In vitro antibacterial effects of topical local anesthetics.

BACKGROUND

The antibacterial activities of local anesthetics are recognized.

OBJECTIVE

To investigate in vitro the activity of topical local anesthetic ointments at clinical doses.

METHODS

The activity of two different local anesthetic ointments including lidocaine 5% and lidocaine/prilocaine 2.5% was tested against Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli, Pseudomonas aeruginosa, Streptococcus pyogenes and Enterococcus faecalis by the disc-diffusion method. Sterile discs containing topical local anesthetic drugs were prepared taking into account the doses of ointments used in clinical practice. The validity of the methodology was confirmed using topical antibacterial mupirocin. The inhibition zones of the discs were measured.

RESULTS

Mupirocin inhibited all the bacteria. Both local anesthetic ointments were found to be most effective on E. coli, whereas they had no effects on P. aeruginosa. Lidocaine 5% revealed antibacterial activity against S. aureus, S. epidermidis, E. coli, S. pyogenes and E. faecalis, but lidocaine/prilocaine 2.5% showed no activity on E. faecalis and inhibited S. pyogenes only at double doses. It was also observed that the antibacterial activity was in a dose-dependent manner.

CONCLUSION

In the light of these findings, it might be concluded that topical local anesthetic ointments in routine settings may have a preventive role against some bacteria.