Combined Effects of Ephedrine-Containing Dietary Supplements, Caffeine, and Nicotine on Morphology and Ultrastructure of Rat Hearts.

Cigarette smokers have an increased risk for coronary artery disease. Nicotine present in cigarettes can adversely affect the cardiovascular system via stimulation of both sympathetic and parasympathetic neurons. Caffeine, another cardiovascular and central nervous system (CNS) stimulant, is commonly found in Ephedra and Ephedra-free dietary supplements. These caffeine-containing supplements also have been linked to cardiovascular toxicities. Although no longer on the U.S market, Ephedra-containing supplements are another source of cardiovascular and CNS stimulants, namely the ephedrine alkaloids. Together caffeine, nicotine, and ephedrine can individually stress the cardiovascular system, and an overlap of these agents is predicted in smokers and dieters. To understand the collective effects of these stimulants on the heart morphology and ultrastructure, rats were exposed to synthetic combinations of nicotine (0.2 mg/kg/day), ephedrine (0-30 mg/kg/day), and/or caffeine (0-24 mg/kg/day) as well as an extract from a caffeine-containing Ephedra supplement (Metabolife 356). After exposure for 3 days, the hearts were removed and examined for hypersensitivity myocarditis and myocardial necrosis. None of the drugs tested alone affected heart tissue morphology, nor were atypical cardiac cells observed. However, in combination, significant interactions were found between caffeine and ephedrine; the interventricular septum was most susceptible, with a significant increase in atypical cardiac cells observed. Nicotine pretreatment caused greater susceptibility to cardiotoxicity associated with combinations of caffeine + ephedrine or Metabolife, particularly in the left ventricle wall. These results indicate that sympathomimetic combinations present in Ephedra supplements may have produced cardiotoxicity reported in consumers of these products. Moreover, the presence of nicotine exacerbates these toxic effects.