Methadone Side Effects

Methadone is a opioid pain reliever, similar to morphine. An opioid is sometimes called a narcotic. It also reduces withdrawal symptoms in people addicted to heroin or other narcotic drugs without causing the “high” associated with the drug addiction.

Methadone is used as a pain reliever and as part of drug addiction detoxification and maintenance programs.

Taking methadone improperly will increase your risk of serious side effects or death. Even if you have used other narcotic medications, you may still have serious side effects from methadone. Follow all dosing instructions carefully. Methadone may be habit forming and should be used only by the person it was prescribed for. Never share methadone with another person, especially someone with a history of drug abuse or addiction. Keep the medication in a place where others cannot get to it.

Do not use methadone if you have ever had an allergic reaction to a narcotic medicine (examples include codeine, morphine, Oxycontin, Darvocet, Percocet, Vicodin, Lortab, and many others). You should also not take methadone if you are having an asthma attack or if you have a bowel obstruction called paralytic ileus.

To make sure you can safely use methadone, tell your doctor if you have any of these other conditions:

  • a personal or family history of “Long QT syndrome”;
  • asthma, COPD, sleep apnea, or other breathing disorders;
  • liver or kidney disease;
  • underactive thyroid;
  • curvature of the spine;
  • a history of head injury or brain tumor;
  • epilepsy or other seizure disorder;
  • low blood pressure;
  • gallbladder disease;
  • Addison’s disease or other adrenal gland disorders;
  • enlarged prostate, urination problems;
  • mental illness; or
  • a history of drug or alcohol addiction.

FDA pregnancy category C. It is not known whether methadone will harm an unborn baby. Methadone may cause addiction or withdrawal symptoms in a newborn if the mother takes the medication during pregnancy. Tell your doctor if you are pregnant or plan to become pregnant while using this medicine. Methadone can pass into breast milk and may harm a nursing baby. Do not use this medication without telling your doctor if you are breast-feeding a baby.

Get emergency medical help if you have any of these signs of an allergic reaction to methadone: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

  • shallow breathing;
  • hallucinations or confusion;
  • chest pain, dizziness, fainting, fast or pounding heartbeat; or
  • trouble breathing, feeling light-headed, or fainting.

Less serious methadone side effects may include:

  • feeling anxious, nervous, or restless;
  • sleep problems (insomnia);
  • feeling weak or drowsy;
  • dry mouth, nausea, vomiting, diarrhea, constipation, loss of appetite; or
  • decreased sex drive, impotence, or difficulty having an orgasm.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect. You may report side effects to FDA at 1-800-FDA-1088.

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