Minute Electrical Current Could Replace Buccal Anesthesia

Researchers at the University of Sao Paulo (Brazil) conducted a study to find out if iontophoresis—a strategy to increase the penetration of drugs through biological membranes—could also be used in the oral mucosa.

To do so, they prepared two anesthetic drugs, prilocaine hydrochloride (PCL) and lidocaine hydrochloride (LCL) as hydrogels, using a polymer to enhance mucoadhesive properties. They tested the hydrogel formulation on a pig, applying the iontophoresis electric current to test anesthetic efficacy. The semisolid hydrogels were developed at two different pH’s (7.0 and 5.8).

The results showed that at pH 7.0, iontophoresis increased the permeation rate of PCL 12-fold, and did not significantly change LCL flux when compared to the passive permeation rate of the combined drugs. When the researchers combined both drugs, an increase in both PCL (86-fold) and LCL (12-fold) accumulation in the mucosa was achieved, as compared with each isolated drug. The researchers thus concluded that iontophoresis applied to a semisolid drug combination at pH 7.0 could serve as a needle-free strategy to speed the onset and prolong the duration of buccal anesthesia. The study was published in the December 2015 issue of Colloids and Surfaces B: Biointerfaces.

“Needle-free administration could save costs, improve patient compliance, facilitate application, and decrease the risks of intoxication and contamination,” said senior author Prof. Renata Fonseca Vianna Lopez, PhD, of the USP school of pharmaceutical sciences. “This may facilitate access to more effective and safe dental treatments for thousands of people around the world.”

Iontophoresis is a physical process in which ions flow diffusively in a medium, driven by an applied electric field; the transport is measured in units of chemical flux (commonly µmol/cm2 ·h). In practice, a small electric current is applied to an iontophoretic chamber placed on the skin, containing a charged active agent and its solvent vehicle; another chamber or a skin electrode carries the return current. The positively charged chamber, the anode, repels positively charged chemicals, whereas the negatively charged chamber, the cathode, repels negatively charged ones into the skin or mucosa.

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University of Sao Paulo