Newer Systemic Antifungal Agents

Comparative pharmacodynamic interaction analysis of triple combinations of caspofungin and voriconazole or ravuconazole with subinhibitory concentrations of amphotericin B against Aspergillus spp

Triple combination therapy with an antifungal triazole, echinocandin and amphotericin B (AmB) is used in some centres to treat refractory aspergillosis. The objective of this study was to investigate the effect of subinhibitory concentrations of AmB on the double combinations of caspofungin (CAS) + voriconazole (VOR) or ravuconazole (RAV) against Aspergillus fumigatus, Aspergillus flavus and Aspergillus terreus. Isolates were studied in triplicate against CAS/VOR and CAS/RAV combinations by chequerboard broth microdilution. AmB was added to each double combination at concentrations of 0, 0.1 and 0.2 microg ml(-1). The fractional inhibitory concentration (FIC) index was calculated for the double and triple combinations. Comparative analysis was performed by repeated measures analysis followed by Dunnett's post-test. The double combinations of CAS/RAV and CAS/VOR were synergistic or additive in most conditions. Addition of AmB to the double combinations resulted in increased FIC indices for A. fumigatus and A. flavus. By contrast, AmB increased the synergism of the double combinations decreasing FIC indices for A. terreus (P < 0.05). RAV and VOR displayed similar synergistic activity with CAS. The addition of sub-inhibitory amphotericin B concentrations reduced but did not eliminate the synergistic interaction between the echinocandin and triazole against A. fumigatus and A. flavus, while it increased the synergy against A. terreus.

Anidulafungin: a novel echinocandin for candida infections

A third echinocandin, anidulafungin, has recently been approved for Candida infections in the non-neutropenic patient. In the EU it is indicated for invasive candidiasis; in 2006 it was approved in the USA for candida esophagitis, candidemia, and two types of invasive infections, peritonitis and intra-abdominal abscesses. It is fungicidal against Candida species and fungistatic against Aspergillus species. In addition to its favorable tolerability in studies to date, it does not need adjustment for renal or hepatic insufficiency and has no known drug interactions. A steady state concentration can be achieved on day 2 following a loading dose of twice the maintenance concentration on day 1, and the drug is administered intravenously once daily. Cross resistance with other classes of antifungals is not a concern as it possesses a unique mechanism of action.

Isavuconazole: a new and promising antifungal triazole for the treatment of invasive fungal infections

Invasive fungal infections (IFIs) are an important cause of morbidity and mortality. Isavuconazole (BAL4815) is a promising novel broad-spectrum triazole in late-stage clinical development that has proven to be active in vitro against Aspergillus, Candida and Cryptococcus neoformans, the most common agents of IFIs. Furthermore, isavuconazole has a pharmacokinetic profile that allows oral and intravenous administration with no severe toxicity. In vivo data from animal models are also encouraging. However, very little information on clinical efficacy is available. Four clinical trials are currently in progress to demonstrate the safety and efficacy of isavuconazole for the treatment and prevention of IFIs. In the absence of clinical and cost data, the real possibilities of this agent as a competitor for the treatment and prevention of IFIs in the clinical setting are still unknown.

Pharmacotherapy of yeast infections

The rise of immunocompromised individuals in our society has provoked a significant emergence in the number of patients affected by opportunistic pathogenic yeast. The microorganisms with a major clinical incidence are species from the genera Candida (especially Candida albicans) and Cryptococcus (particularly Cryptococcus neoformans), although there has been a significant increase in other pathogenic yeasts, such as Trichosporon spp. and Rhodotorula spp. In addition, there are an increasing number of patients infected by yeasts that were not previously considered as pathogenic, such as Saccharomyces cerevisiae. The management of these infections is complicated and is highly dependent on the susceptibility profile not only of the species but also of the strain. The available antifungal compounds belong mainly to the polyene, azole and candin families, which show a distinct spectrum of activity. This review summarizes the current knowledge about the use of the main antifungals for treating infections caused by the yeast species with the most significant clinical relevance, including the susceptibility profiles exhibited by these species in vitro.

Treatment of invasive candidiasis in immunocompromised pediatric patients

In the last 3 decades, systemic candidiasis has become increasingly recognized as a major source of morbidity and mortality in immunocompromised pediatric patients. As the number of children receiving chemotherapy and bone marrow transplantations continue to increase, clinicians should expect that invasive infections from Candida spp. will also increase in these vulnerable hosts. Fortunately, in the past 15 years, the evolution of older antifungals coupled with the discovery of new classes of antifungal agents has equipped physicians with reasonable options for treating these otherwise life-threatening infections.This review aims to familiarize the reader with the evolving epidemiology of candidiasis in immunocompromised children as well as discuss therapeutic options from each class of antifungal agents. Mechanisms of action, pharmacokinetics, toxicities, resistance patterns, chemotherapy interactions, and clinical relevance in immunocompromised children are reviewed for polyenes, flucytosine (5-fluorocytosine), azoles, and echinocandins.

A Retrospective Analysis of Antifungal Susceptibilities of Candida Bloodstream Isolates From Singapore Hospitals

Introduction: Worldwide, Candida albicans is the most common Candida species implicated in bloodstream infections. However, the proportion of non-albicans bloodstream infections is increasing. Fluconazole resistance is known to be more common in non-albicans species, but is also reported in C. albicans. This retrospective study was performed to determine the species epidemiology of Candida bloodstream infections in Singapore hospitals, and to perform susceptibility testing to a range of antifungal drugs. Materials and Methods: Candida spp. isolated from bloodstream infections from October 2004 to December 2006 were collected from 3 participating hospitals: a tertiary referral hospital (Singapore General Hospital), a secondary referral hospital (Changi General Hospital) and an obstetrics/paediatric hospital [KK Women’s and Children’s Hospital (KKWCH)]. Isolate collection was also retrospectively extended to January 2000 for KKWCH because of the limited number of cases from this hospital. Isolates were identified by a common protocol, and antifungal susceptibility testing was performed by microbroth dilution (Sensititre One, Trek Diagnostics, United Kingdom). Results: The most common isolates were C. albicans (37%), C. tropicalis (27%) and C. glabrata (16%). There were differences in species distribution between institutions, with C. parapsilosis and C. albicans predominant in KKWCH, and C. albicans and C. tropicalis predominant in the other 2 institutions. Fluconazole resistance was detected in 3.2% of all Candida spp., and 85.3% were classified as susceptible. All C. albicans and C. parapsilosis were susceptible to fluconazole and voriconazole, while susceptibility to fluconazole was much more variable for C. glabrata and C. krusei. Conclusion: This study shows that C. albicans remains the predominant Candida species isolated from bloodstream infections in the 3 participating hospitals. However, non-albicans species accounted for nearly two-thirds of all cases of candidaemia. Resistance to fluconazole was uncommon, and was generally confined to C. krusei and C. glabrata. Key words: Antifungal agents, Antifungal drug resistance, Fungaemia

Antifungal therapy strategies in hematopoietic stem-cell transplant recipients: early treatment options for improving outcomes

Changes in clinical practice permit more patients to undergo hematopoietic stem-cell transplantation but also have increased the risk for invasive fungal infection (IFI) in this population. Given the difficulties in the diagnosis of fungal infection and the correlation between delays in therapy and poor outcome, earlier treatment, and prophylactic strategies are attractive options for the management of IFIs in high-risk patients. The selection of the most effective antifungal treatment strategy requires a thorough knowledge of IFI risk factors, potential causative organisms, and the safety and efficacy of appropriate antifungal agents.

Development and validation of an efficient HPLC method for quantification of voriconazole in plasma and microdialysate reflecting an important target site

Voriconazole is a very potent antifungal agent used to treat serious fungal infections (candidiasis); it is also the therapy of choice for aspergillosis. After standard dosing, several factors affect exposure of voriconazole, resulting in large variability and demanding further elucidation of drug distribution. For measurements at the site of action, microdialysis is considered to be an outstanding minimally invasive method. For determination of voriconazole in microdialysate and human plasma a new, efficient, reliable, and robust HPLC assay using UV detection at 254 nm has been developed and validated. After simple sample preparation using acetonitrile for plasma and for microdialysate, 20 microL were injected and separated on an RP-18 column. The chromatographic run time was less than 4 min. Overall, the assay showed high precision (CV 93.9 to 99.5%) and accuracy (RE -96.7 to +107%) for both matrices. Of the 36 drug products typically co-administered with voriconazole, none except ambroxol interfered with its peak signal, and this interference was successfully managed. In summary, the method is highly suitable for application in (pre)clinical microdialysis studies, e.g., of critically ill patients with invasive mycoses.

Vascular catheter-associated infections: a microbiological and therapeutic update

The increasing incidence of central venous catheter (CVC)-related infections can be ascribed to the wider indications to central venous catheterization, to the higher attention to this issue paid by clinicians and microbiologists, and to the patient population referred to hospitals, increasingly characterized by different degrees of immunosuppression and often in critical clinical conditions. This phenomenon implies a higher health care burden and higher related costs, as well as a significant attributable mortality, that varies however according to the pathogen involved. The microorganisms most frequently involved in CVC-related infections are coagulase-negative staphylococci, Staphylococcus aureus, aerobic Gram-negative bacilli, and Candida albicans. In the management of suspected or proven central venous catheter-related infections, several issues need to be addressed: the need to remove the device or the possibility of salvage, the immediate start of calculated antibiotic therapy or the possibility of waiting for results of microbiological diagnostics and proceeding to etiologically-guided therapy. The preferred conservative method is the "Antibiotic-Lock technique" (ALT), based on the endoluminal application of antibacterials at extremely high concentrations in situ for a period of time long enough to ensure bactericidal activity. On the other hand, immediate catheter removal and initiation of appropriate calculated therapy immediately after an adequate diagnostic work-up are strongly recommended in a clinical setting of severe sepsis or septic shock.

Role of flavin-containing monooxygenase in oxidative metabolism of voriconazole by human liver microsomes

Voriconazole is a potent second-generation triazole antifungal agent with broad-spectrum activity against clinically important fungi. It is cleared predominantly via metabolism in all species tested including humans. N-Oxidation of the fluoropyrimidine ring, its hydroxylation, and hydroxylation of the adjacent methyl group are the known pathways of voriconazole oxidative metabolism, with the N-oxide being the major circulating metabolite in human. In vitro studies have shown that CYP2C19, CYP3A4, and to a lesser extent CYP2C9 contribute to the oxidative metabolism of voriconazole. When cytochrome P450 (P450)-specific inhibitors and antibodies were used to evaluate the oxidative metabolism of voriconazole by human liver microsomes, the results suggested that P450-mediated metabolism accounted for approximately 75% of the total oxidative metabolism. The studies presented here provide evidence that the remaining approximately 25% of the metabolic transformations are catalyzed by flavin-containing monooxygenase (FMO). This conclusion was based on the evidence that the NADPH-dependent metabolism of voriconazole was sensitive to heat (45 degrees C for 5 min), a condition known to selectively inactivate FMO without affecting P450 activity. The role of FMO in the metabolic formation of voriconazole N-oxide was confirmed by the use of recombinant FMO enzymes. Kinetic analysis of voriconazole metabolism by FMO1 and FMO3 yielded K(m) values of 3.0 and 3.4 mM and V(max) values of 0.025 and 0.044 pmol/min/pmol, respectively. FMO5 did not metabolize voriconazole effectively. This is the first report of the role of FMO in the oxidative metabolism of voriconazole.

[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.

Rhino-orbital-cerebral mucormycosis and aspergillosis: differential diagnosis and treatment

In immunocompromised patients, symptoms and the pathogen spectrum of sinusitis are frequently atypical. If progressive loss of vision occurs, an infection of the anterior skull base or nasal sinuses should be considered. We report on four patients with orbit-associated symptoms. CT-imaging revealed bony defects in sinus borders to orbits or endocranium. In all the cases immediate surgical drainage was performed because complications following sinusitis were suspected. Histopathological diagnosis revealed two cases of aspergillosis and mucormycosis. The possibility of opportunistic infections by saprophytic fungi must be taken into account in immunocompromised patients, as they may endanger both vision and survival. Immediate diagnosis and therapy are essential. Nowadays, therapeutic success can be achieved due to advances in antimicrobial therapy, hyperbaric oxygen therapy and treatment of the underlying disease. Radical procedures like orbital exenteration must be considered in all cases. The current state of diagnostics, therapy and prognosis is discussed based on these case reports and the recent literature.

Novel antifungal agents as salvage therapy for invasive aspergillosis in patients with hematologic malignancies: posaconazole compared with high-dose lipid formulations of amphotericin B alone or in combination with caspofungin

In patients with hematologic malignancy, invasive aspergillosis continues to be associated with high mortality even when treated with conventional antifungal therapy. To investigate novel antifungal agents, we compared 53 patients who received posaconazole salvage therapy to 52 contemporary control patients who received high-dose lipid formulation of amphotericin B (HD-LPD/AMB at > or = 7.5 mg kg(-1) per day) and 38 other control patients who received caspofungin plus HD-LPD/AMB. Patients in the three groups had similar. The overall response rate to salvage therapy was 40% for posaconazole, 8% for HD-LPD/AMB (P < or = 0.001) and 11% for combination therapy (P < 0.002). Aspergillosis contributed to the death of 40% of posaconazole group, 65% of the HD-LPD/AMB group and 68% of the combination group (P < or = 0.008). By multivariate analysis, posaconazole therapy independently improved response (9.5; 95% confidence interval, 2.8-32.5; P < 0.001). HD-LPD/AMB alone or in combination was associated with a significantly higher rate of nephrotoxicity (P < or = 0.02) and hepatotoxicity (P < 0.03). In conclusion, posaconazole salvage therapy demonstrated greater efficacy and safety than HD-LPD/AMB alone or in combination with caspofungin in the salvage therapy of invasive aspergillosis in hematologic malignancy.

Biosynthetic requirements for the repair of sublethally injured Saccharomyces cerevisiae cells after pulsed electric fields

AIMS

The aim was to evaluate the biosynthetic requirements for the repair of sublethal membrane damages in Saccharomyces cerevisiae cells after exposure to pulsed electric fields (PEF).

METHODS AND RESULTS

The partial loss of the integrity and functionality of the cytoplasmic membrane was assessed by adding sodium chloride to the recovery medium. More than 2 log(10) cycles of survivors were sublethally injured after PEF. Repair of sublethal membrane damages occurred when survivors to PEF were incubated in Sabouraud Broth for 4 h at room temperature. The addition of inhibitors, such as chloramphenicol, rifampicin, 5-fluorocytosine, nalidixic acid, cycloheximide, cerulenin, miconazol and sodium azide to the liquid repair medium showed that the repair of PEF-injured cells required energy and protein synthesis. The extent of the sublethal damages was greater in PEF-treated cells at pH 4.0 than at pH 7.0.

CONCLUSIONS

This work confirms that membrane damage is an important event in the PEF-inactivation of yeast. The mechanism of yeast inactivation by PEF seems to differ from that of bacteria, as the repair of sublethal damages requires protein synthesis.

SIGNIFICANCE AND IMPACT OF THE STUDY

Knowledge about the damages inflicted by PEF leads to a better description of the mechanism of yeast inactivation.

Antifungal agents in neonates: issues and recommendations

Fungal infections are responsible for considerable morbidity and mortality in the neonatal period, particularly among premature neonates. Four classes of antifungal agents are commonly used in the treatment of fungal infections in pediatric patients: polyene macrolides, fluorinated pyrimidines, triazoles, and echinocandins. Due to the paucity of pediatric data, many recommendations for the use of antifungal agents in this population are derived from the experience in adults. The purpose of this article was to review the published data on fungal infections and antifungal agents, with a focus on neonatal patients, and to provide an overview of the differences in antifungal pharmacology in neonates compared with adults. Pharmacokinetic data suggest dosing differences in children versus adult patients with some antifungals, but not all agents have been fully evaluated. The available pharmacokinetic data on the amphotericin B deoxycholate formulation in neonates exhibit considerable variability; nevertheless, the dosage regimen suggested in the neonatal population is similar to that used in adults. More pharmacokinetic information is available on the liposomal and lipid complex preparations of amphotericin B and fluconazole, and it supports their use in neonates; however, the optimal dosage and duration of therapy is difficult to establish. All amphotericin-B formulations, frequently used in combination with flucytosine, are useful for treating disseminated fungal infections and Candida meningitis in neonates. Fluconazole, with potent in vitro activity against Cryptococcus neoformans and almost all Candida spp., has been used in neonates with invasive candidiasis at dosages of 6 mg/kg/day, and for antifungal prophylaxis in high-risk neonates. There are limited data on itraconazole, voriconazole, and posaconazole use in neonates. Caspofungin, which is active against Candida spp. and Aspergillus spp., requires higher doses in children relative to adults, and dosing is best accomplished based on body surface area. Micafungin shows a clear trend toward lower levels in the smallest patients. There are no data on the use of other new antifungal drugs (ravuconazole and anidulafungin) in neonates. In summary, the initial data suggest dosage differences in neonates for some antifungal agents, although the newer agents have not been fully tested for optimal administration in these patients.

Animal models: an important tool in mycology

Animal models of fungal infections are, and will remain, a key tool in the advancement of the medical mycology. Many different types of animal models of fungal infection have been developed, with murine models the most frequently used, for studies of pathogenesis, virulence, immunology, diagnosis, and therapy. The ability to control numerous variables in performing the model allows us to mimic human disease states and quantitatively monitor the course of the disease. However, no single model can answer all questions and different animal species or different routes of infection can show somewhat different results. Thus, the choice of which animal model to use must be made carefully, addressing issues of the type of human disease to mimic, the parameters to follow and collection of the appropriate data to answer those questions being asked. This review addresses a variety of uses for animal models in medical mycology. It focuses on the most clinically important diseases affecting humans and cites various examples of the different types of studies that have been performed. Overall, animal models of fungal infection will continue to be valuable tools in addressing questions concerning fungal infections and contribute to our deeper understanding of how these infections occur, progress and can be controlled and eliminated.

Tetracycline-inducible expression of individual secreted aspartic proteases in Candida albicans allows isoenzyme-specific inhibitor screening

The yeast Candida albicans possesses a gene family that encodes secreted aspartic proteases (Saps), which are important for the virulence of this human fungal pathogen. Inhibitors of the Saps could therefore be used as novel antimycotic agents for the treatment of C. albicans infections. In the present study, we established a bioassay which allows testing of the activity of potential protease inhibitors against specific Sap isoenzymes by their ability to inhibit protease-dependent growth of C. albicans. In a medium containing bovine serum albumin (BSA) as the sole source of nitrogen, C. albicans specifically expresses the Sap2p isoenzyme, which degrades the BSA and thereby enables the fungus to grow. As the other SAP genes are not significantly expressed under these conditions, mutants lacking SAP2 are unable to utilize BSA as a nitrogen source and cannot grow in such a medium. To investigate whether forced expression of SAP genes other than SAP2 would also allow growth on BSA, we constructed a set of strains expressing each of the 10 SAP genes from a tetracycline-inducible promoter in a sap2Delta mutant background. Expression of Sap1p, Sap2p, Sap3p, Sap4p, Sap5p, Sap6p, Sap8p, and a C-terminally truncated, secreted Sap9p restored the growth of the sap2Delta mutant with different efficiencies. This set of strains was then used to test the activities of various aspartic protease inhibitors against specific Sap isoenzymes by monitoring growth on BSA in the presence of the inhibitors. While pepstatin blocked the activity of all of the Saps tested, the human immunodeficiency virus protease inhibitors ritonavir and saquinavir inhibited growth of the strains expressing Sap1p to Sap3p and Sap1p, respectively, but not that of strains expressing other Saps. Therefore, the strain set can be used to test the activity of new protease inhibitors against individual C. albicans Sap isoenzymes by their ability to block the growth of the pathogen.

Antifungal agents

The four main classes of antifungal drugs are the polyenes, azoles, allylamines and echinocandins. Clinically useful "older" agents include topical azole formulations (for superficial yeast and dermatophyte infections), first-generation triazoles (fluconazole and itraconazole, for a range of superficial and invasive fungal infections), amphotericin B formulations (for a broad range of invasive fungal infections) and terbinafine (for dermatophyte infections). Clinically important "newer" agents include members of the echinocandin class (eg, caspofungin) and second-generation triazoles (eg, voriconazole and posaconazole). Voriconazole and posaconazole have broad-spectrum activity against yeasts and moulds, including Aspergillus species. Posaconazole is the only azole drug with activity against zygomycete fungi. Caspofungin and the other echinocandins are effective in treating Candida and Aspergillus infections. The azoles are relatively safe, but clinicians should be aware of drug-drug interactions and adverse effects, including visual disturbances (with voriconazole), elevations in liver transaminase levels, and skin rashes. Caspofungin has minimal adverse effects. Combination antifungal therapy may be appropriate in selected patients with invasive fungal infections, but is empiric and driven by individual physician practice.

Cytochrome P450 2C19 loss-of-function polymorphism is associated with an increased treatment-related mortality in patients undergoing allogeneic transplantation

The polymorphic gene expression of CYP2C19 causes individual variability in drug metabolism and thereby in pharmacologic and toxicologic responses. We genotyped 286 patients and their donors for the CYP2C19 gene who underwent allogeneic transplantation for various diseases and analyzed their outcome. Patients were classified as: poor metabolizers (PMs; 3.1%), intermediate metabolizers (IMs; 24.5%) and extensive metabolizers (EMs; 72.5%). Patients genotyped as PMs had significant higher hepato- and nephrotoxicities compared to IMs or EMs. Maximum bilirubin and serum creatinine levels measured after transplant were approximately twofold higher than those of EMs or IMs. The increased toxicity resulted in an increased 4-year estimate for transplant-related mortality (TRM) with 50+/-18.6% for PMs compared to 25.1+/-3.7% for EMs (P<0.018) and 22.7 +/-5.6% for IMs (P<0.042), whereas no significant influence for relapse rate, overall survival or incidence of acute graft-versus-host disease grade 2-4 were found between the groups. Multivariate analysis including all potential factors that might influence TRM confirmed that the genotype of CYP2C19 is an independent factor, which influenced TRM significantly. These results suggest that genotyping for CYP450 2C19 can help to identify patients with higher risk for TRM.

Voriconazole and fluconazole increase the exposure to oral diazepam

OBJECTIVE

We assessed the effect of voriconazole and fluconazole on the pharmacokinetics and pharmacodynamics of diazepam.

METHODS

Twelve healthy volunteers took 5 mg of oral diazepam in a randomised order on three study sessions: without pretreatment, after oral voriconazole 400 mg twice daily on the first day and 200 mg twice daily on the second day, or after oral fluconazole 400 mg on the first day and 200 mg on the second day. Plasma concentrations of diazepam and N-desmethyldiazepam were determined for up to 48 h. Pharmacodynamic variables were measured for 12 h.

RESULTS

In the voriconazole phase, the area under the plasma concentration time curve (AUC 0-infinity) of diazepam was increased (geometric mean ratio) 2.2-fold (p < 0.05; 90% confidence interval [CI] 1.56 to 2.82). This was associated with the prolongation of the mean elimination half-life (t(1/2)) from 31 h to 61 h (p < 0.01) after voriconazole. In the fluconazole phase, the AUC 0-infinity of diazepam was increased 2.5-fold (p < 0.01; 90% CI 1.94 to 3.40), and the t(1/2) was prolonged from 31 h to 73 h (p < 0.001). The peak plasma concentration of diazepam was practically unchanged by voriconazole and fluconazole. The pharmacodynamics of diazepam were changed only modestly.

CONCLUSION

Both voriconazole and fluconazole considerably increase the exposure to diazepam. Recurrent administration of diazepam increases the risk of clinically significant interactions during voriconazole or fluconazole treatment, because the elimination of diazepam is impaired significantly.

Safety and efficacy of posaconazole in the long-term treatment of azole-refractory oropharyngeal and esophageal candidiasis in patients with HIV infection

PURPOSE

To evaluate safety and efficacy of long-term posaconazole in HIV-infected patients with azole-refractory oropharyngeal candidiasis and/or esophageal candidiasis.

METHOD

In this noncomparative, open-label study, participants received oral posaconazole 400 mg twice daily (bid) for 3 months. Enrolled patients (N = 100) included 60 from a previous 1-month acute study of posaconazole and 40 posaconazole-naïve participants. Participants with a clinical response could be followed untreated for up to 1 month afterwards. Participants who relapsed during follow-up, showed improvement at the end of 3 months of treatment (EOT), or were cured but likely to benefit from further therapy could continue on posaconazole 400 mg bid for up to 12 months.

RESULTS

In the modified intent-to-treat population, clinical response (cure or improvement) occurred in 85.6% (77/90) at EOT. The results were similar in the previously treated participants and the posaconazole-naïve participants, 88.1% (52/59) and 80.6% (25/31), respectively. Posaconazole was well-tolerated, showing a similar safety profile during the 3-month study period and during suppressive therapy. The most frequently reported treatment-related adverse event was vomiting (4/100, 4%) during the early follow-up period (on or before day 105) and elevated hepatic enzymes (3/51, 6%) during the long-term follow-up (after day 105).

CONCLUSION

Oral posaconazole 400 mg bid demonstrated long-term safety, tolerability, and efficacy, offering a long-term, suppressive treatment option for HIV-infected participants with azole-refractory mucosal candidiasis.

Economic evaluation of voriconazole versus caspofungin for the treatment of invasive aspergillosis in Spain

BACKGROUND AND OBJECTIVE

Invasive fungal infections are becoming increasingly prevalent and are more frequently the aetiological agents responsible for nosocomial infections. Since mid-2002, two new antifungal drugs - voriconazole, a third-generation azole, and caspofungin, a member of a new class of drugs called echinocandins - have been marketed in Spain. Both drugs have proven [corrected] efficacy in the treatment of aspergillosis, are better tolerated than amphotericin B and are cheaper [corrected] than liposomal amphotericin B. The objective of this study was to conduct an economic evaluation of voriconazole versus caspofungin for the treatment of invasive aspergillosis in Spain.

METHODS

This was a cost-minimisation analysis (2006 costs) from the hospital perspective. Duration of treatment and bodyweight of patients were obtained from the Fungcost study and the incidence of adverse events was obtained from different published sources. Only direct costs were considered. Mean expected cost and incremental cost were calculated, and univariate and bivariate (bodyweight/treatment duration) sensitivity analyses were conducted.

RESULTS

The mean expected cost per episode was 6041.93 euro (intravenous treatment acquisition cost 5524.75 euro) for voriconazole and 7174.05 euro (intravenous treatment acquisition cost 6672.80 euro) for caspofungin in invasive aspergillosis; the incremental cost was 1132.18 euro. Results were robust for any treatment duration and sensitive to bodyweights <103.42 kg.

CONCLUSION

Voriconazole is a more cost-effective option than caspofungin in invasive aspergillosis in patients with a bodyweight <103.42 kg.

Advances in topical and systemic antifungals

Topical antifungal agents are generally used for the treatment of superficial fungal infections unless the infection is widespread, involves an extensive area, or is resistant to initial therapy. Systemic antifungals are often reserved for the treatment of onychomycosis, tinea capitis, superficial and systemic candidiasis, and prophylaxis and treatment of invasive fungal infections. With the development of resistant fungi strains and the increased incidence of life-threatening invasive fungal infections in immunocompromised patients, some previously effective traditional antifungal agents are subject to limitations including multidrug interactions, severe adverse effects, and their fungistatic mechanism of actions. Several new antifungal agents have demonstrated significant therapeutic benefits and have broadened clinicians' choices in the treatment of superficial and systemic invasive fungal infections.

Resistance to echinocandin-class antifungal drugs

Invasive fungal infections cause morbidity and mortality in severely ill patients, and limited drug classes restrict treatment choices. The echinocandin drugs are the first new class of antifungal compounds that target the fungal cell wall by blocking beta-1,3-d-glucan synthase. Elevated MIC values with occasional treatment failure have been reported for strains of Candida. Yet, an uncertain correlation exists between clinical failure and elevated MIC values for the echinocandin drugs. Fungi display several adaptive physiological mechanisms that result in elevated MIC values. However, resistance to echinocandin drugs among clinical isolates is associated with amino acid substitutions in two "hot-spot" regions of Fks1, the major subunit of glucan synthase. The mutations, yielding highly elevated MIC values, are genetically dominant and confer cross-resistance to all echinocandin drugs. Prominent Fks1 mutations decrease the sensitivity of glucan synthase for drug by 1000-fold or more, and strains harboring such mutations may require a concomitant increase in drug to reduce fungal organ burdens in animal infection models. The Fks1-mediated resistance mechanism is conserved in a wide variety of Candida spp. and can account for intrinsic reduced susceptibility of certain species. Fks1 mutations confer resistance in both yeasts and moulds suggesting that this mechanism is pervasive in the fungal kingdom.

Inherited long QT syndrome revealed by antifungals drug?drug interaction

A 14-year-old Tahitian girl with acute myeloid leukaemia and a suspected mucormucosis infection was treated with intravenous voriconazole and caspofungin. Because of worsening of fungal infection, voriconazole was switched to posaconazole. During the switch, the patient presented with QT interval prolongation with 'torsades de pointes' and reversible cardiac arrest. Voriconazole plasma level measured 15 h after the last administration was 7 mg/L. Genotyping suggested that the patient was an extensive metabolizer with respect to CYP2C9 and CYP2C19. The association of antifungal agents with pro-arrhythmogenic drugs and other risk factors led to torsades de pointes and the revealing of inherited QT syndrome.

Fungal keratitis in Melbourne

BACKGROUND

Description of the clinical and microbiological spectrum of fungal keratitis at a tertiary eye care hospital in Melbourne, Australia.

METHODS

Retrospective review of all patients with keratitis with positive fungal cultures from corneal or associated samples presenting to the Royal Victorian Eye and Ear Hospital, Melbourne, Australia from July 1996 to May 2004. Demographic data, predisposing factors, features on presentation, management, outcomes and microbiological data were collected and analysed.

RESULTS

The study included 56 eyes of 56 patients. Thirty-five patients were treated as 'typical' fungal keratitis and used for description and analysis, with a mean follow up of 18 months. Ocular trauma (37.1%), chronic steroid use (31.4%) and poor ocular surface (25.7%) were the major predisposing factors. Perforation was seen in 25.7% of patients, penetrating keratoplasty was required in 9 (25.7%) patients and evisceration was performed in 2 (5.7%) patients. Candida albicans (13 patients, 37.2%) was the most common fungal isolate accounting for more than one-third of all organisms followed by Aspergillus fumigatus (six patients, 17.1%) and Fusarium sp. (five patients, 14.3%).

CONCLUSIONS

The present study describes the clinical patterns of fungal keratitis in Melbourne, Australia and contrasts them with reports from other areas of the world. A high incidence of C. albicans infection and the prior use of steroids in high proportion of the patients are highlighted in this study.

Voriconazole : a review of its use in the management of invasive fungal infections

Voriconazole (VFEND), a synthetic second-generation, broad-spectrum triazole derivative of fluconazole, inhibits the cytochrome P450 (CYP)-dependent enzyme 14-alpha-sterol demethylase, thereby disrupting the cell membrane and halting fungal growth. In the US, intravenous and/or oral voriconazole is recommended in adults for the treatment of invasive aspergillosis, candidaemia in non-neutropenic patients, disseminated infections caused by Candida spp., oesophageal candidiasis, and in patients with scedosporiosis and fusariosis who are refractory to or intolerant of other antifungal therapy. In Europe, intravenous and/or oral voriconazole is recommended in adults and paediatric patients of at least 2 years of age for the treatment of invasive aspergillosis, candidaemia in non-neutropenic patients, fluconazole-resistant serious invasive Candida spp. infections, scedosporiosis and fusariosis. In large randomised trials, voriconazole was an effective and generally well tolerated primary treatment for candidiasis and invasive aspergillosis in adults and adolescents. More limited data also support the use of voriconazole for the treatment of invasive fungal infections in children, in those with rare fungal infections, such as Fusarium spp. or Scedosporium spp., and in those refractory to or intolerant of other standard antifungal therapies. The availability of both parenteral and oral formulations and the almost complete absorption of the drug after oral administration provide for ease of use and potential cost savings, and ensure that therapeutic plasma concentrations are maintained when switching from intravenous to oral therapy. On the other hand, the numerous drug interactions associated with voriconazole may limit its usefulness in some patients. Further clinical experience will help to more fully determine the position of voriconazole in relation to other licensed antifungal agents. In the meantime, voriconazole is a valuable emerging option for the treatment of invasive aspergillosis and rare fungal infections, including Fusarium spp. and Scedosporium spp. infections, and provides an alternative option for the treatment of candidiasis, particularly where the causative organism is inherently resistant to other licensed antifungal agents.

[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.

[Importance of invasive candidiasis in critical non-neutropenic patients]

Invasive candidiasis (IC) is the most frequent fungal infection in high risk patients in intensive care setting. IC is associated with high attributable mortality and increased healthcare cost. In this review current, epidemiological, diagnostic and clinical management is updated and discussed in the critically ill non netropenic patient.

To test or not to test: a cost minimization analysis of susceptibility testing for patients with documented Candida glabrata fungemias

This cost minimization analysis investigated the financial impact of the treatment of fungemias due to Candida glabrata from a hospital perspective using three competing alternatives: (i) performing in-house susceptibility testing on all C. glabrata isolates and changing patients to less expensive fluconazole therapy for isolates that test susceptible; (ii) susceptibility testing at outside laboratories with delayed deescalation to fluconazole if isolates test susceptible; and (iii) no routine susceptibility testing with full echinocandin treatment course. Sensitivity analyses and Monte Carlo simulation enhanced the robustness of the model through variation of all assumptions and costs. In the base case, the use of in-house testing displayed a cost advantage over the options of send-out testing and no susceptibility testing ($2,226 versus $2,410 versus $3,136, respectively). Sensitivity analyses determined that the cost of echinocandin therapy and the turnaround time for send-out testing had the potential to impact the base case model. The decision model indicated that in-house susceptibility testing of C. glabrata isolates should result in lower overall treatment costs in patients with documented C. glabrata fungemias.

Anidulafungin: a new echinocandin for candidal infections

Anidulafungin, a new echinocandin, has recently been approved for the treatment of esophageal candidiasis, candidemia and other forms of invasive candidiasis, such as peritonitis and intra-abdominal abscesses in non-neutropenic patients. It is fungicidal against Candida spp. including those that are azole- and polyene-resistant and fungistatic against Aspergillus spp. Owing to its poor oral bioavailability it can only be administered intravenously. Its pharmacokinetics allow for once-daily dosing and a steady state concentration is easily achieved on day 2 following a loading dose of double the maintenance dose on day 1. It does not need adjustment for hepatic or renal insufficiency; there are no known drug interactions and it has a favorable tolerability profile. Its mechanism of action, which differs from other classes of antifungals, should prevent cross-resistance with azoles and polyenes.