Final answer:
A child with ADHD prescribed methylphenidate should be aware of possible side effects like decreased appetite, insomnia, and potential behavioral changes.
Step-by-step explanation:
A child with ADHD who is prescribed methylphenidate, commonly known as Ritalin or Concerta, should be advised of potential side effects. The nurse should inform the client about common side effects including decreased appetite, insomnia, increased heart rate, increased blood pressure, and potential for behavioral changes, such as increased anxiety or irritability. As with all medications, it's important to monitor for any adverse reactions and communicate with healthcare professionals if concerns arise.