ADD Drugs aren’t licensed for adults where you are? Really? Wow, that is totally awful 
My doc was able to look up proper dosage for adults of my weight and everything. I take Adderall XR, and sometimes the short release pill (sometimes I forget to take my medicine in the morning, and the XR stays in my system too long to take it after 10:00am, when I remember, finally. Then I take half of a short release pill, which will get me to the afternoon. Usually happens on the weekend, when my schedule is different).
Yes, they are licensed, and even advertised for adult use here in the US. Sometimes, things depend on the state in which you live (I’m currently in Kansas), but for the most part, if the FDA approves it, most states will allow it’s use.
Are you the person from Great Britain?
REPORT ABUSE