Determination of Sodium Metamizole by High Performance Liquid Chromatography Taking into Account its Decomposition in Aqueous Solutions in the Study of Dissolution Profiles

Abstract A procedure for the quantitative HPLC determination of sodium metamizole is developed and validated to study dissolution profiles of the PENTALGIN IC® medicinal preparation, tablets, taking into account the decomposition of sodium metamizole in aqueous solutions. In the study of dissolution profiles, along with the release of sodium metamizole from the finished dosage form, its hydrolysis to the decomposition product, methylaminophenazone, occurs. The decomposition reaction is unimolecular; therefore, the chromatograms of the test and reference solutions have two peaks, corresponding to metamizole and methylaminophenazone. It is shown that, for the correct calculation of the amount of sodium metamizole passed to the solution from the tablet, one should determine it from the sum of areas of both peaks, taking into account detector response factors.