Preparation and evaluation of procaine gels for the enhanced local anesthetic action.

To develop the new procaine gel formulations with a suitable bioadhesive property, the gel was formulated using hydroxypropyl methylcellulose (HPMC) and poloxamer containing an enhancer and the local anesthetic action were evaluated. As the drug concentration in the gels and the temperature of surrounding solutions increased, the drug release increased. The activation energy of drug permeation was 4.35 kcal/mol for procaine. The effects of permeation enhancers on the permeation rate of drug through skin were studied using various enhancers, such as the glycols, the non-ionic surfactants, and the bile salts. Among the enhancers used, polyoxyethylene 2-oleyl ether Showed the most enhancing effects on drug permeation through skin. The analgesic activity was examined using a tail-flick analgesimeter. From the area under the efficacy curve of the rat-tail flick tests, procaine gel containing polyoxyethylene 2-oleyl ether showed about 1.77-fold increase in analgesic activity compared with the control. These results support that the enhanced local anesthetic gels containing an enhancer could be developed using the bioadhesive polymer gels based on HPMC and poloxamer.