To the Editor:
I am writing with respect to the case report by Thomas and colleagues,1 published in the Texas Heart Institute Journal, regarding ST-segment-elevation myocardial infarction (STEMI) in a young man who was taking the supplement Nutrex Lipo-6x®. I am not defending the product. The patient most assuredly experienced a cardiovascular event, which may or may not have been associated with the use of the supplement.
Nutrex Lipo-6x contains at least 7 alkaloids. Contrary to the discussion in the original article, one cannot, on the basis of standard structure-to-activity relationships, equate the pharmacokinetic and pharmacodynamic properties of p-synephrine with ephedrine, due to the major structural differences clearly pointed out by the authors. As a result of these stereochemical differences, p-synephrine exhibits little α-adrenergic receptor binding activity and has correspondingly limited cardiovascular effects. Therefore, it is impossible to conclude that one of these alkaloids, namely p-synephrine, was responsible for the event or was “the most likely culprit.”
Of note, widely consumed juice from mandarin oranges grown in Placer County, California, contains as much as 158 mg p-synephrine per liter (U.S. Department of Agriculture). An 8-oz glass of this juice contains about twice the amount of synephrine as a serving of the product in question. Furthermore, more than 100 million doses of p-synephrine have been consumed without apparent ill effects. Thus, the margin of safety of p-synephrine greatly exceeds that of aspirin and acetaminophen, as well as all prescription weight-management drugs.
Rather than point an accusatory finger at synephrine in their title, the authors should have referred to a “multi-alkaloid-containing supplement.” The other case reports cited by the authors also involved such products, and, as pointed out by the authors, there were confounding factors in conjunction with these reports. As a consequence, I contend that any assertion or suggestion that these effects are due to or associated with p-synephrine or Citrus aurantium is not justified.2
Sidney J. Stohs, PhD, FACN, CNS
Dean Emeritus, Creighton University Medical Center, Omaha, Nebraska
References
- 1.Thomas JE, Munir JA, McIntyre PZ, Ferguson MA. STEMI in a 24-year-old man after use of a synephrine-containing dietary supplement: a case report and review of the literature. Tex Heart Inst J 2009;36(6):586–90. [PMC free article] [PubMed]
- 2.Stohs SJ, Shara M. A review of the safety and efficacy of Citrus aurantium in weight management. In: Bagchi D, Preuss HG, editors. Obesity: epidemiology, pathophysiology, and prevention. Boca Raton (FL): CRC Press; 2007. p. 371–82.