Carboxypeptidase G2 rescue in patients with methotrexate intoxication and renal failure

The methotrexate (MTX) rescue agent carboxypeptidase G2 (CPDG2) rapidly hydrolyses MTX to the inactive metabolite DAMPA (4-[[2,4-diamino-6-(pteridinyl)methyl]-methylamino]-benzoic acid) and glutamate in patients with MTX-induced renal failure and delayed MTX excretion. DAMPA is thought to be an inactive metabolite of MTX because it is not an effective inhibitor of the MTX target enzyme dihydrofolate reductase. DAMPA is eliminated more rapidly than MTX in these patients, which suggests a nonrenal route of elimination. In a phase II study (May 1997–March 2002), CPDG2 was administered intravenously to 82 patients at a median dose of 50 U kg−1 (range 33–60 U kg−1). Eligible patients for this study had serum MTX concentrations of >10 μM at 36 h or >5 μM at 42 h after start of MTX infusion and documented renal failure (serum creatinine ⩾1.5 times the upper limit of normal). Immediately before CPDG2 administration, a median MTX serum level of 11.93 μM (range 0.52–901 μM) was documented. Carboxypeptidase G2 was given at a median of 52 h (range 25–178 h) following the start of an MTX infusion of 1–12 g m−2 4–36 h−1 and resulted in a rapid 97% (range 73–99%) reduction of the MTX serum level. Toxicity related to CPDG2 was not observed. Toxicity related to MTX was documented in about half the patients; four patients died despite CPDG2 administration due to severe myelosuppression and septic complications. In conclusion, administration of CPDG2 is a well-tolerated, safe and a very effective way of MTX elimination in delayed excretion due to renal failure

Quenched phosphorescence as alternative detection mode in the chiral separation of methotrexate by electrokinetic chromatography

Quenched phosphorescence was used, for the first time, as detection mode in the chiral separation of methotrexate (MTX) enantiomers by electrokinetic chromatography. The detection is based on dynamic quenching of the strong emission of the phosphorophore 1-bromo-4-naphthalene sulfonic acid (BrNS) by MTX under deoxygenated conditions. The use of a background electrolyte with 3 mg/mL 2-hydroxypropyl-β-cyclodextrin and 20% MeOH in 25 mM phosphate buffer (pH 7.0) and an applied voltage of 30 kV allowed the separation of l-MTX and its enantiomeric impurity d-MTX with sufficient resolution. In the presence of 1 mM BrNS, a detection limit of 3.2 × 10−7 M was achieved, about an order of magnitude better than published techniques based on UV absorption. The potential of the method was demonstrated with a degradation study and an enantiomeric purity assessment of l-MTX. Furthermore, l-MTX was determined in a cell culture extract as a proof-of-principle experiment to show the applicability of the method to biological samples

Liquid chromatography of dibutyldithiocarbamate degradation products

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High-performance liquid chromatographic determination of dibutyldithiocarbamate degradation products in cucumbers and soil

no abstrac