BMA Concise Guide to Medicine & Drugs

Methadone

Brand names Eptadone, Methadose, Metharose, Physeptone, Synastone

Used in the following combined preparations None

QUICK REFERENCE

Drug group Opioid analgesic

Overdose danger rating High

Dependence rating High

Prescription needed Yes

Available as generic Yes

GENERAL INFORMATION

Methadone is a synthetic drug belonging to the opioid analgesic group. It is used in the control of severe pain, and as a cough suppressant in terminal illness, but it is more widely used to replace morphine or heroin in the treatment of dependence. For this, methadone can be given once daily to prevent withdrawal symptoms. In some cases, dosage can be reduced until the drug is no longer needed.

Tolerance to methadone is marked. Although the initial dose for a person not used to opioids is very low, the dose needed by someone who is dependent could be fatal for a non-user.

INFORMATION FOR USERS

Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken/used Tablets, liquid, injection.

Frequency and timing of doses Pain 3–4 x daily; 2 x daily (prolonged use). Cough 4–6 x daily (starting dose); 2 x daily (prolonged use). Opioid addiction Once daily.

Adult dosage range Pain 5–10mg per dose initially, adjusted according to response. Cough 1–2mg per dose. Opioid addiction 10–20mg (starting dose); 40–60mg daily (maintenance dose).

Onset of effect 15–60 minutes.

Duration of action 36–48 hours.

Diet advice None.

Storage Keep in original container at room temperature out of the reach of children. Protect injections and liquids from light.

Missed dose Take as soon as you remember and return to your normal dosing schedule as soon as possible. If you missed the dose because it caused you to vomit, or if you cannot swallow, consult your doctor.

Stopping the drug If the reason for taking methadone no longer exists, the drug can be slowly reduced and safely stopped. Discuss with your doctor.

OVERDOSE ACTION

Seek immediate medical advice in all cases. Take emergency action if symptoms such as slow or irregular breathing, severe drowsiness, or loss of consciousness occur.

POSSIBLE ADVERSE EFFECTS

Nausea, vomiting, and drowsiness are common side effects but diminish as the body adapts to the drug. Constipation is also common and may be longer lasting. Dizziness and confusion is another fairly common effect and should be reported to your doctor. If the drug causes loss of consciousness or slow, difficult breathing, it should be stopped and immediate medical attention sought.

INTERACTIONS

Phenytoin, carbamazepine, rifampicin, and ritonavir may reduce the effects of methadone.

Monoamine oxidase inhibitors (MAOIs) and selegiline Taken with methadone, these drugs may produce a dangerous rise or fall in blood pressure.

Erythromycin, clarithromycin, fluconazole, cimetidine and ritonavir may increase the effects of methadone.

Sedatives The effects of all drugs that have a sedative effect on the central nervous system are likely to be increased by methadone.

SPECIAL PRECAUTIONS

Be sure to tell your doctor if:

· You have heart or circulatory problems.

· You have liver or kidney problems.

· You have lung problems such as asthma or bronchitis.

· You have thyroid disease.

· You have a history of epileptic seizures.

· You have a phaeochromocytoma (a type of adrenal gland tumour).

· You have problems with alcohol abuse.

· You are taking other medicines.

Pregnancy Not prescribed in pregnancy if possible. May cause breathing difficulties in the newborn baby. Discuss with your doctor.

Breast-feeding Safety not established. The drug passes into breast milk and may affect the baby adversely. Discuss with your doctor.

Infants and children Not recommended.

Over 60 Reduced dose necessary.

Driving and hazardous work Your underlying condition may make such activities inadvisable. Discuss with your doctor.

Alcohol Avoid. Alcohol increases the sedative effects of the drug and may depress breathing.

PROLONGED USE

Treatment with methadone is always closely monitored. If the drug is being taken long-term, the dose must be carefully reduced before the drug is stopped.