Coumarins in herbal cold remedy are safe

Regarding your review¹ of the Lizogub study on Pelargonium sidoides:²

1. The product used in the study is sold in the United States. In fact, the introduction to the Lizogub study states: “An alternative treatment for the common cold is a liquid herbal drug preparation from the roots of Pelargonium sidoides (Willmar Schwabe Pharmaceuticals, Karlsruhe, Germany), the active ingredient in Umcka ColdCare and Zucol in the United States. Zucol is a rapid melt delivery form sold in the mass market by a subsidiary of Nature’s Way known as Abkit.”
2. Regarding the statement in the safety section, about plant coumarins and potential interactions with warfarin and aspirin, I offer a synopsis of a pharmacology study³ completed in Germany: At oral doses of 10, 75, and 500 mg/kg per day for 2 weeks, the liquid herbal drug preparation 7630 did not influence the thromboplastin time (TPT), the partial TPT (PTPT), or thrombin time (TT) in rats. If the animals were given preparation 7630 (500 mg/kg PO) and warfarin (0.05 mg/kg PO) concomitantly for 2 weeks, there was no evidence of a statistically significant change in the anticoagulant effect of warfarin. Furthermore, pretreatment of rats with preparation 7630 (500 mg/kg PO) for 2 weeks had no effect on the pharmacokinetics of a single dose application of warfarin (0.2 mg/kg PO). This study demonstrates that sub-acute administration of preparation 7630 over a wide dose range has no effect on TPT, PTPT, and TT in the rat. Similarly, the anticoagulant effect of warfarin is not affected by concomitant application of preparation 7630, and pretreatment with preparation 7630 produces no change in the pharmacokinetics of warfarin. Moreover, as the coumarins identified do not possess structural characteristics required for anticoagulant activity, it appears unlikely that an increased tendency to hemorrhage will occur in patients treated with preparation 7630.

In short, the plant coumarins in Pelargonium sidoides are structurally dissimilar to agents that would affect coagulation and are unlikely to cause any interaction with these drugs.

Donald Brown, ND,
VP, Scientific and Educational Affairs,
Nature’s Way Products, Springville, UT