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Last updated June 29, 2020. 3 minute read

How much icariin equals Viagra? Is it proven to work?

Both horny goat weed (icariin) and sildenafil (brand name Viagra) work in similar ways: They inhibit phosphodiesterase 5 (PDE5), an enzyme that “turns off” an erection. Icariin is a much milder PDE5 inhibitor than Viagra and other prescription ED medications: It’s about 80 times less potent than Viagra.

Self Written by Michael Martin
Reviewed by Mike Bohl, MD, MPH

Erectile dysfunction (ED) happens when you can’t get or maintain an erection sufficient for satisfying sex. That can include erections that are softer or don’t last as long as you would like, erections that don’t last as long, and less frequent erections.

ED can be distressing, but it’s very common. Experts estimate that more than 30 million American men have experienced ED (Nunes, 2012).

Vitals

  • Icariin (the active ingredient in horny goat weed, or yin yang huo) is an herb used in traditional Chinese medicine.
  • It works similarly to Viagra by blocking the enzyme that tells your body to “turn off” an erection.
  • But icariin is a much milder PDE5 inhibitor than prescription ED medications.
  • Human trials on icariin’s efficacy for ED are lacking.

What is icariin?

Icariin is a traditional Chinese medicinal herb. It’s extracted from the epimedium plant, a wildflower endemic to China.

It’s the active ingredient in horny goat weed (yin yang huo), a supplement that is mainly taken as an aphrodisiac or treatment for ED.

Icariin is available in tablets, capsules, teas, and powders.

Horny goat weed vs. Viagra

Both horny goat weed (icariin) and sildenafil (brand name Viagra) work in similar ways: They inhibit phosphodiesterase 5 (PDE5), an enzyme that “turns off” an erection (Dell’Agli, 2008). 

Icariin is a much milder PDE5 inhibitor than Viagra and other prescription ED medications: It’s about 80 times less potent than Viagra (Dell’Agli, 2008).

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When you get an erection, a natural chemical called cGMP causes the smooth muscle in blood vessels in the penis to relax, allowing those veins to dilate and blood to fill the spongy tissues of the penis. When PDE5 is released, it breaks down cGMP, prompting blood to leave the penis and returning it to its flaccid state. When PDE5 is inhibited, an erection lasts longer (Huang, 2013).

Viagra requires a prescription and is available in different strengths.

Icariin isn’t as potent as Viagra in its natural state. It’s available over-the-counter as horny goat weed or as one ingredient in various supplement formulations.

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So does horny goat weed work? Several animal studies have found that icariin inhibits PDE5 in cavernosal smooth muscle, the kind of tissue that relaxes and allows the penis to fill with blood during an erection. Another study found that horny goat weed seemed to benefit rats who had blood vessel damage, allowing them to synthesize nitric oxide in penile tissue better than a placebo. Read more about horny goat weed and whether it works here.

But a word of caution here: Human trials on horny goat weed and ED haven’t been conducted. Icariin might work differently in the human body than on lab animals.

Other treatments for ED

If you’re experiencing ED, it’s a good idea to consult a healthcare provider and discuss your full medical history. In some cases—such as when ED suddenly happens in young, healthy men—ED can be the sign of a serious health condition, including heart disease, high blood pressure, or diabetes.

A healthcare provider can also prescribe ED medications. These medications—including sildenafil (brand name Viagra), tadalafil (brand name Cialis), and vardenafil (brand name Levitra)—are highly effective.

Some men have found that certain supplements can help with occasional ED. Several are supported by preliminary scientific research, including yohimbe and red ginseng. Read more about natural supplements for ED here.

Your erections will be best when you’re healthy. Making simple lifestyle changes, such as getting regular exercise, eating a healthy diet, quitting smoking, and limiting your alcohol consumption, might be enough to improve ED.