Isovaline may be a new alternative to opioids for anesthesia and procedural sedation, new data published in Anesthesia & Analgesia has shown. 

Isovaline is an analgesic that acts on the GABAB neuroreceptor whereas opioids act on GABAA receptors. Isovaline acts only on peripheral neuroreceptors outside the central nervous system (CNS) as it does not cross the blood-brain barrier. 

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Use of isovaline with anesthetics may avoid the need for opioids and thus avoid the risk of potentially serious adverse events such as opioid-related respiratory depression. Scientists from The University of British Columbia, Vancouver, conducted studies in female mice to see if isovaline could be a safer alternative to opioids (eg, morphine and related drugs) for use in anesthesia. The study mice received propofol with either isovaline or fentanyl. 

When given with an effective dose of propofol, isovaline produced both general anesthesia and conscious sedation; propofol alone only exerted a hypnotic effect. Propofol with fentanyl led to general anesthesia but with an increased risk of respiratory depression. Isovaline at its maximum dose did not cause respiratory depression or other adverse events. 

Study findings suggest that isovaline may be an effective alternative for general anesthesia and procedural sedation. It can improve the efficacy of both types of anesthesia without increasing the risk of serious adverse events since it does not exert CNS effects. Researchers concluded that the margin of safety for propofol with isovaline was “considerably higher” than that for propofol with fentanyl. Additional research is needed to see how these results translate to clinical anesthesia for humans.


Whitehead R, Schwarz S, Asiri Y, Fung T, Puil E, MacLeod B. The Efficacy and Safety of the Novel Peripheral Analgesic Isovaline as an Adjuvant to Propofol for General Anesthesia and Conscious Sedation. Anesth Analg. 2015;121(6):1481-1487. doi:10.1213/ane.0000000000000996.

This article originally appeared on MPR