The likelihood is termed addiction liability and depends upon a combination of factors including Route of administration Rate at which the drug crosses the blood-brain barrier and stimulates the reward pathway Time to onset of effect Ability to induce tolerance and / or withdrawal symptoms Scheduled drugs In the US, the Comprehensive Drug Abuse Prevention and Control Act of 1970 and subsequent modifications require the pharmaceutical industry to maintain physical security of and strict record keeping for certain classes of drugs (controlled substances—see table).