Topical anesthetics are drugs used to numb the skin and reduce the pain sensation associated with some medical conditions or procedures. According to the US Food and Drug Administration, these products are available in a cream, ointment, or gel form. When applied locally, topical anesthetics may be absorbed through the skin into the blood stream, especially if the area irritated or inflamed,. Usually, this does not present a problem if the topical agent was applied only to a small area. These topical anesthetics contain drugs such as lidocaine, tetracaine, benzocaine, and prilocaine
Lidocaine, Epinephrine, and Tetracaine
Lidocaine, epinephrine, and tetracaine (LET) is a very common combination in topical anesthetics, as indicated by an article published in the July 2002 issue of "American Academy Family Physician" (AAFP) journal. This product is not available over the counter; it must be specially prepared as a liquid or a gel form. Its main use is in skin wounds. Applying lidocaine, epinephrine, and tetracaine (LET) to the edge of the wound facilitates the wound repair or the injection of further local anesthetic agent if needed. The AFP journal further reports that it is less effective on the extremities and does not result in any severe adverse effects.
Tetracaine, Adrenaline (Epinephrine), and Cocaine
According to the same article in the AAFP journal, tetracaine, adrenaline and cocaine is an older local anesthetic combination that was the first reported to be effective in treating skin and scalp lacerations. It is rarely used nowadays because its safety profile is worse than the above discussed LET. This is because cocaine is more toxic. Federal regulations are very strict on using medications containing cocaine because they can lead to serious complications that include seizures and sudden cardiac death.
Lidocaine and Prilocaine mixtures (EMLA)
Lidocaine and prilocaine is touted by the article in the AAFP Journal as the most common topical anesthetic formulation. How well this Lidocaine and Prilocaine mixture numbs the areas of the skin it is applied to depends on the length of time the cream stays in contact with the skin. Application in a thick layer for 90 minutes is usually considered sufficient. This mixture is also available in over-the-counter creams approved by Food and Drug Administration. The application of this cream may cause initial blanching or whitening of the skin. It could also cause a burning sensation and mild redness, which are symptoms of contact dermatitis. Patients with a blood disorder called methemoglobinaemia are prohibited from using this formulation. Also, the risk of this blood disorder is greater if the Lidocaine and Prilocaine mixture is applied to infants less than three months of age. Therefore, it is better avoided in neonates of this age until risks are better assessed. It should not be administered to the palms and soles because it can penetrate through the skin.
