The application of intraurethral prostaglandin E1 (alprostadil) can be done by a urologist or self-administered to the distal male urethra via a drug deliver system. It appears to produce cavernosal vasodilation to initiate erection.
There are no RCT studies in this area. In a series of 15 men with SCI, Bodner et al. (1999) found that the use of intraurethral alprostadil (PGE1) was ineffective in sustaining an adequate erection, and without a penile ring to sustain any increase in penile circumference (tumescence), patients experienced hypotension from the medication. Based on the evidence to date, such studies do not appear to be worth pursuing.
There is level 4 evidence (from a post-test study: Bodner et al. 1999) which suggests that the use of intraurethral preparations is not effective as treatment for erectile dysfunction in men with SCI.
There is level 4 evidence (from a pre-post study: Strebel et al. 2004) that found some success using apomorphine SL to facilitate erections.