A more hands-on medical option presented on the site as highly effective, but one that requires care and proper guidance.
This page describes Alprostadil as an injection-based treatment that can produce a long-lasting erection, but also one that needs more caution and medical oversight.
This is an injection that allows you to keep an erection for up to 4 hours. If you are hard for any longer than that, you have to get yourself to the nearest A&E to get medical assistance.
It comes in 5, 10, 15 and 20mg powder form, which has to be dissolved with a simple procedure and then injected directly into the penis.
This is the one that I strongly recommend, for a number of reasons. For one, there are no time restrictions as such. And two, it does not matter how many times I orgasm, I keep the erection.
I was very wary of needles and only asked about it again after seeing how effective they were.
Make sure that you use an intermittent before injecting unless you are into watersports.
The original site also notes that orgasm can trigger autonomic dysreflexia in some spinal injury cases. That is another reason to discuss this treatment with your clinicians rather than relying on anecdote alone.
Recreational drugs can have a negative effect on the performance of alprostadil.