Dr Lee has raised an important point regarding the long-term safety of butterbur therapy. To my knowledge, the longest (published) treatment period with any butterbur preparation has been 16 weeks.1 Normally, this length of time would be sufficient for the treatment of a seasonal condition such as intermittent allergic rhinitis. However, the fact remains that formal long-term safety data are lacking and are urgently needed. Until such data are available, and in view of the excellent results in short-term studies, my colleagues and I have limited our use of butterbur (leaf extract) to short-term treatments of no more than 16 weeks (typically 8-12 weeks), according to patient response and tolerability. Importantly, long-term data, when obtained, may not be transferable to all butterbur formulations, as the toxicity potential of root extracts as used in some of the published studies (compare references 3-5 in Dr Lee's letter and reference 1 in this reply) may be totally different from that of leaf extracts, since the alkaloid concentration in the leaf is already 10 times less than that in the roots.2 This is particularly important with regard to the final content of hepatotoxic pyrrolizidine alkaloids, which are not detectable (limit of detection, 30 parts per billion) for the leaf extract that we used, and which was one of the main reasons for our choice of butterbur formulation. As we leave behind the alleged empirical practices of traditional herbal pharmacy to embrace modern-day herbal medicine, it is important to bear in mind that formulation is crucial to ensure exclusion of the natural products’ (often) toxic constituents, while retaining those constituents with the desired pharmacological effect.
Schapowal A. Addressing the Long-term Safety Aspects of Butterbur Therapy: A Call for Immediate Action—Reply. Arch Otolaryngol Head Neck Surg. 2005;131(6):540. doi:10.1001/archotol.131.6.540