Though Ritalin has been around for more than 40 years, experts still aren't exactly sure how the drug works.
Most experts agree that it affects the midbrain, the part of the brain that controls impulses.
Methylphenidate most likely changes the balance of chemicals in the brain, so that it can more selectively respond to impulses. Ritalin allows the patient to focus better on the task at hand. Determining a starting dose is fairly simple, Zarowitz said. Physicians usually use a chart based on age and weight to start with a low dose while gauging the effect. When the tablet is taken, dramatic effects are seen in as little as 20 minutes.