https://jmrionline.com/jmri/article/view/119
So what were the improvements in curvature for each group?
Stai away From Cavallini, he is a firm believer of the non-existence of venous leak.
Of course, anything transdermal has a much higher chance of having an effect than oral intake.
The penis is special in that regard as it has a much lower bloodflow than an arm or leg.
Many oral medications have a low half life and circle through the blod without ever reaching the penis before dispersed by the kidney's etc.
Slow release oral medication can help with that to an extend, and so do doses broken up taken several times a day. But when there's bad blood flow to the penis it still might be "wasted".
Another thing to consider is that from mechanical, location standpoint, many plaques sit in the tunica. The tunica hasn't as much blood flow like for example the smooth muscle chambers. So even with a good blood circulation to the penis the agent might not reach the plaque.
Transdermal applications can reach it directly and can "bath" the plaque with the active agent.