Yohimbine is a well known alkaloid that was isolated from Pausinystalia johimbe tree in the end of IXX century. In the folk medicine, it was used as an aphrodisiac. Yohimbine is actually a very well known pharmacological research tool in the field of adrenoreceptor research because of its ability to block alpha-2 adrenoreceptor (and, thus, increase hyperadrenergic effects) selectively provided that the doses are low [1]. Hence, it is not surprising that there are more than 25 000 papers associated with yohimbine. While it was used in the folk medicine and early european medicine as an aphrodisiac, the use of yohimbine in the modern human medicine is low today.
Yohimbine is generally well tolerated in lower doses but higher doses may cause agitation, anxiety, hypertension and tachycardia at a level that is difficult to tolerate [2], it can not only amplify stress response that may beneficial or the opposite, it can cause stress reaction by itself. At higher doses, yohimbine will start to affect alpha-1 adrenereceptor that may cause severe drop of blood pressure. When yohimbine and yohimbe tree bark are compared, the latter is associated with higher frequency of adverse effects [3], although deaths associated with yohimbine overdoses have been reported [4]. Clearly enough, the mechanism of action comprising alpha-2 adrenoreceptor antagonism is prone to pharmaceutical interactions.
As concerns the uses that may yield effects that are beneficial to humans, the level of evidence that is available regarding yohimbine does not meet the efficacy, efficiency and safety requirements set by regulatory agencies that can usually be met by large studies initiated by pharmaceutical industry. The evidence regarding yohimbine’s effects that are related to folk medicine and preclinical pharmacological research such as weight loss and aphrodisiac properties are contradictory indeed.
As concerns weight loss, there are studies that demonstrate that yohimbine is not effective for fat loss in the overweight men [5] as well as ones that show exactly the opposite in soccer players [6]. It would be probably be premature to discard the discrepancies as noise or statistical variance. This topic very pertinent for body composition and change thereof – including safety – is nuanced and pertinent and rather well covered in scientific literature and online discussions based on science. Ambivalence applies to sexual enchancement: there are results that speak in favor of [7,8] and against [9] yohimbine.
Yohimbine is able to increase blood pressure, which may be useful in some contexts [10]. Yohimbine has potential to affect mood [11,12] but it is probably contingent on the type of baseline mood state and, definitely, on the dose of yohumbine. It has been observed that yohimbine can increase working memory [13] as well as decrease it [14]. Since yohimbine is an old drug that cannot be protected by a patent, conduction of studies that compare in quality with those initiated by pharmaceutical industry seems unlikely.
[1] https://www.ncbi.nlm.nih.gov/pubmed/26366943
[2] https://www.ncbi.nlm.nih.gov/pubmed/22432773
[3] https://www.ncbi.nlm.nih.gov/pubmed/20442348
[4] https://www.ncbi.nlm.nih.gov/pubmed/23846025
[5] https://www.ncbi.nlm.nih.gov/pubmed/1960007
[6] https://www.ncbi.nlm.nih.gov/pubmed/17214405
[7] https://www.ncbi.nlm.nih.gov/pubmed/22952481
[8] https://www.ncbi.nlm.nih.gov/pubmed/9315493
[9] https://www.ncbi.nlm.nih.gov/pubmed/9123711
[10] https://www.ncbi.nlm.nih.gov/pubmed/2920499
[11] https://www.ncbi.nlm.nih.gov/pubmed/28318897
[12] https://www.ncbi.nlm.nih.gov/pubmed/24237691
[13] http://www.sciencedomain.org/abstract/7854
[14] https://www.ncbi.nlm.nih.gov/pubmed/10516956