Incompatibility between Calcium and Sulfate Ions in Solutions for Injection

Objective: To investigate the potential physical compatibility of magnesium sulfate injection with calcium‐containing injections in various infusion solutions and to demonstrate that gross visual inspection alone, is often inadequate in determining the safety of an admixture. Method: Magnesium sulfate (49.3%) injection was added to various infusion solutions followed by either calcium chloride (10%) injection or calcium gluconate (10%) injection. Admixtures were examined for the presence of haze, precipitation, gas evolution or colour change. Solutions which appeared free from incompatibility after 24 hours, were further examined microscopically to verify the absence of precipitate. Results: Incompatibility between magnesium sulfate and calcium chloride injections was observed in the majority of the admixtures. Calcium gluconate injection demonstrated a lower potential to interact with magnesium sulfate injection, but still showed evidence of incompatibility in a number of the admixtures when examined microscopically. Conclusion: The combination of magnesium sulfate and calcium chloride or gluconate injections should be avoided in infusion solutions other than total parenteral nutrition (TPN). Magnesium chloride should be substituted for magnesium sulfate injection when admixture, or infusion via Y‐site with calcium‐containing injections, is required. The physical compatibility of IV solutions should not be based upon a single visual inspection performed shortly after admixture. All results obtained after inspection with the naked eye should be verified microscopically.