Good answer, Earl's Brain. This is true; eventually, varicies can develop in the penis, which can cause the blood to leak past the venous valves, resulting in the loss of erection.
Another form of damage is the overuse, and subsequent inability of Neuro Transmitters, and Receptor Sites to perform; specifically, the Pleasure Sites. Most Recreational Drugs have this byproduct; because, after all, we take them for pleasure. Unfortunately; when we take these medications addictively, or AMA, they lead to a chemical imbalance of our normal system. Quite a few of us say that when we have taken the drugs, we feel "Normal" for the first time; and this is normal. Some of us weren't "balanced", to begin with.
Recommendations are to stop taking "Self-perscribed" medications, and allow your body to "Catch back up" with its own level. If you still find that you have problems, or you don't feel "Quite right", talk to a doctor.
