A study concludes that a Chinese herb known as thunder god vine improves symptoms in people with rheumatoid arthritis (RA) better than a prescription medication.

Researchers at the National Institutes of Health in Bethesda, MD, and the University of Texas in Dallas and nine rheumatology clinics around the country randomly assigned 121 patients with six or more painful and swollen joints to take either 60 milligrams of thunder god vine root extract three times per day or 1 gram of sulfasalazine (Azulfidine) two times a day for 6 months. All study participants were also allowed to take prednisone and nonsteroidal anti-inflammatory drugs, or NSAIDs. 

Scientists assessed participants using a standard measure of joint involvement.

Patients in both groups experienced side effects, with stomach complaints and digestive symptoms being the most common. And about half of participants dropped out of the study before it was completed, with more dropping out in the sulfasalazine group than in the thunder god vine group.

But of the 62 patients who continued treatment for the full six months, 65 percent saw improvements in joint pain, joint function and inflammation with thunder god vine, compared to just 36 percent with sulfasalazine.

The study was published in the Annals of Internal Medicine.

Thunder god vine is the English translation for a vine-like plant that grows in Asia called lei gong teng. The leaves, flowers and outer skin of the plant’s root are poisonous and potentially lethal. Honey from the plant’s pollen is also toxic and the herb can be deadly if it isn’t extracted correctly. For these reasons, it’s believed this plant, in ancient times, was likely used as a murder weapon.

But thunder god vine also has healing properties that come from the pulp of the peeled roots. It has been used for thousands of years in traditional Chinese medicine to treat everything from rheumatoid arthritis and swelling to leprosy, fever and boils.

Thunder god vine is also known to have a wide range of side effects that includes diarrhea, upset stomach and skin reactions. Men may experience temporary infertility and women may stop having menstrual periods while taking it.

Researchers, who were not available for comment, wrote in the study’s conclusion that for those who can tolerate oral prednisone and nonsteroidal anti-inflammatory drugs, thunder god vine may be an attractive and affordable alternative to traditional DMARDs.

But other herbal medicine experts say they aren’t yet sure that the benefits of taking thunder god vine outweigh its considerable risks.