• Rohnelt Machado de Oliveira, Pedro Paulo Tanaka, and Sergio Bernardo Tenorio.
• Universidade Federal do Paraná, Anesthesiologist of Hospital Nossa Senhora das Graças.
• Rev Bras Anestesiol. 2011 Nov 1; 61 (6): 736-47.

Background And ObjectivesTo achieve better therapeutic benefits of local anesthetics in the control of postoperative pain through controlled-release carrier. The objective of this study was to compare the characteristics of sensory and motor blockade between microspheres without local anesthetic: racemic bupivacaine-loaded microspheres; 50% enantiomeric excess bupivacaine-loaded microspheres; and free 50% enantiomeric excess bupivacaine.MethodsWistar rats were distributed into four groups: A (Microsphere); B (S50-R50 bupivacaine-loaded microsphere); C (50% enantiomeric excess bupivacaine-loaded microsphere); and D (50% enantiomeric excess bupivacaine). Inhalation anesthesia was performed before the sciatic nerve block (2% halothane and 100% O(2)). Sensorial blockade was measured by the time required for each rat to withdraw its paw from a hot plate at 56°C (positive>4 sec). Motor blockade was measured by the time between drug injection until recovery of a motor score of 2 on the established criterion.ResultsThe sensory response was significantly more frequent in groups B, C, and D than in group A (p<0.001). There were no statistically significant differences in the response to the sensory test in groups B, C, and D (p>0.05). The response to the motor test was also significantly more frequent in groups B, C, and D than in group A (p=0.02). A tendency to greater positivity in the motor test was more frequently found in groups B and D than in group C (p=0.10).ConclusionsControlled-release of 50% enantiomeric excess bupivacaine-loaded microspheres showed similar results regarding analgesia and less motor blockade when compared to other anesthetic formulations.Copyright © 2011 Elsevier Editora Ltda. All rights reserved.

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