Yohimbine

Yohimbine (/joʊˈhɪmbiːn/), also known as quebrachine, is an indole alkaloid derived from the bark of the African tree Pausinystalia johimbe (yohimbe) and from the bark of the unrelated South American tree Aspidosperma quebracho-blanco. Yohimbine is an α2-adrenergic receptor antagonist and has been utilized in various research projects. It also serves as a veterinary drug to reverse sedation in dogs and deer.

While yohimbine acts as an aphrodisiac in some mammals, it does not produce the same effect in humans. It has been prescribed for erectile dysfunction; however, its clinical benefits are generally modest, leading to its replacement by the PDE5 inhibitor class of medications. Products marketed as extracts from the yohimbe tree are sold as dietary supplements for various purposes, but they contain widely varying amounts of yohimbine, if any, and there is no published scientific evidence supporting their effectiveness.

Uses

Dietary supplementation

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Erectile dysfunction

Yohimbine has been used to treat female sexual dysfunction, but there are few reported clinical trials, and these do not demonstrate that it is more effective than a placebo.

Yohimbine has been largely superseded by PDE5 inhibitor drugs such as sildenafil (Viagra). Prescriptions for it are now rare, and most US pharmaceutical manufacturers have discontinued production of prescription capsules and tablets.

Yohimbe

Confusion

Yohimbine should not be confused with yohimbe, but it often is.

Yohimbe is the common English name for the tree species P. johimbe (also known as Corynanthe johimbe) and, by extension, refers to a medicinal preparation made from the bark of that tree, sold as an aphrodisiac. In contrast, yohimbine is a pure alkaloid that can be isolated from yohimbe bark.

Yohimbine is just one of at least 55 indole alkaloids extracted from the bark. While it is described as the most active among these, it comprises only 15% of the total alkaloid content. Other alkaloids include rauwolscine, corynanthine, and ajmalicine; the bark also contains non-alkaloids, about which virtually nothing is known.

Being a complex mixture, Yohimbe has been studied much less thoroughly than yohimbine, the pure compound. Pharmaceutical-grade yohimbine is typically presented as the hydrochloride, which is more soluble.

Effect on sexual function

Yohimbe is used in folk medicine as an aphrodisiac. In 1900, it attracted scientific interest in Germany, where an initial report claimed that yohimbe exerted a strong aphrodisiacal effect in animals and humans. Attention soon shifted from the plant to its active constituents, particularly yohimbine.

Yohimbe and dietary supplements

In the US, "yohimbe" preparations are sold as a dietary supplement for enhancing libido, for weight loss, and as an aid for bodybuilding; but "There is virtually no published research on yohimbe which supports these or any other claims". Often, these products explicitly claim to contain yohimbine.

One study found that samples of brands sold in American brick-and-mortar stores contained highly variable amounts of yohimbine, with some containing none at all. Labeling claims were often misleading. Similar results have been reported by other laboratories for products sold in the US, as well as in other countries and online. One study indicated that many brands labeled "yohimbe" might not even originate from the P. johimbe tree. According to another source, the yohimbe available in markets in West Africa, where the tree grows, is frequently mixed with other species from the genus Pausinystalia, which contain little yohimbine. The amounts of alkaloid found in authentic P. johimbe bark vary considerably, depending on the source of the bark (roots, stem, branches, height, etc.).

Some over-the-counter brands were found to contain more yohimbine per serving than a standard pharmaceutical dose; yet, in the US, pharmaceuticals are subject to a strict regulatory framework regarding medicines. It is illegal to introduce or deliver "drugs" into interstate commerce without the approval of the US Food and Drug Administration (FDA). The FDA has stated that some yohimbine-containing products qualify as "drugs" because they are marketed in a way that indicates they are intended for the cure, mitigation, treatment, or prevention of disease: 21 U.S.C. § 321(g)(1)(B). However, the legal situation is not entirely straightforward, and as of February 1, 2019, there does not seem to be any record of a successful prosecution.

Due to insufficient reliable scientific data on yohimbe, the European Food Safety Authority Panel on Food Additives concluded that it was impossible to determine its safety or establish a health-based guidance value. They stated:

Overall, the missing information includes quantitative data on the composition and specifications of yohimbe bark and its preparations used in food and dietary supplements, covering other alkaloids besides yohimbine. It also includes data on the bioavailability of active ingredients from yohimbe bark extract and information on the toxicity of well-specified individual preparations of yohimbe bark and the major yohimbe bark alkaloids, especially regarding subchronic toxicity.

Side effects

Side effects of yohimbine in humans at high doses include hypertension (high blood pressure), tachycardia (rapid heartbeat), agitation, hypervigilance, anxiety, and urinary frequency.

More information is available at [ Wikipedia:Yohimbine ]

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