Radiometric Determination of the Concentration of Amphotericin B in Body Fluids

Hopfer, Roy L.; Gröschel, D

doi:10.1128/aac.12.6.733

Cited by 3 publications

(2 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, the reagents are costly and have a relatively short shelf life (7), and test results are affected by 5-fluorocytosine and other antifungal agents (11). In addition, because of deviations from linearity in the standard curve, specimens with amphotericin 13 concentrations greater than 2.0 ,ug/ml must be diluted.…”

Section: Discussionmentioning

confidence: 99%

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

Granich¹,

Kobayashi²,

Krogstad³

1986

Antimicrob Agents Chemother

View full text Add to dashboard Cite

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 (.90%), and the standard curve was linear from 0.04 to at least 10.0 ,ug/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 (>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).Amphotericin B is a polyene antifungal agent that is presently the drug of choice for the treatment of most severe systemic fungal infections. Use of the drug, however, is limited by its toxicity, particularly by its impairment of renal function. The pharmacokinetics of amphotericin B are complex, involving a rapid initial decrease in serum levels for approximately 24 h, followed by a long (15-day half-life) terminal elimination phase (1,4,8). Other pharmacokinetic properties, such as elimination pathways, are not completely understood. Renal and biliary excretion have each been estimated to account for up to 20% of a dose of amphotericin B (6, 16). The lack of a clearly defined relationship between serum levels and toxicity or clinical outcome has prevented the development of a rational, systematic approach to amphotericin B therapy.Many of the problems associated with pharmacokinetic studies of amphotericin B arise from difficulty in obtaining rapid, accurate, and reproducible measurements of drug levels in various biological fluids. Most researchers have used bioassay systems that involve either serial tube dilution or plate diffusion with a variety of indicator organisms, including Paecilomyces varioti, Candida tropicalis, and Saccharomyces cerevisiae (2-4, 6-8, 17-19). Bioassays, however, vary widely in their accuracy, precision, sensitivity, and specificity, making the comparison of data from different papers difficult.Several high-pressure liquid chromatographic (HPLC) assays have been reported recently which offer faster and more accurate and reproducible alternatives to bioassays for both pharmacokinetic studies and routine clinical use (9, 10, 13-15, 17, 20). HPLC also offers improved sensitivity and specificity and is easier to standardize than bioassays are. In this report we describe an HPLC method which incorporates an internal standard for the measurement of amphotericin B in serum and a...

show abstract

Section: Discussionmentioning

confidence: 99%

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

Granich¹,

Kobayashi²,

Krogstad³

1986

Antimicrob Agents Chemother

View full text Add to dashboard Cite

show abstract

“…Freezing of the serum samples produces variable discrepancies in assay results . Assay by a radiometric method may be less time consuming (Hopfer and Groschel, 1977). A more rapid, specific and sensitive high performance liquid chromatographic (HPLC) method therefore offers considerable advantages (Nilsson-Ehle et aI., 1977).…”

Section: Therapeutic Monitoringmentioning

confidence: 99%

Clinical Pharmacokinetics of Systemic Antifungal Drugs

Daneshmend

Warnock

1983

Clinical Pharmacokinetics

171

View full text Add to dashboard Cite

The currently available drugs for the treatment of systemic fungal infections are amphotericin B. flucytosine. miconazole and ketoconazole.Amphotericin B has to be given intravenously in the treatment of deep mycoses. The dose is gradually increased following a small initial dose. though this may delay the attail/menl of therapeutic concentrations. Amphotericin B. serum concentrations are proportiol/al to dose but only up to doses of 50mg. The serum pharmacokinetics fit a 3-compartment model. while cerebrospinal fluid pharmacokinetics fit a 2-compartment model. The precise identities of these compartments have not been determined. In the serum there is a relatively rapid initial half-life of 1 to 2 days. and a slower elimination phase of 15 days. Amphotericin B penetrates poorly into other body tissues. and concentrations are usually well below those in serum. This may partly be due to its high protein binding. The routes of amphotericin B elimination in man are unknown. Amphotericin B invariably causes doserelated renal damage. but this does not markedly alter its pharmacokinetics; mannitol infusions do not reduce this nephrotoxicity. Concurrent gentamicin administration and sodium depletion may enhance amphotericin B nephrotoxicity.Flucytosine may be given orally or intravenously. It has a high (greater than 80%) oral bioavailability. but this is lower in patients with renal failure. Flucytosine absorption is delayed in renal failure and by antacids. The serum pharmacokinetics fit a I-compartment model. and the apparent volume of distribution approximates to body water. Flucytosine has low protein binding and good tissue penetration. There is minimal metabolism in man; conversion to 5-fluorouracil may be the basis of flucytosine toxicity. Since flucytosine is largely eliminated by renal excretion. serum concentrations are markedly increased in the presence of renal impairment. The renal clearance of flucytosine closely parallels creatinine clearance. and in renal failure the half-life is considerably prolonged. Toxicity can be avoided by therapeutic monitoring of serum concentrations and reducing the dose when renal functiol/ is impaired.Miconazole is poorly absorbed from the gut; therefore intravenous administration is required for treatment of systemic fungal infections. Its serum pharmacokinetics fit a 3-compartment model with a short initial half-life of less than 1 hour. an intermediate half-life of 2 hours. and a terminal half-life of 20 hours. Despite this long terminal half-life. miconazole has to be given every 8 hours. It has a high apparent volume of distribution and is highly bound to plasma proteins. Adequate penetration only occurs into certain body tissues. Pen-

show abstract