Methadone

  • a potent synthetic opioid agonist
  • substitutes for heroin, prevents the emergence of opioid withdrawal symptoms and reduces cravings for heroin
  • is well absorbed orally but does not produce rapid intoxication
  • has a long half life and is taken in a single daily dose
  • binds to various body tissues and is very slowly released enabling the individual to be maintained in a stable state
  • diminishes the euphoric effects of additional opioids

 

Treatment Availability
  • Patients need to have just the one doctor and one pharmacy for their methadone or buprenorphine treatment. 
  • Once a doctor to prescribe the methadone or buprenorphine has been found, this doctor will discuss with the patient their expectations of the program. 
  • The doctor needs to obtain a special permit before treating anyone with methadone or buprenorphine so sometimes the patient needs to wait a few hours between their first visit with the doctor and obtaining their prescription.
  • The doctor must sign a recent passport size photo of the patient so the pharmacist is sure whom the prescription is for. Patients must provide the photo.
  • A prescription and the signed photo are then taken to the pharmacy, in a sealed envelope, and the pharmacist and patient agree on how they will work together.
  • methadone is dispensed as a 5mg/mL syrup and is required to be supervised by a pharmacist.  For most individuals, withdrawal symptoms will be alleviated but not eliminated by methadone doses less than 30mg.  Stabilisation on methadone is about titrating the dose against the needs of the individual.  Doses for effective methadone maintenance treatment are typically between 60-100mg per day.

 

Indications (when treatment might be suitable)
  • opioid dependent
  • 18 years or older (check jurisdictional requirements regarding age limits for Methadone Maintenance Treatment)
  • able to provide proof of identity as is required for treatment with all Schedule 8 medications
  • capable of giving informed consent
Contraindications (when treatment will not be suitable)
  • people with severe hepatic impairment (decompensated liver disease) as methadone may precipitate hepatic encephalopathy.
  • generally treatment other than methadone should be considered for a person under the age of 18 years, however, methadone treatment should not be precluded solely on the grounds of age. The prescribing doctor should check jurisdictional requirements regarding age limits for methadone treatment.
  • people who are hypersensitive to methadone or other ingredients in the formulation.
  • other contraindications identified by the manufacturers of methadone include severe respiratory depression, acute asthma, acute alcoholism, head injury and raised intracranial pressure, ulcerative colitis, biliary and renal tract spasm, and patients receiving monoamine oxidase inhibitors or within 14 days of stopping such treatment. It is recommended that specialist advice be sought in these cases.
Effects & mechanism of action

Methadone is a potent synthetic opioid agonist which is well absorbed orally and has a long, although variable plasma half life. The effects of methadone are qualitatively similar to morphine and other opioids.

Effects:

  • Analgesia
  • Sedation

  • Respiratory depression

  • Euphoria (oral methadone causes less
  • euphoria than intravenous heroin)
  • Other Actions
  • Decreased blood pressure

  • Constriction of the pupils

  • Gastrointestinal tract actions
  • —  Reduced gastric emptying
  • —  Reduced motility
  • —  Elevated pyloric sphincter tone
  • —  Elevated tone of Sphincter of Oddi 
can result in biliary spasm
  • Skin actions
— Histamine release
  • Endocrine actions including
  • —  Reduced Follicle Stimulating 
Hormone
  • —  Reduced Luteinising Hormone
  • —  Elevated Prolactin
  • —  Reduced Adreno-Cortico-Trophic 
Hormone
  • —  Reduced testosterone 
(Endocrine function may return to normal after 2-10 months on methadone)
  • —  Elevated Anti Diuretic Hormone
  • Antitussive (cough suppressant)

Most people who have used heroin will experience few side effects from methadone. Once on a stable dose, tolerance develops until cognitive skills and attention are not impaired. Symptoms of constipation, sexual dysfunction and occasionally increased sweating can continue to be troubling for the duration of Methadone maintenance treatment.

Methadone is fat soluble and binds to a range of body tissues including the lungs, kidneys, liver and spleen such that the concentration of methadone in these organs is much higher than in blood. There is then a fairly slow transfer of methadone between these stores and the blood. Because of its good oral bioavailability and long half life, methadone is taken in an oral daily dose.

Methadone is primarily broken down in the liver via the cytochrome P450 enzyme system.  

Approximately 10% of methadone administered orally is eliminated unchanged. The rest is metabolised and the (mainly inactive) metabolites are eliminated in the urine and faeces. Methadone is also secreted in sweat and saliva.

  • Onset of effects:
 30 minutes
  • Peak effects: Approx 3 hours
  • 
Half life (in maintenance therapy)
: approx. 24 hours
  • Time to reach stabilisation: 3-10 days

 

Source: Clinical Guidelines and Procedures for the Use of Methadone
in the Maintenance Treatment of
Opioid Dependence

Authors: Sue Henry-Edwards, Linda Gowing, Jason White, Robert Ali, James Bell, Rodger Brough, Nick Lintzeris,
 Alison Ritter & Allan Quigley

August 2003

Potential side effects & risks (including overdose)

Potential side effects

  • Sleep disturbances
  • Nausea and vomiting
  • Constipation
  • Dry mouth
  • Increased sweating
  • Itching
  • Vasodilation (widening of blood vessels)
  • Menstrual irregularities in women
  • Gynaecomastia (benign enlargement of breast tissue in males)
  • Sexual dysfunction including impotence in males
  • Fluid retention and weight gain

Risks
Overdose

  • Overdose is the main risk and increases in the first two weeks of induction to methadone maintenance therapy and when methadone is used in combination with other sedative drugs.
  • Toxic effects of overdose may become life threatening several hours after ingestion due to the slow onset of action and long half life of methadone
  • Because methadone levels rise progressively with successive doses during induction into treatment, most deaths in this period have occurred on the third or fourth day of treatment.

Drug Interactions

  • Toxicity and death have resulted from interactions between methadone and other drugs.
  • Some psychotropic drugs may increase the actions of methadone because they have overlapping, additive effects (e.g. benzodiazepines and alcohol add to the respiratory depressant effects of methadone).
  • Other drugs interact with methadone by influencing (increasing or decreasing) metabolism. Drugs which induce the metabolism of methadone can cause a withdrawal syndrome if administered to patients maintained on methadone. These drugs should be avoided in methadone.

 

Risk of relapse
Longer duration and greater intensity of pre-treatment opioid use is associated with an increased probability of relapse to opioid use after leaving treatment.

The likelihood of a person maintaining abstinence after leaving treatment is increased in people who have established drug-free social supports, are in stable family situations, employed, and with good psychological strengths.

From: Clinical Guidelines and Procedures for the Use of Methadone
in the Maintenance Treatment of
 Opioid Dependence

Authors: Sue Henry-Edwards, Linda Gowing, Jason White, Robert Ali, James Bell, Rodger Brough, Nick Lintzeris,
 Alison Ritter & Allan Quigley

August 2003

Ceasing or withdrawing from treatment
  • Should be done very slowly over months
  • Requires careful reduction planning and monitoring
  • Occasionally stabilisation on reduced dose may be required before attempting further reduction
  • Similar to heroin withdrawal but later onset
  • Those who “jump off” doses of more than 20 mg will suffer severe withdrawal symptoms for 5-10 days
  • Symptomatic medication may alleviate these symptoms

It is recommended that people be encouraged to remain in treatment for at least 12 months to achieve enduring lifestyle changes.

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