Finally, Ritalin should be used with great caution in children below the age of six, as safety in this age group has not been established. The two most commonly reported problems are loss of appetite and sleep disturbances. Decreased appetite can lead to lack of growth, but this seems to rebound when the medication is discontinued. In addition, irritability, tearfulness, headaches, stomach aches, skin rashes, racing heart rate, and fatigue all have been observed. Liver enzymes can be altered and the possibility of long-term liver damage exists.
Psychotic reactions are unusual but possible.
Finally, Ritalin has been shown to cause movement or tic disorders, especially in children with a positive family history. As with most psychiatric drugs, Ritalin should be introduced at a low dosage and gradually increased until effective benefit is seen or side effects become a problem. Because Ritalin is a very short acting drug, it needs to be given in divided doses, usually about four hours apart. A slow-release form of Ritalin is also available, and is supposed to be effective for about eight hours.