Yohimbine

What it is

Yohimbine comes from the bark of Pausinystalia yohimbe, a tree from West and Central Africa. The bark was traditionally used as an aphrodisiac; the isolated alkaloid later became a drug. In Germany, yohimbine hydrochloride is prescription-only and approved for the supportive treatment of mild to moderate erectile dysfunction.

In the fitness world, yohimbine has a second life. It is sold as a single product or as an ingredient in pre-workout and fat-burner blends, mainly from the US. Besides yohimbine, the bark contains other alkaloids such as rauwolscine and corynanthine. In 39 percent of the US products examined, these accompanying substances were missing, which points to synthetic or heavily processed yohimbine, even when bark was stated on the label. Of those who called the California poison control system because of symptoms from yohimbine, 27.7 percent had taken it for sexual enhancement, 9.2 percent for weight loss and 7.6 percent as a stimulant.

How it is supposed to work

Alpha-2 receptors are located at nerve endings and on fat cells. At the nerves they act like a feedback brake: once enough noradrenaline has been released, they throttle the supply. On fat cells they inhibit fat breakdown. Yohimbine blocks these receptors. The result is more noradrenaline, more sympathetic activity and potentially more released fatty acids.

This has been measured in humans. In a study of fasting women, plasma noradrenaline doubled and free fatty acids rose. With the beta blocker propranolol, the effect fell by 70 percent, so fat breakdown runs mainly via more noradrenaline at the beta receptors. In 25 patients with high blood pressure, noradrenaline rose by 66 percent and mean blood pressure by an average of 5 mm Hg.

The pharmacokinetics are unusual. The half-life is around half an hour, and bioavailability varied between 7 and 87 percent in one study. Yohimbine is broken down by the liver enzyme CYP2D6, whose activity varies greatly for genetic reasons. In a study with 16 healthy people, clearance after the same dose ranged from 25.3 to 15,864 mL/min.

Yohimbine in anxiety research

Because yohimbine specifically pushes the stress system, psychiatry has long used it as a tool. One idea behind this: more noradrenaline during exposure therapy could strengthen the unlearning of fear. In 40 adults with social anxiety disorder who received yohimbine or placebo before 4 exposure sessions, symptoms improved faster in self-reports, but not in clinician ratings.

In 67 people with fear of flying, yohimbine brought no additional benefit to virtual reality therapy, although the stress markers rose as expected. In a pilot study with 26 veterans with post-traumatic stress disorder, depression improved faster after a single dose before the first exposure, but the core symptoms did not. A field of research, then, not an established procedure, and in the hands of therapists, not for self-use.

What the studies show

Professional footballers and body fat

In a randomized, placebo-controlled study, 20 professional footballers took yohimbine or placebo for 21 days. In the yohimbine group, body fat percentage fell from 9.3 to 7.1 percent; under placebo it was 9.2 percent at the end. Weight, muscle mass and performance tests did not change. No side effects were reported.

Six months without effect

The longest controlled study ran for 6 months with 47 men with an average age of 42, at a high dose and double-blind. 33 completed it. Neither weight nor body fat nor the fat distribution measured by CT differed from placebo.

Diet plus yohimbine

In a small study with 20 overweight women, 3 weeks of a diet with 1,000 kcal per day were followed by a double-blind phase with yohimbine or placebo. In these 3 weeks, the women on yohimbine lost 3.55 kg, those on placebo 2.21 kg.

Sprints with a single dose

In 18 physically active women, a single dose before three 15-second sprints on a cycle ergometer was tested. With yohimbine, mean power and total work were higher, fatigue and lactate lower, and adrenaline rose. Perceived exertion was the same.

California poison control

An analysis of the California poison control system found a total of 238 adults with symptoms after yohimbine products for the years 2000 to 2006, 98.7 percent of them after herbal supplements rather than medicines. The frequency of such calls rose during this period from 1.8 to 8.0 per 10,000 adult contacts.

Where the data stop

For fat loss the studies contradict each other: two small positive papers with 20 participants each stand against a negative 6-month study. There is no meta-analysis or large modern study. For performance there is essentially one single-dose study with 18 women; the football study found no performance effect. The erection studies are also old and methodologically not up to current standards. In the more recent meta-analysis, yohimbine alone did not significantly improve overall sexual function.

Added to this is the variability. With bioavailabilities between 7 and 87 percent and widely differing CYP2D6 activity, no study allows conclusions about how an individual person will react. Yohimbine is also being researched as an aid in exposure therapy for anxiety, with mixed results: in 40 people with social anxiety, yohimbine doses helped in self-reports; in 67 people with fear of flying there was no additional benefit.

Status, approval and legal

In Germany, yohimbine is a prescription-only drug and is approved only for the supportive treatment of erectile dysfunction. Yohimbe bark and preparations made from it have been banned in food throughout the EU since Regulation (EU) 2019/650, after manufacturers failed to submit safety data. German food control authorities object to yohimbine hydrochloride in food supplements as a medicinal substance, and in the European rapid alert system RASFF there have been a total of 102 notifications with yohimbe or yohimbine in the subject since 2017. In the US, yohimbine is sold as a supplement; in Canada, Australia, the Netherlands and the United Kingdom, yohimbe preparations are banned. Yohimbine is not on the WADA Prohibited List 2026.

Safety

Common side effects according to the prescribing information are insomnia, anxiety, restlessness, headache, nausea and frequent urination. Of 238 cases at the California poison control system, 43 percent had a racing heart, 33 percent anxiety or agitation and 25 percent high blood pressure; severe courses were considerably more frequent than in average poisoning calls. There are documented deaths; in four people poisoned at the same time, blood levels differed 22-fold despite presumably the same amount. Yohimbine is not suitable for people with heart disease, blood pressure problems, liver or kidney impairment, stomach ulcers, glaucoma, epilepsy, or anxiety and affective disorders; in anxiety patients it triggered panic attacks in half of cases. There are interactions with blood pressure medications, clonidine, antidepressants and stimulants. In US products, the stated amount was rarely correct; of 49 brands, only 2 had correct amounts and warnings.

Sources

• Ernst and Pittler, Journal of Urology 1998 – meta-analysis on yohimbine in erectile dysfunction
• Wibowo et al., Turkish Journal of Urology 2021 – systematic review and meta-analysis
• Ostojic, Research in Sports Medicine 2006 – body composition and performance in professional footballers
• Sax, International Journal of Obesity 1991 – no effect on fat distribution in men
• Barnes et al., International Journal of Environmental Research and Public Health 2022 – repeated sprints
• Guthrie et al., European Journal of Clinical Pharmacology 1990 – bioavailability in humans
• Vay et al., Clinical Pharmacokinetics 2020 – yohimbine and CYP2D6
• Kearney et al., Annals of Pharmacotherapy 2010 – cases at the California poison control system
• Cohen et al., Drug Testing and Analysis 2016 – yohimbine content in US supplements
• Regulation (EU) 2019/650 – ban on yohimbe in food