Thin-layer chromatographic determination of major metamizole metabolites in serum and urine

Thin-layer chromatographic (TLC) methods were developed for pharmacokinetic studies of major metamizole metabolites in serum and urine. These methods proved practicable, selective, accurate and sensitive with detection limits as follows: 4-methylaminoantipyrine 0.6 micrograms/ml serum and 2.0 micrograms/ml urine; 4-aminoantipyrine 0.16 micrograms/ml serum and 1.0 micrograms/ml urine; 4-acetylaminoantipyrine 0.14 micrograms/ml serum and 0.6 micrograms/ml urine; 4-formylaminoantipyrine 0.12 micrograms/ml serum and 1.0 micrograms/ml urine. Samples of 250 microliter suffice for TLC analysis. Following chromatographic separation, detection is performed in the ultraviolet range at 265 nm. Serum and urine levels were determined following a single oral dose of 1 g of metamizole sodium to eight volunteers. These results were compared with those following an accidental overdose of 49 g.