I am so frustrated with the continuing decline in quality, efficacy and effectiveness of the 20mg immediate release tabs. I barely get off on them anymore. Seems like it lasts about 12 hours and the party's over, even if I redose. I experience nausea, headaches, irritation and some dizziness now. I've been taking it for years and never had these side effects before. Heck, I remember about 15 of the 20mg tabs kept me up for 3-4 days when I used to use them recreationally! Now, just 12 hours of the high peak and the fun's over and all downhill after that. A waste of them to even redose now, doesn't help. I still use recreationally on occasion, but I have a legal script for 60 a month from my doc. Not my imagination, as I have seen hundred's of negative posts and complaints on here about them. Idk what's going on? They're just no fun anymore. No good anymore. Teva used to be the cream of the crop, but apparently no longer. Too bad, as it seems a lot of prescribed stims/downer meds and street drugs like meth are watered down and just aren't fun anymore.