Fallout: Van Buren
Generally, after 24 hours, the character goes through withdrawal, and suffers whatever associated penalties that substance has. They also lose their ability to heal (see Healing, below). After another 24 hours, they suffer that withdrawal effect again(they stack). After another 24 hours, the character lapses into unconsciousness. They then must make an Endurance check every hour (with their modified Endurance if applicable). If the character has five successful checks in a row, they wake up and have shaken the addiction. If they fail to make five in a row successfully within 24 hours, they wake up and are permanently addicted. Doctors can remove addiction for a cost, and fixer can temporarily relieve ones symptoms, as can taking more of the drug.