i too fall asleep after taking my meds sometimes. the comedown is somewhat noticeable too, because instead of a come down, it's almost like a "come up", and i experience increased heart rate and agitation.
for instance, today i was taking a very big test, and i always keep a small amount of adderall on me that i can pop during the test in case i start to "come up" and get agitated (the tests are long). Anyways, i could tell i was starting to "come up" so what i do is place a small amount under my tongue and take it sublingually in situations like these. I only need like 2.5 or 5mg placed under the tongue, and within about 5-10 mins, i can already feel my heart rate go back down and all the agitation i was experiencing disappears.