Sexual enhancers reviewed by consumerlab.com: Reprinted with their permission; Product Review: Sexual Enhancement Supplements (L-Arginine, Yohimbe, Horny Goat Weed) Initial Posting: 1/11/06 Background: Sexual Dysfunction and Current Drug Therapies Sexual dysfunction is estimated to affect 43% of women and 31% of men in the U.S. For women, sexual dysfunction consists primarily of loss of libido (sexual drive) and inability (or great difficulty) in achieving an orgasm. For men, sexual dysfunction primarily takes the form of impotence, known technically as erectile dysfunction. (Premature ejaculation is another problem; it is sometimes treated with antidepressants.) In both men and women, sexual stimulation causes activity in the nervous system which, in turn, causes local release of nitric oxide in the genitals, stimulating a substance called cGMP that increases blood flow causing sexual arousal — an erection in men and clitoral enlargement in women. The biochemical steps that lead to orgasm, however, are poorly understood. Viagra and similar drugs block the breakdown of cGMP in the penis specifically. The net effect is to increase cGMP's effect in the penis, producing a more lasting and possibly more complete erection than would otherwise occur. Viagra was the first markedly successful drug treatment for erectile dysfunction, but it and similar drugs like Cialis and Levitra have limitations. They are expensive — costing as much as $10 per pill — and often not covered by medical insurance. They are not to be used by men taking medicines that contain nitrates — such as nitroglycerin — because they may cause blood pressure levels to drop significantly. And they can cause mild to moderate side effects such as headache and visual disturbances, and, in rare instances, men have reported erections that lasts many hours, which can potentially cause damage to the penis. Heart attack, stroke, irregular heart beats, and death have also been reported rarely in men taking Viagra, although it is not possible to determine whether these events were directly related to Viagra. At present, there are no impressively successful prescription drug treatments for female sexual dysfunction. The Evidence for Supplements: Many supplements have been promoted and used to improve sexual function. These products contain a wide array of herbal and other ingredients. It is easy to see from the summary below that there is not good clinical evidence to support the use of most of these ingredients. This does not necessarily mean that they are not effective, but statistically significant improvements have not been documented. Clinical studies could also help determine the appropriate dose and identify possible safety concerns. Be aware, that supplements often combine more than one of these ingredients in a product. Unless they have been clinically studied, it is hard to judge what the combined effect will be. The evidence below focuses on improvements in sexual function. There are also numerous products sold, particularly on the web, for the purpose of penile enlargement, often accompanied by enthusiastic testimonials. A review of the literature failed to find any such support for penile enlargement products. Many of the "penis enlargement" products claim the same ingredients found in products for treating erectile dysfunction. At best, these products will only help with an erection — a temporary increase penis size. It should also be noted that some natural products may decrease libido. Soy isoflavones and licorice may lower testosterone in men, and the supplement androstenedione may raise estrogen levels in men without raising testosterone; either of these effects could lead to reduced libido in men. Ingredients with moderate clinical evidence for sexual enhancement: Arginine: One of the more popular supplement ingredients for sexual dysfunction is L-arginine, also referred to as arginine. Arginine is required to carry out the synthesis of nitric oxide, a compound that, working through cGMP, relaxes blood vessels and allows more blood to flow through arteries. It has been hypothesized that taking extra arginine will increase nitric oxide levels and in turn increase blood flow to the penis. However, in some pharmaceutical studies leading up to the creation of Viagra, drugs that increased the levels of nitric oxide in the penis were not found to be effective; rather, it was found necessary to increase sensitivity to the rise of nitric oxide. The body may simply accommodate to higher background levels of nitric oxide. Nonetheless, arginine might offer modest benefit for sexual dysfunction in men. A double-blind, placebo controlled trial of 50 men with erectile dysfunction tested arginine at a dose of 5,000 mg per day for six weeks. Only about a third of the participants who received arginine showed improvement, but that was significantly greater than in the placebo group where 10% showed improvement. Studies in animals provide some evidence for effectiveness as well, though there have been negative human and animal trials. Although arginine alone has not been studied as a treatment for sexual dysfunction in women, a reasonably good preliminary double-blind trial found evidence for benefit with a combination treatment (ArginMax for Women) providing a daily dose of 2,500 mg of L-arginine, as well as amounts of Panax ginseng, Ginkgo biloba extract, damiana, plus numerous vitamins and minerals. In a four-week, double-blind study, 77 women with decreased libido were given either the combination product (ArginMax) or placebo. As expected, a high percentage of participants taking placebo showed improvement. However, participants taking the product showed statistically greater improvement such as increased reported sexual desire level in 71% of participants given the treatment vs. 42% in the placebo group. Other improvements noted included: relative satisfaction with sex life (74% vs. 37%), improved frequency of orgasms (47% vs. 30%), and improved clitoral sensation (53% vs. 35%). No significant side effects were seen in either group. There have been other studies of arginine for sexual dysfunction in women, but because they were not double-blind, placebo-controlled trials, they are of little scientific value. Yohimbe: Yohimbe is made from the bark of the Pausinystalia johimbe tree found in Africa. Among its chemical constituents, it contains the chemical, yohimbine, which is an FDA-approved drug that is marginally effective for male erectile dysfunction. Yohimbine is believed to act through the nervous system to increase blood flow to the penis. Most clinical studies have been conducted with yohimbine rather than yohimbe bark or bark extract. In the pharmaceutical market, Viagra and related drugs have almost entirely superceded yohimbine for reasons of safety and effectiveness. (See Concerns and Cautions). Yohimbe is sometimes promoted as enhancing libido and acting as an aphrodisiac. The compound yohimbine itself is not know to have this effect. While it is possible that other compounds in yohimbe bark may have this or other effects, this has not been studied. Ginseng (see ConsumerLab.com's Ginseng Product Review for additional information). The herb Panax ginseng has a traditional reputation for enhancing sexual function in men. Two studies enrolling a total of 135 men support this use for a particular form of ginseng: the steamed and heat-dried product called red ginseng. One of these was a three month double-blind, placebo-controlled study that evaluated the effects of Korean red ginseng in 90 men with erectile dysfunction. Participants received either red ginseng at a dose of 1,800 mg daily, the drug trazodone (an antidepressant with marginal effects on erectile dysfunction) or placebo. The results indicated that red ginseng improved erectile function compared to placebo. Contrary to some reports, ginseng does not appear to affect estrogen or testosterone levels, or mimic their effects. Carnitine: The supplement carnitine, in various forms (propionyl-L-carnitine, acetyl-l-carnitine) has shown growing promise as a treatment for male sexual dysfunction and also male infertility. In one study, a 6-month, double-blind trial of 120 men, use of carnitine as propionyl-l-carnitine 2 g/day plus acetyl-l-carnitine 2 g/day proved more effective than placebo for improving erectile function. In two other double-blind studies, carnitine enhanced the effectiveness of Viagra. Acetly-l-carnitine supplements also have also been used for memory enhancement and several have been tested by ConsumerLab.com — see the Product Review of Memory Enhancement Supplements. A separate Review is planned for supplements made with L-carnitine (a slightly different form than propionyl-L-carnitine and acetyl-l-carnitine). Ingredients with preliminary clinical evidence for sexual enhancement: DHEA (dehydroepiandosterone) is a hormone naturally produced by the adrenal gland. It is converted in the body to both the female hormone estrogen and the male hormone testosterone. Preliminary research has suggested that it may help improve sexual function and libido in women over seventy. Some evidence hints that DHEA may be helpful for male sexual function as well. (See ConsumerTips for How to Use and Concerns and Cautions for DHEA). DHEA has other potential uses, including the treatment of lupus. ConsumerLab.com has conducted a separate Product Review of DHEA Supplements, including a listing of quality approved products. Maca (Lepidium meyenii) The herb maca is widely sold as an aphrodisiac. In one small double-blind, placebo-controlled study, use of maca at 1.5 or 3 grams daily enhanced male interest in sex (effects on erectile function were not studied.) Ephedra The herb ephedra contains the drug ephedrine, and is frequently standardized to ephedrine content. Although the herb ephedra has not been tested for treating sexual dysfunction, one study tested the effects of ephedrine on sexual function in 20 women without sexual problems. This double blind trial of 20 sexually functional women found increases in sexual arousability with a one-time dosage of ephedrine (50 mg), as measured by physical responses to an erotic film. However there are many reports of serious cardiovascular effects with ephedra, and, due to safety concerns, it cannot be legally sold according to the FDA. Epimedium (Horny goat weed or Epimedium grandiflorum) in combination with maca, dopa bean (Mucuna pruriens or velvet bean) and polypody (Polypodium vulgare) The herbs in this popular combination formulation each have a reputation for male sexual enhancement. While there is little meaningful supporting evidence for any one of them individually (except maca, as described above), one unpublished trial provides some supporting evidence for the combination. The first part of the study was not double-blind, however, and therefore indicate nothing about the effect of the treatment. However, after that portion of the study was completed, 13 men who had reported enhanced sexual function from the combination were randomly assigned to receive either herb (808 mg twice daily) or a placebo for a period of 15 days. The results showed that 6 out of 7 men given the active treatment experienced a continuation of the improvement in sexual function, while none of the men given placebo did so. However, no statistical analysis was performed. Nonetheless, the apparently positive results of this trial indicate that the combination therapy should be investigated further. None of the herbs in this combination have undergone comprehensive safety testing (see Concerns and Cautions). Butea superba According to a small double-blind study performed in Thailand, the herb Butea superba may enhance erectile function. OPCs OPCs (oligomeric proanthocyanidins), substances found in grape seed and pine bark, have shown some promise for erectile dysfunction in preliminary trials. Vitamin C (see ConsumerLab.com's Vitamin C Product Review for additional information). One double-blind study suggests that vitamin C at a high dose of 3 grams daily might increase female libido. Ingredients with little or no clinical evidence for sexual enhancement: Both men and women with sexual dysfunction show considerable response to placebo treatment. For that reason, studies that do not involve a placebo group mean little; improvement would be expected even if the treatment had no specific effect. A number of treatments are marketed for sexual dysfunction based solely on such inadequate studies. We briefly describe them here. Some of these ingredients may have other, better-studied, applications that are discussed in more detail in Product Reviews (indicated below) in which products have been tested. Ginkgo (see CL's Product Review of Ginkgo Biloba for more information) Case reports and open trials had suggested that Ginkgo biloba may be an effective treatment for antidepressant-induced sexual dysfunction in both men and women. However, the two properly designed double-blind studies on the subject failed to find ginkgo more effective than placebo. St. John's Wort (see CL's Product Review of St. John's Wort, for more information) An uncontrolled study found that use of the herb St. John's wort improved sexual function in post-menopausal women; these are essentially meaningless results, however, as placebo can also be expected to improve sexual function. Deer Velvet Antler One study failed to find deer velvet antler more effective than placebo for enhancing male sexual function. Miscellaneous Ingredients: The herb Tribulus terrestris (tribulus) is said to increase DHEA levels, so it has been proposed as a treatment for sexual dysfunction. However, one well designed study of tribulus failed to find that it affected sex hormones in young men, and there is no positive evidence that it affects human sexual function. Other proposed herbs and supplements for sexual dysfunction in men or women that lack meaningful clinical evidence for efficacy include Eurycoma longifolia, Pimpinella pruacen, Muira puama and damiana, saw palmetto (see CL's Product Review of Saw Palmetto for more information), codonopsis, schizandra, royal jelly, Pygeum africanus, catuaba bark, chuchuhuasi bark, abuta, androstenedione, ashwaghanda, zinc (see CL's Product Review of Zinc), lipoic acid (see CL's Product Review of Alpha-Lipoic Acid), gamma-linolenic acid (see CL's Product Review of GLA and other oils for more information) and many others. Based on their popularity and the clinical evidence supporting their potential benefits and risks in sexual dysfunction, ConsumerLab.com focused its testing on products containing one or more of the following ingredients: L-arginine, yohimbe, and epimedium (horny goat weed). As noted, products containing some of the other ingredients of potential use (ginseng, acetyl-L-carnitine, DHEA, and vitamin C) have been tested in other Reviews on this site. Quality Concerns and What CL Tested for: Neither the FDA nor any other federal or state agency routinely tests supplements for quality prior to sale. In order to help consumers identify products of better quality, ConsumerLab.com tested sexual enhancement products containing L-arginine, yohimbe, and/or epimedium (horny goat weed) for the parameters discussed below. See Testing Methods for more details. Claimed Ingredient: To be of the highest quality, herbal products must be made from the correct plants and plant parts — otherwise you may not be getting what you expect. To be sure of their identity, they are often expected to contain defined amounts of specific plant compounds. Products were tested to determine if one or more key ingredients matched what was listed on the label in terms of ingredient identity and amount. Unlisted Ingredients: Another concern, particularly among sexual enhancement products, is that they not be "spiked" with ingredients not listed on their labels, such as pharmaceutical agents. It has been reported, for example, that a large number of "herbal" products for erectile dysfunction sold in China (as well as one product sold in Canada) have illegally contained the synthetic compound sildenafil citrate that is the active ingredient in Viagra. All products were screened to determine whether the active compounds from Viagra, Levitra, and Cialis, or related constituents, had been illegally added. Lead Contamination: Lead is a potential contaminant in natural products. In children, infants, and fetuses, even low levels of lead can adversely affect neurobehavioral development and cognitive function. In adults, lead at somewhat higher levels can cause elevated blood pressure, anemia, and adversely affect the nervous and reproductive systems. Lead is of particular concern during pregnancy as the mother can transfer it to the fetus. All yohimbe and horny goat weed products were tested for lead. Tablet Disintegration: All supplements sold as tablets were tested for their ability to break apart — as this is necessary for them to release their contents in the body. What CL Found Among the eleven products that ConsumerLab.com selected for testing, only six passed testing. Problems identified are noted below by type of ingredient. Arginine: All three of the products tested for L-arginine passed testing. Yohimbe: Of four products tested for yohimbe's active compound yohimbine, all but one contained the expected amount. Natrol™ Yohimbe Bark 500 mg only contained 54% of the minimum expected amount of yohimbine. Unlike most other yohimbe products, this product did not state an amount of yohimbine to be found. However, yohimbe bark is generally expected to contain at least 0.2% yohimbine. Based on the amount found, only 0.1% of the ingredient was yohimbine, suggesting that it was either made with low quality material or with less ingredient than claimed. Even in its maximum recommended serving, this product provided about 1.5 mg of yohimbine per day, a fairly small amount. One of the products that passed testing, Libido-Max, also provided a fairly low daily dose of yohimbine — although it was in proper proportion to the amount of yohimbe. The low dose may have been chosen because of possible synergistic effects with other ingredients in this combination product — but this does not appear to be scientifically established. Epimedium (Horny goat weed): None of the four products tested for their Horny Goat Weed content passed testing. To pass testing, products were expected to contain no more than 0.5 mcg of lead in a daily serving — the limit set by the State of California for supplements to be sold without a lead warning. Two products exceeded this limit. Products were also expected to contain specific amounts of the compound icariin — a component of Horny Goat Weed. Three products (including one contaminated with lead) fell short of their icariin levels — suggesting that they either contained less ingredient than promised or were made with low quality material. The following products failed testing: Pinnacle Horny Goat Weed only contained 31% of the amount of icariin claimed per capsule. Dymatize® Nutrition Excite™ Male Performance, had 0.95-2.86 mcg lead in its suggested daily dose of one to three capsules per day. It also had only 76% of its claimed amount of icariin. Planetary Formulas® Full Spectrum™ Horny Goat Weed, had 2.98 mcg lead in its suggested daily dose of two tablets. Source Naturals® Male Response™, only contained 52% of the amount of icariin claimed per tablet. Test Results by Product: Listed below are the test results for thirteen different products containing one or more ingredients used as sexual enhancers. Products are shown alphabetically within the category of ingredient for which they were tested. Each product was tested for one key ingredient. ConsumerLab.com selected eleven products. Two other products (each indicated with an asterisk) were tested at the request of their manufacturers/distributors through CL's Voluntary Certification Program and are included for having passed testing. Also noted is a product sold that is the same as one that passed but sold under a different brand name. Also shown are the claimed amount and form of the tested ingredient(s) and serving sizes recommended on labels. Products listed as "Approved" met their label claims and ConsumerLab.com's quality criteria (see Passing Score). The full list of ingredients is available for each product by clicking on the word "Ingredients" in the first column. CONSUMERLAB.COM RESULTS FOR SUPPLEMENTS USED FOR SEXUAL ENHANCEMENT (L-ARGININE, YOHIMBE, AND HORNY GOAT WEED) Tested for L-Arginine Name of Product and Labeled Amount of L-Arginine per Unit Manufac- turer or Distri- butor Daily Amount of L-arginine (mg) Test Results: (See Passing Score for More Information. Explanation gives primary reason for not achieving Passing Score.) APPROVAL STATUS: APPROVED (Passed) or NOT APPROVED (Failed) Contained Labeled Amount of Key Ingredi- ent(s) Broke Apart Properly (NA = Not Applic- able) ArginMax® for Women, 416.7 mg per tablet, 6 per day Ingredients Dist. by The Daily Wellness Company® 2500 mg APPROVED1 Nature's Harmony L-Arginine, 500 mg per capsule, 3 per day Ingredients Dist. by Purity Life Health Products Ltd. 1500 mg APPROVED2 NA PL® L-Arginine, Hypoallergenic, 500 mg, 500 mg per capsule, 1 per day (marketed for cardiovascular function) Ingredients Mfd. by Progressive Laboratories, Inc. 500 mg APPROVED2 NA Tested for Yohimbe Name of Product and Labeled Amount of Yohimbe Bark per Unit (Click on "Ingredients" for Full Listing) Manufac- turer or Distri- butor Daily Amount of Yohimbe Bark or Extract (mg) Daily Amount of Yohimbine Claimed (C) (or Minimum Expected (E) if Not Claimed) mg Test Results: (See Passing Score for More Information. Explanation gives primary reason for not achieving Passing Score.) APPROVAL STATUS: APPROVED (Passed) or NOT APPROVED (Failed) Contained Labeled Amount of Key Ingredi- ent(s) Broke Apart Properly (NA = Not Applic- able) Libido-Max™, 33.75 mg yohimbe bark (0.5% yohimbine) per softgel, 4 per day Ingredients Dist. by Applied Nutrition 135 mg yohimbe bark 0.675 mg (C) yohimbine APPROVED1,2 But very low dose of yohimbe and other ingredients NA Natrol™ Yohimbe 500 mg, (500 mg yohimbe bark) per capsule, 1-3 per day Ingredients Mfd. by Natrol Inc. 500-1500 mg bark 0.95 mg - 2.85 mg (E) yohimbine NOT APPROVED2 Only found 54% of minimum expected yohimbine (1.54 mg in maximum daily dose) NA Nature's Bounty® Power V, 125 mg yohimbe extract (2% yohimbine) per tablet, 2 per day* Ingredients Mfd. by Nature's Bounty, Inc. 250 mg extract 5 mg (C) yohimbine APPROVED1,2 TwinLab® Yohimbe Fuel®, 400 mg yohimbe extract (standardized to 8 mg yohimbine alkaloids) per capsule, 2 per day Ingredients Dist. by Twin Laboratories Inc. 800 mg extract 16 mg (C) yohimbine alkaloids APPROVED NA Ultimate Nutrition® Yohimbe Bark Extract, 800 mg yohimbe extract (1% yohimbine) per tablet, 1 per day Ingredients Dist. by Ultimate Nutrition, Inc. 800 mg extract 8 mg (C) yohimbine APPROVED2 Tested for Epimedium (Horny Goat Weed) Name of Product and Labeled Amount of Horny Goat Weed per Unit (Click on "Ingredients" for Full Listing) Manufac- turer or Distri- butor Daily Amount of Horny Goat Weed (mg) Daily Amount of Icariin Claimed (C) (or Minimum Expected (E) if Not Claimed) mg Test Results (Based on Product's Suggested Daily Serving) APPROVAL STATUS: APPROVED (Passed) or NOT APPROVED (Failed) Contained Labeled Amount of Key Ingredi- ent(s) Purity = Low Level of Lead Broke Apart Properly (NA = Not Applic- able) Dymatize® Nutrition Excite™ Male Performance, 250 mg (10% icariin) per capsule, 2-4 per day Ingredients Dist. by Dymatize Enterprises Inc. 500 - 1000 mg 50 - 100 mg (C) icariin NOT APPROVED1 Found only 76% of claimed icariin Lead Contami- nation: 0.95-2.86 mcg of lead per daily serving NA Pinnacle Horny Goat Weed, 250 mg (10% icariin) per capsule, 4 per day Ingredients Dist. by Bodyonics, Ltd. 1000 mg 100 mg (C) icariin NOT APPROVED1 Found only 31% of claimed icariin NA Planetary Formulas® Full Spectrum™ Horny Goat Weed, 500 mg extract (10% flavonoids as icariin) and 100 mg whole leaf per tablet, 2 per day Ingredients Dist. by Planetary Formulas 1000 mg extract and 200 mg whole leaf 100 mg as flavonoids(C) (at least 6 mg icariin expected). NOT APPROVED Found 60%of flavonoids to be icariin Lead Contami- nation: 2.98 mcg of lead per daily serving Puritan's Pride® Horny Goat Weed with Maca, For Men, 250 mg (10% icariin) per capsule, 4 per day* Ingredients Dist. by Puritan's Pride, Inc. 1000 mg 100 mg (C) icariin APPROVED1 NA Source Naturals® Male Response, 100 mg horny goat weed extract (10% icariin) per tablet, 3 - 5 per day Ingredients Dist. by SourceNaturals, Inc. 300 - 500 mg Horny Goat Weed 30-50 mg (C) icariin NOT APPROVED1 Found only 52% of claimed icariin Similar to APPROVED Product:** Vitamin World® Horny Goat Weed with Maca, 250 mg (10% icariin) per capsule, 4 per day Ingredients Mfd. by Vitamin World, Inc. 1000 mg 100 mg (C) icariin Similar to Puritan's Pride Horny Goat Weed with Maca *Tested through CL's Voluntary Certification Program prior to, at time of, or after the posting of this Product Review. **Each product identical in formulation and manufacture to a product that has passed testing but sold under a different brand. For more information see CL's Multi-Label Testing Program. 1 Contains multiple sexual enhancement ingredients. Click on "Ingredients" in first column for list of all ingredients. Other ingredients not tested. 2 Suggested daily serving provides less of the tested ingredient than generally recommended when used as a single agent for sexual enhancement. In products with multiple ingredients, possible synergistic effects may account for lower dose. Unless otherwise noted, information about the products listed above is based on the samples purchased by ConsumerLab.com (CL) for this Product Review. Manufacturers may change ingredients and label information at any time, so be sure to check labels carefully when evaluating the products you use or buy. If a product's ingredients differ from what is listed above, it may not necessarily be of the same quality as what was tested. The information contained in this report is based on the compilation and review of information from product labeling and analytical testing. CL applies what it believes to be the most appropriate testing methods and standards. The information in this report does not reflect the opinion or recommendation of CL, its officers or employees. CL cannot assure the accuracy of information provided to it by third parties. Liability to any person for any loss or damage caused by errors, omissions, or inaccuracies in this report is hereby disclaimed. Copyright ConsumerLab.com, LLC, 2006. All rights reserved. Not to be reproduced, excerpted, or cited in any fashion without the express written permission of ConsumerLab.com LLC. ConsumerTips™: What to Consider When Buying: Arginine L-Arginine in supplements is in the form of L-arginine HCl. The hydrochloride (HCl) portion makes up about 17% of the weight of this molecule. Some products include this in the listed amount of L-arginine and some do not. It is important to know how much of the "free" L-arginine you are getting. Regardless of what the front label says, if the ingredients list in the Supplement Facts area on the back label says L-arginine HCl, you need to deduct 17% to determine the amount of actual free L-arginine. Yohimbe To help assure that you are getting the right herb, expect to find the following name and plant part in the Supplement Facts list of ingredients: Name: Pausinystalia johimbe K. Schum. or Corynanthe yohimbe K. Schum (yohimbe); Plant part: Bark or bark extract. Often yohimbe bark in supplements is in the form of an extract. This extract is preferably standardized (typically 2% to 6%) to contain a certain amount of the active compounds known as "yohimbe alkaloids" or, more specifically one of the active compounds can be labeled as "yohimbine." The amount of yohimbine is 10 -15% of the total yohimbe alkaloids. Care must be taken when reading the labels, as the standardization may be expressed as a percentage, such as "2% yohimbine," or as an amount such as "8 mg yohimbine in 400 mg of yohimbe bark extract" (which would also be a 2% standardization). If only yohimbe bark powder (and not "extract") is used, it will be less concentrated than the extract with a lower percentage of active compounds, so higher amounts would be needed to be equivalent to an equal weight of extract. Epimedium (Horny goat weed) Like yohimbe and other herbal products, to help assure that you are getting the right herb, expect to find the following name and plant part in the Supplement Facts list of ingredients: Name: Epimedium grandiflorum Morr. (barrenwort), Epimedium brevicornum Maxim. (epimedium), Epimedium koreanum Nakai (epimedium), or Epimedium sagittatum; Plant part: Dried aerial part of the plant (leaves and some stems/stalks). Often epimedium in supplements is in the form of an extract. Preferably, this is standardized to contain a certain amount (typically 8% to 10%) of icariin — a marker compound for epimedium. This standardization may be expressed as a percentage, such as 10% icariin, or as an amount such as 25 mg icariin in 250 mg of epimedium herb extract (which would also be a 10% standardization). If only epimedium herb powder is used, it will be less concentrated than the extract (typically 1% to 3% for the herb), with a lower percentage of active compounds, so higher amounts would be needed to be equivalent to an equal weight of extract. What to Consider When Using: Arginine In studies of arginine for sexual dysfunction in women, typical dosages have ranged from 2,500 to 6,000 mg daily. In men, some evidence suggests that 5,000 mg daily may be effective, while 1,500 mg daily is not. Results may take up to four weeks. Epimedium (Horny goat weed): Optimal doses have not been well established. Products typically suggest a dose of 500 to 1,000 mg per day, standardized to 10% icariin — a marker compound for epimedium. Yohimbe A typical dosage of yohimbine (one of the active chemical in yohimbe) for erectile dysfunction is 5.4 mg three times daily, preferably after meals — although one of the doses may be taken before bedtime for overnight activity. Higher doses are not necessarily more effective than lower ones; in fact, for some people the reverse is true. If side effects occur (see Concerns and Cautions below), it is advisable to reduce the dose by half. Since yohimbine is only a small percentage of the weight of yohimbe bark powders or extracts, to yield a 5.4 mg dose of yohimbine, you would need, for example, approximately 1,350 mg of a yohimbe bark extract standardized to 4% yohimbe alkaloids (yohimbine is approximately 10% of the total yohimbe alkaloids) or about 2,700 mg of a yohimbe bark extract standardized to 2% yohimbe alkaloids. The combination of yohimbine plus arginine has shown some promise for treatment of sexual dysfunction in women. In a small double-blind, placebo-controlled trial, participants with sexual arousal disorder were given a one-time dose of yohimbine (6 mg) plus arginine (6 grams); yohimbine alone, or placebo. Testing showed that the combination therapy enhanced physiological response to visual sexual stimulus as compared to placebo; however, yohimbine alone did not produce superior effects to placebo. Concerns and Cautions: Arginine In clinical trials, use of oral arginine in healthy individuals has not been associated with any serious adverse effects, other than occasional mild stomach upset. It has been suggested (but not proven) that high dose oral arginine may increase stomach acid levels and worsen esophageal reflux (heartburn). For this reason, individuals with ulcers or esophageal reflux should use caution when taking arginine. In addition, individuals taking medications that irritate the stomach, such as NSAID drugs (medications in the aspirin/ibuprofen family) might increase their risk of developing ulcers if they take arginine as well. Arginine may improve the body's ability to respond to insulin. This could be a benefit, but it could cause problems in individuals taking medications for diabetes. Arginine should not be recommended for people who have had an acute myocardial infarction because a recent study showed an increase in deaths in such people taking arginine versus those who took placebo. Epimedium (Horny Goat Weed) According to one case report, use of Epimedium grandiflorum (horny goat weed) caused rapid heart rate and symptoms that may have represented acute mania (the "up" phase of bipolar disease). Epimedium combinations None of the herbs in this combination have undergone comprehensive safety testing. One of them, Mucuna pruriens, is a natural source of the drug levodopa (l-dopa); this drug, used for Parkinson's disease, has a number of potential risks and side effects. Yohimbe There are safety concerns with yohimbe. Doses not much higher than what is commonly recommended (i.e. exceeding 15 to 20 mg of yohimbine per day) can cause anxiety,increased heart rate, increased urination, rise or fall in blood pressure, and numerous other symptoms. Yohimbe should be avoided by individuals using tricyclic antidepressants, phenothiazines, blood pressure medications, or stimulants or individuals with high blood pressure other heart or kidney-related conditions, or a pre-existing panic disorder. Even at lower doses, there have been reports of side effects including elevated blood pressure and heart rate, nervousness, irritability, tremors and dizziness. For all of the ingredients noted above, safety in pregnant or nursing women or people with severe liver or kidney disease has not been established.