Measuring the Reinforcing Strength of Abused Drugs

Evaluation of addiction liability for four drugs. Comparison of amphetamine, methylphenidate, atomoxetine, and desipramine in animals trained under concurrent FR 30; FR 30 schedules of food delivery and i.v. injections. The abscissa shows the dose per injection. The ordinate shows the distribution of responding on the injection-associated (left, red axis) and food-associated (right, black axis) levers; the dashed line represents 50% responding allocated to each lever, suggesting equal reinforcing strength of the two available reinforcers. Note that the reinforcing strength of some doses of methylphenidate and amphetamine were equal to or greater than that of the alternatively available food pellets. In contrast, food was preferred to all doses of atomoxetine or desipramine. See text for details. [Adapted from (46).]