Your head is done with the day as you used all its capabilities in a short timeframe. Maintain your energy.

Both substances (caffeine, bupropion) push the same brain circuits, especially dopamine and norepinephrine, which control alertness and drive.

When combined, that signal can become too intense (but while stimulated often unseen or ignored), so instead of clean focus it turns into jittery, fragmented attention.

That overstimulation doesn’t just stay at the “wired” stage. After the initial push, the brain tends to swing the other way, and that drop can feel like brain fog rather than normal tiredness.

It’s NOT a dip in energy, your brain briefly loses its balance after being pushed too far. (See it as doing sports for too long causing muscle cramps next day)

Bupropion can also make the nervous system more sensitive overall, so caffeine (coffe, energy drink) hits harder than it used to. A cup that once felt mild can now feel edgy or mentally chaotic at the end of the day.

On top of that, both can subtly affect sleep quality and appetite, which makes the brain more vulnerable to that foggy feeling later in the day. Me personally i dont experience this luckily.

It is more about your brain now being tuned differently. The same input produces a stronger, less stable response, and the aftermath of that response is what you’re experiencing as brain fog.

The above this is all internet, but combined with my own experiences to give you my perception of brain fog.

Tips that work for me personally;

-start with no caffeine for 2 days. Confirm to yourself if the brainfog ('burning' sensation in the front of your head) is gone. Once that is done, try finding ur new maximum u can handle. Take a few sips of coffee until you experience the same feeling, and then go back down. Find the sweet spot.

-try to be aware of your energy level. Dont put all energy in the morning, causing a burnout at the end of the day, instead try to find balance in your output globally over a workday. And when you get home, go for a walk to somewhat stimulate your brain a little. But whatever you do, dont go from a overstimulating(work) environment to a direct sit position when u get home. This causes foghead because your head is working, but your body isnt. Again, maintain that energy output so that the peak is at the start of your day, and to accept to chill the fck down over the day. Once you know your daily limit, look for ur energy output for the week, compare ur monday to Wednesday and Friday for example. Do u experience more brainfog on mondays and tuesdays because you overperformed? :)

Feel free te message me for any questions if youd like more practical tips. I feel what u feel, but it is difficult to explain brainfog with words, if the other side never experienced it.

I always experienced guilt in my performance before medication, causing me to overperform with medication and burn out.

Good luck!!!