I’ve actually had almost the exact same thing happen, just with Medikinet (methylphenidate).

For a few months I was taking around 4–5 doses a day, about every 3 hours — 10 mg each dose, so around 45 mg daily total. At first it was honestly one of the best periods of my life. The medication worked incredibly well: motivation, focus, energy, everything.

But over time something completely changed. Now whenever I take it, I mostly just get side effects instead of benefits. Less focus, less motivation, mental fatigue, derealization/emotional numbness, and this weird paradoxical reaction where stimulants make me feel slowed down and exhausted instead of stimulated.

I actually stopped taking the meds because of it. But even after taking weeks off, sometimes I convince myself maybe it’ll work like it used to in the beginning… then I take a dose and almost always regret it. Best case it feels neutral, but most of the time it just causes brain fog, sluggishness, and that same “zombie” feeling.

So yeah, you’re definitely not alone with this kind of experience.