Generic drugs, are like generic anything, they are made to be sold at a certain price point, and sometimes the quality is not quite as good as the 'name' brand.
A case in point, I used to take Rohypnol (a trade name of Roche for flurniterazepam sp.) they were very smooth acting in comparison to Hypnodorm, and both were 20 mg in strength.
The result was the same, but the action of them was slightly cruder.
"Diana Krall is a Spunk"