[Effect of pH and Additives on the Compatibility between Vancomycin and Furosemide Injections]

The physicochemical compatibility between injections of different agents is very important. An injection of the antibiotic vancomycin (VCM) is acidic and its standard pH range is 2.5-4.5. In clinical treatments, VCM injections are often used with Lasix^® (furosemide) injections. The Lasix^® injection is alkaline and its standard pH range is 8.6-9.6. Therefore, mixing VCM injections with Lasix^® injections may cause compatibility problems. We evaluated the effect of pH on the compatibility between VCM (original and two generic) and Lasix^® injections. Compatibility was not observed in non-pH-adjusted VCM with Lasix^® injections, but white crystals appeared when VCM injections adjusted to pH 2.5 experimentally were mixed with a Lasix^® injection, suggesting that the acidic condition of VCM injections cause compatibility. However, the residual rates of VCM did not change after 24 h in all mixtures. We analyzed the crystals by mass spectrometry and ¹H-NMR, and identified them to comprise furosemide.