High-performance liquid chromatographic analysis of desferrioxamine. Pharmacokinetic and metabolic studies

Quantification of desferrioxamine, ferrioxamine and aluminoxamine by post-column derivatization high-performance liquid chromatography. Non-linear calibration resulting from second-order reaction kinetics

Desferrioxamine B is widely used as therapeutic agent for removal of excess body iron and, more recently, for removal of aluminium. A HPLC-based method for direct sensitive and reliable determination of ferrioxamine, desferrioxamine, aluminoxamine and related metabolites has been developed for use in pharmacokinetic studies. The method consists of complete separation of the analytes by an optimized mobile phase avoiding conversion of desferrioxamine to ferrioxamine by the analytical system and overcoming problems due to peak tailing properties of desferrioxamine. A post-column derivatization reaction with colourless fluoro-complexed iron converts all iron free species to ferrioxamine and allows quantification at 430 nm avoiding interference of UV-absorbing coelutes. This reaction might be of interest for other analytical procedures concerning iron chelators. The influence of the post-column reaction system on the column plate number is characterized. As the reaction rate of desferrioxamine and aluminoxamine with iron(III) is of second-order kinetics, a quadratic calibration function is observed, resulting from a compromise between residence time and peak broadening. A solid-phase extraction procedure is presented for extraction of the analytes from plasma. Limits of detection (S/N ratio of 3) were determined as 1.95 ng for ferrioxamine, 3.9 ng for aluminoxamine and 15.7 ng for desferrioxamine, expressed as on-column load. A new iron-free metabolite was identified with fast atom bombardment-mass spectrometry as N-hydroxylated desferrioxamine.

Low percentage of aluminoxamine and ferrioxamine in uremic serum after desferrioxamine administration

HPLC was used to study the effectiveness of two different desferrioxamine (DFO) administration strategies (15 mg/kg DFO, 1 h or 44 h before dialysis) on generation of aluminoxamine and ferrioxamine in five hemodialysis patients. The percentage of ultrafilterable aluminum and iron in these patients was also investigated by electrothermal atomic absorption spectrometry. The administration of DFO in both schemes increased the ultrafilterable serum aluminum concentrations from a mean of 17.1 ± 1.6% to a mean of 75.7 ± 14.1%. However, 1 h after DFO infusion, only 38.8 ± 7.7% of the total serum aluminum was bound to DFO; 44 h after DFO infusion, only 15.8 ± 8.0% was bound. Similar results were obtained for ferrioxamine. These results suggest that the ultrafilterable serum fraction contains aluminum and iron chelated by DFO and by DFO metabolites, which retain similar metal-chelating abilities.

Clinically achievable plasma deferoxamine concentrations are therapeutic in a rat model of Pneumocystis carinii pneumonia

The iron-chelating drug deferoxamine (DFO) has been shown to be active in animal models of Pneumocystis carinii pneumonia (PCP), with effective daily intraperitoneal bolus dosages being 400 and 1,000 mg of DFO mesylate kg of body weight-1 in mouse and rat models, respectively. Continuous infusion produced a moderately improved response in a rat model. The data reported here demonstrate that the response achieved by continuous infusion of 195 and 335 mg of DFO mesylate kg-1 day-1 in the rat model is associated with mean concentrations in plasma of 1.3 and 2.5 micrograms of DFO ml-1 and mean concentrations in lung tissue of 4.9 and 6.0 micrograms of DFO g of lung tissue-1, respectively. Since current clinical use of DFO mesylate for the treatment of iron overload produces higher concentrations in the plasma of patients, DFO may prove to be a useful anti-PCP treatment. The 2.4- to 3.8-fold higher DFO concentration observed in lung tissue compared with that observed in plasma may be important in the response of PCP to DFO.

Separation and identification of desferrioxamine and its iron chelating metabolites by high-performance liquid chromatography and fast atom bombardment mass spectrometry: choice of complexing agent and application to biological fluids

An HPLC-based method capable of separating desferrioxamine (DFO) and its iron chelating metabolites from uv-absorbing species present in biological fluids has been developed. This method relies on the use of nitrilotriacetic acid (NTA) as the complexing agent in the mobile phase, instead of EDTA, previously used in HPLC methods. The use of NTA ensures that iron contamination present in buffers and bound to the column does not interfere with analysis. The disadvantages of using EDTA are discussed. The identity of the iron chelating metabolites of DFO present in the urine of patients with beta-thalassemia major has been established using FAB mass spectrometry. The metabolism of DFO, reported in this study, takes place almost exclusively at the N-terminal region of the molecule and is in many respects similar to the degradation of the amino acid lysine. In addition, a metabolite which corresponds to N-hydroxylation of the terminal amino group has been identified.

Ferrioxamine and its hexadentate iron-chelating metabolites in human post-desferal urine studied by high-performance liquid chromatography and fast atom bombardment mass spectrometry

Three iron-containing fractions were detected by high-performance liquid chromatography (HPLC) on a reverse-phase column in the 24-h urine of two patients with hereditary hemochromatosis following the injection of deferoxamine mesylate (Desferal). These fractions have virtually identical absorption spectra in the visible range, with a broad maximum around 430 nm. Molecular weight determination of these fractions was performed by fast atom bombardment mass spectrometry (FAB-MS), which gave intense ion signals for the protonated molecular ions of the intact iron chelates, namely, at m/z 614 for ferrioxamine (FOA; Mr 613), at m/z 629 for metabolite I (FOA-MI; Mr 628), and at m/z 601 for metabolite II (FOA-MII; Mr 600). The molecular weight of FOA-MI is compatible with deamination of the terminal amino function and oxidation of the adjacent carbon atom to a carboxyl group; the molecular weight of FOA-MII is compatible with loss of a C2H4 unit from FOA-MI by beta oxidation. Quantification of iron in post-Desferal urine samples either by atomic absorption spectrometry (AAS) or by HPLC leads to results which are identical within experimental error. In ten subsequent 12-h urine samples of a patient under therapy (subcutaneous infusion of Desferal), the following distribution of urinary iron was found: FOA-MI, 58.4 +/- 4.7% (arithmetic mean +/- SD); FOA, 33.2 +/- 4.9%; FOA-MII, 8.4 +/- 1.7%. Addition of 2 mM ethylenediaminetetraacetic acid (EDTA) to the chromatographic solvents was used as a stability test for FOA and its two metabolites MI and MII.(ABSTRACT TRUNCATED AT 250 WORDS)