Hooked on a combat drug: miss a dose and go Sickened, then into Withdrawal (-4 all, Nauseated, CON damage).
An addicted character's body has rewired itself around a combat stim, narcotic,
or nootropic -- it needs the chemical to feel normal. While the supply holds
there is no penalty, but missing a dose past the drug's interval imposes the
Sickened condition (-2 across the board) as craving sets in. Going a full day
without pushes them into Withdrawal: -4 to attack, saves, skill and ability
checks, the Nauseated restriction (move action only), and 1d4 Constitution
damage after a week clean. Addiction itself is resisted with a Fortitude save
after repeated doses (the GM tracks exposure), and Withdrawal bouts are
endured with periodic Fortitude saves. The only clean exit is a proper Detox
(extended Medicine DC 20 in a facility) or a careful tapering schedule.