Clinical trials. Planned Ritalin trial for tots heads into uncharted waters.

U.S. scientists are gearing up for a major clinical trial intended to measure the effects of a popular but controversial drug used to treat attention deficit hyperactivity disorder, methylphenidate (Ritalin), on a previously untested population--children aged 3 to 6. But in doing so, they are running up against ethical concerns about using young subjects in clinical trials. The scientists involved in the study admit that they are concerned about the drug's effect on the children's still-developing personalities and brains, as well as their inability to give informed consent. But they believe that such trials are the only way to answer concerns about rising use of the drug among this population.