In some patients prolonged erection or priapism may occur. Patients should be instructed to report to a doctor any erection lasting for 4 hours or longer. Painful erection is more likely to occur in patients with anatomical deformations of the penis. The occurrence of fibrosis of penis may increase with increased duration of use. Regular follow up and careful examination of the penis is recommended.

Patients on anticoagulants may have increased risk for bleeding after the intracavernous injection. Alprostadil should be used with care in patients with unstable cardiovascular disorders. Sexual stimulation and intercourse can lead to cardiac events in patients with coronary heart disease or congestive heart failure.