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Synephrine Is Not Neo-Synephrine–Reply–II

        Comment from the Editor-in-Chief: The dietary supplement Xenadrine EFX is derived primarily from plant materials.
        • Nasir JM
        • Durning SJ
        • Ferguson M
        • Barold HS
        • Haigney MC
        Exercise-induced syncope associated with QT prolongation and ephedra-free Xenadrine.
        The original formulation of Xenadrine EFX contained extracts of Citrus aurantium (ie, bitter orange), a natural source of the sympathomimetic compound synephrine, and indeed the original formulation of Xenadrine EFX contained synephrine, 3 mg per capsule. Xenadrine EFX has since been reformulated to omit C aurantium. Although Mayo Clinic Proceedings is not prepared to comment on all sympathomimetics that are (or are not) present in the original and revised preparations, the manufacturer has informed the journal that chemical testing of their product by ChromaDex, Inc (Santa Ana, Calif), determined that Xenadrine EFX has never contained phenylephrine (ie, Neo-Synephrine) (S. H. Freedman, representing Nutraquest, Inc, written communication, September 29, 2004, and November 2, 2004).
        Hopefully, this exchange of letters, and the accompanying erratum statement published on page 1591 of the current issue, will clarify any misconceptions concerning phenylephrine content within Xenadrine EFX.

        REFERENCE

          • Nasir JM
          • Durning SJ
          • Ferguson M
          • Barold HS
          • Haigney MC
          Exercise-induced syncope associated with QT prolongation and ephedra-free Xenadrine.
          Mayo Clin Proc. 2004; 79: 1059-1062

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        • Synephrine Is Not Neo-Synephrine
          Mayo Clinic ProceedingsVol. 79Issue 12
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            To the Editor: We read with interest the article by Nasir et al1 in the August 2004 issue of Mayo Clinic Proceedings that describes syncope in a patient taking an ephedra-free dietary supplement containing synephrine. Although we agree with the authors about the risks associated with this preparation, we want to correct an important error in their article. They used the terms synephrine and phenylephrine equivalently. Although both compounds have the chemical formula C9H13NO2, in phenylephrine the hydroxyl group is located on the No.
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