After being coaxed into receiving a test injection in the office, most men are pleasantly surprised to learn that it really doesn't hurt. Only 1 to 5 percent of men have this reaction, but it's enough to prevent them from using the drug again. Some men who undergo a radical prostatectomy with one or both neurovascular bundles spared still can't achieve an erection after being injected. The nerves could play a role here but for some it has more to do with the fact that they might have anatomic variations in blood supply to the penis. Complicate this with other risk factors, such as partial nerve injury or diabetes, and an erection can become very difficult to achieve.
Moisture left by urine causes the pellet to dissolve, triggering an erection minutes later.
Many men complain of a burning pain in the penis after the drug has been inserted, and there is a small risk of urethral injury. Injected directly into the base of the penis five minutes before a sexual encounter, the drug increases blood flow and produces an erection. Many men like the convenience of Caverject. It doesn't need to refrigerated and it's easier to transport. I then recommend trimix.