Health Canada reminds Canadians of health risks associated with topical benzocaine products

Health Canada continues to receive reports of benzocaine-related adverse reactions, including MetHb. We continue to evaluate the safety of benzocaine products in light of these reports and will take appropriate regulatory actions as warranted.

Topical benzocaine products are available over-the-counter in various concentrations and formulations, including sprays, gels, liquids and creams, and are used to relieve pain from a variety of conditions such as sore throats, teething, toothache, canker sores, irritation of the mouth and gums, burns, insect bites, itching, and hemorrhoids. They are also used by healthcare practitioners during surgical, dental and other medical procedures to numb the mouth and throat.

MetHb reduces the ability of red blood cells to deliver oxygen throughout the body. Signs and symptoms of MetHb include pale, grey or blue-coloured skin, lips, or nail beds; shortness of breath; fatigue; confusion; headache; lightheadedness; nausea; and change in heart rate. These symptoms can appear within minutes or one to two hours after benzocaine use, and can occur after the first or several uses. In rare severe cases, MetHb can progress to stupor, coma and possibly death.

Other reported side effects associated with topical benzocaine products include breathing or swallowing difficulties, a swollen tongue or mouth, irregular heartbeat, malaise, body twitching, hypersensitivity, burning, redness, itching, rash, and irritation at the site of administration. These effects can occur with any topical benzocaine product, regardless of product type or benzocaine concentration, in sensitive individuals.
As with any health product, Canadians are reminded to carefully read and follow the instructions for product use. If you think you or your child may be experiencing a side effect, including signs or symptoms of methemoglobinemia, seek medical attention. If you have questions or concerns about a topical benzocaine product, speak to a healthcare practitioner.

Health Canada first communicated the risk of MetHb in a Public Advisory and Notice to Hospitals in November 2006. Since that time, Health Canada has received seven reports of serious adverse reactions involving topical benzocaine, four of which were reports of benzocaine-induced MetHb in adults.