Objective: Evaluation of onset and duration of peripheral nerve blockage with alkalinized lidocaine by borate buffer instead of sodium bicarbonate.
Study design: Experimental randomized cross-over study.
Animals: Forty male Sprague-Dawley rats (body weight 200–300 g) were used in this study.
Methods: Four 1.0% lidocaine solutions were prepared from commercially available solutions. The treatment 1(n=10 rats) was lidocaine hydrochloride, treatment 2 was combination of lidocaine and borate buffer, treatment 3 (n=10 rats) was lidocaine –epinephrine, treatment 4 (n=10 rats) was lidocaine-epinephrine-borate buffer. each treatment was received 0.1 ml of the agent  using a 27-G needle connected to an insulin syringe injected around the sciatic nerve. Time to the onset and duration of the superficial and deep analgesia were recorded and analyzed. The results were expressed as mean ±SD and were analyzed by a one-way analysis of variance and Duncan test as a post hoc for time of onset and duration of analgesia.  Graphpad Prism version 5 software program was used for all analyses.
Results: Alkalinization of 1.0% lidocaine with or without epinephrine by borate buffer produced a faster onset than  lidocaine or the combination of lidocaine  and epinephrine.
Conclusion and clinical relevance: We conclude that the injection of lidocaine with added borate buffer and 1: 100,000 epinephrine increases the duration of analgesia and reduces the onset of blockade in the rat model. Further studies on the most appropriate dose of borate buffer are recommended. This combination might prove useful clinically to provide analgesia in infected area such as infected tooth extraction.