Drugs also should have immediate side effects, so you're not able to beef yourself up on Jet, Psycho, Mentats, Buffout, Nuka Colas and cigs all at the same time. Instead, they should be sorted by their effects and paired up, fe. Psycho should also reduce action points, while Jet would drop physical resistance. No long-term addictions should apply then, since drugs would be buffs usable by any character instead of powerbuilds. Lower drawbacks and less drugs used at the same time would make them more accessible to less hardcore players.
Plus, drugs should lower your max health for a duration longer than the first set of drawbacks(by a small amount), thus preventing people from running on drugs most of the time. The effect would stack naturally and if it would be a set amount, drugs would be no longer a tool for rich people to level up quickly aswell.