Gabapentin
"My Husband was given this medication due to suffering long term knee pain. He took it for approx 6 weeks max and had to stop. 
The most awful side effects you can imagine for the whole time blighted him. Maybe he was just unlucky and this med didn't suit him but it's Cons certainly outweighed its Pros in his case. 
Weight gain
Excess gas
Dizzyness
Nausea 
Vomiting 
Diarrhoea 
Headaches......
Not a good one for him at all. 

UK  Based."