Methylphenidate is a central nervous system stimulant that affects chemicals in the brain and nerves that contribute to hyperactivity and impulse control. It is used to treat attention deficit disorder (ADD), attention deficit hyperactivity disorder (ADHD), and narcolepsy in children and adults. Methylphenidate may be habit-forming, and misuse can cause addiction, overdose, or death. It may cause new or worsening psychosis, especially in people with a history of depression, mental illness, or bipolar disorder. It may also cause blood circulation problems that can cause numbness, pain, or discoloration in the fingers or toes. Methylphenidate is available as a generic medication and is sold under various brand names, including Ritalin, Concerta, Medikinet, and Adhansia XR. It is available in different formulations with varying durations of action, such as immediate-release, extended-release, and transdermal. Methylphenidate is contraindicated in patients who have used an MAO inhibitor in the past 14 days, have severe hypertension or heart disease, have a history of drug or alcohol addiction, or have glaucoma. It may interact with other medications, such as blood pressure medications, antidepressants, seizure medications, and cold or allergy medications that contain decongestants. Methylphenidate may cause side effects such as dizziness, drowsiness, changes in vision, dry mouth, headache, stomach pain, nausea, vomiting, loss of appetite, weight loss, nervousness, restlessness, excitability, insomnia, and increased heart rate and blood pressure. It may also cause slow growth and weight loss in children. Methylphenidate should be used as part of a total treatment program that includes social, educational, and psychological treatment.