Comparison of isoflurane and halothane safety margins in rats.
In rat experiments, the dose-effect curves for three different end points of anesthesia [loss of righting reflex (RR), prevention of movement (PM), and heart rate response (HR) to noxious stimuli] and for the lethal effect (LE) due to cardiovascular depression were determined with isoflurane and halothane. The obtained data were used to calculate LD50/ED50 ratios and standard safety margins (SSM) for assessment of each agent's safety. It was found that isoflurane provides an equal degree of separation between dose-effect curves for different end points of anesthesia as halothane does. However, isoflurane provides greater margins of safety. The margin between the highest of anesthetic doses--the loss of HR response--and the lethal dose for isoflurane was twice that for halothane (LD50/HR ED50 4.3 vs. 2.2, P less than 0.01). The standard safety margin for the loss of HR response was also greater with isoflurane (142 vs. 43, P less than 0.05). These results agreed that isoflurane may provide greater cardiovascular safety for anesthesia than halothane does.
D000769:Anesthesia, Inhalation; D000818:Animals; D001921:Brain / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D006221:Halothane / Q000008:administration & dosage / Q000633:toxicity*; D006339:Heart Rate / Q000187:drug effects; D007530:Isoflurane / Q000008:administration & dosage / Q000633:toxicity*; D007928:Lethal Dose 50; D008738:Methyl Ethers / Q000633:toxicity*; D009068:Movement / Q000187:drug effects; D004856:Postural Balance / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains
D008738:Methyl Ethers; D007530:Isoflurane; D006221:Halothane