Fluconazole dosing in continuous veno-venous haemofiltration (CVVHF): need for a high daily dose of 800 mg

The Significance of Bayesian Pharmacokinetics in Dosing for Critically Ill Patients: A Primer for Clinicians Using Vancomycin as an Example

Antibiotic use is becoming increasingly challenging with the emergence of multidrug-resistant organisms. Pharmacokinetic (PK) alterations result from complex pathophysiologic changes in some patient populations, particularly those with critical illness. Therefore, antibiotic dose individualization in such populations is warranted. Recently, there have been advances in dose optimization strategies to improve the utilization of existing antibiotics. Bayesian-based dosing is one of the novel approaches that could help clinicians achieve target concentrations in a greater percentage of their patients earlier during therapy. This review summarizes the advantages and disadvantages of current approaches to antibiotic dosing, with a focus on critically ill patients, and discusses the use of Bayesian methods to optimize vancomycin dosing. The Bayesian method of antibiotic dosing was developed to provide more precise predictions of drug concentrations and target achievement early in therapy. It has benefits such as the incorporation of personalized PK/PD parameters, improved predictive abilities, and improved patient outcomes. Recent vancomycin dosing guidelines emphasize the importance of using the Bayesian method. The Bayesian method is able to achieve appropriate antibiotic dosing prior to the patient reaching the steady state, allowing the patient to receive the right drug at the right dose earlier in therapy.

Correlation of antimicrobial fraction unbound and sieving coefficient in critically ill patients on continuous renal replacement therapy: a systematic review

Background

Fraction unbound has been used as a surrogate for antimicrobial sieving coefficient (SC) to predict extracorporeal clearance in critically ill patients on continuous renal replacement therapy (CRRT), but this is based largely on expert opinion.

Objectives

To examine relationships between package insert-derived fraction unbound (Fu-P), study-specific fraction unbound (Fu-S), and SC in critically ill patients receiving CRRT.

Methods

English-language studies containing patient-specific in vivo pharmacokinetic parameters for antimicrobials in critically ill patients requiring CRRT were included. The primary outcome included correlations between Fu-S, Fu-P, and SC. Secondary outcomes included correlations across protein binding quartiles, serum albumin, and predicted in-hospital mortality, and identification of predictors for SC through multivariable analysis.

Results

Eighty-nine studies including 32 antimicrobials were included for analysis. SC was moderately correlated to Fu-S (R2 = 0.55, P < 0.001) and Fu-P (R2 = 0.41, P < 0.001). SC was best correlated to Fu-S in first (<69%) and fourth (>92%) quartiles of fraction unbound and above median albumin concentrations of 24.5 g/L (R2 = 0.71, P = 0.07). Conversely, correlation was weaker in patients with mortality estimates greater than the median of 55% (R2 = 0.06, P = 0.84). SC and Fu-P were also best correlated in the first quartile of antimicrobial fraction unbound (R2 = 0.66, P < 0.001). Increasing Fu-P, flow rate, membrane surface area, and serum albumin, and decreasing physiologic charge significantly predicted increasing SC.

Conclusions

Fu-S and Fu-P were both reasonably correlated to SC. Caution should be taken when using Fu-S to calculate extracorporeal clearance in antimicrobials with 69%–92% fraction unbound or with >55% estimated in-hospital patient mortality. Fu-P may serve as a rudimentary surrogate for SC when Fu-S is unavailable.

Pharmacokinetic Variability and Target Attainment of Fluconazole in Critically Ill Patients

Background: Fluconazole is one of the oldest antifungal drugs. Previous studies have raised concerns considering variability in exposure and inadequate target attainment in critically ill patients. The current study aims to define variability and target attainment for fluconazole exposure in a large group of critically ill patients. Methods: In this pharmacokinetic study, daily plasma trough samples and, if possible, 24 h urine samples were collected to determine fluconazole concentration. A minimum target trough concentration of 10-15 mg/L was selected, corresponding to a free area under the concentration-time curve above the minimum inhibitory concentration (fAUC/MIC) of at least 100 for an MIC of 4 mg/L. Covariates that significantly influenced fluconazole exposure were identified. Results: In total, 288 plasma samples from 43 patients, with a median age of 66 years, were included. The median fluconazole trough concentration was 22.9 mg/L. A notable component of the measured concentrations was below the target trough concentrations (13% <10 mg/L and 27% <15 mg/L). The intra- and intersubject variability were 28.3% and 50.5%, respectively. The main covariates determining fluconazole exposure were the administered dose (mg/kg), augmented renal clearance, and renal replacement therapy. Conclusions: Fluconazole trough concentrations are variable in critically ill patients and a considerable number of these concentrations was below the predefined target trough concentrations.

Current fluconazole treatment regimens result in under-dosing of critically ill adults during early therapy

PURPOSE

To evaluate current fluconazole treatment regimens in critically ill adults over the typical treatment course.

METHODS

Data from critically ill adults treated with fluconazole (n=30) were used to develop a population pharmacokinetic model. Probability of target attainment (PTA) (fAUC₂₄/MIC >100) was determined from simulations for four previously proposed treatment regimens: (i) 400 mg once daily, (ii) an 800 mg loading dose followed by 400 mg once daily, (iii) 400 mg twice daily, and (iv) a 12 mg/kg loading dose followed by 6 mg/kg once daily. The effect of body weight (40, 70, 120 kg) and renal function (continuous renal replacement therapy (CRRT); 20, 60, 120, 180 mL/min creatinine clearance) on PTA was assessed.

RESULTS

Early (0-48 h) fluconazole target attainment for infections with a minimum inhibitory concentration (MIC) of 2 mg/L was highly variable. PTA was highest with an 800 mg loading dose for underweight (40 kg) patients and with a 12 mg/kg loading dose for the remainder. End-of-treatment PTA was highest with the 400 mg twice daily maintenance dosing for patients who were under- or normal weight and 6 mg/kg maintenance dosing for overweight (120 kg) patients. None of the fluconazole regimens reliably attained early targets for MICs of ≥4 mg/L.

CONCLUSION

Current fluconazole dosing regimens do not achieve adequate early target attainment in critically ill adults, particularly in those who are overweight, have higher creatinine clearance, or are undergoing CRRT. Current fluconazole dosing strategies are generally inadequate to treat organisms with an MIC of ≥4 mg/L.

Elimination of fluconazole during continuous renal replacement therapy. An in vitro assessment

Introduction:

Continuous renal replacement therapy (CRRT) efficiently eliminates fluconazole. However, the routes of elimination were not clarified. Adsorption of fluconazole by filters is a pending question. We studied the elimination of fluconazole in a model mimicking a session of CRRT in humans using the NeckEpur® model. Two filters were studied.

Methods:

The AV1000®-polysulfone filter with the Multifiltrate Pro. Fresenius and the ST150®-polyacrylonitrile filter with the Prismaflex. Baxter-Gambro were studied. Continuous filtration used a flowrate of 2.5 L/h in post-dilution only. Session were made in duplicate. Routes of elimination were assessed using the NeckEpur® model.

Results:

The mean measured initial fluconazole concentration (mean ± SD) for the four sessions in the central compartment (CC) was 14.9 ± 0.2 mg/L. The amount eliminated from the CC at the end of 6 h-session at a 2.5 L/h filtration flowrate for the AV1000®-polysulfone and the ST150®-polyacrylonitrile filters were 90%–93% and 96%–94%, respectively; the clearances from the central compartment (CC) were 2.5–2.6 and 2.4–2.3 L/h, respectively. The means of the instantaneous sieving coefficient were 0.94%–0.91% and 0.99%–0.91%, respectively. The percentages of the amount eliminated from the CC by filtration/adsorption were 100/0%–95/5% and 100/0%–100/0%, respectively.

Conclusion:

Neither the ST150®-polyacrylonitrile nor the AV1000®-polysulfone filters result in any significant adsorption of fluconazole.

Challenges in Antifungal Therapy in Diabetes Mellitus

Diabetic patients have an increased propensity to Candida sp. infections due to disease-related immunosuppression and various other physiological alterations. The incidence of candidiasis has increased in number over the years and is linked to significant morbidity and mortality in critically ill and immunosuppressed patients. Treatment of infection in diabetic patients may be complicated due to the various disease-related changes to the pharmacokinetics and pharmacodynamics (PK/PD) of a drug, including antifungal agents. Application of PK/PD principles may be a sensible option to optimise antifungal dosing regimens in this group of patients. Further studies on PK/PD of antifungals in patients with diabetes mellitus are needed as current data is limited or unavailable.

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.

A Guide to Understanding Antimicrobial Drug Dosing in Critically Ill Patients on Renal Replacement Therapy

A careful management of antimicrobials is essential in the critically ill with acute kidney injury, especially if renal replacement therapy is required. Acute kidney injury may lead per se to clinically significant modifications of drugs' pharmacokinetic parameters, and the need for renal replacement therapy represents a further variable that should be considered to avoid inappropriate antimicrobial therapy. The most important pharmacokinetic parameters, useful to determine the significance of extracorporeal removal of a given drug, are molecular weight, protein binding, and distribution volume. In many cases, the extracorporeal removal of antimicrobials can be relevant, with a consistent risk of underdosing-related treatment failure and/or potential onset of bacterial resistance. It should also be taken into account that renal replacement therapies are often not standardized in critically ill patients, and their impact on plasma drug concentrations may substantially vary in relation to membrane characteristics, treatment modality, and delivered dialysis dose. Thus, in this clinical scenario, the knowledge of the pharmacokinetic and pharmacodynamic properties of different antimicrobial classes is crucial to tailor maintenance dose and/or time interval according to clinical needs. Finally, especially for antimicrobials known for a tight therapeutic range, therapeutic drug monitoring is strongly suggested to guide dosing adjustment in complex clinical settings, such as septic patients with acute kidney injury undergoing renal replacement therapy.

Overview of antifungal dosing in invasive candidiasis

In the past, most antifungal therapy dosing recommendations for invasive candidiasis followed a 'one-size fits all' approach with recommendations for lowering maintenance dosages for some antifungals in the setting of renal or hepatic impairment. A growing body of pharmacokinetic/pharmacodynamic research, however now points to a widespread 'silent epidemic' of antifungal underdosing for invasive candidiasis, especially among critically ill patients or special populations who have altered volume of distribution, protein binding and drug clearance. In this review, we explore how current adult dosing recommendations for antifungal therapy in invasive candidiasis have evolved, and special populations where new approaches to dose optimization or therapeutic drug monitoring may be needed, especially in light of increasing antifungal resistance among Candida spp.

Survival in Patients with Candida glabrata Bloodstream Infection Is Associated with Fluconazole Dose

Robust pharmacodynamic indices that align fluconazole dose or exposure with outcomes in invasive candidiasis due to Candida glabrata remain elusive. The purpose of this retrospective multicenter study was to evaluate a cohort of 127 patients with C. glabrata fungemia treated with fluconazole, using adjusted analyses to identify risk factors for 28-day death. No significant correlations were found between fluconazole area under the curve (AUC), AUC/MIC ratio, or MIC and survival. In multivariate logistic regression analyses, however, higher average fluconazole dose (odds ratio [OR], 1.006 [95% confidence interval [CI], 1.001 to 1.010]; P = 0.008), average fluconazole dose of ≥400 mg (OR, 3.965 [95% CI, 1.509 to 10.418]; P = 0.005), and higher fluconazole dose on day 1 of therapy (OR, 1.007 [95% CI, 1.002 to 1.011]; P = 0.002) were found to be independent predictors of 28-day survival. Additionally, the presence of a central venous catheter at the time of infection was found to be a significant risk factor for death. In conclusion, we found fluconazole dose to be an independent predictor of 28-day survival for patients with C. glabrata fungemia, with doses of ≥400 mg/day being associated with 28-day survival rates approaching 90%. These data indicate the use and efficacy of fluconazole in the treatment of this serious infection. Aggressive dosing appears to be necessary when fluconazole is used for the treatment of C. glabrata fungemia, irrespective of MIC.

The Big Bang of Hemofiltration: The Beginning of a New Era in the Third Millennium for Extra-Corporeal Blood Purification!

Since the last decade, hemofiltration and especially high volume hemofiltration has rapidly evolved from a somewhat experimental treatment towards a potentially effective “adjunctive” therapy in severe septic shock and especially refractory or catecholamine resistant hypodynamic septic shock. Nevertheless, this approach lacks prospective randomized studies (PRT'S) evaluating the critical role of early hemofiltration in sepsis. An important step forward which could be called the “big bang” in term of hemofiltration was the publication of a PRT in patients with acute renal failure (ARF) (1). Before this study (2), nobody believed that hemofiltration could change the survival rate in intensive care. Since that big bang, many physicians consider that hemofiltration at a certain dose can change the survival rate in intensive care. So the world of hemofiltration in ICU is not a definitive world, it is still in expansion. Indeed, we now have to try to define what will be the exact dose we need in septic acute renal failure. This dose might well be “higher” than 35 ml/kg/hour in the septic acute renal failure “group” as suggested by many studies (2–5). At present, it is the issue of continuous dose of high volume hemofiltration that has to be tested in future randomized studies. Since the Vicenza study (2) has shown that 35 ml/kg/h is the best dose in terms of survival, dealing with non septic acute renal failure in ICU, several studies from different groups have shown that, in septic acute renal failure, a higher dose might correlate with better survival. This has also been shown in some way by the study of the “Vicenza group” but not with a statistically significant value (2). New PRT'S have just started in Europe like the IVOIRE study (hIgh VOlume in Intensive caRE) (6) and the RENAL study. Another large study is looking more basically at dose in non septic acute renal failure in Australasia and is led by the group of Rinaldo Bellomo in Melbourne (7) as well as the ATN study (8) led by Palevsky and colleagues in the USA, also testing the importance of dose in the treatment for ARF. Nevertheless, “early goal-directed hemofiltration therapy” like early goal directed therapy (9) has to be studied in our critical ill patients. Regarding this issue, fewer studies, mainly retrospective exist, but again the IVOIRE study (6) will address this issue by studying septic patients with acute renal injury according to the Rifle classification (10). So, this review focuses on the early application and on the adequate dose of continuous high volume hemofiltration in septic shock in order to improve not only hemodynamics, but survival in this very severely ill cohort of patients. This could well be called the “big bang of hemofiltration” as one could never have anticipated that an adequate dose of hemofiltration could markedly influence the survival rate of ICU-septic acute renal failure patients. On top of the use of early and adequate dose of hemofiltration in sepsis, a higher dose could also provide better renal recovery rate and reduce the risk of associate chronic dialysis in these patients. Furthermore, this paper also reviews “brand” new theories regarding the rationale for hemofiltration in sepsis. Finally, this paper also addresses the so-called negative studies as well anticipated side effects.

Long QTc Interval and Torsade de Pointes Caused by Fluconazole

Objective:

To describe a patient who developed torsade de pointes while being treated with fluconazole.

Case Summary:

A 33-year-old woman with a 5 year history of systemic lupus erythematosus was admitted to the intensive care unit because of respiratory insufficiency due to Candida albicans pneumonia. Therapy with intravenous fluconazole 200 mg/day, with dose later adjusted according to her renal function, was started. Prolongation of the QTc interval and torsade de pointes occurred. Initially, domperidone, which had been initiated the day before fluconazole, was suspected as the possible cause and was discontinued; ultimately, both drugs were discontinued. However, torsade de pointes recurred several weeks later when the patient was treated with fluconazole for a second time and disappeared again on withdrawal of the drug. According to the Naranjo probability scale, this adverse reaction was highly probable.

Discussion:

The risk of torsade de pointes does not correlate in a linear fashion with prolongation of the QTc interval, but an interval beyond 500 msec is considered a significant risk factor. Given that both fluconazole and domperidone are metabolized by the cytochrome P450 system, they may intensify each other's proarrhythmic effects, particularly in patients with concurrent renal dysfunction. These risks are of particular concern in patients whose baseline QTc interval is prolonged for any reason.

Conclusions:

From the case history, as well as use of the Naranjo scale, we concluded that fluconazole was the highly probable cause of the development of torsade de pointes in our patient.

Antimicrobial dosing in critically ill patients with sepsis-induced acute kidney injury

Severe sepsis often leads to multiple organ dysfunction syndromes (MODS) with acute kidney injury (AKI). AKI affects approximately, 35% of Intensive Care Unit patients, and most of these are due to sepsis. Mortality rate of sepsis-induced AKI is high. Inappropriate use of antimicrobials may be responsible for higher therapeutic failure, mortality rates, costs and toxicity as well as the emergence of resistance. Antimicrobial treatment is particularly difficult due to altered pharmacokinetic profile, dynamic changes in patient's clinical status and, in many cases, need for renal replacement therapy. This article aims to describe the appropriate antimicrobial dosing and reviews the factors contributing to the difficulties in establishing precise guidelines for antimicrobial dosing in sepsis-induced AKI patients.

SEARCH STRATEGY

Text material was collected by systematic search in PubMed, Google (1978-2013) for original articles.

Anti-infective drugs during continuous hemodialysis - using the bench to learn what to do at the bedside

PURPOSE

The main objective of this study was to investigate the clearance of 11 selected anti-infectives in an in vitro model of continuous veno-venous hemodialysis (CVVHD), in order to suggest rational dosing strategies for clinical practice.

METHODS

Ceftazidime, ciprofloxacin, flucloxacillin, gentamicin, linezolid, meropenem, metronidazole, piperacillin, rifampicin, vancomycin and voriconazole were studied in two different solvents (sodium chloride 0.9% and HSA 5%) using a multifiltrate dialysis device by Fresenius Medical Care (Bad Homburg, Germany). For each solution, prefilter, postfilter, and dialysate samples were drawn simultaneously during one hour of dialysis and were assayed.

RESULTS

The clearance of all drugs except rifampicin in sodium chloride 0.9% was comparable (mean 1.76 ± 0.11 l/h). The clearance of these agents in human serum albumin solution 5% was reduced by between 5.3% and 72.2%. The unbound drug fraction correlated with a lower clearance in HSA 5% (Pearson correlation coefficient r = 0.933; p = 0.00008). No correlation between clearance in HSA 5% and the drugs' molecular weight was found (Pearson correlation coefficient r = 0.388; p = 0.268). Rifampicin was detected to bind to the surface of the polysulfone filter used. Dialysis clearance of ceftazidime, gentamicin, linezolid, meropenem, metronidazole, piperacillin and vancomycin during CVVHD accounted for over 25% of the total body clearance of population pharmacokinetic data for renally impaired patients.

CONCLUSIONS

The results from this study highlight that dose adaptations are needed for most of the drugs under investigation for patients undergoing CVVHD. In combination with polysulfone filters, rifampicin should be used with care in this setting.

Pharmacokinetics of fluconazole in critically ill patients with acute kidney injury receiving sustained low-efficiency diafiltration

Fluconazole is a widely used antifungal agent in critically ill patients. It is predominantly (60-80%) excreted unchanged in urine. Sustained low-efficiency diafiltration (SLED-f) is increasingly being utilised in critically ill patients because of its practical advantages over continuous renal replacement therapy. To date, the effect of SLED-f on fluconazole pharmacokinetics and dosing has not been studied. The objective of this study was to describe the pharmacokinetics of fluconazole in critically ill patients with acute kidney injury receiving SLED-f and to compare this with other forms of renal replacement therapy. Serial blood samples were collected at pre- and post-filter ports within the SLED-f circuit during SLED-f and from an arterial catheter before and after SLED-f from three patients during one session. Fluconazole concentrations were measured using a validated chromatography method. Median clearance (CL) and 24-h area under the concentration-time curve (AUC0-24) were 2.1L/h and 152 mg·h/L, respectively, whilst receiving SLED-f. Moreover, 72% of fluconazole was cleared by a single SLED-f session (6h) compared with previous reports of 33-38% clearance by a 4-h intermittent haemodialysis session. CL and AUC0-24 were comparable with previous observations in a pre-dilution mode of continuous venovenous haemodiafiltration. The observed rebound concentration of fluconazole post SLED-f was <2%. Although a definitive dosing recommendation is not possible due to the small patient number, it is clear that doses >200mg daily are likely to be required to achieve the PK/PD target for common pathogens because of significant fluconazole clearance by SLED-f.

Fluconazole pharmacokinetics in a morbidly obese, critically ill patient receiving continuous venovenous hemofiltration

Current fluconazole dosing strategies can be described using either standardized doses (800 or 400 mg) or as weight-based dosing recommendations (12 mg/kg loading dose followed by 6 mg/kg maintenance dose). The ideal method of fluconazole dosing is still unclear for certain patient populations, such as those receiving renal replacement therapy or the morbidly obese. We describe a 48-year-old man with a body mass index of 84 kg/m(2) who was receiving continuous venovenous hemofiltration (CVVH) and was treated with fluconazole by using a weight-based dose determined by lean body weight, infused at a rate of 200 mg/hour. Blood samples were collected at hour 0 (i.e., ~24 hrs after the loading dose was administered) and at 3.5, 6.8, and 11.3 hours after the start of the 600-mg maintenance dose, infused over 3 hours. Pharmacokinetic parameters calculated were maximum serum concentration 9.64 mg/L, minimum serum concentration 5.98 mg/L, area under the serum concentration-time curve from 0-24 hours (AUC0-24 ) 184.75 mg/L•hour, elimination rate constant 0.0199 hour(-1) , elimination half-life 34.8 hours, and total body clearance 3.25 L/hour. Our data, when combined with previously published literature, do not support using a linear dose-to-AUC approximation to estimate drug dosing needs in the critically ill patient population receiving CVVH. In addition, our results suggest that morbidly obese patients are able to achieve pharmacodynamic goals defined as an AUC:MIC ratio higher than 25 by using a lean body weight for fluconazole dosing calculations.

EPICO 2.0 project. Development of educational therapeutic recommendations using the DELPHI technique on invasive candidiasis in critically ill adult patients in special situations

BACKGROUND

Although there has been an improved management of invasive candidiasis in the last decade, still controversial issues remain, especially in different therapeutic critical care scenarios.

AIMS

We sought to identify the core clinical knowledge and to achieve high agreement recommendations required to care for critically ill adult patients with invasive candidiasis for antifungal treatment in special situations and different scenarios.

METHODS

Second prospective Spanish survey reaching consensus by the DELPHI technique, conducted anonymously by electronic e-mail in the first phase to 23 national multidisciplinary experts in invasive fungal infections from five national scientific societies including intensivists, anesthesiologists, microbiologists, pharmacologists and infectious disease specialists, answering 30 questions prepared by a coordination group after a strict review of literature in the last five years. The educational objectives spanned four categories, including peritoneal candidiasis, immunocompromised patients, special situations, and organ failures. The agreement among panelists in each item should be higher than 75% to be selected. In a second phase, after extracting recommendations from the selected items, a meeting was held with more than 60 specialists in a second round invited to validate the preselected recommendations.

MEASUREMENTS AND MAIN RESULTS

In the first phase, 15 recommendations were preselected (peritoneal candidiasis (3), immunocompromised patients (6), special situations (3), and organ failures (3)). After the second round the following 13 were validated: Peritoneal candidiasis (3): Source control and early adequate antifungal treatment is mandatory; empirical antifungal treatment is recommended in secondary nosocomial peritonitis with Candida spp. colonization risk factors and in tertiary peritonitis. Immunocompromised patients (5): consider hepatotoxicity and interactions before starting antifungal treatment with azoles in transplanted patients; treat candidemia in neutropenic adult patients with antifungal drugs at least 14 days after the first blood culture negative and until normalization of neutrophils is achieved. Caspofungin, if needed, is the echinocandin with most scientific evidence to treat candidemia in neutropenic adult patients; caspofungin is also the first choice drug to treat febrile candidemia; in neutropenic patients with candidemia remove catheter. Special situations (2): in moderate hepatocellular failure, patients with invasive candidiasis use echinocandins (preferably low doses of anidulafungin and caspofungin) and try to avoid azoles; in case of possible interactions review all the drugs involved and preferably use anidulafungin. Organ failures (3): echinocandins are the safest antifungal drugs; reconsider the use of azoles in patients under renal replacement therapy; all of the echinocandins to treat patients under continuous renal replacement therapy are accepted and do not require dosage adjustment.

CONCLUSIONS

Treatment of invasive candidiasis in ICU patients requires a broad range of knowledge and skills as summarized in our recommendations. These recommendations may help to optimize the therapeutic management of these patients in special situations and different scenarios and improve their outcome based on the DELPHI methodology.

[Pharmacokinetic and pharmacodynamic aspects in antibiotic treatment]

Severe sepsis and septic shock have a high mortality and, therefore require fast and effective antibiotic treatment with low toxicity. Because of sepsis-induced pathophysiological changes, pharmacokinetics of antimicrobial agents can be altered. Particularly water-soluble drugs display an enhanced volume of distribution during early sepsis. Therefore high loading doses are necessary. Renal clearance can also be increased at this time. Later on, organ damage frequently occurs resulting in delayed drug elimination which requires further dose adjustment. The different classes of antibiotics differ in their relevant pharmacokinetic-pharmacodynamic target parameters. Thus, the efficacy of an antimicrobial agent can depend on its concentration, on the exposure time, and on the total exposure as expressed by the area under the time-concentration curve. During treatment with time-dependent antibiotics (e.g. β-lactams), their concentration should be maintained above the minimal inhibitory concentration (MIC) warranting more frequent administration or continuous infusion. For concentration dependent agents (e.g. aminoglycosides), the single dose is pivotal, whereas the dosage interval can be extended. Drug-drug interactions involving antibiotics are mainly caused by inhibition of their metabolism, particularly of cytochrome P 450 iso-enzymes, or by additive toxic effects. They can result in severe complications such as renal failure or ventricular arrhythmias. Conversely, enzyme induction may lead to subtherapeutic drug levels. When continuous renal replacement therapy is required, the dosage of antibiotics has to be adapted according to the results of respective pharmacokinetic studies.

[Antifungal treatment options in the critically ill patient]

Invasive fungal infections, especially in the critical care setting, have become an excellent target for prophylactic, empiric, and pre-emptive therapy interventions due to their associated high morbidity, mortality rate, increased incidence, and healthcare costs. For these reasons, new studies and laboratory tests have been developed over the last few years in order to formulate an early therapeutic intervention strategy in an attempt to reduce the high mortality rate associated with these infections. In recent years, evidence-based studies have shown the roles that the new antifungal drugs play in the treatment of invasive mycosis in seriously ill and complex patients, although data from critically ill patients are more limited. New antifungal agents have been analyzed in different clinical situations in critical care units, and the increasing number of non-Candida albicans species suggest that the application of early echinocandin therapy in critically ill patients with invasive candidiasis is a good option. Voriconazole should be recommended for invasive aspergillosis as a first line option.

Fluconazole inhibits human adrenocortical steroidogenesis in vitro

The antifungal agent ketoconazole is often used to suppress cortisol production in patients with Cushing's syndrome (CS). However, ketoconazole has serious side effects and is hepatotoxic. Here, the in vitro effects of ketoconazole and fluconazole, which might be less toxic, on human adrenocortical steroidogenesis were compared. The effects on steroidogenesis were examined in primary cultures of nine human adrenocortical tissues and two human adrenocortical carcinoma cell lines. Moreover, the effects on mRNA expression levels of steroidogenic enzymes and cell growth were assessed. Ketoconazole significantly inhibited 11-deoxycortisol (H295R cells; maximum inhibition 99%; EC(50) 0.73 μM) and cortisol production (HAC15 cells; 81%; EC(50) 0.26 μM and primary cultures (mean EC(50) 0.75 μM)). In cultures of normal adrenal cells, ketoconazole increased pregnenolone, progesterone, and deoxycorticosterone levels, while concentrations of 17-hydroxypregnenolone, 17-hydroxyprogesterone, 11-deoxycortisol, DHEA, and androstenedione decreased. Fluconazole also inhibited 11-deoxycortisol production in H295R cells (47%; only at 1 mM) and cortisol production in HAC15 cells (maximum inhibition 55%; EC(50) 35 μM) and primary cultures (mean EC(50) 67.7 μM). In the cultures of normal adrenals, fluconazole suppressed corticosterone, 17-hydroxypregnenolone, and androstenedione levels, whereas concentrations of progesterone, deoxycorticosterone, and 11-deoxycortisol increased. Fluconazole (1 mM) slightly increased STAR mRNA expression in both cell lines. Neither compound affected mRNA levels of other steroidogenic enzymes or cell number. In conclusion, by inhibiting 11β-hydroxylase and 17-hydroxylase activity, pharmacological concentrations of fluconazole dose dependently inhibit cortisol production in human adrenocortical cells in vitro. Although fluconazole seems less potent than ketoconazole, it might become an alternative for ketoconazole to control hypercortisolism in CS. Furthermore, patients receiving fluconazole because of mycosis might be at risk for developing adrenocortical insufficiency.

Population pharmacokinetics of fluconazole in critically ill patients receiving continuous venovenous hemodiafiltration: using Monte Carlo simulations to predict doses for specified pharmacodynamic targets

Fluconazole is a widely used antifungal agent that is extensively reabsorbed in patients with normal renal function. However, its reabsorption can be compromised in patients with acute kidney injury, thereby leading to altered fluconazole clearance and total systemic exposure. Here, we explore the pharmacokinetics of fluconazole in 10 critically ill anuric patients receiving continuous venovenous hemodiafiltration (CVVHDF). We performed Monte Carlo simulations to optimize dosing to appropriate pharmacodynamic endpoints for this population. Pharmacokinetic profiles of initial and steady-state doses of 200 mg intravenous fluconazole twice daily were obtained from plasma and CVVHDF effluent. Nonlinear mixed-effects modeling (NONMEM) was used for data analysis and to perform Monte Carlo simulations. For each dosing regimen, the free drug area under the concentration-time curve (fAUC)/MIC ratio was calculated. The percentage of patients achieving an AUC/MIC ratio greater than 25 was then compared for a range of MIC values. A two-compartment model adequately described the disposition of fluconazole in plasma. The estimate for total fluconazole clearance was 2.67 liters/h and was notably 2.3 times faster than previously reported in healthy volunteers. Of this, fluconazole clearance by the CVVHDF route (CL(CVVHDF)) represented 62% of its total systemic clearance. Furthermore, the predicted efficiency of CL(CVVHDF) decreased to 36.8% when filters were in use >48 h. Monte Carlo simulations demonstrated that a dose of 400 mg twice daily maximizes empirical treatment against fungal organisms with MIC up to 16 mg/liter. This is the first study we are aware of that uses Monte Carlo simulations to inform dosing requirements in patients where tubular reabsorption of fluconazole is probably nonexistent.

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.

Pharmacokinetic evaluation of fluconazole in critically ill patients

INTRODUCTION

Invasive candidiasis has emerged over the last few decades as an increasingly important nosocomial problem for the critically ill, affecting around 2% of intensive care unit patients. Although poor outcomes associated with invasive candidiasis among critically ill patients may relate to severe underlying disease processes and delayed institution of antifungal therapy, inadequate dosing of antifungal agents may also contribute.

AREAS COVERED

This drug evaluation provides a critical appraisal of the published literature pertaining to the pharmacokinetics of fluconazole in critically ill, obese or severely burned patients, including those receiving acute renal replacement therapy. The pharmacodynamics of fluconazole is also covered, as well as the likely clinical implications for optimal dosing and the toxicity of fluconazole. Last, variations in fluconazole susceptibility patterns of Candida spp. are also discussed.

EXPERT OPINION

Recently, there has been an increased but geographically variable prevalence of non-albicans Candida spp., causing invasive candidiasis and an overall trend towards reduced fluconazole susceptibility. The pathophysiological changes of critical illness, coupled with a lack of dose finding studies, support the use of local susceptibility patterns to guide fluconazole dosing until such time as pharmacokinetic-pharmacodynamic information to guide optimal fluconazole dosing strategies and pharmacodynamic targets becomes available.

Antibiotic dosing in critically ill patients with acute kidney injury

A common cause of acute kidney injury (AKI) is sepsis, which makes appropriate dosing of antibiotics in these patients essential. Drug dosing in critically ill patients with AKI, however, can be complicated. Critical illness and AKI can both substantially alter pharmacokinetic parameters as compared with healthy individuals or patients with end-stage renal disease. Furthermore, drug pharmacokinetic parameters are highly variable within the critically ill population. The volume of distribution of hydrophilic agents can increase as a result of fluid overload and decreased binding of the drug to serum proteins, and antibiotic loading doses must be adjusted upwards to account for these changes. Although renal elimination of drugs is decreased in patients with AKI, residual renal function in conjunction with renal replacement therapies (RRTs) result in enhanced drug clearance, and maintenance doses must reflect this situation. Antibiotic dosing decisions should be individualized to take into account patient-related, RRT-related, and drug-related factors. Efforts must also be made to optimize the attainment of antibiotic pharmacodynamic goals in this population.

Antimicrobial dosing strategies in critically ill patients with acute kidney injury and high-dose continuous veno-venous hemofiltration

PURPOSE OF REVIEW

Delivery of appropriate antimicrobial therapy is a great challenge during continuous veno-venous hemofiltration (CVVH), particularly if the recommended higher doses are applied. The present contribution discusses the principles of drug dosing during CVVH and compares the various proposed dosing strategies.

RECENT FINDINGS

The basic principles underlying removal of antibiotics during CVVH and the published dosing strategies are reviewed. The key factor to consider is the fractional CVVH clearance (FrCVVH). Critical illness and acute kidney injury, however, may dramatically affect the pharmacokinetic properties of a drug and thus FrCVVH. Five dosing strategies have been proposed on the basis of either available references, total creatinine clearance, the reduction in total body clearance, the maintenance dose multiplication factor, or therapeutic drug monitoring. Dose predictions according to the various strategies show reasonable approximations for some but not all antibiotics.

SUMMARY

The delivery of appropriate antimicrobial therapy during CVVH leaves us with uncertainty and presents a great challenge. To ensure efficacy and prevent toxicity, therapeutic drug monitoring is highly recommended. In the absence of therapeutic drug monitoring, adequate concentrations can only be inferred from clinical response. For nontoxic antibiotics overdosing is preferred to underdosing because the danger of underdosing is far greater than that of overdosing.