Yohimbine, a Sexy Stimulant?
Yohimbine is an herbal alkaloid derived from the bark of Corynanthe yohimbi, which grows throughout jungles of West Africa, Cameroon, and the Congo; and it has been used for more than 70 years in Africa as a general stimulant tonic and aphrodisiac. It is an odorless, crystalline substance that is available as a powder, tablet, and intravenous solution as a prescription in the United States. Its “adrenaline-like” effects have made it popular among some nootropic users who are looking for decreasing fatigue and enhancing sexual performance.
In regard to its clinical pharmacology, Yohimbine is an indole derivative similar to reserpine, a unique central alpha-2 selective antagonist. The substance enhances norepinephrine release from nerve terminals by preferential blockade of presynaptic alpha-2 receptors without interfering with post-synaptic alpha-1 receptors; thus, the result is increased sympathetic tone. In this way, Yohimbine readily penetrates the CNS and produces a complex array of responses in lower doses than those required to produce peripheral alpha-adrenergic blockade.
In these studies  , Yohimbine increased sexual motivation and sperm production in male rats as evidenced by increased mounting performance in mating tests conducted after genital anesthetization, increased percentage of male rats ejaculating in their first heterosexual encounter, and induction of copulatory behavior in sexually inactive male rats. Furthermore, the present results demonstrated that yohimbine produces a dose-related antinociception in the formalin test in rats which is mediated in part by the agonistic actions at 5-HT(1A) receptors. These results elucidated the role of free radical species in cytological and reproductive changes, possibly, under the influence of yohimbine on neurotransmitters, including serotonin and norephinephrine.
The main problem with yohimbine is that you cannot really regulate the amount in a dosage. Unfortunately, it depends on what part of the tree it comes from and how it it cultivated; hence he amount of extract you get will vary. In this study, twelve commercial raw materials of yohimbe were analyzed by microscopic and ultra performance liquid chromatography-UV-MS methods. The study revealed that three samples were probably adulterated and four other samples contained various levels of impurities. Yohimbine was not detected in one sample, whereas its presence in other samples was found to be in the range 0.1-0.91%. In this way, while 5.4 to 10 milligrams three times daily has been studied and regarded as generally safe for erectile dysfunction, you have to make particularly sure your provider is trustworthy.
Finally, few data are available about yohimbine toxicity . However, this is a case of a large ingestion of yohimbine (5g) in which severe hemodynamic and neurotoxic manifestations occurred and elevated blood levels of yohimbine were detected after 2h after yohimbine ingestion. While this case seems to be isolated and yohimbine is, in general, a well tolerated substance, moderation and caution is urged.
“…in general, a well tolerated substance (Yohimbine),
moderation and caution is urged”
 Morales A, Surridge DH, Marshall PG, et al. Nonhormonal pharmacological treatment of organic impotence. J Urol 1982; 128:45–47.