Hey StupidFool! (LOL!)--
I'm sure it's the sudden absence of nicotene that's making your dad feel lousy and drowsy. Nicotene is a stimulant, so of course if it's suddenly not there any longer, you're going to feel different. (less stimulated). He should be okay in a few days after his body adjusts to being without nicotene. By all means tell him not to smoke,

even if it has to come down to going back on patches, which is much better than smoking.
Also congratulate him for me too. (and please tell him he's welcome to join us).
DEDA