• Biomolecules & Therapeutics
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• v.19 no.3
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• pp.357-363
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• 2011

In relieving local pains, ropivacaine has been widely used. In case of their application such as ointments and creams, it is difficult to expect their effects for a significant period of time, because they are easily removed by wetting, movement and contacting. Therefore, the new formulations that have suitable bioadhesion were needed to enhance local anesthetic effects. The effect of drug concentration and temperature on drug release was studied from the prepared 1.5% Carboxymethyl cellulose (CMC) (150MC) gels using synthetic cellulose membrane at $37{\pm}0.5^{\circ}C$. As the drug concentration and temperature increased, the drug release increased. A linear relationship was observed between the logarithm of the permeability coefficient and the reciprocal temperature. The activation energy of drug permeation was 3.16 kcal/mol for a 1.5% loading dose. To increase the skin permeation of ropivacaine from CMC gel, enhancers such as saturated and unsaturated fatty acids, pyrrolidones, propylene glycol derivatives, glycerides, and non-ionic surfactants were incorporated into the ropivacaine-CMC gels. Among the enhancers used, polyoxyethylene 2-oleyl ether showed the highest enhancing effects. For the efficacy study, the anesthetic action of the formulated ropivacaine gel containing an enhancer and vasoconstrictor was evaluated with the tail-flick analgesimeter. According to the rat tail-flick test, 1.5% drug gels containing polyoxyethylene 2-oleyl ether and tetrahydrozoline showed the best prolonged local analgesic effects. In conclusion, the enhanced local anesthetic gels containing penetration enhancer and vasoconstrictor could be developed using the bioadhesive polymer.

• Journal of Pharmaceutical Investigation
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• v.30 no.4
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• pp.273-278
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• 2000

Several topical preparations containing lidocaine, a widely used local anesthetic agent, have been developed and marketed recently for the treatment of premature ejaculation. In this study, microemulsion(ME)-based hydrogels containing lidocaine were prepared by dispersing ME to hydrogel bases such as Carbopol, sod. alginate, and sod. carboxymethylcellulose. Lidocaine-containing ME was thermodynamically stable over 6 months and had a diameter ranging from 10 to 100 nm. In vitro skin penetration of lidocaine from ME-based hydrogels followed apparent zero-order kinetics. ME-based hydrogel showed higher drug penetration during fifteen minutes after application than alcoholic hydrogel, reference preparation. Tail flick test in rat was introduced to compare in vivo local anesthetic effects of different hydrogels, and the results showed that ME-based hydrogels are superior to other hydrogels. In optical microscopy, recrystallization of lidocaine was observed within 5 min after application of reference hydrogel, but there was no change in ME-based hydrogels even after 30 minnute. These results indicated that ME-based hydrogels had some advantages in skin penetration, anesthetic effect and physical stability compared with alcoholic hydrogels. Finally it is possible to conclude that ME-based hydrogels containing lidocaine is a good topical drug delivery system for the treatment of premature ejaculation.