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Interaction of metronidazole with antibiotics containing the 2-aminothiazole moiety

A B Thakur1, M Abdelnasser, A T Serajuddin

  • 1Bristol-Myers Squibb Pharmaceutical Research Institute, New Brunswick, New Jersey 08903.

Pharmaceutical Research
|November 1, 1991
PubMed

Insights

Metronidazole parenteral solutions can produce pink discoloration when mixed with aztreonam due to nitrite ions. These ions react with aztreonam

Area of Science:

  • Pharmaceutical Chemistry
  • Drug Compatibility Studies
  • Analytical Chemistry

Background:

  • Incompatibility between metronidazole and aztreonam causes pink discoloration in IV admixtures.
  • Nitrite ion formation in metronidazole solutions is temperature and light-dependent.

Purpose of the Study:

  • To elucidate the chemical mechanism behind the pink discoloration.
  • To identify the reacting species and the resulting product.

Main Methods:

  • Chromatographic isolation of the pink product.
  • Structural elucidation using mass spectrometry and NMR analysis.

Main Results:

  • Nitrite ions from metronidazole react with aztreonam's aminothiazole moiety under acidic conditions.
  • A diazo-coupling reaction forms the pink-colored product.
  • Similar reactions occur with other beta-lactam antibiotics containing the 2-aminothiazole moiety.

Conclusions:

  • The study clarifies the incompatibility mechanism between metronidazole and aztreonam.
  • Understanding this reaction is crucial for safe intravenous admixture preparation.
  • The findings have implications for other beta-lactam antibiotics with similar chemical structures.

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