Comparison of the Potency of Different Propofol Formulations: A Randomized, Double-blind Trial Using Closed-loop Administration

Background: Several commercial formulations of propofol are available. The primary outcome of this study was the required dose of propofol alone or combined with lidocaine to achieve induction of general anesthesia. Methods: This multicenter, double-blinded trial randomized patients (American Society of Anesthesiologists physical status I–III) just before elective surgery with the use of a computer-generated list. Three different propofol 1% formulations—Diprivan® (Astra-Zeneca, Cheshire, United Kingdom), Propofol® (Fresenius-Kabi AG, Bad Homburg, Germany), and Lipuro® (B-Braun, Melshungen AG, Germany)—were compared with either placebo (saline solution) or lidocaine 1% mixed to the propofol solution. Depth of anesthesia was automatically guided by bispectral index and by a computerized closed-loop system for induction, thus avoiding dosing bias. The authors recorded the total dose of propofol and duration of induction and the patient’s discomfort through a behavioral scale (facial expression, verbal response, and arm withdrawal) ranging from 0 to 6. The authors further evaluated postoperative recall of pain using a Visual Analog Scale. Results: Of the 227 patients enrolled, 217 were available for analysis. Demographic characteristics were similar in each group. Propofol® required a higher dose for induction (2.2 ± 0.1 mg/kg) than Diprivan® (1.8 ± 0.1 mg/kg) or Lipuro® (1.7 ± 0.1 mg/kg; P = 0.02). However, induction doses were similar when propofol formulations were mixed with lidocaine. Patient discomfort during injection was significantly reduced with lidocaine for every formulation: Diprivan® (0.5 ± 0.3 vs. 2.3 ± 0.3), Propofol® (0.4 ± 0.3 vs. 2.4 ± 0.3), and Lipuro® (1.1 ± 0.3 vs. 1.4 ± 0.3), all differences significant, with P Conclusion: Plain propofol formulations are not equipotent, but comparable doses were required when lidocaine was concomitantly administered.