Dose Range Evaluation of Liposomal Nystatin and Comparisons with Amphotericin B and Amphotericin B Lipid Complex in Temporarily Neutropenic Mice Infected with an Isolate of Aspergillus fumigatus with Reduced Susceptibility to Amphotericin B

Using an isolate of Aspergillus fumigatus that is less susceptible in vivo to amphotericin B than most other isolates, we compared different doses of liposomal nystatin (L-nystatin), liposomal amphotericin B (L-amphotericin), and amphotericin B lipid complex (ABLC) with amphotericin B deoxycholate. Four experiments with intravenously infected neutropenic mice were conducted. A dose of L-nystatin at 10 mg/kg of body weight was toxic (the mice had fits or respiratory arrest). The optimal dosage of L-nystatin was 5 mg/kg daily on days 1, 2, 4, and 7 (90% survival). This was superior to L-amphotericin (5 mg/kg [P = 0.24] and 1 mg/kg [P < 0.0001]), ABLC (5 mg/kg [P = 0.014] and 1 mg/kg [P < 0.0001]), and amphotericin B deoxycholate (5 mg/kg [P = 0.008]). In terms of liver and kidney cultures, L-nystatin (5 mg/kg) was superior to all other regimens (P = 0.0032 and <0.0001, respectively). Higher doses of L-amphotericin (25 and 50 mg/kg) in one earlier experiment were more effective (100% survival) than 1 mg of L-amphotericin per kg and amphotericin deoxycholate (5 mg/kg) in terms of mortality and both liver and kidney culture results and to L-amphotericin (5 mg/kg) in terms of liver and kidney culture results only. ABLC (25 mg/kg) given daily for 7 days was superior to ABLC (50 mg/kg [P = 0.03]) but not to ABLC at 5 mg/kg or amphotericin B deoxycholate in terms of mortality, although it was in terms of liver and kidney culture results. No dose-response for amphotericin B (5 and 1 mg/kg) was demonstrable. In conclusion, in this stringent model, high doses of L-amphotericin and ABLC could overcome reduced susceptibility to amphotericin B deoxycholate, but all were inferior to 5- to 10-fold lower doses of L-nystatin.     

Comparison of In Vitro Antifungal Activities of Free and Liposome-Encapsulated Nystatin with Those of Four Amphotericin B Formulations

The in vitro activity of a multilamellar liposomal formulation of nystatin (Nyotran) was compared with those of free nystatin and four pharmaceutical preparations of amphotericin B. MICs for 200 isolates of two Aspergillus spp., seven Candida spp., and Cryptococcus neoformans were determined by a broth microdilution adaptation of the method recommended by the National Committee for Clinical Laboratory Standards. Minimum lethal concentrations (MLCs) of the six antifungal preparations were also determined. Both nystatin formulations possessed fungistatic and fungicidal activities against the 10 species tested. Liposomal nystatin appeared to be as active as free nystatin, with MICs and MLCs that were similar to, or lower than, those of the latter. Neither formulation of nystatin was as active as amphotericin B deoxycholate (Fungizone) or amphotericin B lipid complex (Abelcet), but both were more effective than liposomal amphotericin B (AmBisome). Our results suggest that further evaluation of liposomal nystatin is justified.     

New Medium for In Vitro Susceptibility Studies with Amphotericin B

Antibiotic medium 20 FDA and antibiotic medium 3 FDA were compared to determine if antibiotic medium 3 would be suitable for in vitro susceptibility testing with amphotericin B.     

Pharmacodynamics of Amphotericin B Deoxycholate,Amphotericin B Lipid Complex,and Liposomal Amphotericin B against Aspergillus fumigatus

Amphotericin B is a first-line agent for the treatment of invasive aspergillosis. However, relatively little is known about the pharmacodynamics of amphotericin B for invasive pulmonary aspergillosis. We studied the pharmacokinetics (PK) and pharmacodynamics (PD) of amphotericin B deoxycholate (DAMB), amphotericin B lipid complex (ABLC), and liposomal amphotericin B (LAMB) by using a neutropenic-rabbit model of invasive pulmonary aspergillosis. The study endpoints were lung weight, infarct score, and levels of circulating galactomannan and (1→3)-β-d-glucan. Mathematical models were used to describe PK-PD relationships. The experimental findings were bridged to humans by Monte Carlo simulation. Each amphotericin B formulation induced a dose-dependent decline in study endpoints. Near-maximal antifungal activity was evident with DAMB at 1 mg/kg/day and ABLC and LAMB at 5 mg/kg/day. The bridging study suggested that the “average” patient receiving LAMB at 3 mg/kg/day was predicted to have complete suppression of galactomannan and (1→3)-β-d-glucan levels, but 20 to 30% of the patients still had a galactomannan index of >1 and (1→3)-β-d-glucan levels of >60 pg/ml. All formulations of amphotericin B induce a dose-dependent reduction in markers of lung injury and circulating fungus-related biomarkers. A clinical dosage of liposomal amphotericin B of 3 mg/kg/day is predicted to cause complete suppression of galactomannan and (1→3)-β-d-glucan levels in the majority of patients.     

Comparative Chemotherapeutic Activity of Amphotericin B and Amphotericin B Methyl Ester

The comparative efficacy of amphotericin B and amphotericin B methyl ester (AME) against experimental histoplasmosis, blastomycosis, cryptococcosis, and candidosis in mice was assessed by determining the effect of daily intraperitoneal therapy on 21-day survival and persistence of organisms in internal organs. AME, like amphotericin B, was effective against each of the experimental infections, but the efficacy was lower than the parent compound. For Histoplasma and Blastomyces infections the mean effective dose (ED(50)) of amphotericin B was 0.3 mg/kg, whereas the corresponding values for AME, respectively, were 2.4 and 2.8 mg/kg. For Cryptococcus infection the ED(50) for amphotericin B was 0.2 mg/kg compared with 2.0 mg/kg for AME. The ED(50) of amphotericin B for Candida infection was lower than 0.05 mg/kg and the value of AME was between 0.5 to 0.05 mg/kg. The colony counts from internal organs of the surviving animals after the therapeutic regimens were compatible with the data on survival.     

Amphotericin B Pharmacokinetics in Humans

The pharmacokinetics of amphotericin B were studied in two patients at the conclusion of long-term therapy for disseminated histoplasmosis. The distribution kinetics of this drug were adequately described by a three-compartment mamillary model with a total distribution volume averaging 4 liters/kg. The elimination phase half-life of amphotericin B was approximately 15 days, reflecting slow release of amphotericin B from a peripheral compartment. In accordance with previous reports, renal excretion accounted for only 3% of total amphotericin B elimination. The pharmacokinetic model for one of the patients also was used to compare the simulated amphotericin B serum levels that would be expected if initial therapy followed two recommended regimens.     

Comparative Efficacies of Lipid-Complexed Amphotericin B and Liposomal Amphotericin B against Coccidioidal Meningitis in Rabbits

In separate previous studies, we have shown that lipid-complexed amphotericin B (Abelcet [ABLC]) and liposomal amphotericin B (AmBisome [AmBi]) are efficacious against coccidioidal meningitis in rabbits. Here, we compared ABLC and AmBi directly in a coccidioidal meningitis model. Male New Zealand White rabbits were infected with 5 × 10⁴ Coccidioides posadasii arthroconidia by direct cisternal puncture. Therapy with intravenous ABLC or AmBi at 7.5 or 15 mg/kg of body weight or sterile 5% dextrose water (D5W) began 5 days later. Clinical assessments were done daily; cerebrospinal fluid and blood samples were obtained on day 15 and upon euthanasia. Survivors to day 25 were euthanatized, the numbers of CFU in their tissues were determined, and histology analyses of the brains and spinal cords were done. Controls showed progressive disease, whereas animals treated with either dose of either drug showed few clinical signs of infection. All ABLC- or AmBi-treated rabbits survived, whereas eight of nine D5W-treated rabbits were euthanatized before day 25 (P < 0.0001). Numbers of CFU in the brains and spinal cords of ABLC- or AmBi-treated animals were 100- to 10,000-fold lower than those in the corresponding tissues of D5W-treated animals (P < 0.0006 to 0.0001). However, only two or fewer given a regimen of ABLC or AmBi were cured of infection in both tissues. Fewer ABLC-treated rabbits (four of eight treated with 7.5 mg/kg and five of eight treated with 15 mg/kg) than controls (nine of nine) had meningitis at any level of severity (P, 0.015 or 0.043 for animals treated with ABLC at 7.5 or 15 mg/kg, respectively). Although groups of rabbits treated with AmBi regimens did not have significantly fewer animals with meningitis than the control group (P > 0.05), ABLC and AmBi were not significantly different. In this model, intravenous ABLC and AmBi were similarly highly effective, with few clinical signs of infection, 100% survival, and significantly reduced fungal burdens among treated animals. There appeared to be little benefit in using the 15-mg/kg dosage of either formulation. There was no significant advantage of one drug over the other for this indication. Further studies are required to determine the lowest effective doses of these formulations.Coccidioidal meningitis remains a severe and lethal infection (4, 7, 9-11). If left untreated, it is considered uniformly fatal within 2 years. Despite advances in oral azole therapy over the last decade, therapy is prolonged, often considered to be lifelong, and relapses can occur (3, 8). In addition, cure of the disease may not be attainable using oral azoles, regardless of the treatment duration (3). The use of conventional amphotericin B is limited, since the intravenous administration of conventional amphotericin B is ineffective for treatment. The intrathecal administration of amphotericin B is effective in many instances but is suboptimal because of associated side effects and toxicities and because of technical issues of administration. Thus, improvements in therapy are needed for the treatment of this devastating manifestation of coccidioidomycosis.In previous individual studies, we have shown that intravenous lipid-complexed amphotericin B (Abelcet [ABLC]) and liposomal amphotericin B (AmBisome [AmBi]) are efficacious in a rabbit model of coccidioidal meningitis (1, 2). Dosages of amphotericin B as ABLC or AmBi of 7.5 and 15 mg per kg of body weight given three times per week for 3 weeks were most effective and resulted in cures in some animals, whereas 1 mg/kg of conventional amphotericin B was much less effective and noncurative in the rabbit. These results suggest that intravenous therapy with ABLC or AmBi may be effective, whereas no dose of conventional amphotericin B is effective by this route in humans. Although both lipid formulations are effective in the model, the question of whether one formulation was superior to the other when the two were given at equivalent doses was unanswered. Comparing drug efficacies across studies done at different times does not account for possible variations in the inoculum level or the virulence of the organism, induced disease severity, or variation in the experimental animals and may lead to an incorrect conclusion. Slight differences in disease severity may result in a drug''s being efficacious in a moderately severe infection model but ineffective in a highly severe infection model. Therefore, it is important to do comparisons of the efficacies of drugs side by side, with the variables of the experimental system constant. Thus, the aim of the present study was to compare ABLC and AmBi directly in the same experiment to determine their efficacies against experimental coccidioidomycosis.     

Comparative Susceptibility of Candida albicans to Amphotericin B and Amphotericin B Methyl Ester

The in vitro antifungal activities of amphotericin B (AMB) and amphotericin B methyl ester (AME) were compared against 465 clinical isolates of Candida albicans. AMB and AME possessed comparable activity against half of the strains, but against the remainder of the strains the activity of AME was slightly lower than that of AMB. Rarely did AME show superior antifungal activity to AMB.     

Superiority of radiobinding assay over ELISA for detection of IAAs in newly diagnosed type I diabetic children

OBJECTIVE: Liquid- or solid-phase assays have been used for insulin autoantibody (IAA) determination, and the method of IAA measurement has not been standardized. RESEARCH DESIGN AND METHODS: IAAs were determined by radiobinding assay (RBA) and enzyme-linked immunosorbent assay (ELISA) in two large age-matched groups of nondiabetic and newly diagnosed insulin-dependent (type I) diabetic children. RESULTS: Positivity for IAA by RBA (greater than or equal to nondiabetic mean + 3SD) was 2 of 178 (1.1%) and 55 of 173 (32%) in nondiabetic and diabetic children, respectively. Prevalence of IAA by RBA was significantly higher in the youngest age-group (63% between 0-4 yr). Positivity for IAA by ELISA was 1 of 178 (0.6%) and 8 of 169 (4.7%) in nondiabetic and diabetic children, respectively. Concordance rates between both assays were 0 of 3 (0%) in control subjects and 5 of 58 (8.6%) in diabetic children. CONCLUSIONS: We conclude that RBA is more appropriate than ELISA for IAA detection at the onset of the disease. In addition, because available data suggest that IAAs detected by RBA only are high-affinity antibodies, it is tempting to speculate that IAAs reflect a mature immune reaction against endogenous insulin.     

Amphotericin B in lung transplant recipients

Although the verdict may still be out on the clinical utility of prophylactic administration of amphotericin B, the findings presented by Marra et al. strengthen the argument for its theoretical use by demonstrating that a relatively reproducible range of concentrations can be achieved in the target patient group. Additionally, it was demonstrated that at an inhaled dose of 30 mg, amphotericin B concentrations at the interface of epithelial lining fluid and the lung tissue, the battleground for host invasion, approach therapeutically relevant concentrations. Even though the debate over the utility of aerosolized administration of antimicrobials is far from over, data continue to accumulate that demonstrate the tolerability and describe the characteristics of drug distribution of nebulized amphotericin B. Even with the absence of definitive clinical data, aerosolized administration of amphotericin B may become a viable option for prophylaxis against serious pulmonary fungal infections owing to the severity of disease, lack of serious toxicities associated with this route of administration, and pharmacokinetic and susceptibility data, suggesting a theoretical basis for activity.     

Comparative In Vitro Antifungal Activity of Amphotericin B and Amphotericin B Methyl Ester

The in vitro antifungal activity of amphotericin B methyl ester (AME), a water-soluble derivative of amphotericin B, was compared to that of the parent compound against a variety of pathogenic and potentially pathogenic fungi. AME has a significant antifungal activity, but the activity of AME was slightly lower than that of amphotericin B. Among the yeast-like organisms, only the yeast cells of Sporothrix schenckii were more resistant than others to both antibiotics, with a minimal fungicidal concentration of 5 to 10 mug/ml. The yeast cells of other fungi were killed at concentrations of 1 mug or less of either antibiotic per ml. The filamentous forms of S. schenckii and Oidiodendron kalrai were more resistant than the filamentous forms of other dimorphic fungi to both drugs. The minimal fungicidal concentration for S. schenckii was 10 mug/ml and for O. kalrai, 50 mug/ml. The dermatophytes, phycomycetes, and dematacious and other potentially pathogenic fungi were inhibited fairly well by both drugs, but up to 50 mug/ml was required for fungicidal action. The water solubility and wide spectrum of antifungal activity of AME warrant evaluation of its chemotherapeutic activity against experimental fungal infections.     

Erythropoietin Concentration in Amphotericin B-Induced Anemia

Amphotericin B was given to six patients with systemic fungal infections. A dose averaging 1.78 g, administered from 42 to 144 days, was associated with a fall in hematocrit to a mean value of 25.8%. Despite this degree of anemia, no elevation of erythropoietin concentrations in urine or serum could be detected. Thus, amphotericin appears to cause anemia by inhibiting erythropoietin production rather than by suppressing bone marrow activity directly.     

Stability of Amphotericin B in Infusion Bottles

Intravenous solutions of amphotericin B in 5% dextrose water with or without hydrocortisone or heparin demonstrated no appreciable loss of activity when exposed to fluorescent light for up to 24 h at 25 C (room temperature).     

Pharmacokinetics and Pharmacodynamics of Amphotericin B Deoxycholate,Liposomal Amphotericin B,and Amphotericin B Lipid Complex in an In Vitro Model of Invasive Pulmonary Aspergillosis

The pharmacodynamic and pharmacokinetic (PK-PD) properties of amphotericin B (AmB) formulations against invasive pulmonary aspergillosis (IPA) are not well understood. We used an in vitro model of IPA to further elucidate the PK-PD of amphotericin B deoxycholate (DAmB), liposomal amphotericin B (LAmB) and amphotericin B lipid complex (ABLC). The pharmacokinetics of these formulations for endovascular fluid, endothelial cells, and alveolar cells were estimated. Pharmacodynamic relationships were defined by measuring concentrations of galactomannan in endovascular and alveolar compartments. Confocal microscopy was used to visualize fungal biomass. A mathematical model was used to calculate the area under the concentration-time curve (AUC) in each compartment and estimate the extent of drug penetration. The interaction of LAmB with host cells and hyphae was visualized using sulforhodamine B-labeled liposomes. The MICs for the pure compound and the three formulations were comparable (0.125 to 0.25 mg/liter). For all formulations, concentrations of AmB progressively declined in the endovascular fluid as the drug distributed into the cellular bilayer. Depending on the formulation, the AUCs for AmB were 10 to 300 times higher within the cells than within endovascular fluid. The concentrations producing a 50% maximal effect (EC₅₀) in the endovascular compartment were 0.12, 1.03, and 4.41 mg/liter for DAmB, LAmB, and ABLC, respectively, whereas, the EC₅₀ in the alveolar compartment were 0.17, 7.76, and 39.34 mg/liter, respectively. Confocal microscopy suggested that liposomes interacted directly with hyphae and host cells. The PK-PD relationships of the three most widely used formulations of AmB differ markedly within an in vitro lung model of IPA.Aspergillus fumigatus is an environmentally ubiquitous mold that is a leading cause of morbidity and mortality in immunocompromised patients (18). Despite the advent of newer diagnostic and therapeutic modalities, the mortality rate remains approximately 50% (22). An improved understanding of the pharmacology of existing agents represents an important strategy to improve the outcomes of patients with this rapidly progressive and frequently lethal infectious syndrome.Amphotericin B (AmB) is a polyene derived from Streptomyces nodosus. This compound was discovered in the mid-1950s and remains a first-line agent for the treatment of invasive aspergillosis and other life-threatening invasive fungal infections (23, 24). Amphotericin B is amphipathic; i.e., it has both hydrophilic and hydrophobic moieties that render it insoluble in water. Aqueous solubility is achieved by formulation with deoxycholate or a variety of lipid carriers. Amphotericin B deoxycholate (DAmB) is a highly potent antifungal formulation, but its clinical utility is limited by a high frequency of adverse effects, such as infusional toxicity and nephrotoxicity (3, 27). Lipid formulations are better tolerated than DAmB and are increasingly used for the treatment of invasive pulmonary aspergillosis (IPA). Three licensed lipid-based formulations have been developed for clinical use: liposomal amphotericin (LAmB), amphotericin B lipid complex (ABLC), and amphotericin B colloidal dispersion (ABCD). These formulations differ significantly in their structures and pharmacological properties (1).Here, we describe the pharmacokinetics and pharmacodynamics (PK-PD) of the frequently used clinical formulations of amphotericin B by the use of an in vitro model of IPA. This model enabled assessment of the extent of drug penetration into a number of tissue subcompartments that are relevant to the pathogenesis of IPA.     

Neutrophil Toxicity of Amphotericin B

The toxicity of amphotericin B (AmB) for neutrophils and the protective effect of serum cholesterol were investigated. Neutrophils were exposed in vitro to varying concentrations of AmB. As judged by trypan blue exclusion, neutrophil viability decreased by 40% (P < 0.001) within 30 min of incubation in sterol-free buffer containing 5 μg of AmB per ml. In the presence of 4 mg of cholesterol per 100 ml in buffer, the AmB concentration could be increased to 50 μg/ml before significant (P < 0.01) neutrophil toxicity occurred. Hexose monophosphate shunt activity of neutrophils incubated in serum or cholesterol-containing buffer with 10 μg of AmB per ml was normal. These results suggest that serum contains a protective factor, probably cholesterol, which protects neutrophils in vitro from the toxic effects of AmB.     

碳酸氢钠联合制霉菌素治疗小儿鹅口疮患者临床疗效观察

目的研究碳酸氢钠联合制霉菌素治疗小儿鹅口疮临床治疗效果及预后。方法选取2014年9月~2016年8月我院治疗小儿鹅口疮患者102例,随机分为对照组和观察组各51例。对照组给予制霉菌素涂抹治疗,观察组给予碳酸氢钠+制霉菌素治疗。观察对比两组患儿临床疗效、并发症发生率及复发率。结果观察组治疗总有效率为92.16%,显著高于对照组的74.51%,差异具有统计学意义(P0.05);观察组并发症发生率为11.76%,显著低于对照组的29.41%,观察组复发率为7.84%,显著低于对照组的25.49%,差异具有统计学意义(P0.05)。结论碳酸氢钠联合制霉菌素可提高小儿鹅口疮的临床疗效,改善预后。     

Comparative Pharmacology of Amphotericin B and Amphotericin B Methyl Ester in the Non-Human Primate, Macaca mulatta

The pharmacokinetics of amphotericin B methyl ester hydrochloride (AME) and commercial deoxycholate-stabilized amphotericin B (AMB) were compared after single doses of 5 mg and 1 mg/kg of body weight, respectively, given intravenously in a period of 3 h to adult female rhesus monkeys (Macaca mulatta). By bioassay, the concentrations of AME were 12.2 to 7.2 times higher in the serum and 7.8 to 2.5 times higher in the urine during the 8 h after infusion. The decline in concentrations of the drugs in sera was consistent with a three-compartment, open pharmacokinetic model; rate constants of transfer of the drugs between the compartments and volumes of distribution were calculated. The overall rate of elimination from the central compartment (the bloodvascular space) was about four times greater for AME than for AMB. Serum urea nitrogen and creatinine concentrations were mildly and transiently increased after infusion of AME, whereas the more severe azotemia that followed infusion of AMB persisted for 5 days. AME was less toxic and achieved a greater urinary outfall than AMB. As the antifungal activity of AME is comparable to that of AMB by testing in vitro, further study is warranted.     

Comparative Pharmacodynamics of Amphotericin B Lipid Complex and Liposomal Amphotericin B in a Murine Model of Pulmonary Mucormycosis

We compared the kinetics of amphotericin B (AMB) lung accumulation and fungal clearance by liposomal amphotericin B (L-AMB) and amphotericin B lipid complex (ABLC) in a neutropenic murine model of invasive pulmonary mucormycosis (IPM). Immunosuppressed BALB/c mice were inoculated with 1 × 10⁶ Rhizopus oryzae spores and administered L-AMB or ABLC at daily intravenous doses of 1, 5, or 10 mg/kg of body weight for 5 days starting 12 h after infection. At a dose of 10 mg/kg/day, both L-AMB and ABLC were effective at reducing the R. oryzae lung fungal burden and achieved lung tissue concentrations exceeding the isolate mean fungicidal concentration (MFC) of 8 μg/ml by 72 h. When ABLC was dosed at 5 mg/kg/day, the ABLC-treated animals had significantly higher AMB lung concentrations than the L-AMB treated animals at 24 h (6.64 and 1.44 μg/g, respectively; P = 0.013) and 72 h (7.49 and 1.03 μg/g, respectively; P = 0.005), and these higher concentrations were associated with improved fungal clearance, as determined by quantitative real-time PCR (mean conidial equivalent of R. oryzae DNA per lung, 4.44 ± 0.44 and 6.57 ± 0.74 log₁₀, respectively; P < 0.001). Analysis of the AMB tissue concentration-response relationships revealed that the suppression of R. oryzae growth in the lung required tissue concentrations that approached the MFC for the infecting isolate (50% effective concentration, 8.19 μg/g [95% confidence interval, 2.81 to 18.1 μg/g]). The rates of survival were similar in the animals treated with L-AMB and ABLC at 10 mg/kg/day. These data suggest that higher initial doses may be required during L-AMB treatment than during ABLC treatment of experimental IPM.Invasive pulmonary mucormycosis (IPM) is an uncommon but frequently fatal angioinvasive mold infection that has increased in incidence over the last decade, especially in patients with hematological malignancies and recipients of hematopoietic stem cell transplantation (HSCT) (23). In a recent multicenter, prospective observational study of invasive fungal infections in HSCT recipients, mucormycosis was the third most common invasive fungal infection (7.2%), behind invasive aspergillosis (59.2%) and invasive candidiasis (24.8%) (21). Data from the Centers for Disease Control and Prevention Transplant Associated Infection Surveillance Network (TRANSNET) reported that the incidence of mucormycosis in U.S. transplant centers increased nearly sixfold from 2001 to 2004, with Rhizopus being the most frequently isolated genus (22).Although new diagnostic and treatment options have improved the survival rates in patients with invasive pulmonary aspergillosis (IPA) over the last decade, the prognosis for patients with IPM remains poor, as only one-third of the patients survive beyond 12 weeks after the diagnosis (13, 21, 23). The outcome of IPM is heavily dependent on a timely diagnosis, as the initial clinical manifestations and radiographic appearance of IPM are often indistinguishable from those of IPA, and the first-line antifungals used to treat aspergillosis, such as voriconazole, lack activity against members of the order Mucorales (24). In one case series, 84% of leukemia and HSCT patients were receiving ineffective antifungal therapy at the time of diagnosis of IPM (15). Similarly, we found that delays in the administration of lipid amphotericin B (AMB) formulations as few as 6 days from the time of the initial appearance of symptoms was associated with a doubling of the 12-week mortality rate for IPM (48.6% and 82.9%, respectively; P = 0.029) (6). These data suggest that the rapid delivery to infected organs of antifungals active against Mucorales is critical to suppress fungal proliferation and reduce the potential for angioinvasion and subsequent dissemination (6).Although no prospective randomized trials have compared antifungals for the primary treatment of IPM, lipid formulations of AMB are considered the first-line treatment during the acute phases of infection due to their spectra of activity and predictable pharmacokinetics (12). Currently, two lipid formulations are frequently prescribed for the treatment of IPM: AMB lipid complex (ABLC) and liposomal AMB (L-AMB). These formulations differ in their compositions, particle sizes, and pharmacokinetic behaviors. L-AMB consists of small unilamellar particles (60 to 70 nm) that avoid uptake by the mononuclear phagocytic system (MPS) (28). Hence, the intravenous administration of L-AMB results in sustained, high concentrations of encapsulated AMB in the bloodstream and a somewhat delayed distribution of free drug into tissue. Conversely, the intravenous administration of the larger-particle ABLC formulation (1,600 to 11,000 nm) results in relatively lower AMB bloodstream concentrations due to the rapid uptake and distribution to tissues rich in mononuclear phagocytic cells, including lung tissue (9, 18, 19). The clinical relevance of these pharmacokinetic differences between L-AMB and ABLC, however, remains unknown.In a previous study, we examined how pharmacokinetic differences between L-AMB and ABLC affected the rate and extent of fungal clearance in a neutropenic murine model of IPA (16). At daily doses of <10 mg/kg of body weight per day, ABLC treatment achieved significantly higher concentrations of AMB in lung tissue at earlier time points of therapy, and the higher concentrations were associated with the more rapid clearance of Aspergillus fumigatus. However, both formulations were effective after 5 days of therapy for the treatment of this AMB-susceptible isolate. Nevertheless, formulation-dependent differences in antifungal pharmacokinetics may be more critical in the treatment of pulmonary infections caused by more angioinvasive, amphotericin B-tolerant pathogens, such as Rhizopus orzyae. Therefore, we examined whether the differences in the pharmacokinetics between L-AMB and ABLC may require the use of different dosing approaches for the treatment of mucormycosis. To explore this question, we compared (i) the patterns of AMB accumulation in lung tissue following intravenous treatment with L-AMB or ABLC and (ii) the dose-dependent patterns of Rhizopus oryzae clearance from the lung in an experimental model of IPM.(This work was previously presented at the 48th Interscience Conference on Antimicrobial Agents and Chemotherapy [15a].)