Stability and compatibility of an intramuscular fetal anesthetic cocktail for fetal intervention.

ABSTRACT

INTRODUCTION: To evaluate chemical stability and physical compatibility when combining fentanyl, rocuronium, and atropine in a fixed ratio to support intramuscular drug delivery during fetal intervention and surgery. METHODS: A highly concentrated combination of fentanyl, rocuronium, and atropine was created based on common prescribing practices at a maternal fetal care center. Chemical stability testing was completed using liquid chromatograph mass spectrometry-mass spectrometry (LC/MS-MS) to detect and quantitate atropine, rocuronium, and fentanyl, with fentanyl-d5 being an internal standard at 6-, 12, 24-, and 36-hours following sample preparation. Physical compatibility testing was completed using United State Pharmacopeia (USP)<788> recommended analytical technique of light obscuration (LO) in addition to novel backgrounded membrane imaging (BMI) at 6- and 24-hours following sample preparation. Physical compatibility was determined using USP<788> particle count limits for both techniques. RESULTS: Based on LC/MS-MS results, the samples retained expected medication concentrations at all time points tested. For physical compatibility testing, the particle counts met criteria to be considered compatible per USP<788> large volume particle count thresholds at 6 hours by both methods but exceeded tolerable thresholds at 24 hours. DISCUSSION/CONCLUSION: The combination of rocuronium, fentanyl, and atropine for intramuscular fetal administration are physically compatible and chemically stable for 6 hours.