I know you use it every day for erectile dysfunction cause of your great age, oldbuddy
... but fact is I know of some guys who took it right before stepping onstage for the swelling effect it has on the muscle bellies... seems to work quite well, especially if you have lagging bodyparts like arms, chest or shoulders... gives a "rounder", fuller look to the said muscle.
Since I've never done it myself, I can't really tell about the doses, but I guess it's safe to say that you need to give it a first run in your prep before doing it on contest days. Caverject usually comes in 5mg, 10mg and 20mg pre-loaded pen... if I had to experience with it, I'd start with 10mg in each desired bodypart... from there, and depending on the results (real - temporary- increase that looks natural... or puffy look and blurred definition), I'd either decrease the dose to 5mg or increase it to 20mg... trial and errors if you see what I mean.
If you wanna get max results out of it, never take ephedrine at the same time cause it annihilates alprostadil effects.
Hope that helped a little.