Evaluation of the in-line filters for the intravenous infusion of amphotericin B fluid

OBJECTIVE: To evaluate the effects of four types of in-line filters on filtration rate, amphotericin B concentration and particulate matter. METHODS: Filtration rates of amphotericin B fluid through in-line filters under maximum gravity flow were examined. The concentrations of amphotericin B and the particulate matter in the non-filtered and filtered amphotericin B fluid at the flow rate of 500 ml/24 h were measured. RESULTS: Filtration through a 1.2 microm or 0.2 microm polyethersulphone (PES) filter under maximum gravity flow took less than 40 min. The 0.2 microm positively charged nylon 66 and 0.2 microm nylon 66 filters took 70 and 100 min, respectively, to filter 500 ml of amphotericin B fluid. The 0.2 microm positively charged nylon 66 filter and the 0.2 microm nylon 66 filter, but not the PES filter (1.2 and 0.2 microm), decreased the concentrations of amphotericin B in the filtered fluid by 100% within 1 h and by 66% within 24 h after the start of filtration, respectively. The particulate count in the non-filtered amphotericin B fluid was 27+/-5 particles/ml, exceeding the limit defined by USP XXIII. The 1.2 microm and 0.2 microm PES filters significantly decreased particulate matter by 83 and 97%, respectively, just after filtration. CONCLUSION: The present results indicate that the 0.2 microm PES filter is optimal for intravenous infusion of amphotericin B fluid to minimize the introduction of particulate matter, microbial contaminants and endotoxin into patients.     

Antioxidant-stabilized amphotericin B

A review of several recent reports shows that many compounds possessing antioxidant or mild reducing properties can enhance the bioactivity of amphotericin B. Antioxidants apparently retard autoxidative inactivation of this primary antifungal antibiotic. Stabilization of amphotericin B in this manner might have practical applications. Some important possibilities are identified and discussed.     

Comparative in vitro and in vivo evaluation of N-D-ornithyl amphotericin B methyl ester, amphotericin B methyl ester, and amphotericin B.

N-D-Ornithyl amphotericin B methyl ester (O-AME), a semisynthetic derivative of amphotericin B methyl ester (AME), was compared with amphotericin B (AMB) and AME. In vitro, O-AME was more active than the other two against Candida spp. and other fungi and was only slightly affected by inoculum size, addition of serum, or changes in pH. In vivo, the dose of O-AME required to produce a 10,000-fold reduction of Candida albicans in a mouse kidney infection was similar to that of AMB and 1/10 that of AME. After intravenous treatment of infected mice and rats and subcutaneous treatment of mice, average 50% protective doses for O-AME and AMB were similar. Acute intravenous 50% lethal doses in mice indicated that O-AME was one-ninth as toxic as AMB but twice as toxic as AME. Acute renal function tests in rats indicated that Sch 28191 was less than 1/10 as toxic as AMB and slightly more toxic than AME. On this basis, the calculated advantage relative to AMB (with AMB equal to 1) was 8 for O-AME and 1.5 for AME.     

Plasma protein binding of amphotericin B and pharmacokinetics of bound versus unbound amphotericin B after administration of intravenous liposomal amphotericin B (AmBisome) and amphotericin B deoxycholate

Unilamellar liposomal amphotericin B (AmBisome) (liposomal AMB) reduces the toxicity of this antifungal drug. The unique composition of liposomal AMB stabilizes the liposomes, producing higher sustained drug levels in plasma and reducing renal and hepatic excretion. When liposomes release their drug payload, unbound, protein-bound, and liposomal drug pools may exist simultaneously in the body. To determine the amounts of drug in these pools, we developed a procedure to measure unbound AMB in human plasma by ultrafiltration and then used it to characterize AMB binding in vitro and to assess the pharmacokinetics of nonliposomal pools of AMB in a phase IV study of liposomal AMB and AMB deoxycholate in healthy subjects. We confirmed that AMB is highly bound (>95%) in human plasma and showed that both human serum albumin and alpha(1)-acid glycoprotein contribute to this binding. AMB binding exhibited an unusual concentration dependence in plasma: the percentage of bound drug increased as the AMB concentration increased. This was attributed to the low solubility of AMB in plasma, which limits the unbound drug concentration to <1 microg/ml. Subjects given 2 mg of liposomal AMB/kg of body weight had lower exposures (as measured by the maximum concentration of drug in serum and the area under the concentration-time curve) to both unbound and nonliposomal drug than those receiving 0.6 mg of AMB deoxycholate/kg. Most of the AMB in plasma remained liposome associated (97% at 4 h, 55% at 168 h) after liposomal AMB administration, so that unbound drug concentrations remained at <25 ng/ml in all liposomal AMB-treated subjects. Although liposomal AMB markedly reduces the total urinary and fecal recoveries of AMB, urinary and fecal clearances based on unbound AMB were similar (94 to 121 ml h(-1) kg(-1)) for both formulations. Unbound drug urinary clearances were equal to the glomerular filtration rate, and tubular transit rates were <16% of the urinary excretion rate, suggesting that net filtration of unbound drug, with little secretion or reabsorption, is the mechanism of renal clearance for both conventional and liposomal AMB in humans. Unbound drug fecal clearances were also similar for the two formulations. Thus, liposomal AMB increases total AMB concentrations while decreasing unbound AMB concentrations in plasma as a result of sequestration of the drug in long-circulating liposomes.     

In vitro antifungal activities of amphotericin B and liposome-encapsulated amphotericin B.

The in vitro activities of liposome-encapsulated amphotericin B and free amphotericin B against Candida albicans 336 were comparable. Amphotericin B concentrations 12-fold and greater than 50-fold higher were required to kill the same organism when cholesterol and ergosterol were incorporated into the liposomes. The addition of cholesterol to liposomes caused a significant increase in the minimal fungicidal concentration of amphotericin B in 7 of 19 other yeast strains tested, whereas ergosterol caused an increase in 18 of the 19 strains.     

Comparative in vitro antifungal activity of amphotericin B lipid complex, amphotericin B and fluconazole

Amphotericin B (AMB) is considered the gold standard in the treatment of serious systemic mycoses in spite of its nephrotoxicity and adverse effects. Association with lipids enables larger doses of AMB to be given with a longer t((1/2)) and C(max), without the toxic effects at lower concentrations. Liposome-encapsulated AMB shows a lower affinity for mammalian cells and improves V(d), thus decreasing toxicity. Amphotericin B lipid complex (ABLC) is an AMB formulation associated with a biodegradable phospholipid matrix (5% molar) from which the drug is released by cell phospholipases. ABLC is recommended for serious mycoses refractory to conventional antifungal therapy or when AMB is contraindicated. We compared the in vitro antifungal activity of ABLC, AMB and fluconazole (FLZ) against 328 strains of clinically significant opportunistic fungi using a microdilution method (NCCLS, M-27A). 64.9% of the yeasts were inhibited by MIC of ABLC 相似文献   

High purity amphotericin B

OBJECTIVES: Amphotericin B (AmB) is a drug of choice for treatment of disseminated fungal infections, but its use is often associated with severe adverse effects. Our observation that generic formulations of AmB contain multiple polyene components led us to propose that removal of other polyenes would yield a high purity AmB (AmBHP) with an improved therapeutic index. METHODS: To test that premise, AmBHP was first isolated from generic AmB by semi-preparative reverse phase high-pressure liquid chromatography and then its effects were compared in vitro and in vivo with those of commercial AmB formulations. RESULTS: AmBHP proved to be as active as generic AmB against Candida albicans in vitro and as efficacious as both generic and lipid-complexed AmB in a Candida-infected mouse model. AmBHP appeared to be less toxic to human THP-1 monocytic cells than was generic AmB at low concentrations (<2 microM), as indicated by exclusion of Trypan Blue and incorporation of [(3)H]thymidine. At higher concentrations, effects of AmBHP and generic AmB (Pharma-Tek AmB, PTAmB) on thymidine incorporation and cytosolic calcium concentration were similar. General toxicity to AmBHP in vivo, as indicated by its apparent LD(50) and survival of Candida-infected mice, was roughly twofold less than that to generic or lipid-complexed AmB. Likewise, AmBHP decreased mean glomerular filtration rate about half as much as did a 10-fold lower dose of PTAmB. CONCLUSIONS: Taken together, these data indicate that AmBHP may represent a refinement of currently marketed AmB formulations, offering equal, if not better, efficacy with less toxicity.     

In-vitro antifungal activity of liposomal nystatin in comparison with nystatin, amphotericin B cholesteryl sulphate, liposomal amphotericin B, amphotericin B lipid complex, amphotericin B desoxycholate, fluconazole and itraconazole.

The in-vitro susceptibilities of 120 clinical isolates of yeasts to liposomal nystatin were compared with those to amphotericin B lipid complex (ABLC), liposomal amphotericin B (LAB), amphotericin B cholesteryl sulphate (ABCD), amphotericin B desoxycholate, nystatin, fluconazole and itraconazole. Yeast isolates examined included strains of Candida albicans, Candida parapsilosis, Candida glabrata, Candida krusei, Candida guilliermondii, Candida tropicalis, Candida kefyr, Candida viswanathii, Candida famata, Candida rugosa, Rhodotorula rubra, Trichosporon spp., Cryptococcus laurentii and Cryptococcus neoformans. The mean MICs for all strains examined were: liposomal nystatin 0.96 mg/L; nystatin 0.54 mg/L; ABLC 0.65 mg/L; LAB 1.07 mg/L; ABCD 0.75 mg/L; amphotericin B 0.43 mg/L; fluconazole 5.53 mg/L; and itraconazole 0.33 mg/L. No significant differences were seen between the activity of liposomal nystatin and the polyene drugs or itraconazole, but liposomal nystatin was more active than fluconazole. MICs were lower than the reported blood concentrations following therapeutic doses of this drug, indicating the potential for a therapeutic use of liposomal nystatin in humans. These results indicate good activity in vitro against medically important yeasts, which compares favourably with the activities of other currently available antifungal drugs. Liposomal nystatin may have a role in the treatment of disseminated and systemic mycoses.     

In vitro and in vivo comparisons of amphotericin B and N-D-ornithyl amphotericin B methyl ester.

N-D-Ornithyl amphotericin B methyl ester (N-D-ornithyl AmE) has a lower toxicity for animals than does amphotericin B (AmB), and peak serum levels can be achieved that are fourfold higher than those obtained with an equivalent dose of AmB. However, N-D-ornithyl AmE has one-fourth the in vitro activity and between one-fifth and one-eighth the in vivo activity of AmB. N-D-ornithyl AmE and the corresponding lysyl derivative also lack the immunoadjuvant effects of AmB.     

Nebulized amphotericin B combined with intravenous amphotericin B in rats with severe invasive pulmonary aspergillosis

Nebulized amphotericin B (AMB) combined with intravenous AMB was studied in persistently leukopenic rats with invasive pulmonary aspergillosis. Pulmonary concentrations of AMB after aerosol treatment were substantially higher than after intravenous liposomal AMB. Nebulized liposomal AMB in addition to intravenous AMB resulted in significantly prolonged survival compared to controls.     

Amphotericin B tissue distribution in autopsy material after treatment with liposomal amphotericin B and amphotericin B colloidal dispersion

OBJECTIVES: Tissue concentrations of amphotericin B were determined in autopsy material of patients who had been treated with liposomal amphotericin B or amphotericin B colloidal dispersion (colloidal amphotericin B) for suspected or proven invasive fungal infection. PATIENTS AND METHODS: Amphotericin B tissue levels were measured in liver, spleen, lung, kidney, and myocardial and brain tissue of 20 patients who had been treated with lipid-formulated amphotericin B, before they died from multi-organ failure. Seven patients had been treated with liposomal amphotericin B (AmBisome) and thirteen with colloidal amphotericin B (Amphocil). Tissue samples were obtained during routine autopsy, homogenized and extracted with methanol. Amphotericin B concentrations were measured using HPLC after purification by solid phase extraction. RESULTS: The highest amphotericin B levels were found in liver and spleen, followed by kidney, lung, myocardium and brain. In the lung higher amphotericin B concentrations were found after treatment with amphotericin B colloidal dispersion than after therapy with liposomal amphotericin B. CONCLUSIONS: The choice of lipid formulation may influence amphotericin B penetration into the lung.     

Pharmacokinetics of amphotericin B in children.

Amphotericin B is the most effective agent for the majority of systemic fungal infections but often causes toxicity, and specific dosage guidelines for amphotericin B in pediatric patients are lacking. The purpose of this study was to characterize the pharmacokinetics of amphotericin B in children. Twelve patients (mean age, 6.6 years; range, 4 months to 14 years) receiving amphotericin B, 0.68 +/- 0.34 mg/kg per day (mean plus or minus standard deviation), were studied. Four to eight blood samples were collected during a 24-h period and analyzed by high-pressure liquid chromatography. The peak concentration of amphotericin B in serum was 2.9 +/- 2.8 micrograms/ml. The mean total clearance, apparent volume of distribution, and elimination half-life were 0.46 +/- 0.20 ml/min per kg, 0.76 +/- 0.52 liters/kg, and 18.1 +/- 6.6 h, respectively. Total clearance decreased with age (p less than 0.01). In children aged 8 months to 9 years, the mean total clearance was 0.57 +/- 0.15 ml/min per kg, and in children older than 9 years, it was 0.24 +/- 0.02 ml/min per kg. Interpatient variation in the clearance and volume of distribution of amphotericin B was greater than threefold and greater than eightfold, respectively. However, pharmacokinetic parameters did not change in two stable patients who were studied again. Because clearance decreased substantially with age, older children may require lower doses of amphotericin B per kilogram to decrease the potential for toxicity.     

Comparative efficacy of amphotericin B colloidal dispersion and amphotericin B deoxycholate suspension in treatment of murine coccidioidomycosis.

The efficacy of a novel sterol-complexed preparation of amphotericin B, amphotericin B colloidal dispersion, was compared with that of deoxycholate-complexed amphotericin B in an acute murine model of systemic coccidioidomycosis. Mice (CD-1, female) were infected intravenously with 180 or 200 arthroconidia of Coccidioides immitis, and intravenous therapy was begun 3 days later. Six doses in various regimens of either preparation were given over 14 days, and deaths were tallied for an additional 35 days. All regimens that were not acutely lethal prolonged the survival of mice over that of controls (P less than 0.001). Quantitative determination of residual burdens of C. immitis in the spleen, liver, and lungs of survivors revealed that the colloidal dispersion was not as effective as the deoxycholate suspension on a milligram-per-kilogram basis. Deoxycholate suspension at 1.3 mg/kg cleared the organs in all mice, whereas colloidal dispersion at 5.0 mg/kg was the lowest dose that cleared organisms from all animals. Lower doses cleared organisms from fewer animals or cleared only selected organs. Deoxycholate suspension was more efficacious than colloidal dispersion in clearing C. immitis from the liver or lungs (P less than 0.05 to 0.01, dose and organ dependent) at identical doses. No overt toxicity was observed in mice treated with colloidal dispersion at 10 mg/kg. In contrast, deoxycholate suspension at 2.0 mg/kg was acutely toxic; 50% of the treated mice died after treatment. The two complexes were not equivalent on a milligram-per-kilogram basis; the deoxycholate suspension was three to four times more efficacious and also greater than 5- to greater than or equal to 8-fold more toxic. Thus, the therapeutic index of the colloidal dispersion complex is greater than that of the deoxycholate complex. The amount of amphotericin B per dose could also be increased when given as a colloidal dispersion to an optimally level. Amphotericin B colloidal dispersion shows promise for the therapy of disseminated coccidioidomycosis and should be tested in other animal models and in humans.     

Comparative efficacies of amphotericin B lipid complex and amphotericin B deoxycholate suspension against murine blastomycosis.

Amphotericin B as a lipid complex and as a deoxycholate suspension (Fungizone) was tested against murine blastomycosis. All doses of each form prolonged survival (P less than 0.05 to 0.001). Fungizone was more effective than lipid complex at doses of 0.8 mg/kg of body weight. However, lipid complex at 12.8 mg/kg was not toxic and superior in efficacy (P less than 0.001) to 2.0 mg of Fungizone per kg (a toxic dose), and it cleared all animals of infection. Lipid complex is an effective therapy for murine blastomycosis.     

Effects of amphotericin B on hepatitis B virus.

We investigated the effects of amphotericin B (AmB) on the ultrastructure and biochemistry of hepatitis B virus (HBV) and hepatitis B surface antigen (HBsAg) particles. These effects were compared with those reported for AmB and other polyene antibiotics on other lipid-enveloped viruses and artificial membranes. Treatment of HBV particles with concentrations of AmB ranging from 5 to 250 microgram/ml resulted in (i) an increase in HBV deoxyribonucleic acid polymerase activity as the concentration of Amb increased; (ii) changes in the electron microscopic appearance of HBV ranging from increased penetration of negative stain into the lipid envelope to disruption of the virus; and (iii) an increase in density form 1.165 to 1.225 g/ml. In addition, AmB treatment of HBsAg particles resulted in disruption into a nonparticulate HBsAg-reactive fraction and an HBsAg-AmB complex fraction with no HBsAg immunoreactivity.     

Elimination of amphotericin B in impaired renal function

The influence of impaired renal function on the steady-state plasma clearance of amphotericin B was determined in seven patients with creatinine clearances ranging from zero to normal. Contrary to previous reports, steady-state plasma concentrations of total drug were lower in uremic patients than in patients with normal renal function. Total plasma clearance of amphotericin B ranged from 16.7 to 39.9 ml/min, correlated directly with the plasma creatinine concentration, and correlated inversely with the creatinine clearance. Urinary excretion of unchanged drug accounted for less than 10% of the dose. In 10 healthy subjects, mean percent of amphotericin B unbound in plasma was 3.55 +/- 0.32 (SD). Binding was determined in a further group of 10 uremic patients. Mean unbound percent (4.15 +/- 0.73, SD) was higher than in the healthy subjects, and the binding ratio (molar concentration of bound to unbound drug) correlated weakly with the creatinine clearance. This suggests that plasma clearance of unbound amphotericin B and, therefore, steady-state plasma concentrations of unbound drug are not affected by renal impairment, and that dosage requirements will be overestimated if based on measurements of total drug plasma concentration.     

Pharmacokinetics of aerosol amphotericin B in rats.

The distributions of amphotericin B (AmB) in tissue were compared after intraperitoneal or aerosol administration. Rats were sacrificed 24 h after receiving single or repeated daily doses; AmB concentrations in tissues were determined by high-performance liquid chromatography. After intraperitoneal doses of 4 mg/kg of body weight per day for 7 days, mean concentrations of AmB were 122.7, 55.2, and 4.31 micrograms/g in the spleen, liver, and lung, respectively. After aerosol doses (aero-AmB) of 1.6 mg/kg per day, the mean concentrations of AmB in the lung were 2.79 micrograms/g after a single dose and 9.88 micrograms/g after four doses, while the drug was undetectable (less than 0.1 micrograms/g) in serum, spleen, liver, kidney, and brain. The half-life of elimination of AmB from the lungs was 4.8 days according to serial sacrifices done after a single dose of 3.2 mg of aero-AmB per kg. Treatment with 60 mg of aero-AmB per kg was well tolerated and produced no histopathologic changes in the lungs. The aerosol route was much more efficient than the systemic route in delivering AmB to the lungs, and it limited the accumulation of AmB in other organs. Because AmB is eliminated slowly, infrequent dosing schedules can be used. These pharmacokinetic characteristics and its proven effectiveness in an animal model make aero-AmB a highly promising new method for the prevention of pulmonary aspergillosis. Aero-AmB should also be considered for use as an adjunct to intravenous AmB for treatment of fungal pneumonias.