--with both gabapentin (Neurontin) and Lyrica (Pregabalin), fluid retention and urination frequency changes are listed as fairly common side effects.

These two drugs are among the minority of medications that are not appreciably processed through the liver, but generally excreted "whole" through the actions of the kidneys. That generally means good kidney function is a prerequisite for taking them, and many people notice differences in their urinary patterns while on appreciable doses of them.

Of course, the problem is if one has neuropathy--particularly autonomic types--one can have urinary, and colonic, and other symptoms due to the effects of the neuropathy, and it may be hard to distinguish these from medication side effects.