In future, the treatment at the dentist could be much more pleasant. Renata Fonseca Vianna Lopez, University of São Paulo, Ribeirão, Brazil, and colleagues have developed a method to stun teeth and gums by gentle electricity rather than a syringe. The electricity, which only slightly tingles, brings the local anesthetic under the skin, thus ensuring a sufficient pain blockade.

Iontophoresis is a strategy to increase the penetration of drugs through biological membranes. So far, it is only useful for superficial anesthesia. The researchers investigated the influence of iontophoresis in the mucosal penetration of prilocaine hydrochloride (PCL) and lidocaine hydrochloride (LCL) – largely used in dentistry as local anesthetics – when combined in the same formulation. Semisolid hydrogels containing these drugs either alone or in combination were developed at pH 7.0 and 5.8. The gels showed adequate mechanical and mucoadhesive properties for buccal administration, i.e. through the tissues lining the mouth.

The team found that iontophoresis of a hydrogel containing the combination of prilocaine HCl and lidocaine HCl at pH 7.0 enhances the permeation 12-fold and retention of both anesthetics across porcine esophageal mucosa. Iontophoresis did not increase lidocaine hydrochloride permeation through the mucosa, however, it did increase lidocaine salt accumulation.

The researchers see buccal iontophoresis as a strategy for the administration of needle-free anesthesia during dental procedures.

• Needle-free buccal anesthesia using iontophoresis and amino amide salts combined in a mucoadhesive formulation,
  Camila Cubayachi, Renê Oliveira do Couto, Cristiane Masetto de Gaitani, Vinícius Pedrazzi, Osvaldo de Freitas, Renata Fonseca Vianna Lopez,
  Colloids Surf. B 2015, 136, 1193–1201.
  DOI: 10.1016/j.colsurfb.2015.11.005