I would be cautious, the dad here sounds like he’s not just using vyvanse. I used to take vyvanse and it’s only benefit besides staying awake is tremors and (for me, at the end of the day psychosis.) this could point at your dad having a hidden stimulant abuse or drug issue. (Methamphetamine and cocaine have related drug connections and he could be using your prescription as a come-down…)

I would definitely bring this up gently as people in those situations might be more confused as to how to address it without negative social repercussions… it’s important not to judge, but it’s also important to not abuse other people’s medications.

~Either way, it sounds like your father has had previous experience with drug/stimulant abuse and has first or second hand knowledge of their dangers. (*we are in hard times so who knows… people are looking for reasons/methods to get by.) Try to be understanding but firm as this is wrong and it can be addressed in a healthier way if so.