Priapism is a medical term for a potentially dangerous and painful condition in which a man’s penis becomes aroused without psychological or physical stimulation and remains in this state for more than four hours, even after intercourse has ended. The cause is usually rooted in circulatory disorders, in which blood is not removed normally from the penis. Cases of painful arousal in men lasting more than four hours should be referred to a specialist or emergency room immediately, as they can often be life-threatening. The condition is considered a medical emergency because it is associated with a reduced flow of fresh blood to the genital tissues, which can lead to hypoxic lesions, erectile dysfunction and impotence, and in more severe cases: gangrene. Certain medications and substances are known to have side effects leading to priapism. In the first place are papaverine and alprostadil – the active ingredients of many medications treating erectile dysfunction. But similar side effects also come from unexpected places: antidepressants, such as trazodone; anticoagulants; cantharides such as the famous “Spanish fly” and some narcotic substances – alcohol, heroin, cocaine. But, the strangest cause of this condition remains a bite from the Brazilian wandering spider – Phoneutria nigriventer and its relative – Latrodectus hesperus, called the “Black Widow”. NEWS_MORE_BOX Priapism is not only a male problem, women also have similar problems. Clitoris is the medical term for prolonged and painful arousal of the clitoris, which is also unrelated to sexual desire. Although this condition is not associated with more serious complications in women, the pain can greatly disrupt their daily life. Only in the last few years have scientists begun to understand the causes of this dangerous condition. Dr. Yang Xia and his team at the University of Texas Medical Center discovered that the absence or reduced amount of the specific protein ADA, responsible for breaking down the adenosine molecule, causes priapism. The team plans to create an ADA-based therapy to eliminate the threat of priapism. Results of their research are expected to be published in late 2013.