High-pressure liquid chromatographic method for determination of Sch 28191 in biological fluids

Determination of amphotericin B in cerebrospinal fluid by solid-phase extraction and liquid chromatography

A highly sensitive and reproducible liquid chromatography (LC) method for the determination of Amphotericin B in cerebrospinal fluid has been developed and validated. This LC-based method involves using nystatin as an internal standard and solid-phase extraction for sample preparation, followed by reversed-phase separation monitored by absorbance at 410 nm. The method has a limit of quantification of less than 1 ng ml-1 and excellent precision and accuracy, with both percentage relative standard deviation and percentage relative error less than 10%. The established linearity range was 1-10 ng ml-1 (r2 > 0.99). The extraction recovery of Amphotericin B from the cerebrospinal fluid is higher than 90% over the entire linear range. The method has been successfully employed for studying the penetration of Amphotericin B into the central nervous system in dogs and human.

Toxicity and induction of resistance to Listeria monocytogenes infection by amphotericin B in inbred strains of mice

Amphotericin B (AmB) treatment before infection with the bacterium Listeria monocytogenes prolonged survival of AKR mice but shortened survival of C57BL/6 mice compared with survival of untreated infected controls. C57BL/6 mice were also more sensitive to the acute toxic effects of AmB than AKR mice, as were (C57BL/6 X AKR)F1 hybrid mice. Spleen cells and erythrocytes (RBCs) from the C57BL/6 and the F1 hybrid mice were both more sensitive to the lytic and lethal effects of AmB than corresponding cells from AKR mice. Biochemical analysis indicated that catalase levels in RBCs from C57BL/6 and F1 hybrid mice were about 60% of those found in RBCs from AKR mice. The lysis by AmB of RBCs from all these strains of mice was inhibited by catalase or incubation in a low-oxygen environment. These findings suggest that (i) the low catalase levels in C57BL/6 and F1 hybrid mice may limit the protection of cells from the oxidant damage involved in AmB action, and (ii) the toxicity which occurs at low concentrations of AmB in the mouse strains with low intracellular catalase levels may interfere with or ablate the AmB-induced increases in mouse resistance to L. monocytogenes infection.

Sensitive high-pressure liquid chromatographic assay for amphotericin B which incorporates an internal standard

We developed a rapid, sensitive, high-pressure liquid chromatographic (HPLC) procedure which incorporates a commercially available internal standard, 1-amino-4-nitronaphthalene, to measure amphotericin B in serum. Recovery was quantitative (greater than or equal to 90%), and the standard curve was linear from 0.04 to at least 10.0 micrograms/ml. The reproducibility of the assay was good, with intrarun coefficients of variation from 2.0 to 6.8% and interrun coefficients of variation from 4.9 to 10.0%. Comparison by linear regression analysis of the HPLC assay with an agar well diffusion bioassay gave a correlation coefficient of 0.942, with the HPLC assay exhibiting greater precision and sensitivity. No interference was encountered from over 20 drugs and three amphotericin B analogs. However, serum specimens that contained high concentrations of conjugated bilirubin (greater than 3 mg/dl) produced interfering peaks in both this assay and other previously reported HPLC assays for amphotericin B. We also describe a solid-phase extraction procedure which effectively removes this interference and uses an alternative internal standard (N-acetyl amphotericin B).

Comparison of amphotericin B and N-D-ornithyl amphotericin B methyl ester in experimental cryptococcal meningitis and Candida albicans endocarditis with pyelonephritis

Amphotericin B and N-D-ornithyl amphotericin B methyl ester were compared for therapeutic efficacies against experimentally induced cryptococcal meningitis and Candida albicans endocarditis with pyelonephritis in rabbits. Antifungal activity of the two polyenes in vitro was similar for the yeasts used in these experiments. N-D-ornithyl amphotericin B methyl ester gave a slightly higher concentration in serum than amphotericin B did, but both drugs had similar elimination curves, and penetration into the cerebrospinal fluid was poor for both. Despite these similarities between the two polyenes, amphotericin B was much more effective than N-D-ornithyl amphotericin B methyl ester in the treatment of cryptococcal meningitis in rabbits. For C. albicans endocarditis, both polyenes had similar cure rates, but in vitro measurement of fungicidal activity in serum did not predict treatment outcome. For C. albicans pyelonephritis, both polyenes showed efficacy; because higher doses of the less toxic methyl ester could be used, it sterilized the urinary tract more often than amphotericin B. These studies indicate that in vivo and in vitro experiments may be needed to predict the results of treatment with polyenes.

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.

Induction of amphotericin B-specific antibodies for use in immunoassays

High-titered antisera specific for amphotericin B (AmB) were induced by immunization with a protein conjugate of the D-lysyl AmB methyl ester. These polyclonal anti-AmB antibodies reacted preferentially with AmB or the AmB methyl ester and discriminated sharply between nystatin and AmB. A solid-phase radioimmunoassay was developed with radioiodinated immunoglobulin G fractions derived from the anti-AmB antisera. This assay was capable of detecting AmB in the sera in the same concentration range that is regularly achieved during AmB treatment of systemic fungal infections. This study demonstrated the feasibility of immunoassays in measuring the concentration of AmB in blood and tissue fluids.

Comparative pharmacokinetics of Sch 28191 and amphotericin B in mice, rats, dogs, and cynomolgus monkeys

The pharmacokinetics of Sch 28191, the N-D-ornithyl methyl ester of amphotericin B, and amphotericin B were studied in mice, rats, dogs, and cynomolgus monkeys after an intravenous dose of 0.6 mg/kg was administered. The decline in the concentrations of Sch 28191 and amphotericin B in serum appeared to be biphasic in nature. The half-life at the distribution phase and the half-life at the elimination phase of Sch 28191 were similar to those of amphotericin B in all animals studied. The half-life at the distribution phase in serum was 0.9 to 1.5 h in all animals studied. The half-lives at the elimination phase in serum were 25 to 28 h in mice, 16 to 18 h in rats, 44 to 47 h in dogs, and 35 h in cynomolgus monkeys. The areas under the serum concentration-time curves of Sch 28191 were five- to eightfold larger than those of amphotericin B in rats, dogs, and cynomolgus monkeys but were only slightly larger than those of amphotericin B in mice. In dogs, the urinary excretion (over 9 days) of unchanged drug accounted for 23% of the Sch 28191 dose and 25% of the amphotericin B dose. The concentrations of Sch 28191 in serum were also studied after the intravenous administration of 0.3, 0.6, or 1.25 mg/kg to dogs. The serum concentration-time curves were parallel for these doses. There was a linear relationship between the areas under the concentration-time curves and the doses, indicating dose proportionality.