strategies.Expert opinion: Several new antifungal agents are currently in development, including compounds from existing antifungal classes with enhanced pharmacokinetic or safety profiles as well as agents with novel targets for the treatment of IFIs. Given the predictable pharmacokinetics of these newly developed agents, use of routine TDM is not anticipated. However, expanded knowledge of exposure-response relationships of these compounds may yield a role for TDM to improve outcomes for adult and pediatric patients.

Methodologies for in vitro and in vivo evaluation of efficacy of antifungal and antibiofilm agents and surface coatings against fungal biofilms

Unlike superficial fungal infections of the skin and nails, which are the most common fungal diseases in humans, invasive fungal infections carry high morbidity and mortality, particularly those associated with biofilm formation on indwelling medical devices. Therapeutic management of these complex diseases is often complicated by the rise in resistance to the commonly used antifungal agents. Therefore, the availability of accurate susceptibility testing methods for determining antifungal resistance, as well as discovery of novel antifungal and antibiofilm agents, are key priorities in medical mycology research. To direct advancements in this field, here we present an overview of the methods currently available for determining (i) the susceptibility or resistance of fungal isolates or biofilms to antifungal or antibiofilm compounds and compound combinations; (ii) the in vivo efficacy of antifungal and antibiofilm compounds and compound combinations; and (iii) the in vitro and in vivo performance of anti-infective coatings and materials to prevent fungal biofilm-based infections.

Echinocandins: The Expanding Antifungal Armamentarium

The echinocandins are large lipopeptide molecules that, since their discovery approximately 41 years ago, have emerged as important additions to the expanding armamentarium against invasive fungal diseases. Echinocandins exert in vitro and in vivo fungicidal action against most Candida species and fungistatic action against Aspergillus species. However, the population of patients at risk for developing invasive fungal infections continues to increase. New therapeutic strategies using echinocandins are needed to improve clinical outcomes in patients with invasive fungal disease.

Azole-resistant Candida albicans prosthetic joint infection treated with prolonged administration of anidulafungin and two-stage exchange with implant of a mega-prosthesis

Fungal prosthetic joint infection (PJI) is a rare but severe complication of artroplasty. We report a case of PJI due to azole-resistant Candida albicans successfully treated with combination of prolonged administration of anidulafungin and two-stage joint exchange with insertion of a mega-prosthesis.

Rapid development of Candida krusei echinocandin resistance during caspofungin therapy

In invasive candidiasis, there has been an epidemiological shift from Candida albicans to non-albicans species infections, including infections with C. glabrata, C. parapsilosis, C. tropicalis, and C. krusei. Although the prevalence of C. krusei remains low among yeast infections, its intrinsic resistance to fluconazole raises epidemiological and therapeutic concerns. Echinocandins have in vitro activity against most Candida spp. and are the first-line agents in the treatment of candidemia. Although resistance to echinocandin drugs is still rare, individual cases of C. krusei resistance have been reported in recent years, especially with strains that have been under selective pressure. A total of 15 C. krusei strains, isolated from the blood, urine, and soft tissue of an acute lymphocytic leukemia patient, were analyzed. Strains developed echinocandin resistance during 10 days of caspofungin therapy. The molecular epidemiology of the isolates was investigated using two different typing methods: PCR-based amplification of the species-specific repetitive polymorphic CKRS-1 sequence and multilocus sequence typing. All isolates were genetically related, and the mechanism involved in decreased echinocandin susceptibility was characterized. Clinical resistance was associated with an increase in echinocandin MICs in vitro and was related to three different mutations in hot spot 1 of the target enzyme Fks1p. Molecular evidence of the rapid acquisition of resistance by different mutations in FKS1 highlights the need to monitor the development of resistance in C. krusei infections treated with echinocandin drugs.

Limited-sampling strategies for anidulafungin in critically ill patients

Efficacy of anidulafungin is driven by the area under the concentration-time curve (AUC)/MIC ratio. Determination of the anidulafungin AUC along with MIC values can therefore be useful. Since obtaining a full concentration-time curve to determine an AUC is not always feasible or appropriate, limited-sampling strategies may be useful in adequately estimating exposure. The objective of this study was to develop a model to predict the individual anidulafungin exposure in critically ill patients using limited-sampling strategies. Pharmacokinetic data were derived from 20 critically ill patients with invasive candidiasis treated with anidulafungin. These data were used to develop a two-compartment model in MW\Pharm using an iterative 2-stage Bayesian procedure. Limited-sampling strategies were subsequently investigated using two methods, a Bayesian analysis and a linear regression analysis. The best possible strategies for these two methods were evaluated by a Bland-Altman analysis for correlation of the predicted and observed AUC from 0 to 24 h (AUC0-24) values. Anidulafungin exposure can be adequately estimated with the concentration from a single sample drawn 12 h after the start of the infusion either by linear regression (R2=0.99; bias, 0.05%; root mean square error [RMSE], 3%) or using a population pharmacokinetic model (R2=0.89; bias, -0.1%; RMSE, 9%) in critically ill patients and also in less severely ill patients, as reflected by healthy volunteers. Limited sampling can be advantageous for future studies evaluating the pharmacokinetics and pharmacodynamics of anidulafungin and for therapeutic drug monitoring in selected patients. (This study has been registered at ClinicalTrials.gov under registration no. NCT01047267.).

Simultaneous quantification of anidulafungin and caspofungin in plasma by an accurate and simple liquid chromatography tandem mass-spectrometric method

INTRODUCTION

Echinocandins are a valuable addition for the treatment of invasive fungal infections, as they are efficacious, demonstrate low toxicity, and have limited drug-drug interactions. In specific clinical situations when altered pharmacokinetics can be expected or dosing guidelines are conflicting, it may be useful to measure concentrations. For this purpose, a liquid chromatography tandem mass-spectrometric method to measure anidulafungin and caspofungin in ethylenediaminetetraacetic acid plasma was developed.

METHODS

The method was developed on a Thermo Fisher TSQ Quantum LC-MS/MS. For separation, a BetaBasic C4 (100 mm × 3.0 mm; 5 μm) analytical column was used. Sample preparation consisted of protein precipitation directly in the autosampler vial. The internal standard aculeacin A is structurally related, not used in humans, and commercially available. The method was validated according to the guidelines for bioanalytical method validation of the Food and Drug Administration.

RESULTS

The method was accurate (bias ranging from -3.0% to 1.9%) and precise (within-run and between-run coefficients of variation of 2.2% to 7.7% and 1.6% to 9.0%, respectively). All calibration curves were linear over a range of 0.5-10.0 mg/L for anidulafungin and 0.1-20.0 mg/L for caspofungin, and if necessary, samples can be diluted 10-fold. The samples were stable for 3 freeze-thaw cycles, with a bias ranging from 0.6% to 11%. The maximum bias from the worst storage condition, 72 hours at room temperature, was -14.7%. In patient samples, anidulafungin peak concentrations ranged from 2.8 to 8.6 mg/L (n = 20) and trough concentrations ranged from 1.0 to 4.7 mg/L (n = 79). The measured caspofungin concentrations ranged from 1.9 to 7.3 mg/L (n = 20).

CONCLUSIONS

The method developed has a straightforward sample preparation and uses a structural analog as the internal standard. This method has been applied successfully for the measurement of anidulafungin and caspofungin concentrations in patient samples, both for clinical practice and for research.

Tissue penetration of antifungal agents

Understanding the tissue penetration of systemically administered antifungal agents is critical for a proper appreciation of their antifungal efficacy in animals and humans. Both the time course of an antifungal drug and its absolute concentrations within tissues may differ significantly from those observed in the bloodstream. In addition, tissue concentrations must also be interpreted within the context of the pathogenesis of the various invasive fungal infections, which differ significantly. There are major technical obstacles to the estimation of concentrations of antifungal agents in various tissue subcompartments, yet these agents, even those within the same class, may exhibit markedly different tissue distributions. This review explores these issues and provides a summary of tissue concentrations of 11 currently licensed systemic antifungal agents. It also explores the therapeutic implications of their distribution at various sites of infection.

Treatment with echinocandins during continuous renal replacement therapy

Echinocandins are indicated as first-line treatment for invasive candidiasis in moderate to severe illness. As sepsis is the main cause of acute kidney injury, the combination of echinocandin treatment and continuous renal replacement therapy (CRRT) is common. Optimizing antibiotic dosage in critically ill patients receiving CRRT is challenging. The pharmacokinetics of echinocandins have been studied under various clinical conditions; however, data for CRRT patients are scarce. Classically, drugs like echinocandins with high protein binding and predominantly non-renal elimination are not removed by CRRT, indicating that no dosage adjustment is required. However, recent studies report different proportions of echinocandins lost by filter adsorption. Nevertheless, the clinical significance of these findings remains unclear.

Candida infections, causes, targets, and resistance mechanisms: traditional and alternative antifungal agents

The genus Candida includes about 200 different species, but only a few species are human opportunistic pathogens and cause infections when the host becomes debilitated or immunocompromised. Candida infections can be superficial or invasive. Superficial infections often affect the skin or mucous membranes and can be treated successfully with topical antifungal drugs. However, invasive fungal infections are often life-threatening, probably due to inefficient diagnostic methods and inappropriate initial antifungal therapies. Here, we briefly review our current knowledge of pathogenic species of the genus Candida and yeast infection causes and then focus on current antifungal drugs and resistance mechanisms. An overview of new therapeutic alternatives for the treatment of Candida infections is also provided.

Anidulafungin Does Not Require Dosage Adjustment in Subjects With Varying Degrees of Hepatic or Renal Impairment

Two open-label studies assessed the effects of hepatic and renal impairment on anidulafungin pharmacokinetics. A single 50-mg dose was administered intravenously to subjects with varying degrees of hepatic or renal insufficiency or with end-stage renal disease; all were matched to normal healthy controls. Anidulafungin was well tolerated. AUC, CL, C(max), t(max), t(1/2), and V(ss) between renally impaired subjects and controls were not significantly different (P>.05), and no measurable amounts of drug were found in dialysate. The same pharmacokinetic parameters were also not affected (P>.05) by mild or moderate hepatic insufficiency, with respective mean AUCs of 50.6 +/- 11.7 microg x h/mL and 68.6 +/- 14.5 microg x h/mL, compared to 70.0 +/- 13.4 microg x h/mL in controls. Statistically significant decreases (P<05) of AUC (33% change) and C(max) (36% change) in severely hepatically impaired subjects compared to controls--most likely secondary to ascites and edema--were not clinically relevant. Anidulafungin can be safely administered to patients with any degree of hepatic or renal impairment without dosage adjustment and without regard to hemodialysis schedules.

Lack of Pharmacokinetic Interaction Between Anidulafungin and Tacrolimus

The safety and pharmacokinetics of anidulafungin coadministered with tacrolimus were investigated using a single-sequence, open-label design. Healthy volunteers received 5 mg tacrolimus orally on days 1 and 13 of the study. Anidulafungin (200 mg) was administered intravenously on day 4, followed by 100-mg doses on days 5 through 13. Key pharmacokinetic parameters, including C(max), AUC, t((1/2)), CL, and V(ss), were derived from concentration-time data. The 90% confidence intervals (CIs) of the ratios of mean pharmacokinetic parameters of anidulafungin plus tacrolimus to each drug alone were well within the 80% to 125% bioequivalence range, indicating no pharmacokinetic interaction. This ratio was 101.6 (90% CI: 92.77-111.22) for tacrolimus AUC(0-infinity) and 107.2 (90% CI: 105.1-109.4) for anidulafungin AUC(ss). The 2 drugs were well tolerated, and no drug-related serious adverse events were reported. Because of its lack of pharmacokinetic interaction with key immunosuppressive agents, anidulafungin is an important option for the prevention and treatment of invasive fungal infections in transplant recipients.

Activities of systemically administered echinocandins against in vivo mature Candida albicans biofilms developed in a rat subcutaneous model

This study addresses the effects of micafungin, caspofungin, and anidulafungin against Candida albicans biofilms developed in a subcutaneous catheter rat model system. Doses of 5, 10, and 30 mg/kg (of body weight)/day (the last only for micafungin) were given intravenously for 5, 7, and 10 days. All three echinocandins caused a significant reduction of the Candida cell numbers on the implanted catheters and are thus promising for the treatment of biofilm-related infections.

Population pharmacokinetic-pharmacodynamic analysis of anidulafungin in adult patients with fungal infections

To evaluate the exposure-response relationships for efficacy and safety of intravenous anidulafungin in adult patients with fungal infections, a population pharmacokinetic-pharmacodynamic (PK-PD) analysis was performed with data from 262 patients in four phase 2/3 studies. The plasma concentration data were fitted with a previously developed population PK model. Anidulafungin exposures in patients with weight extremities (e.g., 40 kg and 150 kg) were simulated based on the final PK model. Since the patient population, disease status, and efficacy endpoints varied in these studies, the exposure-efficacy relationship was investigated separately for each study using logistic regression as appropriate. Safety data from three studies (n = 235) were pooled for analysis, and one study was excluded due to concomitant use of amphotericin B as a study treatment and different disease populations. The analysis showed that the same dosing regimen of anidulafungin can be administered to all patients regardless of body weight. Nonetheless, caution should be taken for patients with extremely high weight (e.g., >150 kg). There was a trend of positive association between anidulafungin exposure and efficacy in patients with esophageal candidiasis or invasive candidiasis, including candidemia (ICC); however, adequate characterization of the effect of anidulafungin exposure on response could not be established due to the relatively small sample size. No threshold value for exposure could be established, since patients with low exposure also achieved successful outcomes (e.g., area under the curve < 40 mg · h/liter in ICC patients). There was no association between anidulafungin exposure and the treatment-related adverse events or all-causality hepatic laboratory abnormalities.

Comparison of micafungin and voriconazole in the treatment of invasive fungal infections in kidney transplant recipients

WHAT IS KNOWN AND OBJECTIVE

Invasive fungal infections are a major threat to renal transplant recipients. Micafungin and voriconazole are two useful antifungal agents for treating such infections. Our objective is to evaluate the comparative efficacy and safety of micafungin and voriconazole in the initial treatment of such infections.

METHODS

In this prospective, multicentre, open-labelled, randomized, controlled trial, renal transplant recipients with invasive fungal infections were assigned to receive either micafungin or voriconazole. The enrolled subjects received a kidney transplant between March 2008 and March 2010 at one of the two transplant centres in Henan Province, China. The efficacy and adverse effects of the two treatments were compared.

RESULTS AND DISCUSSION

The clinical trial enrolled 65 patients, of whom 31 were treated with micafungin, and 34 with voriconazole. The rates of microbiological evidence of infection in the micafungin and voriconazole groups were 64.5% and 70.5%, respectively, whereas the rates of Candida as the major cultured fungus were 80.0% and 75.0%, respectively. Complicated bacterial infection rates in the two treatment groups were 38.7% and 32.4%, respectively, whereas complicated CMV viral infection occurred at a rate of 19.2% and 23.5%, respectively. Fungal infection within one to 3 months after transplant was 83.6% (26/31) and 85.3% (29/34) in the micafungin and voriconazole groups, respectively. There was no significant difference between the two groups in terms of efficacy, survival beyond 10 days and discontinuation of treatment because of lack of efficacy (P > 0.05). Mortality rates in the micafungin and voriconazole groups were 9.7% (3/31) and 12.1% (4/33), respectively. Rates of adverse effects in the two groups were 41.9% and 51.6% (P > 0.05), respectively.

WHAT IS NEW AND CONCLUSIONS

This is the first comparison of micafungin and voriconazole in renal transplant patients. Our study shows that the effectiveness of micafungin was similar to that of voriconazole in such patients.

Effect of fluid loading during hypovolaemic shock on caspofungin pharmacokinetic parameters in pig

Introduction

Caspofungin treatment is frequently initiated in shock patients. In the present study, we investigated the influence of hypovolaemic shock requiring fluid loading on the plasma and pulmonary pharmacokinetic parameters of caspofungin in the pig.

Methods

After being anaesthetised and mechanically ventilated, 12 pigs were bled to induce a two-hour deep shock and resuscitated using normal saline based on haemodynamic goals. A one-hour infusion of 70 mg of caspofungin was started at the beginning of the resuscitation period. The lungs were removed four hours after caspofungin administration. Sixteen animals served as controls without haemorrhage. Caspofungin concentrations were measured by using high-performance liquid chromatography, and a two-compartment population pharmacokinetic analysis was performed.

Results

In the shock group, the volume of blood removed was 39 ± 7 mL/kg and a volume of 90 ± 17 mL/kg saline was infused throughout the resuscitation period. The extravascular lung water index was higher in the shock group (9.3 ± 1.6 mL/kg vs 5.7 ± 1 mL/kg in the control group; P < 0.01). In the shock group, the median (interquartile range) maximal plasma concentration was 37% lower than in the control group (21.6 μg/mL (20.7 to 22.3) vs 33.1 μg/mL (28.1 to 38.3); P < 0.01). The median area under curve (AUC) from zero to four hours was 25% lower in the shock group than in the control group (60.3 hours × μg/mL (58.4 to 66.4) vs 80.8 hours × μg/mL (78.3 to 96.9); P < 0.01), as was the median lung caspofungin concentration (1.22 μg/g (0.89 to 1.46) vs 1.64 μg/g (1.22 to 2.01); P < 0.01). However, the plasma-to-tissue ratios were not different between the groups, indicating that lung diffusion of caspofungin was not affected after shock followed by fluid loading. Pharmacokinetic analysis showed that the peripheral volume of distribution of caspofungin and intercompartmental clearance were significantly higher in the shock group, as was the total apparent volume of distribution.

Conclusions

Hypovolaemic shock followed by fluid loading in the pig results in a significant increase in the apparent volume of distribution of caspofungin and in a decrease in its plasma and pulmonary exposition. Although our model was associated with capillary leakage and pulmonary oedema, our results should be generalised to the septic shock with caution. Future investigations should focus on monitoring plasma caspofungin concentrations and optimal caspofungin dosing in shock patients.

Comparative in vitro susceptibility of clinical isolates of Candida paparsilosis complex and other Candida species to caspofungin and anidulafungin by Etest

In vitro susceptibility of 141 clinical isolates of Candida species to caspofungin and anidulafungin is reported. the Etest was performed according to recommended procedure and minimum inhibitory concentrations (MICs) were read after 24 h of incubation at 35 °C. Applying a breakpoint of <2 mg/ml, all Candida spp. isolates, except those belonging to C. parapsilosis complex, were susceptible. The geometric mean for caspofungin and anidulafungin for different Candida spp. were as follows: Candida parapsilosis, 0.438 and 3.355 μg/ml; Candida orthopsilosis, 0.210 and 1.456 μg/ml; Candida albicans, 0.049 and 0.007 μg/ml; Candida dubliniensis, 0.077 and 0.009 μg/ml; Candida tropicalis, 0.061 and 0.027 μg/ml; Candida glabrata, 0.120 and 0.032 μg/ml; and Candida krusei, 0.288 and 0.052 μg/ml, respectively. Anidulafungin was significantly more active than caspofungin (p <0.001) except for C. parapsilosis complex spp. isolates. In conclusion, our Etest MICs compared well with epidemiological cutoff values derived from a large number of Candida spp. isolates tested by CLSI method in previous studies. However, considering the differences in MICs of the two echinocandins for C. parapsilosis complex isolates, the Etest needs further evaluation for its suitability.

Endophthalmitis: Pathogenesis, clinical presentation, management, and perspectives

Endophthalmitis is a rare but sight-threatening complication that can occur after ocular surgery or trauma or as a consequence of systemic infection. To optimize visual outcome, early diagnosis and treatment are essential. Over recent decades, advances in hygienic standards, improved microbiologic and surgical techniques, development of powerful antimicrobial drugs, and the introduction of intravitreal antibiotic therapy have led to a decreased incidence and improved management of endophthalmitis. However, endophthalmitis still represents a serious clinical problem. This review focuses on current principles and techniques for evaluation and treatment of endophthalmitis. In addition, it addresses recent developments regarding antimicrobial treatment and prophylaxis of infectious endophthalmitis.

[Micafungin for therapy of invasive candidiasis in solid organ transplant recipients]

BACKGROUND

Micafungin is an echinocandin approved for the prevention of Candida spp. infection in hematopoietic stem cell transplantation and therapy of oesophageal candidiasis, disseminated candidiasis and candidemia in adults, children and neonates.

AIMS

To evaluate the role of micafungin for candidiasis therapy in solid organ transplant recipients.

METHODS

A medical literature review according to micafungin role for candidiasis therapy in transplant patients is performed.

RESULTS

Micafungin has shown fungicide activity against Candida species, including strains resistant or poorly susceptible to fluconazole. No dose adjustment is required when micafungin is administered in combination with other drugs used in transplant patients, excluding sirolimus, nifedipine and itraconazol. With these drugs, a minimal dose reduction is recommended. The results observed in transplant patients included in clinical trials are favourable and similar to results obtained in other kind of patients.

CONCLUSIONS

The clinical results, its safety profile and the low grade of medical interactions permit micafungin to be considered for therapy in specific groups of transplant patients.

Combination therapy of advanced invasive pulmonary aspergillosis in transiently neutropenic rats using human pharmacokinetic equivalent doses of voriconazole and anidulafungin

At present, voriconazole (VOR) is the drug of first choice for treating invasive pulmonary aspergillosis (IPA). However, particularly in advanced stages of disease and in the severely immunocompromised host, the mortality remains substantial. The combination of VOR with an echinocandin may improve the therapeutic outcome. We investigate here whether combining VOR and anidulafungin (ANI) in advanced IPA in transiently neutropenic rats results in a higher therapeutic efficacy. Since VOR is metabolized more rapidly in rodents than in humans, dosage adjustment for VOR is necessary to obtain an area under the plasma concentration-time curve (AUC) in rodents that is equivalent to that of humans. In this study, the pharmacokinetics of VOR and ANI in rats were elucidated, and dosage schedules were applied that produced AUCs similar to those of humans. The developed dose schedules were well tolerated by the rats, without effects on renal and hepatic functions. VOR showed excellent efficacy in early IPA (100% rat survival). In advanced IPA, VOR was less efficacious (50% rat survival), whereas a significant decrease in galactomannan concentrations in lungs and sera was found in surviving rats. ANI administered in advanced IPA resulted in 22% rat survival, and the serum concentrations of fungal galactomannan were slightly but not significantly decreased. The addition of ANI to VOR did not result in significantly increased therapeutic efficacy in advanced IPA, resulting in 67% rat survival and a significant decrease in galactomannan concentration in serum. In conclusion, VOR monotherapy is therapeutically effective in the treatment of advanced-stage IPA and superior to the use of ANI. Combining both agents does not significantly improve the therapeutic outcome.

Use of a serum-based antifungal susceptibility assay to predict the in vivo efficacy of novel echinocandin compounds

In vitro susceptibility assays of antifungal activity do not always accurately predict in vivo efficacy. As well as having a clear clinical importance, the ability to predict efficacy is also essential for effective screening of novel drug compounds. Initial screening of novel compounds must often be based on in vitro data. The present report describes the use of serum-MIC, an in vitro test of antifungal susceptibility, to accurately predict in vivo efficacy of echinocandin drugs in a mouse model of disseminated candidiasis. The basis of the serum-MIC method was to measure the inhibitory activity of a test compound against Candida albicans hyphal growth in the presence of pooled mouse serum. For 13 previously uncharacterized echinocandin compounds, as well as for the known echinocandin drugs, micafungin and caspofungin, serum-MIC determinations were shown to give better correlation to efficacy in the animal model than conventional, CLSI standard, in vitro antifungal susceptibility tests. The most accurate prediction of efficacy was obtained when the serum-MIC was adjusted in relation to the serum concentration at 30 min post-treatment. Furthermore, when the efficacy of micafungin was determined by measuring C. albicans kidney burden in the mouse model of infection, the adjusted serum-MIC consistently reflected the effective serum concentrations. Our data indicate that determination of serum-MIC values will facilitate prediction of the in vivo potency of new antifungal compounds such as novel echinocandins.

[Tolerance of caspofungin in intensive care unit: a prospective study]

OBJECTIVE

Caspofungin has shown efficacy and very low toxicity in empirical antifungal therapy in refractory invasive Aspergillus infections and invasive candidiasis in neutropenic (or non) patients. To date, there is no data on tolerability of caspofungin in ICU patients. The aim of this study was to evaluate caspofungine tolerability in critical care patients.

PATIENTS AND METHOD

Over a 36-month period, 1430 patients were admitted in a general intensive care unit. All patients data were collected in a prospective database. All the clinical or biological side effects reported in the multicentric studies were required. The patients were laminated in two groups, according to the initial hepatic function.

RESULTS

Seventy-three patients were treated with caspofungin (5.1%) and 58% were immunocompromised. Immunosuppression was due to acute leukemia (30%), solid organ transplant (20%) or other causes of immunosuppression. In this group, SAPS2 was higher (51+/-20 versus 44+/-20; p<0.05) as mortality rate was (60% versus 23%). More than 90% of patients were ventilated and 55% needed extrarenal therapy. Caspofungin treatment was initiated for aspergillosis in 12 patients, candidiasis in 33 patients and others indications. Partial or complete response to treatment was 72%. Median duration of caspofungin administration was 11 days, no liver dysfunction or acute renal failure due to caspofungin was reported whatever initial liver function was.

CONCLUSION

This prospective open study demonstrate the very low toxicity of caspofungin even in critical care patients.

[Anidulafungin: a new therapeutic approach in antifungal therapy. Pharmacology of anidulafungin]

Anidulafungin is a new echinocandin antifungal agent which inhibits beta-1,3-D-glucan synthase and disrupts fungal cell-wall synthesis. It has marked antifungal activity against Candida spp. and Aspergillus spp., including amphotericin B and triazole resistant strains. Due to the limited oral availability, anidulafungin in clinical use is available for parenteral administration only. Elimination of anidulafungin takes place via slow non-enzymatic degradation to inactive metabolites. Less than 10% and 1% of the initially administered drug is excreted unchanged into feces and urine, respectively. It does not require dosage adjustment in subjects with hepatic or renal impairment established. Anidulafungin is generally well tolerated. Adverse events appear not to be dose or infusion related. The most common treatment related adverse events are phlebitis, headache, nausea, vomiting and pyrexia. The lack of interactions with tacrolimus, cyclosporine and corticosteroids and its limited toxicity profile places anidulafungin as an attractive new option for the treatment of invasive fungal infections especially in transplant patients.

Pharmacokinetics and tissue distribution of anidulafungin in rats

This study assessed the tissue distribution of anidulafungin in rats. Anidulafungin rapidly distributed into tissues, achieving peak concentrations within 30 min, and maintained levels above MICs for common pathogens over 72 h. In tissues susceptible to fungal infection (liver, lung, spleen, kidney), exposure was 9- to 12-fold higher than in plasma.

Efficacy and safety of caspofungin for the empiric management of fever in neutropenic children

This retrospective review evaluates the response to caspofungin when given to children with febrile neutropenia and describes adverse effects attributable to caspofungin, including risk of hepatotoxicity during concomitant therapy with cyclosporine. Sixty-seven courses of caspofungin administered to 56 patients (1-17 years) were surveyed; 53 (79%) courses resulted in an overall favorable response. Ten children (15% of courses) experienced an adverse drug-related event that was probably or possibly attributable to caspofungin. Rash and hypokalemia were the most commonly identified adverse effects. One of 19 children receiving caspofungin and cyclosporine concurrently developed hepatotoxicity possibly related to caspofungin.

Fungal infections in solid organ transplantation

Renal, liver, heart and lung transplantation are now considered to be the standard therapeutic interventions in patients with end-stage organ failure. Infectious complications following transplantation are relatively common due to the transplant recipients overall immunosuppressed status. The incidence of invasive mycoses following solid organ transplant ranges from 5 to 42% depending on the organ transplanted. These mycoses are associated with high overall mortality rates. Candida and Aspergillus spp. produce most of these infections. This article will review the risk factors, clinical presentation and treatment of invasive fungal infections in solid organ transplant patients, and evaluate the role of prophylactic therapy in this group of patients.

A comparative evaluation of properties and clinical efficacy of the echinocandins

With the increase in prevalence of fungal infections, newer antifungal agents are needed to effectively treat invasive disease, and at the same time minimize adverse effects from therapy. The echinocandins comprise a novel class of antifungals; their mechanism of action involves inhibiting 1,3-beta-D-glucan synthase, which is essential in cell wall synthesis for certain fungi. All three echinocandins are US FDA-approved for the treatment of esophageal candidiasis. Caspofungin and anidulafungin are licensed for the treatment of candidemia, and other select forms of invasive candidiasis. Micafungin is at present the only echinocandin approved for prophylaxis of fungal infections in hematopoietic stem cell transplants; whereas caspofungin is approved for empiric therapy of febrile neutropenia. Although all three echinocandins are active against Aspergillus, only caspofungin is presently approved for salvage therapy in invasive aspergillosis. Combination therapy with echinocandins plus other licensed antifungal therapy shows promise in treating invasive aspergillosis. This article will explore the similarities and differences among the echinocandins.

[Systemic antifungals. Pharmacodynamics and pharmacokinetics]

Invasive fungal infections are important causes of morbidity and mortality in critically ill non neutropenic patients. For many years, amphotericin B and flucytosine have been the only available antifungal agents for invasive fungal infections. Fortunately, the antifungal armamentarium has increased during the past two decades with the addition of several new agents. In addition to itraconazole and fluconazole, lipid formulations of amphotericin B, voriconazole, and caspofungin have been recently licensed. These various antifungal agents differ in their pharmacokinetic and pharmacodynamic profile.