Synthetic opioid agonist used for management of addiction and chronic pain.

Mu-opioid receptor antagonist.

Mainly administered as a mixture of R,S methadone-R has a 10 fold more potent agonist action on mu-opioid receptor and 50 fold higher analgesic potency than S.

It has a very slow onset of action and a long elimination half-life of 24 to 36 hours.

Can lead to drug accumulation and toxicity.

methadone maintenance programs reduces the use of illicit opioids, overdose death rates, criminality, and allows patients to improve their health and social productivity.

Maintenance methadone reduces the transmission of infectious diseases such as hepatitis and HIV, which are associated with heroin addiction.

Its principal effects of maintenance dose are to relieve narcotic craving, suppress withdrawal syndrome, and block the euphoric effects associated with heroin.

It has been the most successful long-term treatment option for severe opioid use disorder.

Its use improves retention in chemical dependency treatment programs and may reduce suicidality in morbidly depressed addicts.

When methadone is used long-term it can build up unpredictably in the body and lead to potentially deadly slowed breathing.

Among the safer opioid drugs for patients with renal insufficiency.

Half-life variable ranging from 17 to 50 hours and up to 190 hours in some patients.

Because the drug has a long half life is hard to predict the half-life which can lead to toxic levels and cause respiratory depression.

It can activate the NMDAreceptor and inhibit serotonin and norepinephrine reuptake.

The drug may interfere with anti-anxiety medicine medications.

Standard opioid substitution treatment for opioid dependence.

Methadone was involved in more than 30% of overdose deaths linked to the use of prescription painkillers in 2009.

The drug made up only about 2% of pain prescriptions in the year 2009.

In 2009 more than 4 million prescriptions for methadone were written, and as result methadone overdose deaths have increased.

There are more than 5000 methadone overdose deaths per year, more than the number of deaths from heroin and cocaine combined.

Use in opioid dependence associated with reduced major risks associated with untreated dependence in individuals willing to undergo treatment.

In contrast with naltrexone, it is not associated with the risk of precipitated withdrawal, so abstinence before the initiation of methadone treatment for opioid use disorders is not necessary.

15-25% of opioid dependent patients do not have a favorable outcome with this agent.

Has a relatively long and unpredictable half life.

Can be administered to patients outside the hospital through an opioid treatment program licensed and regulated at the federal and state levels.

Suggested activities include:mu antagonist, N- methyl-D-aspartate receptor antagonist, monoamine reuptake inhibitor, and alpha receptor agonist.

A useful drug for opioid rotation because of its efficacy, oral bioavailability, lack of active metabolites, incomplete cross tolerance with other agents, and low cost.

Slow elimination phase of 15-60 hours.

Elimination by cytochromes 3A4 and 2B6.

P-glycoprotein participates in preventing central methadone intoxication.

May be associated with prolongation of the QT interval, Torsades de pointes, and sudden deaths have been reported in patients with methadone exposure.

Methadone most common drug causing prolonged QT interval, with ventricular arrhythmias most frequent adverse effect.

The majority of patients require 80 mg to 120 mg per day to achieve desired effects.

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