Gabapentin and neurontin are very similar medications. One may have less side effects or work better than the other for some people. Cymbalta is a completely different medication, as are many others that are used to treat PN. To date, none of them work very well for most people, which explains why so many neurologists and other doctors are frustrated with this disease, as are the patients, of course.
The comment that both are poisons is simplistic and unhelpful. Almost all medications are poisons to some extent. The trick is to take enough to gain some benefit, while not suffering too many side effects.
If this strategy is not something you are willing to engage in, then don't go to see doctors, particularly for problems like PN, which is not yet well understood as to cause, treatment, etc.
Most people are doing their best with a very difficult situation.