It is intended to provide highly safe and efficacious blood flow promoters for cauda equina tissues. Among prostaglandin-like compounds having a weak hypotensive effect, compounds having an effect of promoting the blood flow in cauda equina tissues (excluding limaprost) are useful as highly safe blood flow promoters for cauda equina tissues and, therefore, are efficacious in preventing and/or treating lumbar pain, lower limb pain, lower limb palsy, intermittent claudication, vesicorectal failure, hypogonadism, etc. caused by cauda equina injuries.