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Wang L, Zhang RM, Liu GY, Wei BL, Wang Y, Cai HY, Li FS, Xu YL, Zheng SP, Wang G.
Chinese herbs in treatment of influenza: a randomized, double-blind, placebo-controlled trial.
Respir Med 2010; 104: e1362–9.
The aim of this study was to assess the acute effects of ephedra on autonomic nervous modulation by means of heart rate variability (HRV) analysis, using a randomized, double-blind, placebo-controlled, crossover design. On three separate days, 20 healthy subjects took capsules containing either 1 or 2 g of ephedra dry extract or a placebo, and the sequential percentage changes in HRV measures were compared. After the subjects took ephedra, the normalized low-frequency component (LF) and the ratio of LF to high-frequency component (HF) increased significantly in a dose-dependent manner, whereas the normalized HF (HF%) decreased significantly. We conclude that ingestion of ephedra tilts the sympathovagal balance dose-dependently toward increased sympathetic activity and impairs parasympathetic activity.
Given the popularity of the use of ephedra in traditional Chinese medicine around the world, a greater understanding of its actions is required. This study aims to assess the effects of ephedra on autonomic nervous modulation using power spectral analysis of heart rate variability (HRV).
This was a randomized, double-blind, placebo-controlled, crossover study. Twenty healthy subjects were given 1g of ephedra dry extract or placebo once per day for 14 days in a crossover fashion with a 7-day washout period between treatments. Sequential HRV measures at baseline and at 30, 60, 120, and 180 min after taking ephedra or the placebo on days 1 and 14 were obtained and compared. In addition, the baseline HRV measurements on days 1, 3, 7, 10, and 14 were also obtained and compared.
The normalized low-frequency component (LF%) and the low/high-frequency component ratio (LF/HF) of the HRV were significantly increased, whereas the high-frequency component (HF) and normalized HF (HF%) were significantly decreased at 120 and 180 min after taking ephedra on days 1 and 14. In addition, the baseline LF% and LF/HF were significantly increased, whereas the baseline HF% was significantly decreased on days 10 and 14, as compared to day 1.
By power spectral analysis of the HRV of healthy young adults, it is suggested that ingestion of ephedra dry extract acutely and chronically affects autonomic nervous activity by tilting the sympathovagal balance toward increased sympathetic activity, whereas parasympathetic activity was impaired.