Nausea, vomiting, loss of appetite, dizziness, or blurred vision may occur. If any of these effects persist or worsen, tell your doctor or pharmacist promptly.Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.Tell your doctor immediately if any of these unlikely but serious side effects occur: unusually fast heartbeat, unusually fast breathing, bluish lips/skin, chest pain, mental/mood changes, muscle weakness, difficulty urinating.This drug may rarely cause very serious low blood counts (bone marrow suppression) or liver disease. Seek immediate medical attention if you develop signs of an infection (e.g., fever, chills, persistent sore throat), easy bruising/bleeding, unusual tiredness, pale skin, yellowing eyes/skin, dark urine, stomach/abdominal pain.Dapsone can commonly cause a rash that is usually not serious. However, you may not be able to tell it apart from a rare rash that could be a sign of a severe reaction. Therefore, seek immediate medical attention if you develop any rash.A very serious allergic reaction to this drug is rare. However, seek immediate medical attention if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing.This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.In the US -Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.