FDA heart attack warning for those taking Methadone for pain.
These can be symptoms that you have taken too much (overdose of) methadone (DOLOPHINE), or the dose is too high for you. They can also be symptoms of a heart attack or another type of heart reaction. These symptoms can lead to serious problems or death if not treated right away.
Methadone (DOLOPHINE) can cause your blood pressure to drop. This can make you feel dizzy if you get up too fast from sitting or lying down.
DOLOPHINE can cause physical dependence. Do not stop taking DOLOPHINE or any other opioid without first talking to your doctor. You could become sick with uncomfortable withdrawal symptoms because your body has become used to these medicines. Talk to your doctor about slowly stopping DOLOPHINE to avoid getting sick with withdrawal symptoms. Physical dependency is not the same as drug addiction.
For patients using DOLOPHINE for pain treatment, there is a chance of abuse or addiction with DOLOPHINE. The chance is higher if you are or have been addicted to or abused other medicines, street drugs, or alcohol, or if you have a history of mental problems.
Methadone & Heart Attack 
FDA Overdose Warning: Methadone Can Cause Heart Attack and Death
Overdose risk includes heart attack in those taking methadone for pain
Methadone Side Effects Methadone Side Effects Include Difficulty Breathing and Heart Problems
FDA information on Methadone side effects such as trouble breathing
