Additional New Problems Seen From Thiopental Mixing
To the Editor: Dr. Tinker’s letter in the Spring 1999 issue of the APSF Newsletter pointed out some of the differences between Diprivan (Zeneca) and propofol with sodium metabisulfite (Baxter). I would like to suggest another potential hazard that the introduction of this new formulation of propofol may present.
In the past several years, a number of articles have appeared in the literature regarding the advantages of propofol-thiopental mixtures. Although to my knowledge Zeneca has not endorsed this practice [correct, it has not – Ed.], many anesthesiologists have begun using this mixture. As Dr. Tinker has pointed out, propofol with sulfite is maintained at a significantly lower pH then Diprivan with EDTA. I am not aware of any studies examining the stability of this formulation in combination with thiopental (a drug with a very high pH). In hospitals with both formulations available, the potential exists for one to mix thiopental with the wrong formulation of propofol with unpredictable and potentially disastrous results. I hope that those departments where these mixtures are used will take this into consideration before adding propofol with sulfites to their formulary and wait for the appropriate studies to be performed.
Jonathan Hamburger, MD Greater Baltimore Medical Center Baltimore, MD