Novantrone (mitoxantrone) is an anticancer drug that weakens the immune system. By weakening the immune system it decreases the symptoms of MS. It is given intravenously once every three months. It is very well tolerated except for some nausea and vomiting that can be treated at the time of the injection. One of its side effects is possible damage to the heart. This occurs after a certain dosage of the medication has been given. Most patients can take it safely for up to two years.