DOES IT WORK?Yohimbine has been linked with curing erectile dysfunction but more studies are needed, writes DÓNAL O'MATHÚNA.
Yohimbe is a West African tree that is native to Congo, Cameroon and Gabon. An extract is made from its bark which contains the active ingredient yohimbine. Traditionally, yohimbine was used as an aphrodisiac and a hallucinogen. Yohimbine has been studied for more than a century and is available on prescription only in many countries, including Ireland.
However, with the increased interest in herbal remedies, many products claiming to contain yohimbe bark extract are available. If you get flooded with emails advertising natural alternatives to Viagra, chances are they contain yohimbine.
During the 1980s, yohimbine was studied in a small number of low-quality trials. These showed some effectiveness in about one quarter of the men treated. At the time, however, there was little interest in erectile dysfunction until Viagra arrived. Erectile dysfunction can significantly impact a man’s self-esteem and relationships. With increased awareness of the condition, interest in alternative approaches to treatment increased.
Evidence from studies
Laboratory studies of yohimbine demonstrate that it inhibits what are called alpha-2 adrenergic receptors. These play an important role in the dilation and constriction of blood vessels. Increased flow of blood plays an important role in producing an erection. However, yohimbine acts on several different parts of the nervous system, including the central nervous system (CNS). These multiple influences raise concerns about unwanted side effects with yohimbine.
While studies in the 1980s showed yohimbine had beneficial effects, they did not have control groups and involved very small numbers of men. The first randomised controlled trial found that while the men taking yohimbine fared a little better than those taking a placebo, the differences were not large enough to be statistically significant.
Over the next decade, several small studies found mixed results. Combined summaries of all these results have noted a small overall benefit.
The mixed results may be due to the way the studies are designed. When yohimbine is taken daily, its effectiveness decreases with time. Other studies have shown that it has a half-life of only 35 minutes, which is relatively short.
Supporters of yohimbine are urging that trials be conducted where men take it only shortly before needing its effects. Until such studies are conducted, it will remain unclear just how effective yohimbine may be for erectile dysfunction.
Problematic aspects
Yohimbine’s effect on adrenergic receptors can also lead to adverse effects. Because it influences the diameter of blood vessels, it can lead to rapid heart rate, high blood pressure, headaches and dizziness. More serious effects include insomnia, panic attacks and hallucinations. The difference in dosage between what is helpful with erectile dysfunction and what causes adverse effects is very small. This may be why a California poison-control centre reported last year that yohimbine was the second-most common source of adverse events. It is most commonly found in products that contain several herbs and are marketed as sexual enhancement products.
Many of them contain large quantities of caffeine which can cause some of the same effects. The amounts of active ingredients in these products can vary widely also, thus contributing to the adverse effects.
Anyone with heart, kidney or psychiatric conditions should not take yohimbine.
Recommendations
Viagra has brought into the open the struggles that some men have with erectile dysfunction. Now that it can be talked about, it can be treated. At the same time, others have taken this openness as an opportunity to promote yohimbine within the huge internet market for instant sexual gratification. Yohimbine is advertised in products where little is known of their quality or the quantity of each component. Given its multiple effects on the nervous system, it is not surprising that many adverse effects are reported. While some studies show yohimbine has the potential to be beneficial, much further research is needed.
Dónal OMathúna has a PhD in pharmacy, researching herbal remedies, and an MA in bioethics, and is a Senior Lecturer in the School of Nursing, Dublin City University.