Regarding the cardiovascular effects of an herbal ephedra-caffeine weight loss product.

Abstract

We commend Kalman et al.1 for their study on the cardiovascular effects of an herbal ephedra–caffeine weight loss product, because the occurrence of adverse events associated with ephedra ingestion has not been adequately addressed in the literature. However, to definitively answer research questions regarding the cardiovascular effects of ephedra ingestion, we believe that future studies should incorporate the following suggestions: (1) Assess subjects at more than a single time point. Kalman et al1 compared presupplementation cardiovascular parameters and postsupplementation cardiovascular parameters on different days. Given the large within subject variability in heart rate and blood pressure throughout a typical day, it may be difficult to detect changes based on a single time measurement over a several week period. (2) Determine the time points for cardiovascular assessment based on drug absorption. In one study, the maximal increase in systolic blood pressure (14 mm Hg) occurred 90 min after ephedra ingestion, while the maximum change in heart rate (15 beats min-1) occurred 6 h following ingestion.2 Negative effects of ephedra/ephedrine supplements on blood pressure and heart rate have been reported with higher doses3, 4 and lower doses2 than administered by Kalman et al.1 These discrepancies further demonstrate that timing of dose compared to assessment of cardiovascular function is crucial. (3) Rigorous control over the subject-related factors that are known to influence drug metabolism and disposition (ethnicity, gender, physical activity and fitness level, body size and composition, age, caffeine intake, recent food intake, comedication). For instance, caffeine intake was not reported and appears to have been unregulated in both groups (subjects were allowed to consume up to three cups of coffee or caffeine equivalent per day during the study). (4) An analysis of supplement content. The ephedrine content of Ephedra plants can vary widely,5 resulting in as much as 100% variability in ephedrine content between lots of a given supplement.6 Given the reported poor standardization of ephedra products, it seems prudent to provide an analysis of supplement content.