Clinical use of amphotericin B and derivatives: lore, mystique, and fact

Joint fluid concentrations of amphotericin B after local application with calcium sulphate-report of 2 cases

Fungal periprosthetic joint infections (PJI) are difficult to treat, due to important biofilm formation and limited local penetration of systemically administered antifungals. Calcium sulphate (CaSO4 ) might be a promising carrier to increase local concentration of antifungals. We hypothesized that local amphotericin B release from CaSO4 is high enough to significantly contribute to treatment of fungal PJI. We report joint fluid and serum concentrations of amphotericin B after local application with CaSO4 as an implanted resorbable carrier material as adjunct to standard surgical and systemic antifungal treatment in two cases of PJI with Candida spp. Maximal joint fluid amphotericin B concentration was 14.01 mg/L 5 days after the second local administration of liposomal amphotericin in Case One and 25.77 mg/L 14 days after the second local administration in Case Two. Concentrations higher than minimal inhibitory concentrations (MIC) could be measured for 21 days and 17 days after local administration in Case One and Two, respectively. In Case Two, serum concentration of amphotericin B was <0.01 mg/L 3 days after local administration of 450 mg liposomal amphotericin B. No local or systemic adverse reaction was observed. Fungal PJI was successfully eradicated in both cases with a follow-up of 12 months in Case One and 20 months in Case Two. Application of amphotericin B-loaded CaSO4 was associated with joint fluid concentrations higher than minimal inhibitory concentrations for Candida spp. for approximately 3 weeks, with the advantage that the carrier material dissolves spontaneously and does not require secondary removal. Relapse of fungal infections did not occur in these two patients.

Recent drug development and treatments for fungal infections

Fungal infections are now becoming a hazard to individuals which has paved the way for research to expand the therapeutic options available. Recent advances in drug design and compound screening have also increased the pace of the development of antifungal drugs. Although several novel potential molecules are reported, those discoveries have yet to be translated from bench to bedside. Polyenes, azoles, echinocandins, and flucytosine are among the few antifungal agents that are available for the treatment of fungal infections, but such conventional therapies show certain limitations like toxicity, drug interactions, and the development of resistance which limits the utility of existing antifungals, contributing to significant mortality and morbidity. This review article focuses on the existing therapies, the challenges associated with them, and the development of new therapies, including the ongoing and recent clinical trials, for the treatment of fungal infections. Advancements in antifungal treatment: a graphical overview of drug development, adverse effects, and future prospects.

Lysosomal nanotoxicity: Impact of nanomedicines on lysosomal function

Although several nanomedicines got clinical approval over the past two decades, the clinical translation rate is relatively small so far. There are many post-surveillance withdrawals of nanomedicines caused by various safety issues. For successful clinical advancement of nanotechnology, it is of unmet need to realize cellular and molecular foundation of nanotoxicity. Current data suggest that lysosomal dysfunction caused by nanoparticles is emerging as the most common intracellular trigger of nanotoxicity. This review analyzes prospect mechanisms of lysosomal dysfunction-mediated toxicity induced by nanoparticles. We summarized and critically assessed adverse drug reactions of current clinically approved nanomedicines. Importantly, we show that physicochemical properties have great impact on nanoparticles interaction with cells, excretion route and kinetics, and subsequently on toxicity. We analyzed literature on adverse reactions of current nanomedicines and hypothesized that adverse reactions might be linked with lysosomal dysfunction caused by nanomedicines. Finally, from our analysis it becomes clear that it is unjustifiable to generalize safety and toxicity of nanoparticles, since different particles possess distinct toxicological properties. We propose that the biological mechanism of the disease progression and treatment should be central in the optimization of nanoparticle design.

Case report: Reversible encephalopathy associated with liposomal amphotericin B in a patient with cryptococcal meningitis

Liposomal amphotericin B (L-AMB) is an anti-fungus medicine that has fewer side effects than traditional amphotericin B (AMB). Neurotoxicity of L-AMB has rarely been observed, and only one case of leukoencephalopathy during intravenous L-AMB has been reported. Herein, we described a patient with cryptococcal meningitis presenting with late-onset reversible encephalopathy associated with liposomal amphotericin B.

Antimicrobial-induced cognitive side effects

Introduction

Antimicrobial-induced cognitive side effects are often overlooked or underreported. Literature often reports symptoms of antimicrobial-induced cognitive impairment under more general blanket terms, such as neuropsychiatric side effects, neurotoxicity, or drug-induced delirium or encephalopathy.

Methods

A PubMed search using terms including antibiotics, antifungals, antivirals, antimalarials, side effects, cognitive, neurotoxicity, encephalopathy, and delirium was conducted. Respectively, symptoms of cognitive impairment were teased out of the multiple neurologic complications presented for each case and reported based on antimicrobial class. Articles were excluded if they focused solely on neuropsychiatric side effects such as seizures, psychosis, hallucinations, or mood disturbances, were conducted in animals, or involved antiretroviral medication therapies.

Results

Of over 50 case reviews, case reports, retrospective chart reviews, and prospective cohort studies analyzed, 25 were deemed appropriate for purposes of this review. Common antimicrobial-induced cognitive side effects for all antimicrobial classes included confusion, delirium, encephalopathy, and impaired concentration or attention. Recurring risk factors included, but were not limited to, older age and renal impairment. Mechanisms of cognitive impairment were relatively specific to each antimicrobial class.

Discussion

Awareness of the potential for antimicrobial-induced cognitive side effects, including the general time frame of symptom onset and symptom presentation, is critical in challenging patient cases. This review article aims to summarize the risk factors, clinical symptoms, mechanisms, and management of antimicrobial-induced cognitive side effects. Pharmacists can play a key role in prevention through adjustment of medications for renal or hepatic dysfunction, avoidance of polypharmacy, and knowledge of critical drug interactions that may precipitate cognitive decline.

Pharmacokinetic evaluation of liposomal amphotericin B (L-AMB) in patients with invasive fungal infection: Population approach in Japanese pediatrics

The pharmacokinetic characteristics of liposomal amphotericin B (L-AMB; AmBisome(®)) in patients with invasive fungal infection were investigated. A population pharmacokinetic (PK) model in Japanese pediatric patients was developed based on 159 serum amphotericin B (AMPH-B) concentrations obtained in a post-marketing clinical study. The subjects were 39 patients with a mean age of 8.4 years (SD 4.5) and mean body weight of 27.1 kg (SD 14.1). A two-compartment PK model with zero-order input and first-order elimination was fitted to serum AMPH-B concentrations for L-AMB doses of 1.0, 2.5, and 5.0 mg/kg/day. Body weight showed significant correlations with PK parameters, such as clearance (CL) and distribution volume of the central compartment (Vc). The predicted Cmax/dose and AUC0-24/dose in Japanese pediatric patients were similar to those in non-Japanese pediatric patients and Japanese adult patients. Extremely large increases in Ctrough compared with predicted values were observed in some Japanese pediatric patients, but no relationships with demographic characteristics, clinical laboratory test values, or representative adverse drug reaction (decreased potassium) were found. The population PK parameters in this study are useful for simulating PK profiles of L-AMB and will be helpful for PK exposure comparisons among different populations and in investigations of pharmacokinetic-pharmacodynamic characteristics in patients.

CHEMICAL COMPOUNDS

Amphotericin B Deoxycholate (PubChem CID:23668620); amphotericin B (PubChem CID:5280965); 3-nitrophenol (PubChem CID:11137); methanol (PubChem CID:887).

Acute amphotericin B overdose

OBJECTIVE

To report the clinical course of a woman with cryptococcal meningitis and no previous cardiac disease who developed a fatal cardiac arrhythmia after an acute overdose of amphotericin B and to review its toxicity.

CASE SUMMARY

A 41-year-old woman with a history of proliferative glomerulonephritis from systemic lupus erythematosus was admitted with a diagnosis of cryptococcal meningitis. Liposomal amphotericin B was prescribed at the standard dose of 5 mg/kg/day; however, amphotericin B deoxycholate 5 mg/kg was inadvertently administered (usual dose of the deoxycholate formulation is 0.5-0.8 mg/kg/day). The patient developed cardiac arrhythmias, acute renal failure, and anemia. The medication error was noticed after she had received 2 doses of amphotericin B deoxycholate, and it was then discontinued. Despite treatment in the intensive care unit, the woman died on the sixth day after admission.

DISCUSSION

Amphotericin B deoxycholate has been reported to produce significant cardiac toxicity, with ventricular arrhythmias and bradycardia reported in overdoses in children and in adults with preexisting cardiac disease, even when administered in conventional dosages and infusion rates. Use of the Naranjo probability scale indicated a highly probable relationship between the observed cardiac toxicity and amphotericin B deoxycholate therapy in this patient.

CONCLUSIONS

Given the fulminant course of amphotericin B deoxycholate overdosage and lack of effective therapy, stringent safeguards against its improper administration should be in place.

Optimizing efficacy of amphotericin B through nanomodification

Fungal infections and leishmaniasis are an important cause of morbidity and mortality in immunocompromised patients. The macrolide polyene antibiotic amphotericin B (AmB) has long been recognized as a powerful fungicidal and leishmanicidal drug. A conventional intravenous dosage form of AmB, AmB- deoxycholate (Fungizone or D-AmB), is the most effective clinically available for treating fungal and parasitic (leishmaniasis) infections. However, the clinical efficacy of AmB is limited by its adverse effects mainly nephrotoxicity. Efforts to lower the toxicity are based on synthesis of AmB analogues such as AmB esters or preparation of AmB-lipid associations in the forms of liposomal AmB (L-AmB or AmBisome), AmB lipid complex (Abelcet or ABLC), AmB colloidal dispersion (Amphocil or ABCD), and intralipid AmB. These newer formulations are substantially more expensive, but allow patients to receive higher doses for longer periods of time with decreased renal toxicity than conventional AmB. Modifications of liposomal surface in order to avoid RES uptake, thus increased targetability has been attempted. Emulsomes and other nanoparticles are special carrier systems for intracellular localization in macrophage rich organs like liver and spleen. Injectable nano-carriers have important potential applications as in site-specific drug delivery.

Role of plasma lipids and lipoproteins in predicting amphotericin B-induced nephrotoxicity in pediatric oncology patients

PURPOSE

The objective of this study was to determine if total plasma and lipoprotein cholesterol (C) and triglyceride (TG) concentrations could predict the degree of nephrotoxicity caused by the antifungal agent amphotericin B (AmpB); and to use the average amount of potassium supplementation received daily as a indicator of nephrotoxicity in pediatric oncology patients.

PATIENTS AND METHODS

Plasma samples from 18 patients (ages < 17 years) who were receiving AmpB due to suspected or confirmed fungal infection at British Columbia Children's Hospital were analyzed for lipid concentrations. The high density lipoprotein (HDL) fractions were separated by precipitation; total (TOT) plasma and fraction C and TG concentrations were measured by enzymatic colorimetric assays; and low density lipoprotein (LDL) C levels were determined by Friedewald's formula. Changes in serum creatinine levels from baseline and amounts of potassium supplementation were used as indicators of nephrotoxicity; both were obtained from patients' medical charts. Pearson correlation coefficients (r) were determined and considered significant if P < 0.05.

RESULTS

The total cumulative AmpB dose, adjusted for weight, does not seem to predict AmpB-induced nephrotoxicity. Positive but relatively weak correlations were found between total potassium supplementation and LDL C (r = 0.489, P < 0.02); and TOT C (r = 0.551, P < 0.01). In addition, a positive but relatively weak correlation between the average amount of potassium supplementation per day above baseline and HDL C (r = 0.407; P < 0.02) was observed.

CONCLUSION

Differences in total plasma and LDL cholesterol concentrations may be used as predictors of AmpB-induced nephrotoxicity in pediatric oncology patients.

Water-soluble amphotericin B-polyvinylpyrrolidone complexes with maintained antifungal activity against Candida spp. and Aspergillus spp. and reduced haemolytic and cytotoxic effects

OBJECTIVES

Poor solubility and toxicity severely hinder the clinical use of amphotericin B (AmB), in spite of its attractive chemotherapeutic properties. Water-soluble complexes of AmB and polyvinylpyrrolidone (AmB-PVP) could display lower cytotoxicity while maintaining antifungal activity.

METHODS

AmB-PVP [with PVP of 10, 24 and 40 kDa (AC1, AC2 and AC4)] were compared with free AmB for (i) activity against Candida spp. (five albicans; nine non-albicans) and Aspergillus spp. (four strains), (ii) haemolysis of sheep red blood cells, and (iii) release of lactate dehydrogenase from J774 macrophages [with further comparison with free PVP and a liposomal formulation of amphotericin (AmBisome)].

RESULTS

MICs and MFCs of AC1, AC2 and AC4 against Candida spp. and of AC2 and AC4 against Aspergillus spp. were similar to those of AmB (and even lower for some Candida strains). Killing kinetics (24 h) were also similar. Haemolytic activity of AC2 and AC4 was 2-fold lower than that of free AmB. Cytotoxicity of AC2 towards J774 macrophages was 8-fold lower, and that of AC4 5-fold lower than that of AmB and not significantly different from that of AmBisome. The lower cytotoxicity of AC2, AC4 was correlated with a lower cellular accumulation of amphotericin. Spectroscopic analysis shows that the lower toxicity of AmB-PVP was not owing to significant change in the monomeric/polymeric forms ratio of the drug.

CONCLUSIONS

AmB-PVP complexes compared favourably with AmB for antifungal activity, were less haemolytic and cytotoxic than AmB, and show a similar cytotoxicity profile to AmBisome.

Aspergillus Endocarditis After Cardiac Surgery

Aspergillus species infections are an increasingly common occurrence in hospital wards. Aspergillus endocarditis constitutes one of the manifestations of the disease, which bears a poor prognosis in cardiac surgery patients. A review of the literature on fungal and Aspergillus endocarditis was undertaken. Valvular risk factors, indwelling intravenous catheters, prolonged antibiotics, malignancy, and intravenous drug use increase the risk. Clinical presentation is insidious, with embolic complications often representing the first manifestation of the disease. Blood cultures are typically negative. The mortality rate is almost 100%. Amphotericin B represents the mainstay of medical therapy with several possible adjuncts. Surgery is an essential part of therapy in Aspergillus endocarditis after cardiac surgery and should be undertaken as soon as the diagnosis is made. Aspergillus endocarditis is an ominous complication after cardiac surgery. A high suspicion index, early administration of appropriate antibiotics, and prompt surgical intervention should improve the prognosis, which remains dismal.

Time to positive culture results in neonatal Candida septicemia

To determine the time required for blood cultures to be detected as positive in neonates with invasive Candida infection, we analyzed 207 positive culture episodes in 74 infants. Time to positive result was 37 +/- 14 hours, and 97% of infected neonates were detected by 72 hours if not exposed to antifungal therapy.

Lyophilized lecithin based oil-water microemulsions as a new and low toxic delivery system for amphotericin B

PURPOSE

To develop and investigate lecithin based oil-water microemulsions as potential amphotericin B (AmB) delivery systems and to evaluate their in vivo acute toxicity.

METHODS

AmB was added to the microemulsion and its location was evaluated by partitioning studies and UV-visible spectrophotometric analysis of the drug. Both, non-lyophilized and reconstituted microemulsions were characterised and assessed for their stability. Single-dose acute toxicity of the AmB microemulsion was studied on male albino Webster-derived CD-1 mice and compared with Fungizone.

RESULTS

The studies performed showed that AmB was intercalated on the oil-water interface of the microemulsion as a complex formed with lecithin molecules. AmB addition did not seem to modify the rheological properties of the original system, but had an effect on its particle size distribution. Lyophilization of the microemulsion led to an oily cake, easily reconstituted and stable at the conditions studied. Single-dose acute toxicity studies proved that the LD50 of AmB microemulsions was of 4 mg kg(-1) of animal weight, compared with 1 mg kg(-1) found for Fungizone.

CONCLUSIONS

Lyophilized lecithin based oil-water microemulsions appear to be valuable systems for the delivery of AmB in terms of easy and low-cost manufacturing, stability and safety compared with the formulations already in market.

The role of murine models in the development of antifungal therapy for systemic mycoses

Animal testing is crucial to the development of new antifungal compounds. This review describes the role that murine and other animal models have played in the development of three classes of antifungal agents: the polyenes, the triazoles and the echinocandins and the ways in which these models have been either the positive link in the path from in vitro studies to the patient, or have foreclosed later clinical evaluation. Efficacy studies in particular mycoses are discussed, as well as studies designed to determine whether combinations of antifungal drugs may have value over single agents. Copyright 2000 Harcourt Publishers Ltd.

When to suspect fungal infection in neonates: A clinical comparison of Candida albicans and Candida parapsilosis fungemia with coagulase-negative staphylococcal bacteremia

OBJECTIVES

To determine the epidemiology of candidemia in our neonatal intensive care unit; to compare risk factors, clinical presentation, and outcomes for neonates infected with Candida albicans, Candida parapsilosis, and coagulase-negative staphylococcus (CoNS); and to suggest a rational approach to empiric antifungal therapy of neonates at risk for nosocomial infection.

DESIGN

Retrospective chart review of all neonatal intensive care unit patients with systemic candidiasis or CoNS infection between January 1, 1995 and July 31, 1998 at Duke University Medical Center.

RESULTS

Fifty-one patients were reviewed. Nine of 19 patients infected with C parapsilosis and 5 of 15 patients infected with C albicans died of fungemia. Seventeen neonates had >2 positive cultures for CoNS obtained within 96 hours and 1 died. There was no statistically significant difference in birth weight, gestational age, or age at diagnosis between patient groups; however, candidemic patients had a sevenfold higher mortality rate. Before diagnosis, candidemic patients had greater exposure to systemic steroids, antibiotics, and catecholamine infusions. Of the 51 patients, 32 received third-generation cephalosporins in the 2 weeks before diagnosis and 19 did not. Twenty-nine of the 32 who were treated with third-generation cephalosporins subsequently developed candidemia, while candidemia occurred in only 5 of 19 patients who were not treated with cephalosporins. At the time of diagnosis, candidemic patients were more likely to have required mechanical ventilation and were less likely to be tolerating enteral feeding. Multivariate clustered logistic regression analysis revealed that candidemic patients had more exposure to third-generation cephalosporins. Once the clinician was notified of a positive blood culture for Candida, patients infected with C parapsilosis retained their central catheters longer than patients infected with C albicans.

CONCLUSIONS

In this retrospective review, we were able to identify aspects of the clinical presentation and medication history that may be helpful in differentiating between candidemia and CoNS bacteremia. Those key features may be used by clinicians to initiate empiric amphotericin B therapy in premature neonates at risk for nosocomial infections. Prolonged use of third-generation cephalosporins was strongly associated with candidemia. There was no statistically significant difference in the morbidity and mortality between patients infected with C parapsilosis and those infected with C albicans. Observed delays in removal of the central venous catheter may have contributed to finding a mortality rate from C parapsilosis that was higher than was previously reported.

Suscetibilidade a antifúngicos de cepas de Candida albicans isoladas de pacientes com estomatite protética

Pacientes portadores de próteses totais, apresentam, com freqüência a chamada estomatite protética, com a qual associa-se Candida albicans determinando a chamada candidíase eritematosa. Assim, procuramos avaliar a suscetibilidade dessa levedura a agentes antifúngicos. A suscetibilidade de dezenove cepas de Candida albicans isoladas de pacientes apresentando estomatite protética foi estudada frente a: um derivado poliênico representado, pela anfotericina B (AnB), e dois derivados azóicos, cetoconazol e miconazol. A atividade antifúngica foi estudada a partir da determinação da concentração inibitória mínima (CIM) e da concentração fungicida mínima (CFM), pela técnica de diluição em ágar. Os resultados obtidos, mostraram baixos valores de CIMs e CFMs (< 0,15 <FONT FACE="Symbol">m</font>g/ml) para a AnB frente a todas as leveduras. Para o miconazol e o cetoconazol, foram observadas CIMs invariavelmente <FONT FACE="Symbol">£</font> 4,00<FONT FACE="Symbol"> m</font>g/ml; para as CFMs, foram obtidos valores <FONT FACE="Symbol">³</font> 16,00<FONT FACE="Symbol"> m</font>g/ml frente a maioria das cepas. Conclui-se que a AnB apresentou maior ação fungicida in vitro enquanto os azóis demonstraram ação fungistática mas não fungicida. Acreditamos que a pesquisa de novas drogas, principalmente de uso tópico ainda é necessária, a fim de se tratar, com sucesso, a candidíase eritematosa, comumente observada nas chamadas estomatites protéticas.

A comparative review of conventional and lipid formulations of amphotericin B

Over the past 15 years, factors suh as corticosteroid treatment, cytotoxic chemotherapy, excessive use of broad spectrum antibiotics and HIV have led to an increased risk of serious fungal infections in both adults and pediatric patients. This increase in invasive fungal infections poses increasing difficulty in their treatment. Three new lipid formulations of amphotericin B are now available in the U.S.: amphotericin B lipid complex (Abelcet), amphotericin B colloidal dispersion (Amphotec), and liposomal amphotericin B (AmBisome). These newer formulations are substantially more expensive, but allow patients to receive higher doses for longer periods of time with decreased renal toxicity than conventional amphotericin B. The properties of these new agents are summarized in this review. Discussion of current national guidelines as well as those used at our institution are presented to provide guidance for the development of institution specific guidelines for the most cost-effective drug for most patients, some may benefit more from one of the newer lipid formulations.

Comparison of the toxicity of amphotericin B in 5% dextrose with that of amphotericin B in fat emulsion in a randomized trial with cancer patients

A multicentric randomized trial was undertaken to compare the toxicity of amphotericin B in 5% dextrose with that of amphotericin B in a fat emulsion (Intralipid) in cancer patients. Group 1 (n = 33) received amphotericin B diluted in 5% dextrose with premedication consisting of promethazine plus an antipyretic. Group 2 (n = 28) received amphotericin B diluted in 20% Intralipid without premedication. Amphotericin B was infused daily at a dose of 1 mg/kg of body weight over a 1-h period to members of both groups for empirical antifungal therapy (in neutropenic patients) or for the treatment of documented fungal infections. The majority of patients (80%) received empirical amphotericin B treatment. The two groups were comparable with regard to age, gender, underlying disease, and the following baseline characteristics: use of other nephrotoxic drugs and serum levels of potassium and creatinine. The median cumulative doses of amphotericin B were 240 mg in group 1 and 245 mg in group 2 (P = 0.73). Acute adverse events occurred in 88% of patients in group 1 and in 71% of those in group 2 (P = 0.11). Forty percent of the infusions in group 1 were associated with fever, compared to 23% in group 2 (P < 0.0001). In addition, patients in group 2 required less meperidine for the control of acute adverse events (P = 0.008), and fewer members of this group presented with hypokalemia (P = 0.004) or rigors (P < 0.0001). There was no difference in the proportions of patients with nephrotoxicity (P = 0.44). The success rates of empirical antifungal treatment were similar in the two groups (P = 0.9). Amphotericin B diluted in a lipid emulsion seems to be associated with a smaller number of acute adverse events and fewer cases of hypokalemia than amphotericin B diluted in 5% dextrose.

In vitro and in vivo experimental activities of antifungal agents against Fusarium solani

In the treatment of disseminated Fusarium infections, amphotericin B either alone or in combination with flucytosine and rifampin is the drug therapy most frequently used. The efficacy of these antifungal drugs was evaluated in a murine disseminated-infection model, with five strains of Fusarium solani. All the treatments were clearly ineffective.

Antifungal agents. Part I. Amphotericin B preparations and flucytosine

Traditionally, amphotericin B has been the cornerstone of antifungal treatment. Toxicity, however, is a major dose-limiting factor of amphotericin B deoxycholate. Nevertheless, it continues to have a major role in the treatment of deep-seated mycotic infections. Recently, less nephrotic lipid formulations, including amphotericin B lipid complex, amphotericin B cholesteryl sulfate, and liposomal amphotericin B, have been introduced. The pharmacologic properties, main indications, recommended dosages, related costs, and adverse effects of these various preparations are summarized in this review. Orally administered flucytosine is useful in certain infections, particularly cryptococcal meningitis, but it should be used with caution in patients with renal insufficiency.

Accumulation of amphotericin B in human macrophages enhances activity against Aspergillus fumigatus conidia: quantification of conidial kill at the single-cell level

A cytofluorometric assay that allowed assessment of damage to phagocytosed Aspergillus fumigatus conidia at the single-cell level was developed. After ingestion by monocyte-derived macrophages (MDMs), conidia were reisolated by treatment of the cells with streptolysin O, a pore-forming toxin with lytic properties on mammalian cells but not on fungi. The counts obtained by staining of damaged conidia with propidium iodide and quantification by cytofluorometry correlated with colony counts. By the use of this method, we demonstrate that MDMs differentiated in vitro by low-dose granulocyte-macrophage colony-stimulating factor and gamma interferon have only a limited capacity to damage Aspergillus conidia in vitro. The killing rate 12 h after phagocytosis was found to be only 10 to 15%. However, intracellular loading of the phagocytes with amphotericin B (AmB) dose dependently enhanced the anticonidial activity. Preincubation of macrophages with only 1 microg of AmB per ml resulted in an uptake of 18 fg of AmB/cell, leading to killing rates of 50 to 60%. The experimental protocol provides a new tool for the rapid quantification of anticonidial activity against A. fumigatus in vitro. Intracellular accumulation of AmB may represent an important factor underlying the efficacy of this antifungal drug in the prophylaxis and treatment of Aspergillus infections.

KY-62, a polyene analog of amphotericin B, for treatment of murine candidiasis

KY-62 is a water-soluble analog of amphotericin B. In vitro testing of five clinical isolates of Candida albicans showed KY-62 to have potency similar to that of amphotericin B. KY-62 was administered to mice infected intravenously with C. albicans. In vivo, KY-62 was effective in immunocompetent mice, with potency similar to that of amphotericin B. KY-62 was well tolerated up to 30 mg/kg of body weight per dose, an amount that would be lethal with amphotericin B. KY-62 was less effective in mice rendered neutropenic with 5-fluorouracil. The addition of flucytosine had little effect. KY-62 may have potential for clinical development.

Interactions between amphotericin B and nitroimidazoles against Candida albicans

This work proved that nitroimidazole antiprotozoal agents, such as metronidazole, ornidazole, secnidazole and tinidazole, in concentrations of up to 64 micrograms ml-1 did not present any antifungal activity against 17 strains of Candida albicans. The combination of each drug with amphotericin B showed the occurrence of variable interactions according to the studied strain. Promising results were observed based on synergistic and additive interactions of the polyene with the metronidazole; the inhibitory and lethal activities of the drugs were potentiated against all strains in concentrations reachable in vivo.

Evidence for the formation of amphotericin B-phospholipid complexes in Langmuir monolayers

PURPOSE

To study the interaction of the polyene antifungal amphotericin B with phospholipid Langmuir monolayers and to correlate with stability of phospholipid-stabilized drug emulsions.

METHODS

Pressure-area isotherms of mixed monolayers of amphotericin B (0-20 mol%) and different phospholipid types were recorded using conventional Langmuir trough methods. Emulsion stability of amphotericin B-containing lipid emulsions was measured using dynamic light scattering.

RESULTS

Incorporation of amphotericin B into monolayers composed of saturated phospholipids (Lipoid E80-3) had a profound effect on the shape of the isotherm. This effect was directly related to the concentration of amphotericin B in the monolayer. At high drug concentrations, the shape of the isotherms became progressively similar to that of pure DPPC, thus exhibiting regions attributable to phospholipid in different phase states. This effect on isotherm shape was not observed following incorporation of the drug into monolayers composed of the equivalent unsaturated lecithin (Lipoid E80).

CONCLUSIONS

These results are interpreted as indicating the formation of an amphotericin B-phospholipid complex, resulting in phase separation within the monolayer. The extent and nature of this phase separation was dependent on both the concentration of drug in the system, and the saturation state of the phospholipid component. The relevance of these observations to the stability of amphotericin B drug emulsions stabilised by saturated and unsaturated phospholipid emulsifiers is discussed. These observations may also be relevant to the toxicity of these, and other novel amphotericin B formulations.

Possible reason for preferential damage to renal tubular epithelial cells evoked by amphotericin B

An important determinant of nephrotoxicity, which is the major complication of long-term amphotericin B treatment, is dysfunction of distal tubular epithelial cells. The underlying cause for this rather selective damage to the cells is unknown. In the present investigation, it was shown that kidney epithelial cells were initially damaged by amphotericin B at concentrations of 2.5 to 10 micrograms/ml, as demonstrable by a dramatic drop in cellular K+ levels. Cells could recover from the initial toxic action of the polyene if they were kept in medium of neutral pH, and cellular K+ levels returned to normal after 6 h. However, the recovery mechanisms failed at lower pHs of 5.6 to 6.0. At low pHs, cells became progressively depleted of ATP; they leaked lactate dehydrogenase and became irreversibly damaged after approximately 6 h. The possibility that the low pH characteristic of the distal tubulus lumen renders the renal epithelial cells particularly vulnerable to the toxic action of amphotericin B is raised. The concept is in line with an earlier report that alkalization ameliorates amphotericin B nephrotoxicity in rats.

Visceral leishmaniasis in HIV infected patients: treatment with high dose liposomal amphotericin B (AmBisome)

Visceral leishmaniasis (VL) in patients coinfected with human immunodeficiency virus (HIV) is often atypical, and characteristically relapses after treatment. We treated 10 HIV infected patients (9 men) with parasitologically confirmed VL with liposomal amphotericin B ("AmBisome': L-AMB) at a dose of 4 mg/kg/day on days 1, 2, 3, 4, 5, 10, 17, 24, 31, and 38. Patients were hospitalized for the first 5 days, and were monitored during, and 1 week and 1, 3 and 6 months after, L-AMB therapy. There were no serious adverse events, and L-AMB was well tolerated. 9/10 patients completed therapy, one patient defaulted at day 24. Clinical improvement was seen in all nine patients and the bone marrow aspirate was cleared of visible/culturable parasites in 8/9 patients. During follow-up, one patient defaulted. The seven remaining patients relapsed at 2, 3, 3, 5, 5, 6 and 7 months. Re-treatment with a variety of antileishmanial drugs was unsatisfactory. The time from first diagnosis of VL to death in six patients was 5-40 months (mean 18.8 months). Only one patient remained alive 26 months after treatment. L-AMB is safe and provides a good initial clinical response. Intermittent dosing enables a short period of hospitalization. However, relapse is probably inevitable.

Fungal sinusitis: an update

OBJECTIVE

To review the classification of fungal sinusitis as well as discuss current approaches to diagnosis and management.

DATA SOURCES

A MEDLINE literature search was performed using the index terms sinus infection, fungal, diagnosis, radiology, microbiology, and treatment. The search was restricted to the English language and human subjects. With one exception the references were restricted to the last 10 years. Clinical data from studies performed at our institution were also included.

RESULTS

Fungal sinusitis can be divided into four primary categories: (1) acute/fulminant (invasive), (2) chronic/indolent (invasive), (3) fungus ball, and (4) allergic fungal sinusitis. Each subtype has unique immunologic, pathologic, and clinical features. Allergic fungal sinusitis is the most recently described and most common form. The treatment and prognosis of fungal sinusitis varies significantly among the four different categories.

CONCLUSION

Recent advances in endoscopy and computed tomography have enhanced the understanding of fungal sinusitis; however, they remain diseases surrounded by controversy. New insights into the etiology and pathogenesis of these diseases along with advances in diagnosis and treatment will lead to improved medical therapy.

Amphotericin B infusion-related toxicity: comparison of two- and four-hour infusions

OBJECTIVE

To investigate the influence of infusion duration on infusion-related adverse effects (IRAEs) associated with prophylactic or treatment regimens of amphotericin B in patients with leukemia/bone marrow transplant (BMT).

DESIGN

Randomized, double-blind, 2-arm, complete crossover, prospective clinical trial.

SETTING

A university-affiliated tertiary care teaching hospital.

PARTICIPANTS

The study population consisted of 25 consecutive patients with leukemia/BMT who received 162 prophylactic regimen infusions and 169 treatment regimen infusions of amphotericin B via a central line. Prior to each infusion all patients received a parenteral IRAE prophylaxis regimen of diphenhydramine 25 mg and hydrocortisone 25 mg. No test doses or incremental amphotericin B doses were administered. Patients were monitored closely for IRAEs, which were documented by using a standardized data collection form.

MAIN OUTCOME MEASURES

The incidence and nature of IRAEs during a 6-hour monitoring period following the initiation of each infusion was measured. Patients served as their own controls. IRAEs were compared according to infusion duration and therapeutic indication.

RESULTS

Three hundred and thirty-one 2- and 4-hour amphotericin B infusions were administered. We found no difference between 2- and 4-hour infusions in the incidence and severity of IRAEs, including overall events (29% of 166 2-hour infusions vs. 25% of 165 4-hour infusions), chill scores (8% of 166 2-hour infusions vs. 7% of 165 4-hour infusions; highest score 7 vs. 6), nausea and vomiting (7% vs. 12%; highest score 4 in both groups), fever (3% vs. 2%), highest temperature increase (2.4 vs. 1.6 degrees C), systolic hypotension (6% vs. 2%), greatest decrease from baseline (40 vs. 62 mm Hg), diastolic hypotension (5% vs. 3%), and greatest decrease (30 vs. 28 mm Hg) (p > 0.05). Overall, IRAEs were less common in prophylactic treatment regimens (35 events [22%] in 162 infusions) than in treatment regimens (55 events [32%] in 169 infusions) (p < 0.05).

CONCLUSIONS

This study demonstrates that patients with leukemia/BMT without myocardial or renal dysfunction who receive hydrocortisone and diphenhydramine as premedications can tolerate 2-hour central line infusions of prophylactic or treatment regimens of amphotericin B as well as 4-hour infusions.

Amphotericin B followed by itraconazole in the treatment of disseminated fungal infections in neutropenic patients

The role of the new triazoles in the treatment of disseminated fungal infections in neutropenic patients is at present under scrutiny. Six neutropenic patients with disseminated fungal infections were treated with amphotericin B during neutropenia and itraconazole after bone marrow recovery. There were three pulmonary aspergillomas, one Aspergillus fumigatus sinusitis, one Fusarium-mycosis and one disseminated candidosis. Four patients were cured of the infection. This approach seems to be safe and effective in the treatment of disseminated fungal infections in neutropenic patients, with the advantages of low side-effects and the possibility of early discharge from hospital.

Modulation of amphotericin B activity by association with mannose ester

The biological and molecular properties of a new formulation of Amphotericin B complexed with the surfactant palmitoyl mannose were studied in in vitro as well as in in vivo situations. The properties analyzed include toxicity towards two types of mammalian cells and four fungi strains, effect on macrophage activity, inflammatory properties, acute toxicity in mice and spectral behavior in presence of foetal calf serum or 6% propanol. The results demonstrate that, in presence of palmitoyl mannose, the cytotoxicity of AmB is decreased towards both, fungal and mammalian cells while its fungistatic potential is increased, its inflammatory properties are conserved and its acute toxicity is significantly diminished. These effects can be potentially explained by the formation of a complex between AmB and the sugar ester that impedes the interaction of the drug with either serum components or cell membrane constituents. The overall properties of AmB in the complex would be expected to favor an increase in the immunoadjuvant properties of the drug, a more localized inflammation during fungal infection and consequently a better therapeutic efficiency.