Background: The effects of butterbur (BB), a herbal remedy, as add-on therapy to inhaled corticosteroids in patients with atopic asthma is currently unknown.
Objective: We evaluated the effects of BB, given as add-on therapy to asthmatic patients maintained on inhaled corticosteroids, assessing adenosine monophosphate (AMP) bronchoprovocation (primary outcome variable) along with other surrogate inflammatory markers such as exhaled nitric oxide, serum eosinophil cationic protein and peripheral blood eosinophil count.
Methods: Sixteen atopic asthmatic patients with mean (standard error of mean) forced expiratory volume in 1 s (FEV1) of 78 (4)% predicted, maintained on their constant dose of inhaled corticosteroids throughout the study, received twice daily for 1 week either BB 25 mg or placebo (PL), in a double-blind, cross-over fashion, with a 1-week washout period prior to each randomized treatment. Measurements were made at baselines prior to each randomized treatment and following the randomized treatment period.
Results: Baseline values for the primary and secondary outcomes were not significantly different prior to BB and PL. AMP provocative concentration causing a 20% reduction from baseline FEV1 (PC20) as doubling dilution change from baseline, significantly improved (P<0.05) with BB, 0.6 (0.2), compared with PL, -0.1 (0.3); a 0.7 doubling dilution difference. Exhaled nitric oxide as change from baseline was significantly reduced (P<0.05) with BB, -1.2 (0.8) p.p.b., compared with PL, 0.5 (0.4) p.p.b. Both serum eosinophil cationic protein and peripheral blood eosinophil count as change from baseline were also significantly suppressed (P<0.05) with BB, -3.9 (3.3) microg/L, -31 (28)x106/L compared with PL, 3.3 (2.5) microg/L, 38 (16)x106/L, respectively.
Conclusion: Chronic dosing with BB conferred complementary anti-inflammatory activity in atopic asthmatic patients maintained on inhaled corticosteroids. Further studies are now required to assess the potential role for BB as either monotherapy in milder patients or add-on therapy in more severe asthmatics.