FWIW, I took amitriptyline (30 mg/day) and gabapentin (2000 mg/day) for many years. The amitriptyline had a sexual side effect that I didn't care for, so earlier this year I changed it to tramadol (200 mg/day) and am much happier with that. My level of pain relief is about the same, and I am not aware of any side effects from either, except possibly a mild cognitive and memory impairment. Or maybe that's just the real me, who knows.
Ron