sentences:  Herbal viagras, contrary to what the name suggests, do not normally contain sildenafil citrate.However, sildenafil and chemicals similar to sildenafil have been found as adulterants in many supplements which are sold as herbal viagra or "natural" sexual enhancement products.The United States Food and Drug Administration has warned consumers that any sexual enhancement product that claims to work as well as prescription products is likely to contain such a contaminant.