Applies to methadone: oral solution, oral tablet, oral tablet for suspension.

Serious side effects of Methadone

Along with its needed effects, methadone may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur while taking methadone:

Incidence not known

• Black, tarry stools
• bleeding gums
• blood in the urine or stools
• blurred vision
• bulging soft spot on the head of an infant
• change in the ability to see colors, especially blue or yellow
• changes in skin color
• chest discomfort or pain
• confusion
• cough
• coughing that sometimes produces a pink frothy sputum
• darkening of the skin
• decreased urine output
• diarrhea
• difficult, fast, noisy breathing
• difficulty with swallowing
• dilated neck veins
• dizziness
• dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
• dry mouth
• extreme fatigue
• fainting
• fast, slow, or irregular heartbeat
• headache
• hives, itching, or skin rash
• increased sweating
• increased thirst
• irregular heartbeat
• irregular, fast or slow, or shallow breathing
• loss of appetite
• mental depression
• muscle pain or cramps
• nausea or vomiting
• numbness or tingling in the hands, feet, or lips
• pain
• pale or blue lips, fingernails, or skin
• pinpoint red spots on the skin
• puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
• seizures
• sweating
• swelling of the face, fingers, feet, or lower legs
• tenderness
• trouble breathing
• trouble sleeping
• trouble urinating
• unusual bleeding or bruising
• unusual tiredness or weakness
• weight gain

Get emergency help immediately if any of the following symptoms of overdose occur while taking methadone:

Symptoms of overdose

• Change in consciousness
• chest pain or discomfort
• cold, clammy skin
• constricted, pinpoint, or small pupils (black part of the eye)
• coughing that sometimes produces a pink frothy sputum
• decreased awareness or responsiveness
• increased sweating
• irregular, fast, or slow, or shallow breathing
• loss of consciousness
• no muscle tone or movement
• pale or blue lips, fingernails, or skin
• sleepiness or unusual drowsiness
• slow or irregular heartbeat
• swelling in the legs and ankles,

Other side effects of Methadone

Some side effects of methadone may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects.

Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

Incidence not known

• Absent, missed, or irregular menstrual periods
• anxiety
• blurred or loss of vision
• confusion about identity, place, and time
• constipation
• decreased interest in sexual intercourse
• disturbed color perception
• double vision
• false or unusual sense of well-being
• halos around lights
• inability to have or keep an erection
• irritability
• lack or loss of strength
• loss in sexual ability, desire, drive, or performance
• night blindness
• overbright appearance of lights
• redness, swelling, or soreness of the tongue
• restlessness
• stopping of menstrual bleeding
• tunnel vision
• weight changes
• welts

For Healthcare Professionals

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

Nervous system

Common (1% to 10%): Sedation, drowsiness

Frequency not reported: Headache, seizures, confusion, disorientation, lightheadedness, agitation, confusion, disorientation, dysphoria, euphoria, insomnia, hallucinations, seizures^[Ref]

Cardiovascular

Cases of QT interval prolongation and Torsades de pointes have occurred during treatment; these cases appear to be more commonly associated with higher dose treatment (greater than 200 mg per day). There have been some cases in patients receiving lower doses and in these cases contributing factors such as concomitant medications and/or clinical conditions were present. In vivo studies have confirmed this drug effects the QT interval and in vitro studies have shown it inhibits cardiac potassium channels.^[Ref]

Common (1% to 10%): Edema

Uncommon (0.1% to 1%): Syncope, flushing, hypotension

Rare (less than 0.1%): Bradycardia, palpitations, QT interval prolongation, Torsades de pointes

Frequency not reported: Arrhythmias, bigeminal rhythms, cardiomyopathy, ECG abnormalities, extrasystoles, heart failure, phlebitis, QT interval prolongation, syncope, T-wave inversion, tachycardia, ventricular fibrillation, ventricular tachycardia^[Ref]

Gastrointestinal

Constipation often persists during chronic administration; nausea, and vomiting appear to be more frequent after oral administration.^[Ref]

Very common (10% or more): Nausea, vomiting

Common (1% to 10%): Constipation

Uncommon (0.1% to 1%): Dry mouth, glossitis

Frequency not reported: Abdominal pain, anorexia, biliary tract spasm^[Ref]

Other

Common (1% to 10%): Vertigo, fatigue

Uncommon (0.1% to 1%): Asthenia, hypothermia^[Ref]

Hypersensitivity

Frequency not reported: Anaphylaxis^[Ref]

Anaphylaxis has been reported with ingredients contained in methadone products.^[Ref]

Psychiatric

Common (1% to 10%): Euphoria, hallucinations

Frequency not reported: Agitation, dysphoria, insomnia, mood changes^[Ref]

Endocrine

Uncommon (0.1% to 1%): Galactorrhea, dysmenorrhea, amenorrhea

Frequency not reported: Hypogonadism, decreased serum testosterone, reduced libido and/or potency, reduced ejaculate volume, reduced seminal vesicle and prostate secretions, decreased sperm motility, abnormalities in sperm morphology, gynecomastia, adrenal insufficiency, increased prolactin concentrations^[Ref]

Hypogonadism, decreased serum testosterone, and reproductive effects are thought to be related to chronic opioid use.^[Ref]

Genitourinary

Uncommon (0.1% to 1%): Urinary retention

Frequency not reported: Urinary hesitancy, ureteric spasm^[Ref]

Respiratory

Uncommon (0.1% to 1%): Pulmonary edema, exacerbation of asthma, dry nose, respiratory depression

Frequency not reported: Pulmonary edema^[Ref]

Renal

Uncommon (0.1% to 1%): Antidiuretic effect^[Ref]

Hematologic

Frequency not reported: Reversible thrombocytopenia, lymphocytosis^[Ref]

Reversible thrombocytopenia has been described in opioid addicts with chronic hepatitis.^[Ref]

General

The major adverse reaction of this drug is respiratory depression; to a lesser degree, systemic hypotension, respiratory arrest, shock, cardiac arrest, and death have occurred. The most commonly observed adverse reactions include lightheadedness, dizziness, sedation, nausea, vomiting, and sweating.^[Ref]

Metabolic

Common (1% to 10%): Weight gain

Frequency not reported: Hypokalemia, hypomagnesemia^[Ref]

Ocular

Common (1% to 10%): Miosis, dry eyes

Frequency not reported: Visual disturbances, congenital oculomotor disorders (nystagmus, strabismus)^[Ref]

Dermatologic

Sweating often persists during chronic administration.^[Ref]

Common (1% to 10%): Transient rash, sweating

Uncommon (0.1% to 1%): Pruritus, urticaria, other skin rashes

Rare (less than 0.1%): Hemorrhagic urticaria^[Ref]

Hepatic

Uncommon (0.1% to 1%): Bile duct dyskinesia^[Ref]

Local

Frequency not reported: Local tissue reactions (pain, erythema, swelling) particularly with continuous subcutaneous infusion^[Ref]