Excretion of dipyrone metabolites in human breast milk.

Breast milk and plasma levels of dipyrone metabolites in 8 mothers given a single oral dose of the drug were determined by HPLC. Four metabolites were demonstrated by the analytical method: 4-methylaminoantipyrine (MAA), 4-aminoantipyrine (AA), 4-formylaminoantipyrine (FAA) and 4-acetylaminoantipyrine (AAA). A good correlation was found between the plasma and milk concentrations of the metabolites. The mean (+/- SD) milk to plasma concentration ratios were: MAA = 1.37 +/- 0.28, AA = 1.15 +/- 0.40, FAA = 1.03 +/- 0.09, AAA = 0.97 +/- 0.24. The disposition pattern of the dipyrone metabolites in milk was studied in two mothers. None of the metabolites was detectable 48 h after drug administration.