Persistent priapism is due to?

Priapism refers to a persistent (> 4 hours) and painful erection. It is occurs due to: An excessive release of neurotransmitters Blockage of draining venules (e.g., mechanical interference in sickle cell crisis, leukemia, or excessive use of intravenous parenteral lipids) Paralysis of the intrinsic detumescence mechanism Prolonged relaxation of the intracavernous smooth muscles (most often caused by the use of exogenous smooth-muscle relaxants such as injectable intra-cavernosal prostaglandin E1).