• F Caba, M Echevarría, R Morales, J A Guerrero, and R Rodríguez.
• Servicio de Anestesiología-Reanimación, Hospital Universitario de Valme, Sevilla.
• Rev Esp Anestesiol Reanim. 1993 Mar 1; 40 (2): 69-71.

IntroductionThe purpose of this study was to determine the possible interaction of midazolam and propofol in the induction of anesthesia.MethodsA double-blind study of 90 ASA I-II women undergoing elective general surgery and gynecology was performed. The patients were divided into three groups of 30 patients receiving midazolam, propofol and a combination of both as the anesthesia induction agent. As a test of anesthetic induction the response to the verbal order of opening their eyes was evaluated. The dose-response curves for each group were determined by a logistic regression procedure while isobolographic analysis compared the actions of both agents separately and together.ResultsThe ED50 in the propofol group was 1.56 mg.kg-1 and that of the midazolam group was 0.24 mg.kg-1. In the midazolam-propofol group the ED50 of midazolam was reduced approximately a quarter (0.068 mg.kg-1) when associated to the half of the ED50 of propofol anteriorly obtained. Isobolographic analysis revealed that the conjunctive action of both drugs was synergic (p = 0.04).ConclusionsPropofol potentiates the action of midazolam in anesthetic induction. Although this synergism also reduces with the association of thiopental-midazolam, the mechanism of action is not demonstrated as the same. Thiopental increases the affinity of the benzodiazepines for the GABA complex receptors which has not been described for propofol.

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