Drug information of Methadone


Drug group:

Methadone is an opioid medication. An opioid is sometimes called a narcotic.

Methadone 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. It is available only from a certified pharmacy.

Mechanism of effect

A synthetic opioid that is used as the hydrochloride. It is an opioid analgesic that is primarily a mu-opioid agonist. It has actions and uses similar to those of morphine.


Methadone is an opioid agonist acting by binding to μ, κ and δ opioid receptors .

 Its pharmacodynamic properties, such as analgesia, respiratory depression, dependence and tolerance are primarily triggered by MOR activation.


    • When orally administered it has fast and almost complete absorption. It may be detected in the plasma 30 minutes after oral dose, and time to reach plasma peak concentration is 2.5h for oral solution and 3h for tablets. Bioavailability is high, varying from 67 to 95%7 .
    • It is metabolized in the liver and excreted by the kidneys.
    • Methadone extensively binds to plasma proteins (reaching 86%)
    • It is an opioid agonist with long half-life, approximately 24h, and, being far superior than other opioids used for pain therapy, such as morphine

Drug indications

Pain , Opiate Withdrawal , Chronic Pain


Usual Adult Dose for Opiate Withdrawal:

For detoxification and maintenance of opioid dependence, the drug should be administered in accordance with the treatment standards.
Day 1: Administer initial dose under supervision when symptoms of withdrawal are present.
-Initial dose: 20 to 30 mg orally; an additional 5 to 10 mg may be given orally after 2 to 4 hours if withdrawal symptoms have not been suppressed or if symptoms reappear.
-Maximum day 1 dose: 40 mg
-Adjust dose over the first week based on control of withdrawal symptoms at 2 to 4 hours after dosing.

Usual Adult Dose for Pain
Initiation in Opioid Non-Tolerant Patients:
Initial dose: 2.5 mg to 10 mg IV every 8 to 12 hours
Maintenance dose: Slowly titrate to effect; more frequent administration may be required to maintain adequate analgesia during initiation, however, extreme caution is necessary to avoid overdosing.


  • You should not use methadone if you are allergic to it, or if you have:
    • severe asthma or breathing problems; or
    • a blockage in your stomach or intestines.
  • Methadone may cause a life-threatening heart rhythm disorder. Your heart function may need to be checked during treatment.
  • Tell your doctor if you have ever had:
    • heart disease, a heart rhythm disorder, or a personal or family history of long QT syndrome;
    • any type of breathing problem or lung disease;
    • a head injury, brain tumor, or seizures;
    • drug or alcohol addiction, or mental illness;
    • liver or kidney disease;
    • urination problems;
    • problems with your gallbladder, pancreas, or thyroid; or
    • if you use a sedative like Valium
  • Methadone may be habit-forming, even at regular doses. Never share this medicine with another person, especially someone with a history of drug abuse or addiction. MISUSE OF NARCOTIC MEDICINE CAN CAUSE ADDICTION, OVERDOSE, OR DEATH, especially in a child or other person using the medicine without a prescription. Selling or giving away methadone is against the law.

Points of recommendation

  • Do not drink alcohol . Dangerous side effects or death could occur.
  • Methadone may impair your thinking or reactions. Avoid driving or operating machinery until you know how this medicine will affect you. Dizziness or severe drowsiness can cause falls or other accidents.
  • Grapefruit and grapefruit juice may interact with methadone and lead to unwanted side effects. Discuss the use of grapefruit products with your doctor.
  • You should not stop using this medicine suddenly. Follow your doctor's instructions about tapering your dose.
  • Never use methadone tablets or liquid to make a mixture for injecting the drug into your vein. This practice has resulted in death with the misuse of prescription drugs.

Pregnancy level


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