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Products containing bitter orange (Citrus aurantium) or synephrine are used for their claims of promoting weight loss. However, these products are not authorized by Health Canada for this indication. Synephrine, the main active compound in bitter orange, is claimed to increase metabolism and promote thermogenesis.1 Although their effectiveness remains unclear,1 many products containing bitter orange are being promoted as "Ephedra/ephedrine free," since the use of Ephedra has been restricted in Canada2 and prohibited in dietary supplements in the United States3 owing to adverse cardiovascular and cerebrovascular reactions.
Synephrine, a sympathetic α-adrenergic agonist, is structurally related to ephedrine; thus bitter orange extract may be associated with a spectrum of adverse reactions (ARs) similar to those associated with the use of Ephedra/ephedrine.4 In animals, synephrine use has been associated with dose-related cardiotoxicity, specifically ventricular arrhythmias.5 A case of myocardial infarction in a patient with no history of heart disease has been reported in association with synephrine-containing products.6 Health Canada issued an advisory on a natural health product containing synephrine and other stimulants, cautioning that synephrine may have cardiovascular effects similar to those of ephedrine.4 Synephrine's cardiovascular effects may be increased when...