A range of designer analogs of licensed PDE5 inhibitors such as sildenafil and vardenafil have been detected in recent years in over-the-counter herbal aphrodisiac products, in an apparent attempt to circumvent both the legal restrictions on sale of erectile dysfunction drugs, which are prescription-only medicines in most Western countries, and the patent protection which allows sale of these drugs by competitors only with permission from the patent holders (typically, under a license from the inventors) and to introduce efficacy into otherwise ineffective herbal products. These compounds have been demonstrated to display PDE5 inhibitory activity in vitro and presumably have similar effects when consumed, but have undergone no formal testing in either humans or animals, and as such may represent significant health risks to consumers of these products due to their unknown safety profile. Some attempts have been made to ban these drugs as unlicensed medicines, but progress has been slow so far, as even in those jurisdictions which have laws targeting designer drugs, the laws are drafted to ban analogs of illegal drugs of abuse, rather than analogs of prescription medicines. However, at least one court case has resulted in a product being taken off the market.
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