A commonly used herbal formula enhances the effect of warfarin, an anticoagulant, a research team from Chang Gung University’s School of Traditional Chinese Medicine said, urging caution in the prescription and clinical use of the herbal medicine.
As more people have started to combine traditional herbal and Western medicines, drug interactions between the two, which could compromise their therapeutic effects or cause serious adverse effects, have been gaining attention, said Yang Sien-hung (楊賢鴻), the director of the Department of Chinese Medicine at Chang Gung Memorial Hospital, who led the study.
Shu jing huo xie tang (疏經活血湯), a popular Chinese herbal formula comprised of a mixture of 17 herbs, has been widely used in the treatment of degenerative joint diseases prevalent among elderly patients, Yang said.
Some patients prescribed with the formula had reported bleeding gums and bruises, and it was confirmed later that these patients were also taking anticoagulant warfarin, he said.
“Warfarin is a commonly used drug for anticoagulant therapy among patients with atrial fibrillation and cardiovascular diseases... Many drugs have reported interactions with warfarin that precipitate the risk of bleeding,” the research team said.
The team found that the concurrent use of shu jing huo xie tang and warfarin can cause bleeding, with increased time needed for blood clotting, while “no anticoagulant effects were observed at any dose of shu jing huo xie tang alone.”
The observed effects of the combination of shu jing huo xie tang and warfarin diminished and the coagulation measurements returned to normal within three days after discontinuation of the herbal medication, according to the team.
“It is unclear why this occurs,” the team said.
It could be caused by the accumulation of the chemical compound coumarin, “since many components of shu jing huo xie tang are reported to contain chemical compounds from the coumarin family,” to which warfarin also belongs, the study said.
Yang warned against using the herbal compound without a doctor’s advice, adding that traditional Chinese medicine practitioners should “make sure patients prescribed with shu jing huo xie tang are not taking anticoagulants at the same time, or to treat them with light doses and closely monitor for signs of bleeding if the combination is prescribed.”