Physical compatibility of remimazolam with opioid analgesics, sedatives, and muscle relaxants during simulated Y-site administration

Abstract

Purpose: There is a lack of information on the compatibility of remimazolam with opioid analgesics, muscle relaxants, and other sedatives. This study aimed to evaluate the physical compatibility of remimazolam with these drug classes.

Methods: Remimazolam was combined with 1 or 2 target drugs (remifentanil, fentanyl, rocuronium, vecuronium, dexmedetomidine, and midazolam). Ten physical compatibility tests were conducted, including four 3-drug compatibility tests. Remimazolam was dissolved in 0.9% sodium chloride injection to a final concentration of 5 mg/mL. Other medications were diluted in 0.9% sodium chloride injection to obtain clinically relevant concentrations. Compatibility tests were conducted with 3 test solutions, wherein remimazolam and the target drugs were compounded at equal volume ratios (1:1 or 1:1:1). Visual appearance was assessed and testing of Tyndall effect, turbidity, and pH was performed immediately after mixing and then again 1 hour and 4 hours after mixing. Appearance and turbidity were evaluated by comparison with the control solution of each target drug diluted with 0.9% sodium chloride injection to the same concentration as the test solution.

Results: All drugs tested were determined to be compatible with remimazolam. The drug combination with the highest change of turbidity was remimazolam and vecuronium (a mean increase of 0.16 NTU relative to the remimazolam control solution), 4 hours after mixing. The combination with the highest pH was remimazolam, fentanyl, and vecuronium (mean [SD], 3.76 [0.01]), 4 hours after mixing. The combination of remimazolam and fentanyl showed a larger change in pH at 4 hours after mixing (a mean increase of 2.6%) than immediately after mixing.

Conclusion: Remifentanil, fentanyl, rocuronium, vecuronium, dexmedetomidine, and midazolam are physically compatible with remimazolam during simulated Y-site administration.

Keywords: compatibility; general anesthesia; pH; remimazolam; turbidity.