Health Canada evaluates safety of benzocaine products, link to rare blood condition

Health Canada says it is continuing to evaluate the safety of benzocaine products in light of reports of adverse reactions linked to the pain reliever.

It's also reminding parents and caregivers about health risks associated with use of the topical products, including a rare but potentially serious blood condition known as methomoglobinemia.

The products are used to relieve pain from sore throats, teething, toothache, canker sores, irritation of the mouth and gums, burns, insect bites, itching and hemorrhoids.

They are also used during surgical and dental procedures to numb the mouth and throat.

Health Canada says topical benzocaine products are available over-the-counter in a variety of formulations, including sprays, gels, liquids and creams.

The agency says it first issued an advisory about the risk of methomoglobinemia, or MetHb, in November 2006, and has since received seven reports of serious adverse reactions linked to topical benzocaine — including four reports of MetHb.

MetHb reduces the ability of red blood cells to deliver oxygen throughout the body, Health Canada said.

"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," the agency said in a statement Tuesday.

"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.

Anyone experiencing symptoms is advised to seek medical attention, Health Canada said.