Attention deficit hyperactivity disorder (ADHD) is a disease characterized by one or more symptoms of hyperactivity, impulsivity, or inattention that interfere with school, home, work, or social settings. ADHD does not have clear physical signs that can be seen in an x-ray or a lab test. The disorder only can be identified by looking for certain behaviors, which vary from person to person.~This trial will compare the benefits and side effects of two medications--clonidine and methylphenidate (MPH)--used alone or in combination to treat ADHD in children. MPH is approved by the Food and Drug Administration (FDA) for the treatment of ADHD symptoms in children, and clonidine is FDA-approved for the treatment of hypertension in adults. Stimulant medications such as MPH are known to safely and effectively treat many ADHD symptoms. Such medicines, however, do not cure the condition or improve all ADHD symptoms, and the long-term effectiveness of these medications is not well-known.~In this study, participants will be randomly selected to receive one of four treatments: 1) clonidine; 2) MPH; 3) clonidine and MPH; or 4) a placebo (an inactive substance). Participation in the study is about 16 weeks, and includes a baseline screening and 5 evaluation visits to assess attention, hyperactivity, overall improvement and general functioning, medication side effects, blood pressure, pulse, and weight.
The purpose of this study is to evaluate the safety and efficacy of two medications--clonidine and methylphenidate--alone or in combination to treat attention deficit hyperactivity disorder in children ages 4 through 6.