Propofol and remifentanil often need to be co-administered via the same intravenous catheter line, which predisposes to potential compatibility issues. Our aim was to determine and compare the emulsion stability of three propofol formulations, two with medium chain triglycerides and one with long chain triglycerides, when administered together with remifentanil hydrochloride.
Remifentanil hydrochloride (Ultiva ®) 50 µg/mL was mixed with two concentrations (10 and 20 mg/mL) of each propofol formulation in mixing ratios 10+1, 20+1, 1+1 and 1+20. Emulsion stability was assessed immediately after mixing and 4 hours later by measurements of pH, mean droplet diameter, polydispersity index, and calculating percentage of fat residing in globules>5 µm (PFAT5).
High PFAT5 values were observed in certain mixing ratios. The correlation between elevated PFAT5 and high propofol concentration (20 mg/mL), when remifentanil was in abundance and for long contact time indicated that these factors influenced the stability of the propofol emulsions.
Stability differences between the propofol formulations were identified under extreme test conditions. Co-administration of remifentanil and propofol in the same i.v. line is safe when propofol is in abundance. Caution is advised when remifentanil is present in equal parts or in abundance when co-administered with propofol 20 mg/mL.