The chances of sudden erectile dysfunction can be medical injury in the private part or sudden impact on mind. There can also be some cases related to a sudden heart attack. Except medical injury or some accident, the causes accumulate gradually in the body. Depending on your sudden cause, you can wait for the better conditions to get an erection. But if the erection issue persists, then you need drug for erection. Viagra 150 mg will ensure a hard erection, but you first need to know the reason behind sudden erection issue.