Priapism is a condition in which the penis is continually erect; usually painful and seldom with sexual arousal. Urgent medical attention should be sought for an erection lasting more than four hours; 90% of men with priapism lasting more than 24 hours develop complete erectile dysfunction. Impotence drugs such as Viagra may cause priapism in some men.

There are three different types of priapism:

Low-flow
Ischemic
Anoxic or veno-occlusive priapism
High-flow priapism
Arterial or nonischemic priapism
Recurrent or stuttering priapism - sickle cell is one cause.

Priapism and Sickle Cell Disease
Priapism, an unwanted painful erection of the penis, is a common complication of sickle cell disease. What is known about the prevalence of priapism, efficacy of management approaches, and outcome is drawn primarily from retrospective and single-center reports. Priapism occurs in two patterns: prolonged and stuttering (ie, recurrent brief episodes that resolve spontaneously). If priapism persists for 4 hours or more without detumescence, the patient is at risk for irreversible ischemic penile injury, which may terminate in fibrosis and impotence.

Priapism Questions
Q. Can an herb like tongkat ali or LJ100 cause priapism?
   A. Certain herbs such as yohimbe and the ones you mention can lead to a better and fuller erection, but I don't think they can sustain an erection for several hours.