Paroxetine
"I switched from Paxil to Paroxetene to save co-pay money.  Big mistake.  I learned very quickly that the generic is inferior to the brand, and I would not recommend switching.  The generic can be manufactured anywhere in the world and the chemical formula differs from one manufacturer to the next.  The generic version left me irritable and slightly depressed, even though my Dr. said there was no difference between them.  I spent six months of the generic (job stress was the culprit) and then switched permanently to the brand."