Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2020 Publisher: Macarthys Laboratories Ltd, T/A Martindale Pharma, Bampton Road, Harold Hill, Romford, Essex, RM3 8UG, United Kingdom
Treatment of opioid drug addiction as a narcotic abstinence syndrome suppressant.
The use of injectable methadone for this indication must be initiated by physicians with adequate expertise and experience in addiction therapy.
The use of methadone in opiate addiction must be part of a broader treatment programme, including regular treatment reviews, supervised by specialist services.
Prior to starting treatment with opioids, a discussion should be held with patients to put in place a strategy for ending treatment with methadone in order to minimise the risk of addiction and drug withdrawal syndrome (see section 4.4). The decision to maintain a patient on a long-term opioid prescription should be an active decision agreed between the clinician and patient with review at regular intervals (usually at least three-monthly, depending on clinical progress).
Initially 10-20mg per day, increasing by 10-20mg per day, until there are no signs of withdrawal or intoxication.
Treatment must be managed by physicians with suitable experience.
The initial dose, safe dosage increments and the establishment of a dose that prevents withdrawal symptoms needs to be individualised. The degree of tolerance or neuroadaptation, any additional consumption of oral methadone or other opiates, the cumulative potential of methadone treatment (as opposed to shorter acting opiates) and the general health of the patient must be taken into account. Typical doses for heavily-addicted users can be fatal to those without such neuroadaptation.
The usual dose of injectable methadone, when the addict is stabilised, may need to exceed 100mg daily to prevent symptoms of opiate withdrawal.
The aims of treatment should include reducing criminality and to improve patient’s health and social productivity.
If repeated doses are required, use with caution due to the long plasma half-life.
There may be a greater risk of respiratory depression, with or without any associated renal or hepatic impairment, in this age group.
As methadone has not been studied in children it should not be used in children under the age of 16 years.
In patients with severe liver damage the dose of methadone should be carefully controlled as there is a risk that methadone might precipitate porto-systemic encephalopathy.
The dose may need to be reduced in moderate or severe renal impairment.
Intramuscular, subcutaneous or intravenous injection.
Volumes greater than 2ml given intramuscularly may need to be administered in divided doses at different sites.
Patients should be informed of the signs and symptoms of overdose and to ensure that family and friends are also aware of these signs and to seek immediate medical help if they occur.
Similar to those for morphine.
Respiratory depression, extreme somnolence progressing to stupor or coma, cyanosis, maximally constricted pupils, skeletal muscle flaccidity, cold and clammy skin, bradycardia and hypotension have been observed. Hypoglycaemia has been reported.
In severe overdose apnoea, circulatory collapse, pulmonary oedema, cardiac arrest and death may occur.
Treatment is supportive. Patients should be kept conscious wherever possible.
A patent airway must be established with assisted or controlled ventilation. Narcotic antagonists may be required if there is evidence of significant respiratory or cardiovascular depression. However, treatment with these antagonists must be repeated as necessary because of the longer duration of depressant activity of methadone (36 to 48 hours) compared to the antagonists (1 to 3 hours). Nalorphine or Levallorphine should be given intravenously as soon as possible and repeated every 15 minutes if necessary. In a person addicted to narcotics, administration of the usual dose of a narcotic antagonist will precipitate an acute withdrawal syndrome. In such cases, use of an antagonist should be avoided unless there is serious respiratory depression when they should be administered with great care.
Oxygen, intravenous fluids, vasopressors and other supportive measures should be employed as indicated.
36 months.
Do not store above 25°C.
Keep container in the outer carton.
Clear, colourless Type I glass ampoules.
Pack size: 10 × 1ml ampoules in a cardboard carton.
Methadone is controlled under the Misuse of Drugs Act 1971 (Schedule 2).
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