Yes coffee is a drug. It is a marvelous drug. Better living through chemistry. Do I really want to know about what it is doing to my brain? Yes.
Coffee blocks adenosine receptors. What I didn’t know (but do now) is:
Additionally, some of the brain’s own natural stimulants (such as dopamine) work more effectively when the adenosine receptors are blocked, and all the surplus adenosine floating around in the brain cues the adrenal glands to secrete adrenaline, another stimulant.
So I am now charged up and the adrenals are doing their very best.