A woman from Rhode Island suffered from a rare and potentially life-threatening disorder after using an over-the-counter pain medication she bought to treat her toothache.

The woman's condition deprived her of oxygen and turned her blood dark blue.

Blue Blood

Doctors who reported the case in the New England Journal of Medicine said that the then 25-year-old patient visited the emergency room with complaints of fatigue, muscle weakness and blue discoloration of the skin.

The woman also had low blood oxygen levels, but attempts to treat her symptoms using extra oxygen did not alleviate her condition. Blood drawn from her was also dark blue.

Benzocaine And Methemoglobinemia

Her symptoms began after she had taken the topical version of the benzocaine drug, a fast-acting over-the-counter anesthetic used in the operating room.

This gave doctors some clue on what happened: the woman had methemoglobinemia, a condition characterized by a very high amount of methemoglobin that builds up in the blood.

Methemoglobin is a form of hemoglobin, the iron-rich, red protein in the blood cells that transports oxygen around the body.

Methemoglobin, however, does not bind oxygen, which means that it cannot carry oxygen to tissues, and makes it difficult for the typical hemoglobin to deliver oxygen to cells.

Too much amount of this substance in the body can cause suffocation, so the body produces enzymes that convert methemoglobin back to hemoglobin.

The condition can affect people with rare genetic mutations that affect their hemoglobin or the enzymes that break down methemoglobin, but some drugs including benzocaine may also cause the body to produce more methemoglobin than normal.

It is the surplus of methemoglobin, which is dark brown that can cause the blood to turn blue.

Treatment

Most people who use drugs linked to methemoglobinemia do not develop the condition, but the doctors said that the woman used large amounts of topical benzocaine.

Doctors treated the woman with a chemical called methylene blue, after which, her breathing and skin color returned to normal.