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HERBS AND NATURAL PRODUCTS TO AVOID
Yohimbe (Pausinystalia yohimbe)
Yohimbine is found in nature from the bark of the Pausinystalia yohimbe tree and is used for impotence. Yohimbine is the active constituent and acts by blocking a -2 adenoreceptors centrally. As a result, there is an increase in release of norepinephrine and increases in cholinergic activity. Heightened cholinergic activity is associated physiologically with penile erection. Yohimbine also inhibits monamine oxidase that is responsible for the breakdown of norepinephrine and serotonin without increasing testosterone levels.
A meta-analysis of seven double-blind, placebo-controlled trials that investigated monotherapy with yohimbine in erectile dysfunction has been published. Study sizes varied from 11-100 men with various causes of erectile dysfunction in which dosages ranged from 15-30mg daily. Studies found yohimbine to be more effective than placebo in five of the seven studies, although the primary endpoints were subjective improvements in coïtusual function. Side effect ranged from 10-30% and included hypertension, rash, anxiety, dizziness, increased urinary frequency, GI disturbances, and lethargy. Eight of the patients withdrew due to the seriousness of the side effects. other side effects that could be expected due to its central activity include agitation, tremor, insomnia, sweating, tachycardia, nausea and vomiting.
Once case of a lupus-like syndrome occurred in a 45 year-old man after ingesting 60mg in one day. Yohimbine has been associated with agranulocytosis after prolonged use, but this appears to have been an idiosyncratic response to prolonged therapy. It has also been linked to an allergic reaction that resulted in a lupus-like response and renal failure. Overdoses of 20-30mg/day have resulted in excessive salivation, piloerection, mydriasis, changes in blood pressure and death. Yohimbine is not recommended in individuals with hypertension and liver disease, and should be avoided in schizophrenics as it may exacerbate acute psychotic episodes. It is contraindicated in pregnancy and renal disease, as well as patients with a history of gastric or duodenal ulcer and cardiac disease. Yohimbine should not be taken with tyramine-containing foods (certain cheeses, chocolate, wine, aged meats), or with tyrosine or phenylalanine due to its MAO-I activity and the potential for hypertensive episodes. Clonidine may be used to reverse some of the adverse effects of yohimbine.
Both the German Commission E and the American Urological Association do not recommend the use of yohimbine. The FDA does not recommend the use of yohimbine for erectile dysfunction but has approved it as a prescription mydriatic. Although its use has been banned since 1989 as an aphrodisiac due to lack of safety and efficacy, it is still purchased on the internet; pharmacists should discourage its use.