Fleshner N et al. (2005) Evidence for contamination of herbal erectile dysfunction products with phosphodiesterase type 5 inhibitors. J Urol 174: 636–641

Fleshner et al have shown evidence that a significant proportion of natural and herbal products marketed for the treatment of erectile dysfunction contain phosphodiesterase type 5 (PDE5) inhibitors such as sildenafil and tadalafil.

The authors purchased seven brands of natural products via the internet and from a local health store, which were marketed for the treatment of erectile dysfunction. Products were chosen that claimed efficacy before sexual activity, and stated that they did not need to be taken on a regular basis. Only oral tablets or capsules were used in this study. Twelve tablets were taken from each of the seven products and tested for contamination with PDE5 inhibitors in a blinded analysis using high-performance liquid chromatography and mass spectrometry.

Of the seven products analyzed, two were contaminated with PDE5 inhibitors. One product contained a mean dose of 30.2 mg sildenafil per tablet and the second contained a mean dose of 19.7 mg tadalafil per tablet. No evidence of vardenafil was detected in any of the samples tested.

The authors emphasize the potentially fatal interactions that PDE5 inhibitors can have with commonly used drugs—for example, nitrates—which may cause effects such as hypotension, shock and even death. Furthermore, these products were marketed as safe and causing no adverse side effects. The authors highlight the need for stricter regulation of the natural health products industry.