I don't know if the evidence is more than anecdotal, but I've read that ADHD smokers who are taking adderal have to increase the dose of their treatment to remain functional when they quit smoking.
I've been taking nicotine patches for half a year now, with great success (and it is available OTC unlike other stimulants). Nicotine in itself isn't toxic at these doses (7, 14, 21mg), it's a cool life hack :-).