The effects of morphine thiopental and fentanyl-thiopental combinations on the righting reflex were studied in rats. Doses that block the righting reflex for the agents given alone and for their combinations were determined with a probit procedure and compared with an isobolographic analysis. Interaction between morphine or fentanyl and thiopental on blockade of the righting reflex were both found to be synergistic. The degree of synergism was relatively small for the fentanyl-thiopental combination; the maximal deviation from additive interaction (expected/observed ratio) for ED50 dose level was 1.15 (P < 0.01). The degree of synergism was greater for the morphine-thiopental combination; the maximal deviation from additive interaction was 2.27 (P < 0.001). Comparison of the results with the outcomes of opioid-barbiturate interactions in relation to blockade of purposeful movement response to tail clamping, which was antagonistic, shows that the combination of a barbiturate with an opioid gives different outcomes for different end-points of anesthesia. This suggests that the anesthetic effect of an agent is composed of several components, each with a different mechanism of action.
Skip Nav Destination
Article navigation
Original Articles|
September 1987
Morphine and Fentanyl Hypnotic Interactions with Thiopental
Igor Kissin, M.D., Ph.D.;
Igor Kissin, M.D., Ph.D.
* Professor of Anesthesiology.
Search for other works by this author on:
John O. Mason, III, B.S.;
John O. Mason, III, B.S.
† Senior Research Technician.
Search for other works by this author on:
Edwin L. Bradley, Jr., Ph.D.
Edwin L. Bradley, Jr., Ph.D.
‡ Associate Professor of Biostatistics.
Search for other works by this author on:
Received from the Department of Anesthesiology, University of Alabama at Birmingham, University Station, Birmingham, Alabama. Accepted for publication March 31, 1987. Supported by NIH Grant RO1 GM 35135-01.
Address reprint requests to Dr. Kissin: Department of Anesthesiology, University of Alabama at Birmingham, University Station, Birmingham, Alabama 35294.
Anesthesiology September 1987, Vol. 67, 331–335.
Citation
Igor Kissin, John O. Mason, Edwin L. Bradley; Morphine and Fentanyl Hypnotic Interactions with Thiopental. Anesthesiology 1987; 67:331–335 doi: https://doi.org/10.1097/00000542-198709000-00009
Download citation file: