Arthritis therapy tied to liver injury cases

A "medical food" sold as an arthritis treatment may have caused four cases of temporary liver damage, researchers reported Monday.

The product in question is called flavocoxid, sold under the brand-name Limbrel. It's a mix of plant compounds called flavonoids, including catechins - substances best known as components of green tea.

Limbrel is considered a medical food, which makes it different from a dietary supplement. It is available by prescription only, to treat osteoarthritis - the common, "wear-and-tear" form of arthritis caused by cartilage breakdown in the joints.

But medical foods are different from prescription drugs in that they don't have to be proven safe and effective before hitting the market.

In the new report, published in the Annals of Internal Medicine, researchers describe four cases in which Limbrel users developed temporary liver "injury."

That meant symptoms like abdominal pain, jaundice (yellowing of the skin), intensely itchy skin and fever.

All of the patients recovered after they stopped using the product.

The researchers cannot say with certainty that all four cases were caused by Limbrel.

"There's no single test you can do to say, ‘Bingo, it's caused by this,'" said lead researcher Dr. Naga Chalasani, of Indiana University School of Medicine in Indianapolis.

But he said that three of the cases were "highly likely" to have been caused by Limbrel. The fourth was "possibly" caused by the product.

Timing was a big clue. All four patients developed signs of liver toxicity within three months of starting the arthritis treatment. And all got better within three to 12 weeks of stopping it.

That relatively quick recovery is the good news, Chalasani said. "It seems like you stop taking it, and the liver injury improves pretty quickly, in a matter of weeks."

Scottsdale, Arizona-based Primus Pharmaceuticals, which makes Limbrel, did not return calls seeking a comment.

The four liver-damage cases turned up as part of an ongoing surveillance study of liver injury caused by drugs or herbal supplements. Between 2004 and 2010, researchers at several U.S. medical centers enrolled 877 patients who were thought to have liver damage from a medication or supplement.

Four of those cases were linked to Limbrel.

It's not fully clear why the product would damage the liver.

"That's the million-dollar question," Chalasani said.

But he and his colleagues suspect it may be the catechin content. Green tea extracts, which contain high concentrations of catechins, have been linked to liver toxicity.

Even if catechins are to blame, that still leaves the question of why only certain Limbrel users would develop liver problems. "There has to also be some kind of susceptibility" to liver injury, Chalasani said, noting that it could be a genetic vulnerability.