Australian men are being warned not to take an illegal pill which online retailers claim increases semen production, fertility and orgasm intensity.
The nation's drug regulator has issued an alert about "Semenax" capsules, warning they contain an undeclared substance.
The semenaxdirect.com website declares the medication can increase ejaculation during sex, by creating more "seminal fluid".
"This is attractive not only from a visual standpoint, it is subconsciously attractive on a biological level," the website says.
A testimonial from a man named Stephen describes his semen volume tripling "in just five weeks" while the website also claims many women desire a "strong ejaculation".
But the Therapeutic Goods Administration (TGA) say the unregistered drug poses a serious risk to people's health.
They have been tested and found to contain Yohimbine, a prescription-only substance prohibited from being imported into Australia.
Yohimbine is sometimes used on dogs to reverse the effects of sedatives and has been linked to erectile dysfunction treatments not approved in Australia.
The TGA says its investigations revealed a number of Australians may have ordered the capsules online, and have urged consumers to exercise extreme caution when buying medicines from unknown, overseas-based websites.
It is stepping up monitoring of imports.
"The TGA is working with the Australian Border Force to help stop future shipments of Semenax capsules from entering Australia," a statement said.
"If these capsules are found at the border ... they will be seized and destroyed."
People who have bought the drug are urged to take any remaining product to their local pharmacy for disposal, and consult their doctor if they have any concerns.
Professor Rob McLachlan from the Hudson Institute of Medical Research and Andrology Australia condemned the website and described the illegal pill as "manipulative, exploitative and completely unsubstantiated by any medical evidence".
"Men can feel embarrassed or uncomfortable when it comes to matters of andrology so they will seek out the anonymity and immediacy of purchasing online drugs to try and fix it themselves," he said.
"But it's an incredibly dangerous space because you don't know what you are getting and anyone who takes these substances is risking their life.
"The people behind these dangerous drugs run unrecognised organisations, they often making outrageous claims that are just scientifically impossible."
He said vulnerable men had fallen victims to similar dangerous substances masked as impotence drugs or artificial Viagra in recent years.
In 2009, an erectile-dysfunction drug contained the diabetes drug glyburide which lead to hypoglycemia in almost 150 men in Hong Kong and Singapore.
Seven Singaporean patients remained in a coma because of prolonged sugar starvation of the brain, four of whom later died.
"The message to men is to please go and see your local GP or andrology expert if you are having sexual reproductive issues.
"They are trained and more than willing to provide safe and effective advice," he said.
A request for comment sent to the retailers of Semenax was not immediately responded to.