Anaesthetic efficacy of bupivacaine 2-hydroxypropyl-β-cyclodextrin for dental anaesthesia after inferior alveolar nerve block in rats

Bupivacaine is a long-acting local anaesthetic that is widely used in medicine and dentistry. The duration and intensity of its sensory blockade in animal models is increased by its inclusion in complexes with cyclodextrins. The aim of the present study was to evaluate the anaesthetic efficacy of bupivacaine 2-hydroxypropyl-β-cyclodextrin (HPβCD) inclusion complex for dental anaesthesia after inferior alveolar nerve block in rats. Thirty rats were each given an injection close to the mandibular foramen of 0.2 ml of one of the following formulations: 0.5% bupivacaine alone; 0.5% bupivacaine with 1:200,000 epinephrine; and 0.5% bupivacaine-HPβCD inclusion complex (bupivacaine-HPβCD). The other sides were used as controls, with either 0.9% saline or anaesthetic-free HPβCD solution being injected. The onset, success, and duration of pulpal anaesthesia were assessed by electrical stimulation (“pulp tester”) on inferior molars. Results were analysed using ANOVA (Tukey), log rank, and chi square tests (α = 5%). There were no differences among the formulations in onset of anaesthesia (p = 0.59) or between the bupivacaine plus epinephrine and bupivacaine plus HPβCD in duration of anaesthesia, but bupivacaine plus epinephrine gave significantly higher values than bupivacaine alone (p = 0.007). Bupivacaine plus epinephrine was a better anaesthetic than bupivacaine alone (p = 0.02), while Bupi-HPβCD gave intermediate results, and therefore did not differ significantly from the other 2 groups (p = 0.18 with bupivacaine alone; and p = 0.44 with bupivacaine plus epinephrine). The bupivacaine-HPβCD complex showed similar anaesthetic properties to those of bupivacaine with epinephrine.