Anesthetic Efficacy of Ropivacaine Formulations in Rats Infraorbital Nerve Block

Method: 24 rats (8/group) received 0.1 mL of the following formulations as IONB: 0.5% ropivacaine – Ropi, 0.5% ropivacaine complexed with 2-hydroxypropil-β-cyclodextrin (a controlled drug release system) – Ropi-HP-β-CD and 0.5% ropivacaine with 1:200,000 epinephrine – Ropi-Epi. The solutions were applied near to the infraorbital foramen on the right side; the left side received the respective controls (saline or 2-hydroxypropil-β-cyclodextrin solution). Success and duration of anesthesia were assessed by upper lip pinching every 5 minutes. Data were submitted to Log-Rank and Tukey tests (α=5%).

Result: All the animals presented immediate anesthesia of the right upper lip after injection. The left side did not show upper lip anesthesia. Anesthesia success and duration are presented on table. Ropi-Epi provided higher anesthesia success and duration (p<0.0001) than Ropi-HP-BCD; Ropi presented lower anesthesia success and duration than the other formulations.

Conclusion: The complexation with 2-hydroxypropil-β-cyclodextrin increases ropivacaine efficacy but epinephrine is more potent than 2-hydroxypropil-β-cyclodextrin to improve the anesthetic efficacy in the rat infraorbital nerve block.

Table. Anesthesia success (%) and duration (mean and standard deviation, in minutes).