The mechanism by which propofol exerts its action is poorly understood, but may involve an nonspecific effect on lipid membrane and has been shown to potentiate GABA-mediated synaptic inhibition. And, midazolam also acts through GABA receptor
mediated
increased chloride conductance.
The aim of this study was to evaluate the dose response of midazolam, propofol and combination of these drugs, and determine possible interaction between two drugs in patients. The effect of propofol on the dose response curve for midazolam was
studied
in 260 nonpremedicated ASA physical status ⅠorⅡfemale patients who were scheduled for elective operation. The response to the verbal command was used as an end-point of hypnosis.
Dose response curves for midazolam, propofol, and their type of interaction was determined using Instat software package, nonlinear regression analysis, and algebraic(fractional) analysis of interaction. ED50 of midazolam and propofol was 0.11
mg/kg,
1.13 mg/kg, and ED95 was 0.18 mg/kg, 1.67 mg/kg respectively. ED50 of combined drug(midazolam+propofol ) in combined dose curve was 29% of each drug and the type of interaction between two drugs was found to be synergistic.(Korean J Anesthesiol
1995;
29: 484∼489)
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