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Lidocaine and benzocaine are both medications that are used as local anesthetics. They share structural similarities, and have similar means of acting on the human body, but they also have important differences. These drugs have somewhat different anesthetic and chemical properties, which determine how appropriate they are for use in different medical situations.
During orthodontic surgery, lidocaine and benzocaine are common choices to reduce the pain of drilling and other procedures. Studies have shown that injections of both substances are about equal in relieving pain caused directly to the roof of the mouth. Lidocaine has been shown in at least one study to be superior at numbing the nerves in the roots of the teeth when provided by injection, compared to treatment with a topical benzocaine gel.
Lidocaine and benzocaine are absorbed at slightly different rates when applied topically. Benzocaine is somewhat less water soluble than lidocaine, meaning that it crosses through the tissue of the mouth less readily when it is directly applied. Roughly 35 percent of a lidocaine solution will pass into the gums and other mouth tissue when applied as a gel, however.
These two medications have somewhat different durations of action. Lidocaine tends to exhibit effects for around three to four hours, making it appropriate for somewhat more intricate surgeries than benzocaine, which does not have effects that last as long. Benzocaine may be used for post-surgical pain relief, however, since it can be re-applied multiple times a day.
The similarities of these substances also include similar side effects. The most common side effects can include stinging or tenderness at the area where these medications were applied, although both drugs are usually well-tolerated. Allergic reactions can occasionally result to one medication or the other. They are structurally different enough, however, that a reaction to one drug does not usually entail an allergy to the other. This means that a patient that shows a benzocaine allergy may safely use lidocaine.
More severe side effects are sometimes seen with lidocaine and benzocaine. One potentially life-threatening side effect is known as methemoglobinemia. This medical condition may occur in response to one medication, but not the other, in certain patients. It necessitates immediate medical assistance, and can cause effects like shortness of breath, blue or grey lips or mouth, and light-headedness. These effects are due to a drop in the amount of oxygen carried in the blood.