Priapism is an erection that lasts more than 4 hours without sexual stimulation. It can be very painful. Often the cause of priapism is not known. In adults, some causes include sickle cell disease and side effects from medicine or from drugs. Some prescription medicines and shots (injections) have been linked to priapism. So have alcohol, marijuana, and cocaine.
Children with leukemia can get priapism. This is because blood flow in the penis gets blocked by the large number of white blood cells in the blood.
Priapism is very serious. When erections last over 4 hours, there is less blood flow to the penis. This can cause cell damage from lack of oxygen. The longer you have the erection before treatment, the worse the outcome. Those treated within 4 to 6 hours do best. But up to 50% of all men who get priapism will have some degree of erection problems in the future.