The determination of unapproved drugs in New Zealand dietary supplements using validated chromatographic methods

Abstract

In line with the increasing popularity of dietary supplements, adulteration of these products is becoming more common globally. In this study, validated LC and GC methods were used to test 68 dietary supplements found in the New Zealand online marketplace, spanning products advertised for sexual enhancement and weight loss. Of the sexual enhancement supplements, 11% of those tested contained an unapproved substance that was not listed on the product label, with the erectile dysfunction drug tadalafil and the prescription medicine yohimbine detected in these samples. For the product that contained tadalafil, a consumer taking the listed maximum serving size would consume more than double the maximum daily recommended dose for tadalafil (>40 mg). While no unapproved substances were detected in weight loss supplements, high caffeine levels were observed, with two weight loss supplements having listed maximum daily serving sizes that corresponded to greater than 400 mg caffeine. Caffeine was also detected in one sexual enhancement product that did not list caffeine or tea extract on its label. While these results represent a subset of the dietary supplements available, the observation of high-risk products indicates that stricter regulations may be warranted to protect consumers from unknowingly ingesting prescription medicine.