Drug manufacturer Berlex has voluntarily issued letters to physicians around the country reminding them of the rare risk of liver toxicity linked to the use of the multiple sclerosis drug Betaseron (interferon alfa-1b). The correspondence, distributed in mid-April, reminds doctors of the need to perform liver function tests on patients before prescribing the medication. The letter stated, "Since market introduction in 1993, the Betaseron prescribing information has recommended liver function testing at regular intervals (one, three, and six months) following introduction to Betaseron therapy, and then periodically thereafter in the absence of clinical symptoms."

A Rare Risk
The letter was prompted by post-marketing reports of serious liver injury in people receiving beta-interferon therapy. Cases of autoimmune hepatitis and severe liver damage led to liver failure and liver transplant in some instances, according to the letter posted on the website of MedWatch, the FDA's safety information and adverse event reporting arm.

But Berlex stresses that this is not new information. The risk has always been included in Beta-Seron's prescribing information, the manufacturer stated.

Further, the letter stresses that cases of liver toxicity were rare, and occurred in people taking other medications or who had been diagnosed with other illnesses. "In some cases, these hepatotoxic events reported for patients on beta-interferons have occurred in the presence of other drugs and/or co-morbid medical illnesses associated with hepatic injury," the letter stated, adding that the drug "remains an efficacious and safe treatment of relapsing forms of multiple sclerosis to reduce the frequency of clinical exacerbations."

What is Betaseron?
Betaseron is a type of synthetic interferon designed to treat relapsing-remitting multiple sclerosis, the most common form of the disease that is characterized by episodes of acute worsening of neurologic function followed by partial or complete recovery periods. The medication is given as an injection every other day.¹

1. National Multiple Sclerosis Society. Living With MS. Medications Used in MS. Available at: http://www.nationalmssociety.org/Meds-InterferonBeta1b.asp. Accessed May 27, 2005.

John Martin is a long-time health journalist and an editor for Priority Healthcare. His credits include overseeing health news coverage for the website of Fox Television's The Health Network, and articles for the New York Post and other consumer and trade publications.