Background and Objectives. Intradermal injection of local anesthetics prior to percutaneous needle insertion is often painful. This study evaluated the effect of diluting lidocaine and mepivacaine with balanced salt solution on perception of pain on intradermal injection.

Methods. Twenty healthy volunteers were each intradermally injected with six solutions in random order. These solutions were: normal saline (NS), 0.9% benzyl alcohol in NS, 0.2% lidocaine in NS, 0.2% lidocaine in balanced salt solution, 0.2% mepivacaine in NS, and 0.2% mepivacaine in balanced salt solution. Discomfort of each injection was reported on a 0-2 pain scale. The degree of anesthesia at each site was evaluated by pinprick every minute for 20 minutes.

Results. Benzyl alcohol and lidocaine and mepivacaine in balanced salt solution caused the least injection pain. However, mepivacaine in NS and NS alone caused the most pain. The anesthetic effect of benzyl alcohol was judged adequate for only 4 minutes whereas both lidocaine and mepivacaine in either NS or balanced salt solution gave adequate anesthesia for at least 15 minutes.

Conclusions. The dilution of lidocaine and mepivacaine with balanced salt solution produces a solution that is both painless on injection and of moderate duration.