Methadone Side Effects

Some side effects of methadone may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

For the Consumer

Applies to methadone: oral concentrate, oral solution, oral tablet, oral tablet dispersible

Get emergency medical help if you have any of these signs of an allergic reaction while taking 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 side effects of methadone 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.

For Healthcare Professionals

Applies to methadone: compounding powder, injectable solution, oral concentrate, oral solution, oral tablet, oral tablet dispersible

Nervous system

Other neurologic side effects are rare, but include tardive dyskinesia and choreic movements.

Nervous system side effects have included agitation, confusion, disorientation, dysphoria, euphoria, seizures, sleepiness or insomnia, and dizziness.

Cardiovascular

Cardiovascular side effects have included hypotension, bradycardia, arrhythmias, bigeminal rhythms, cardiomyopathy, ECG abnormalities, extrasystoles, flushing, heart failure, palpitations, phlebitis, QT interval prolongation, syncope, T-wave inversion, tachycardia, torsade de pointes, ventricular fibrillation, ventricular tachycardia and edema. Rare cases of cardiac arrest have also been reported.

Gastrointestinal

Methadone may cause contraction of the sphincter of Oddi, which may increase intrabiliary pressure and worsen, rather than relieve, biliary colic.

Gastrointestinal side effects have included constipation, abdominal pain, biliary tract spasm, dry mouth, glossitis, and appetite abnormalities.

Other

Other side effects have included increased sweating which has been common after chronic methadone use.

Hypersensitivity

Hypersensitivity side effects to methadone are rare, and have included rash, pruritus, and edema.

Psychiatric

One study has suggested that detoxification from methadone maintenance therapy may result in the development of an organic mood syndrome in many patients.

Psychiatric side effects have included psychological dependence. A case of obsessive compulsive symptoms precipitated by methadone tapering has been reported.

Endocrine

Endocrine side effects have included stimulation of thyroxine binding globulin (TBG), resulting in increased TBG, total T3 and T4, but unaltered free T3 and T4. Hyperprolactinemia has also been associated with methadone therapy.

Genitourinary

Genitourinary side effects have included amenorrhea, antidiuretic effect, reduced libido and/or potency, urinary hesitancy, and urinary retention.

Respiratory

Respiratory side effects have included pulmonary edema, respiratory depression, and a blunted response to hypercarbia.

Renal

A case of rhabdomyolysis and subsequent acute renal failure following ingestion of large doses of methadone has been reported.

Hematologic

Hematologic side effects associated with methadone have included mild lymphocytosis and increased serum protein, albumin, and globulin.

General

General side effects including asthenia, edema, and headache have been reported.

Metabolic

Metabolic side effects including hypokalemia, hypomagnesemia, and weight gain have been reported.

Ocular

Ocular side effects have included visual disturbances.

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