Oxilofrine, 4-[1-hydroxy-2-(methylamino)propyl]phenol, is a stimulant which increases the heart rate and the blood pressure and to improve oxygen exchange. In the USA, it has never been approved as a drug or as a dietary supplement due to severe health risks, such as vomiting and cardiac arrest. However, since 2009, several athletes have been tested positive for oxilofrine and claimed this is only due to the consumption of dietary supplements.

Pieter A Cohen, Harvard Medical School, Boston, USA, and colleagues used ultra-high performance liquid chromatography (UHPLC) coupled with quadrupole time-of-flight mass spectrometry (TOF-MS) to identify and quantify oxilofrine in 27 different brands of dietary supplements sold in the USA and labelled to contain methylsynephrine, a synonum of oxilofrine. They found oxilofrine in over 50 % of the tested supplements. Six of the supplements contained an amount of oxilofrine in pharmaceutically active dosages.

This finding is in contradiction to US law, which regulates dietary supplements and does not allow the addition of pharmaceutical drugs. The team reasons that methylsynephrine may have misled consumers as well as regulators, as synephrine alone is a natural ingredient in citrus species and, hence, a legal supplement. The researchers think it might be possible that other brands of supplements on sale in the USA may also contain oxilofrine without listing methylsynephrine on the label.

• Pharmaceutical doses of the banned stimulant oxilofrine found in dietary supplements sold in the USA,
  Pieter A. Cohen, Bharathi Avula, Bastiaan Venhuis, John C. Travis, Yan-Hong Wang, Ikhlas A. Khan,
  Drug Test. Anal. 2016.
  DOI: 10.1002/dta.1976