Beserol was a drug that was marketed worldwide for the treatment of several conditions, primarily anxiety and chronic pain. The manufacturer voluntarily took the drug off the market after the World Health Organization began to issue withdrawals of approval for any drug containing Beserol's active ingredient in countries around the world. The severe side effects of Beserol were the main reason for the drug's failure, and it is no longer available in regulated areas.
The active ingredients of Beserol were linked by the WHO to adverse side effects, because all drugs containing these active ingredients were removed from the market worldwide. Warnings have been issued by the WHO for chlormezanone and metamizole sodium, found in dozens of trade names worldwide, including Beserol. Another ingredient of Beserol that has not been removed from the market is acetaminophen, a common pain reliever and fever reducer found in over-the-counter drugs. Although acetaminophen has also been found to have potential negative side effects and complications, acetaminophen was not the focus of regulatory action against Beserol and related drugs.
The major side effects caused by chlormezanone in Beserol were symptoms of a condition known as Stevens-Johnson syndrome. Chlormezanone in Beserol and other related drugs was found to result in high incidence of the disease, in which the skin and mucus membranes react to the medication. Symptoms include fever and other flu-like symptoms, followed by a severe rash and shedding of the outer layer of skin.
Beserol also had the potential to cause a number of permanent or life-threatening side effects as a result of complications of Stevens-Johnson syndrome. Following the rash and shedding of skin, patients are at risk for infection through sores in the skin, sepsis of the blood and related shock or organ failure and permanent organ damage. The severe rash caused by chlormezanone through Stevens-Johnson syndrome can also cause permanent skin and eye damage and loss of hair or nails.
The only solution for the side effects of Beserol and related drugs was to remove the cause of the reaction that produces Stevens-Johnson syndrome. Thus, doctors typically advise patients to stop medication and permanently avoiding all related chemical compounds. Because Beserol and other drugs containing chlormezanone resulted in such a high incidence of Stevens-Johnson syndrome, the drugs were universally withdrawn rather than simply being cautioned against for a few patients.
Approval of Beserol and other drugs containing chlormezanone began to be withdrawn by the WHO in 1996 after the serious side effects had been discovered, and continued for several years until all countries regulated by the WHO had issued warnings against the family of drugs. A universal warning against Beserol was also issued in 2003 in a comprehensive report by the WHO.