Yohimbe and Priapism

May 1, 2010, 8:56 pm


Refractory Priapism Associated with Ingestion of Yohimbe Extract.  Myers A et al.  J Med Toxicol 2009;5:223-225.


Yohimbine is an alkaloid found in the bark of the African evergreen tree Pausinystalia yohimbe (picture). An alpha-2 adrenergic antagonist, over-the-counter yohimbine is sometimes ingested as an aphrodisiac to enhance male erections.  Common adverse effects include gastrointestinal distress, hypertension, tachycardia, headache, and anxiety.

This case report describes a rarer — but clinically important — side effect of the herb.  A 42-year-old male with a history of HIV and depression presented to the emergency department complaining of an erection that began shortly after he ingested yohimbine the day before, and had persisted for 20 hours.  On examination, his pulse and blood pressure were unremarkable but he was moderately uncomfortable. He had an erect penis that was tender to palpation but was not cyanotic or discolored.  A carvernosal blood gas showed pH 7.17, pCO2 58, pO2 46, consistent with ischemic priapism.  The priapism was resistant to intracorporeal phenylephrine injections, corporal aspiration and flushing, and a distal corpus spongiosum (Winter’s) shunt. The patient was taken to the operating room where a left proximal carvernosum spongiosum (Quackles) shunt achieved detumescence.

Some interesting points raised touched on by this article:

• A cavernosal blood gas analysis can help differentiate ischemic (low-flow) from the more rare non-ischemic (high-flow) priapism. I’d leave this procedure to the urologists.

• Other drugs and toxins associated with priapism include citalopram, clozapine, prazosin, trazodone, chlorpromazine, cocaine, phosphodiesterase type-5 inhibitors such as sildenafil (Viagra), canthinides (Spanish Fly), and the bite of the Brazilian wandering spider.

• The clinician should be extremely careful not to confuse Quackle’s Shunt — an invasive treatment for priapism — with Quackle — a computerized crossword puzzle game based on artificial intelligence. Unfortunate things can happen if one does.


  1. precordialthump Says:

    I can’t help but add scorpion envenoming, lactrodectism and Irukandji syndrome to the toxinological priapism list… and ciguatera?


  2. Leon Says:


    You are quite right. Nasty encounters with scorpions, black widow spiders, Carukia barnesi, and perhaps certain reef fishes all have reported associations with priapism. Thanks for adding these to the list!

  3. Neuroskeptic Says:

    What about mirtazapine? It’s become a very popular antidepressant in the past few years and at high doses it’s an a2 antagonist.

    There must be loads of mirtazapine ODs but do they cause priapism? Now this is really interesting… according to PubMed there are no hits for (mirtazapine AND priapism).

    Does that imply that something about mirtazapine protects against the a2-associated risk of priapism? Quite possible since mirtazapine hits a whole slew of receptors. does that imply that hitting some of those receptors might help treat priapism?

  4. Sean Says:

    great post, man! 🙂