My current knowledge is Wellbutrin (bupriopion) XL which is said to be actually roughly 24 hrs
That is the extent of my knowkedge or understanding of the longest-acting I am [currently] aware of.
I believe there is a newer ADHD med that is like tri-Adderall (16-18 hours) but I am not confident in those figures since that is not available in my country nor would I likely self-advocate to be prescribed such a long-acting substance
If you’re specifically talking about ADHD meds (Wellbutrin can be used for it), then mydayis is taken at night and is timed to start releasing in about 8 hours and is supposed to last 16 after that. Never tried it myself, just know of it.
I think that was it