Hyperactivity and methylphenidate: rate-dependent effects on attention.

The behavioral effects of CNS stimulants on attention deficit disorder (hyperactive) children's attention are inversely related to their pre-drug rate of behavior, i.e. the effects are rate-dependent. The strength and shape of this relationship are affected by dose and the child's unique reaction to the drug, yet appear unrelated to body weight. Dosage should be directly manipulated in pediatric psychopharmacological studies and the practice of using mg/kg dosage schedules may no longer be necessary.