Methylphenidate and growth: demonstration of a growth impairment and a growth-rebound phenomenon.

Methylphenidate (MPH), the drug of choice in the treatment of attention deficit disorder with hyperactivity (ADD/H), has been shown to reduce the body stature of some patients. The present study was undertaken to determine if MPH suppresses growth in rats, and whether the clinical observation of a growth rebound phenomenon could be experimentally demonstrated. Our results demonstrate that neonatal rats treated with MPH show a reduction in femur length and a reduction in thyroid, pituitary, testis, adrenal gland, and brain weights immediately following drug cessation. However, a growth-rebound phenomenon occurs such that there are no differences between treated and control groups within 30 days of the last drug exposure. These data, along with those from the clinical literature, suggest that growth impairment is most likely a result of the acute effects of the drug. Further, these data suggest that when administered at therapeutic doses which avoid significant weight loss in the patient, MPH is not likely to cause growth impairment in children.