I asked this question in a roundabout fashion before, but can someone developed side effects from a drug after being on it for years?

Almost 5 years ago I was prescribed Gabapentin for SFN. After about 2 years I had to switch to Gralise (extended release Gabapentin) because of constipation. Things have gone okay on it, until fall 2013 I developed severe sinusitis that resolved after a few months. Then last spring I developed GERD and was put on a PPI. I've never had so much as heartburn in my life. Once again last fall I developed severe sinusitis that won't seem to resolve. I am now seeing an ENT who thinks Gralise could be a factor drying my sinuses. Recently I had to switch PPIs because the GERD came back.

Out of desperation and thinking the Gralise was a factor I voluntarily dropped my dose from 1200 mg to 900. It seems to be relieving some of the sinusitis.

A good optometrist I see says he has heard stories of folks being on drugs for years and suddenly develop side effects. My pain doc takes an indignant tone disagreeing she's never heard of this.

So have you heard of this - developed side effects from a drug after being on it for years?