Impotence, or erectile dysfunction, is the inability to achieve an erection. Impotence may occur for any of at least 15 possible causes, including diabetes, drug side effects, pituitary tumors, hardening of the arteries, hormonal imbalances, and psychological factors. A few of these conditions respond to specific treatment. For example, if a blood pressure drug is causing impotence, the best approach is to change drugs. If a pituitary tumor is secreting the hormone prolactin, treating that tumor may result in immediate improvement. However, in most cases, conventional treatment of impotence is nonspecific.

The drugs Viagra and Cialis have revolutionized treatment for erectile dysfunction. These medications work by increasing tissue sensitivity to the blood-vessel-dilating substance nitric oxide (NO) in the penis. Older methods include mechanical devices that utilize a vacuum to produce an erection, drugs for self-injection, and implantation of penile prostheses.


Proposed Treatments for Impotence

Korean Red Ginseng

Two double-blind, placebo-controlled]]> trials, involving a total of about 135 people, have found evidence that Korean red ginseng may improve erectile function. ]]>13,14]]>

In the better of the two trials, 45 participants received either placebo or Korean red ginseng at a dose of 900 mg 3 times daily for 8 weeks. ]]>14]]> After a 1-week period of no treatment, the two groups were switched. The results indicate that while using Korean red ginseng men experienced significantly better sexual function than while they were taking placebo.

In an analysis combining the results of 6 controlled trials, researchers found some evidence for the benefits of Korean red ginseng. However, the small size and generally low quality of the studies left some doubt about this conclusion. ]]>37]]>

For more information, including safety issues, see the full ]]>Ginseng]]> article.


The substance nitric oxide (NO) plays a role in the development of an erection. Dugs like Viagra increase the body's sensitivity to the natural rise in NO that occurs with sexual stimulation. A simpler approach might be to raise NO levels, and one way to accomplish this involves use of the amino acid L-arginine. Oral arginine supplements may increase nitric oxide levels in the penis and elsewhere. Based on this, L-arginine has been advertised as "natural Viagra." However, there is as yet little evidence that it works. Drugs based on raising nitric oxide levels in the penis have not worked out for pharmaceutical developers; the body seems to simply adjust to the higher levels and maintain the same level of response.

The main support for the use of arginine in erectile dysfunction comes from a small double-blind trial in which 50 men with erectile dysfunction received either 5 g of L-arginine or placebo daily for 6 weeks. ]]>2]]> More men in the treated group experienced improvement in sexual performance than in the placebo group.

A double-blind crossover study of 32 men found no benefit with 1,500 mg of arginine given daily for 17 days; ]]>11]]> the much smaller dose and shorter course of treatment may explain the discrepancy between these two trials.

Arginine has also been evaluated in combination with the drug yohimbine (made from the herb ]]>yohimbe]]> ). ]]>15]]> A double-blind, placebo-controlled trial of 45 men found that one-time use of this combination therapy an hour or two prior to intercourse improved erectile function, especially in those with only moderate erectile dysfunction scores. Arginine and yohimbine were both taken at a dose of 6 g.

Note : Do not use the drug yohimbine (or the herb yohimbe) except under physician supervision, as it presents a number of safety risks.

For more information, including dosage and safety issues, see the full ]]>L-arginine]]> article.


In a 6-month, double-blind trial of 120 men, average age 66, carnitine (propionyl-l-carnitine 2 g/day plus acetyl-l-carnitine 2 g/day) and testosterone (testosterone undecanoate 160 mg/day) were separately compared to placebo. ]]>22]]> The results indicated that both carnitine and testosterone improve erectile function; however, while testosterone significantly increased prostate volume, carnitine did not.

Another double-blind, placebo-controlled study found that propionyl-l-carnitine at 2 g/day enhanced the effectiveness of sildenafil (Viagra) in 40 men with diabetes who had previously failed to respond to sildenafil on at least eight occasions. ]]>23]]>

In another double-blind study, a combination of the propionyl and acetyl forms of carnitine enhanced the effectiveness of Viagra in men who suffered from erectile dysfunction caused by prostate surgery. ]]>31]]>

Carnitine has also shown promise for treating male infertility. For more information, including dosage and safety issues, see the full ]]>Carnitine]]> article.

Other Treatments

A proprietary combination therapy containing arginine along with Ginkgo biloba , ginseng, and vitamins and minerals has shown some promise in an unpublished study. ]]>32]]>

In a 3-week, double-blind, placebo-controlled trial, 20 men with erectile dysfunction received either placebo or a special form of ]]>magnet therapy]]> called pulsed electromagnetic field therapy (PEMF). ]]>18]]> PEMF was administered by means of a small box worn near the genital area and kept in place as continuously as possible over the study period; neither participants nor observers knew whether the device was actually activated or not. The results showed that use of PEMF significantly improved sexual function compared to placebo.

A double-blind, placebo-controlled study enrolled 40 men with difficulty achieving or maintaining an erection who also had low measured levels of ]]>dehydroepiandrosterone (DHEA)]]> . ]]>1]]> The results showed that DHEA at a dose of 50 mg daily improved sexual performance; however, the authors failed to provide a statistical analysis of the results, making the meaningfulness of this study impossible to determine.

Severe ]]>zinc]]> deficiency is known to negatively affect sexual function. Since marginal zinc deficiency is relatively common, it is logical to suppose that supplementation with zinc may be helpful for some men. However, this hypothesis has only been studied in men receiving kidney dialysis. ]]>16,17]]> The results were promising.

The herb Butea superba has shown some promise for erectile dysfunction, according to a 3-month randomized, double-blind study performed in Thailand. ]]>24]]>

Weak evidence hints at potential benefit with pomegranate juice, ]]>36]]>]]>melatonin]]> , ]]>9]]> and ]]>oligomeric proanthocyanidin complexes (OPCs)]]> (alone or in combination with ]]>arginine]]> ). ]]>25,26]]>

Based on exceedingly preliminary evidence, the herb ]]>maca]]> ( ]]>Lepidium meyenii]]> ) has been advertised as "herbal Viagra." In one study in rats, use of maca enhanced male sexual function. ]]>33]]> There is one published human trial as well. In this small, 12-week, ]]>double-blind, placebo-controlled]]> study, use of maca at 1,500 mg or 3,000 mg increased male libido. ]]>34]]> While this was an interesting finding, the study did not report benefits in male sexual function—just in desire. Since loss of sexual function is a more common problem in men than loss of sexual desire, these results do not justify the herbal Viagra claim. Contrary to some reports, maca does not appear to affect testosterone levels. ]]>19]]>

Many other herbs are also reputed to improve sexual function in men , including ]]>ashwagandha]]> , ]]>Avena sativa]]> (oat straw), catuaba, ]]>cordyceps]]> , ]]>damiana]]>]]>diindolylmethane]]> (DIM), ]]>eleutherococcus]]> (so-called “Siberian ginseng”), ]]>L-citrulline]]> , Macuna pruriens , ]]>molybdenum]]> , ]]>muira puama]]> (potency wood), ]]>pygeum]]> , Polypodium vulgare , ]]>Rhodiola rosea]]> , ]]>saw palmetto]]> , ]]>schisandra]]> , ]]>suma]]> , ]]>traditional Chinese herbal medicine]]> , and ]]>Tribulus terrestris]]> . However, there is as yet no real evidence that they offer any benefits.

Numerous case reports and uncontrolled studies had indicated that the herb ]]>Ginkgo biloba]]> offers dramatic benefits for male (and female) sexual problems caused by antidepressants. ]]>3-8]]> However, as always, double-blind, placebo-controlled studies are necessary to truly establish efficacy. (For the reasons why, see ]]>Why Does This Database Rely on Double-blind Studies?]]> ) When studies of this type were performed, it became clear that people had been misled about ginkgo’s efficacy by the power of suggestion: ginkgo failed to improve sexual function to any greater extent than placebo. ]]>20,27]]>

In a small single-blind study, ]]>acupuncture]]> proved superior to fake acupuncture for treatment of erectile dysfunction. ]]>28]]> However, because the treating practitioners administrating the control treatment were aware that they were providing sham acupuncture, it is quite likely that they unconsciously communicated lack of confidence as they provided it; this is an inherent limitation of ]]>single-blind studies]]> .

Deer or antelope ]]>velvet antler]]> is a popular treatment for sexual dysfunction. However, the one double-blind study performed on the subject failed to find benefit. ]]>29]]>

Herbs and Supplements to Use Only With Caution

The US Food and Drug Administration (FDA) warned consumers not to purchase or consume a several brands of dietary supplements after samples were found adulterated with the prescription drug tadalafil (Cialis), an analogue of sildenafil (Viagra). The products named in the warning are SIGRA, STAMINA Rx, STAMINA Rx for Women, Y-Y, Spontane ES, and Uroprin (all manufactured by NVE, Inc., and distributed by Hi-Tech). For more information, see the FDA's Public Health Advisory on this subject.

The herb ]]>yohimbe]]> is the source of the drug yohimbine, which has been shown to be modestly better than placebo for impotence. However, due to many drug interactions and other risks, we do not recommend using yohimbine except under the supervision of a physician. Because there is no agency regulating herbal product quality and labeling, the herb yohimbe presents even more risks, such as unpredictable yohimbine content.

]]>Soy]]> or ]]>soy isoflavones]]> , ]]>21]]> as well as the herb ]]>licorice]]> , ]]>10]]> may reduce testosterone levels in men. For this reason, men with impotence, ]]>infertility]]> , or decreased libido may want to avoid these natural products.

One report claims that both ]]>tea tree oil]]> and lavender oil have estrogenic (estrogen-like) and antiandrogenic (testosterone-blocking) effects. ]]>35]]> If this were true, men with erectile dysfunction would be advised to avoid use of these herbs. However, a literature search failed to find any other published reports that corroborate this claim.

One case report suggests that a product containing the herb ]]>Epimedium grandiflorum]]> (horny goat weed) caused rapid heart rate and symptoms similar to mania. ]]>30]]>

The supplement ]]>androstenedione]]> , often taken for male sexual dysfunction in the belief that it increases testosterone levels, actually appears to increase estrogen levels in men, and might therefore increase problems with erectile function.