(HealthDay News) — Supplement users may be unaware of the presence of pharmacologically active substances in supplements, including tamoxifen that has been identified in samples of the dietary supplement Esto Suppress, according to a letter published online February 13 in BMJ.

Noting that the Esto Suppress label contains one of the chemical names of tamoxifen, Michael Evans-Brown, PhD, from the European Monitoring Centre for Drugs and Drug Addiction in Portugal, and colleagues analyzed four samples of Esto Suppress purchased at different times between late 2011 and early 2012. Samples were assessed using reference standards and gas chromatography coupled with flame ionization and mass spectrometry detectors.

The researchers identified tamoxifen in samples one (3.8mg), two (0.9mg), and three (3.0mg), but not in sample four. In the case of sample one the suggested dosage of two capsules a day may have provided 7.6mg of tamoxifen, with 10–20 mg used clinically for treating gynecomastia. The researchers write that it is unknown whether currently marketed Esto Suppress contains tamoxifen.

“Since the 2000s, a growing number of off-the-shelf ‘food,’ ‘herbal,’ or ‘dietary’ ‘supplements’ — aimed at gym goers and people wanting to lose weight or enhance their sex lives — have contained pharmacologically active substances,” the authors write. “Most users will be unaware that they are taking these substances. Health care professionals should ask their patients about their use of ‘supplements’ and report suspected adverse reactions.”

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