Background Physicochemical incompatibilities of parenteral drugs cause several problems in hospital practice. These incompatibilities can be represented by precipitation, complexation or colour change before or during administration to patients. Understanding these incompatibilities allow pharmacists to avoid many problems during preparation and administration.

Purpose To determine physicochemical incompatibilities of a cytotoxic drug widely used in paediatric oncology (methotrexate) with certain trace elements existing in food and medicines, as well as in food supplements.

Material and methods We performed several mixtures to study physicochemical reactions between methotrexate reconstituted in infusion bags (25 mg/ml) and five cations: calcium (Ca2+), copper (Cu2+), iron (bivalent and trivalent), magnesium (Mg2+) and zinc (Zn2+). An interaction was elucidated by formation of a precipitate visible to the naked eye. Infrared spectroscopy was the method of authentication of precipitates.

Results Precipitates were formed with the copper, zinc, bivalent and trivalent iron. On the other hand, there was no precipitate with calcium and magnesium. Functional analysis of infrared spectra of precipitates showed the presence of methotrexate.

Conclusion The study of the physicochemical incompatibilities of methotrexate can avoid possible interactions with medicines, food or nutritional supplements containing trace elements.

Recording to the results, methotrexate precipitates in the presence of copper, zinc and iron ions. The absence of the precipitate or change of colour in the other mixtures does not exclude a possible complexation.

Reference and/or Acknowledgements 1. Benaji B, et al. Compatibility study of methotrexate with PVC bags after repackaging into two types of infusion admixtures. Int J Pharma1994;105(1):83–87.

No conflict of interest