Stability and compatibility of fluorouracil and mannitol during simulated Y-site administration.

The stability and compatibility of fluorouracil admixtures with mannitol during simulated Y-site administration was studied. Fluorouracil injection 50 mg/mL was diluted with 5% dextrose injection, 0.9% sodium chloride injection, and 5% dextrose and 0.45% sodium chloride injection to final concentrations of 1 and 2 mg/mL. Combinations of fluorouracil admixtures with 20% mannitol injection were made using equal volumes in glass test tubes; immediately after mixing and at one, two, and four hours, the samples were examined for visual incompatibilities. Duplicate combinations of fluorouracil admixtures with 20% mannitol injection were made using equal volumes in plastic syringes; immediately after mixing with internal standard in glass test tubes and at 2, 4, 8, and 24 hours, samples were removed for chemical analysis. A high-performance liquid chromatographic assay was used to determine fluorouracil concentrations. No evidence of precipitation, color change, or haze was observed. During the 24-hour study, fluorouracil concentrations remained within 6% of initial concentrations for all combinations with mannitol. Fluorouracil 1 and 2 mg/mL in 5% dextrose injection, 0.9% sodium chloride injection, and 5% dextrose and 0.45% sodium chloride injection was chemically stable and visually compatible when combined with 20% mannitol injection during simulated Y-site administration.

In vitro measurement of phosphorylated zidovudine in peripheral blood leucocytes.

A method has been developed to measure the concentration of total phosphorylated zidovudine (ZDV) inside peripheral blood leucocytes (PBLs) using a modified commercial radioimmunoassay (RIA) specific for ZDV. ZDV 5'-monophosphate was readily synthesized and used as a procedural control for RIA modification. PBLs were isolated from healthy volunteers and incubated with ZDV for 24 h to allow metabolic phosphorylation. Viable cells were counted, washed, and extracted overnight with 60% methanol. After evaporation, the extract was reconstituted in Tris buffer, pH 9.5. Because of minimal RIA antibody cross reactivity with phosphorylated ZDV, samples were split into two fractions, one of which was treated with alkaline phosphatase (AP) to liberate phosphate groups. Each fraction was then assayed for ZDV. Concentrations of phosphorylated ZDV were determined by subtracting the concentration of the non-AP-treated fraction from that of the treated fraction. Recovery of phosphorylated ZDV from cell extracts was approximately 90%, and reproducibility was acceptable (coefficients of variation less than 15% for concentrations greater than or equal to 0.25 ng/ml). Intracellular concentrations (0.1-1.4 pmoles/10(6) cells) followed a nonlinear dose-response relationship over the range 0-50 microM extracellular ZDV, with concentration-dependent saturation. These results demonstrate the feasibility of determining concentrations of phosphorylated ZDV in HIV-infected patients, a potentially key step in establishing a therapeutic range and optimal dosing regimen for these patients.

Liquid-chromatographic monitoring of cytosine arabinoside and its metabolite, uracil arabinoside, in serum.

This is a "high-performance" liquid-chromatographic method for quantifying the antileukemic drug cytosine arabinoside (cytarabine; 1-beta-D-arabinofuranosylcytosine; Ara-C), with a structural analog, 5-methylcytidine, as the internal standard. We used a C18 reversed-phase column and ammonium acetate (0.5 mol/L, pH 6.5) as the mobile phase, monitoring the column effluent at 280 nm. Tetrahydrouridine was present in the sample-collection tubes to inhibit conversion of cytosine arabinoside to uracil arabinoside. The standard curve is linear to 100 mg/L. Analytical recovery is 98%. Coefficients of variation for within-run and between-run imprecision were 2.0% and 4.3% at 20 mg/L and 2.7% and 2.7% at 80 mg/L, respectively. Assay sensitivity was limited by the amount of endogenous material in each patient's serum, making assay of a pre-infusion sample necessary for accurate calculations. In a trial patient population, the assay was shown to have potential for the detection of toxic concentrations in patients receiving high doses of Ara-C.

Comparison of Abbott TDx fluorescence polarization immunoassay, Sandoz radioimmunoassay, and high-performance liquid chromatography methods for the assay of serum cyclosporine.

We have had the opportunity to compare the new FPIA method for the measurement of serum Cs to established assays. The technique used a precipitation step prior to the fluorescence polarization measurement. We compared serum HPLC and RIA to the FPIA procedure. The within run coefficients of variation were 7.2%, 9.5%, and 4%, respectively. Between run CVs were 8.0%, 12.2%, and 3.8%. The correlation coefficient for HPLC and both of the immunoassays was less than 70%, showing the influence of the different specificities of the techniques. Medical centers that have based patient care on the HPLC assay that measures only parent drug will have difficulty using an immunoassay that measures a combination of parent and metabolites. There was a good correlation (R2 = 0.93) between the two immunoassays indicating that those currently using the serum RIA for monitoring could, through careful correlation studies in their patient population, use the FPIA technique. The regression equation was as follows: serum FPIA = 1.27 serum RIA + 1.9. This indicates the higher bias of the FPIA measurements. The advantages of the FPIA assay are that 20 assays could be done in less than one hour. This is in contrast to the longer turnaround time of the standard Sandoz RIA procedure. The technical competence required to perform the assay is less than that needed to perform the current RIA procedure. The assay can be recommended for replacement of the serum RIA; however, a correlation of levels with clinical experience is necessary in view of the difference in values between RIA and FPIA.

The influence of N-acetylneuraminic acid on the properties of human orosomucoid.

Little is known of the relationships that may exist among the three principal functionalities of glycoproteins. Orosomucoids of closely defined N-acetylneuraminic acid content were examined for evidence of influence of N-acetylneuraminic acid content on the physical properties of the glycoprotein. Fluorescence spectroscopy gave no indication of conformational change in the protein core upon desialylation. Small changes in the chromatographic partition coefficient, sigma, and thermal stability, Td, are interpreted to reflect loss of water of hydration and increased glycan stem-protein interaction without a major repositioning of the chains. Ligand-binding measurements indicate no alteration in the hydrophobic binding domain and a possible interaction between chlorpromazine and N-acetylneuraminic acid. All changes seen are progressive and occur through a region where changes in biological activity are not found. It is suggested that the dependence of biological activity on N-acetylneuraminic acid content in orosomucoid reflects, not coupled changes in protein conformation, but a charge-density-related interaction such that, below a contribution of four or five N-acetylneuraminic acid residues, activity is modified.