Rationale  

The reinforcing effects of stimulant drugs are modulated by behavioral demands following drug administration.

Objective  

The objective of this study was to assess the reinforcing effects of modafinil, a drug with purportedly low abuse potential, under different behavioral demands using a modified progressive-ratio procedure.

Methods  

The reinforcing effects of oral modafinil (0, 100, 200, and 400 mg) were assessed in six healthy adult volunteers under both performance and relaxation conditions. Performance sessions required volunteers to complete simple arithmetic problems for three 50-min blocks. Relaxation sessions required volunteers to sit quietly in a semireclined position in a darkened room for three 50-min blocks. Two sampling sessions (one performance and one relaxation session) always preceded two self-administration sessions (one performance and one relaxation session), and the order of performance and relaxation sessions was constant within a dose condition.

Results  

Modafinil significantly increased break point and number of capsules earned on the modified progressive-ratio procedure as an increasing function of dose under the performance, but not the relaxation, condition. Modafinil produced comparable stimulant-like subjective ratings under both the performance and relaxation conditions.

Conclusion  

The findings of the present experiment demonstrate that modafinil can function as a reinforcer and that the reinforcing effects of modafinil are influenced by behavioral demands following drug administration, similar to those of other stimulant drugs.