Side effects are a non-negligible problem during drug treatment and a particular concern for parents. The first-line drugs for ADHD, such as methylphenidate and tomoxetine, do not have significant side effects, and there are individual differences. Some children have some adverse reactions at the beginning of taking them, which are usually not serious, and some have none. Common side effects are mainly gastrointestinal reactions, such as nausea, abdominal pain, and decreased appetite. Long-term use of therapeutic doses of the drug will not affect a child’s growth and development or intelligence, and there is no need to review liver function while taking the drug.