The Full Story
Lidocaine is an anesthetic; anesthetics have a numbing effect and are used to block pain. Topical (intended to be used on body surfaces such as the skin) lidocaine is a common medicine cabinet item. Topical anesthetics like lidocaine are available as gels, creams, liquids, sprays, eye drops, and patches. They work by blocking nerves from sending pain signals to the brain. The result is temporary numbness of the area on which they are applied (a "local" anesthetic).
Because of their numbing effect, topical anesthetics are effective in treating pain such as sunburns, cuts or scrapes, insect bites, cold sores, rashes, hemorrhoids, injuries of the eye, or a sore throat. However, they should not be used to relieve teething discomfort in children.
When used sparingly and as directed, topical lidocaine is generally safe. However, misuse, overuse, or overdose can lead to a number of serious health problems and even death.
Ingestion of lidocaine can cause numbness of the mouth and throat, which can lead to trouble swallowing and even choking. If a substantial amount is ingested, enough can be absorbed into the bloodstream to affect vital organs, primarily the brain and heart. Symptoms can range from mild drowsiness and headache to confusion, seizures, coma, and cardiac arrest. It is important to note that these effects can result from excessive topical use or misuse of lidocaine as well. For example, covering a large area of the body with lidocaine or leaving it on the skin for a long time can lead to absorption of the drug into the bloodstream. This can also occur when it’s applied to skin that is not intact such as open wounds, blisters, or burns. Wrapping the treated area also increases absorption.
Another serious effect of lidocaine is a condition known as methemoglobinemia. Lidocaine can impair the ability of iron in red blood cells to carry oxygen to the tissues. Methemoglobinemia is the condition of having blood that has this altered kind of iron. Methemoglobinemia can result even from normal use of lidocaine, especially in children. Because the blood is not able to carry enough oxygen to the tissues, people with methemoglobinemia appear very pale or even blue, feel very tired, and have shortness of breath. Methemoglobinemia can be life-threatening.
It's easy to make dosing errors when using lidocaine. Such errors can be potentially toxic, especially in children. Use it carefully.
If someone has been exposed to lidocaine, check the webPOISONCONTROL® online tool or call Poison Control at 1-800-222-1222 for help.
Serkalem Mekonnen, RN, BSN, MPH
Certified Specialist in Poison Information
- Store lidocaine and other topical anesthetics completely out of sight and reach of children and pets.
- Keep lidocaine in its original, labeled container at all times.
- Before using lidocaine, read the Drug Facts section of the medicine label carefully and be sure to understand and follow its instructions.
- Use as little as possible and never more than the amount specified on the label.
- Avoid using lidocaine on broken skin.
- Lidocaine should not be used to treat children with teething pain.
- Do not wrap or cover treated areas.
This Really Happened
A 15-year-old girl was scheduled for laser hair removal. Prior to the procedure, the girl’s mother helped her apply a cream containing lidocaine to the areas being treated (legs, underarms, and mustache line). The cream was washed off after about 30 minutes. The mother had used a very large amount to cover the areas–about 2-3 tubes! The procedure was completed without any problems.
About 3 hours later, the girl began to complain of feeling dizzy and nauseated. The mother was concerned and called Poison Control for advice, which advised her to take the girl to the nearest ER. The ER doctor called Poison Control and reported that the girl’s symptoms seemed to have improved but that her methemoglobin level was 15.1% (normal is around 1%). The capacity of the girl’s blood to carry oxygen was greatly reduced.
Poison Control recommended observation and supportive therapy. Although there is an antidote that can be given for methemoglobinemia, it is usually reserved for more severe poisoning. The following day, the girl’s methemogobin level was down to 6.8%. Since she was doing well, she was allowed to go home.