Anesthetic efficacy of ropivacaine with 2-hydroxypropyl-beta-cyclodextrin formulation in infraorbital and inferior alveolar nerve blocks and in surgical wound, in rats

Author(s)

Cleiton Pita dos Santos

• Document type: Master's Dissertation
• Press: Piracicaba, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Odontologia de Piracicaba
• Defense date: 2012-02-29

Examining board members

Maria Cristina Volpato; Rogério Heládio Lopes Motta; Carina Denny

• Advisor: Francisco Carlos Groppo; Maria Cristina Volpato

Abstract

This study evaluated the anesthetic efficacy (success, onset and duration of anesthesia) of 0.5% ropivacaine complexed with 2- hydroxypropil- ß-cyclodextrin (a controlled drug release system), plain 0.5% ropivacaine and 0.5% ropivacaine with 1:200,000 epinephrine in three experimental models: infraorbital nerve block (IONB, soft tissue anesthesia), subcutaneous infiltration in surgical wound (SISW, post surgical analgesia in inflamed tissue) and inferior alveolar nerve block (IANB, pulpal anesthesia). The study was blind and the groups and injections were randomized. For IONB 24 rats (8/group) received 0.1mL of the anesthetic formulations next to the right infraorbital foramen, the left side received the respective control formulation (NaCl 0.9% or 2- hydroxypropil- ß-cyclodextrin). Anesthesia was evaluated by upper lip pinching. For SISW 60 rats (12/group) were submitted to evaluation of baseline force sensation of the right hind paw (von Frey aesthesiometer) followed by incision and suture. After 24 hours the animals that presented at least 20% decrease in the force for paw withdrawal received an injection of 0.1mL of the anesthetic formulations or controls at the side of the surgical wound and were evaluated each 5min. For IANB, after fixation of copper wires to the mandibular molars, the animals (15/group) were submitted to an injection of 0.2mL of the anesthetic formulations next to right mandibular foramen; the respective control was injected in the left side. Pulpal anesthesia was assessed by electric stimulus (pulp tester) applied each 2min until onset of anesthesia was reached and each 5min until perception of electric stimulus. Data were submitted to Log Rank, Kruskal-Wallis, Student-Newman-Keuls and Tukey tests ('alpha'=5%). No differences in anesthesia onset were observed among groups (p>0.05). Ropivacaine with epinephrine provided higher success rate and duration of anesthesia than the other formulations in all studied models (p<0.05). Ropivacaine with 2- hydroxypropil- ß-cyclodextrin showed higher success rate and duration of anesthesia than plain ropivacaine in IONB and SISW models (p<0.05). No differences between these two formulations were found in the IANB study (p>0.05). In conclusion, 2- hydroxypropil- ß-cyclodextrin increases ropivacaine anesthetic efficacy in inflamed and non-inflamed soft tissues (IONB and SISW), and could be an option for postoperative surgical pain control. Epinephrine is more potent to improve the anesthetic efficacy in all studied models being the only effective additive for pulpal anesthesia (AU)

• FAPESP's process: 09/12009-7 - Anesthetic efficacy of ropivacaine with hydroxypropyl-beta-cyclodextrin formulation in infraorbital and inferior alveolar nerve blocks and in surgical wound, in rats.
• Grantee: Cleiton Pita dos Santos
• Support Opportunities: Scholarships in Brazil - Master