Methadone

Last updated

Methadone
Methadone.svg
Skeletal formula
Methadone-from-xtal-Mercury-3D-bs-v2.png
Ball-and-stick model based on the crystal structure [1] [2]
Clinical data
Trade names Dolophine, Methadose, Methatab, [3] others
AHFS/Drugs.com Monograph
MedlinePlus a682134
License data
Pregnancy
category
  • AU:C
Addiction
liability 		High [4]
Routes of
administration 		By mouth, intravenous, insufflation, sublingual, rectal
Drug class Opioid
ATC code
Legal status
Legal status
Pharmacokinetic data
Bioavailability 15–20% subcutaneous [6]

100% intravenous [6]

41–99% (by mouth) [6]
Protein binding 85–90% [6]
Metabolism Liver (CYP3A4, CYP2B6 and CYP2D6-mediated) [6] [7]
Onset of action Rapid [8]
Elimination half-life 15 to 55 hours [7]
Duration of action Single dose: 4–8 h
Prolonged use:
• Withdrawal prevention: 1–2 days [8]
• Pain relief: 8–12 hours [8] [9]
Excretion Urine, faeces [7]
Identifiers
  • (RS)-6-(dimethylamino)-4,4-diphenylheptan-3-one
CAS Number
PubChem CID
IUPHAR/BPS
DrugBank
ChemSpider
UNII
KEGG
ChEBI
ChEMBL
CompTox Dashboard (EPA)
ECHA InfoCard 100.000.907 OOjs UI icon edit-ltr-progressive.svg
Chemical and physical data
Formula C21H27NO
Molar mass 309.453 g·mol−1
3D model (JSmol)
Chirality Racemic mixture
  • CCC(C(C1=CC=CC=C1)(C2=CC=CC=C2)CC(N(C)C)C)=O
  • InChI=1S/C21H27NO/c1-5-20(23)21(16-17(2)22(3)4,18-12-8-6-9-13-18)19-14-10-7-11-15-19/h6-15,17H,5,16H2,1-4H3 Yes check.svgY
  • Key:USSIQXCVUWKGNF-UHFFFAOYSA-N Yes check.svgY
 X mark.svgNYes check.svgY  (what is this?)    (verify)

Methadone, sold under the brand names Dolophine and Methadose among others, is a synthetic opioid used medically to treat chronic pain and opioid use disorder. [8] Prescribed for daily use, the medicine relieves cravings and opioid withdrawal symptoms. [10] Withdrawal management using methadone can be accomplished in less than a month, [11] or it may be done gradually over a longer period of time, or simply maintained for the rest of the patient's life. [8] While a single dose has a rapid effect, maximum effect can take up to five days of use. [8] [12] After long-term use, in people with normal liver function, effects last 8 to 36 hours. [8] [9] Methadone is usually taken by mouth and rarely by injection into a muscle or vein. [8]

Contents

Side effects are similar to those of other opioids. [8] These frequently include dizziness, sleepiness, nausea, vomiting, and sweating. [8] [13] Serious risks include opioid abuse and respiratory depression. [8] Abnormal heart rhythms may also occur due to a prolonged QT interval. [8] The number of deaths in the United States involving methadone poisoning declined from 4,418 in 2011 [14] to 3,300 in 2015. [15] Risks are greater with higher doses. [16] Methadone is made by chemical synthesis and acts on opioid receptors. [8]

Methadone was developed in Germany in the late 1930s by Gustav Ehrhart and Max Bockmühl. [17] [18] It was approved for use as an analgesic in the United States in 1947, and has been used in the treatment of addiction since the 1960s. [8] [19] It is on the World Health Organization's List of Essential Medicines. [20]

Medical uses

Opioid addiction

Methadone is used for the treatment of opioid use disorder. [21] It may be used as maintenance therapy or in shorter periods to manage opioid withdrawal symptoms. Its use for the treatment of addiction is usually strictly regulated. In the US, outpatient treatment programs must be certified by the federal Substance Abuse and Mental Health Services Administration (SAMHSA) and registered by the Drug Enforcement Administration (DEA) to prescribe methadone for opioid addiction.

A 2009 Cochrane review found methadone was effective in retaining people in treatment and the reduction or cessation of heroin use as measured by self-report and urine/hair analysis and did not affect criminal activity or risk of death. [22]

Treatment of opioid-dependent persons with methadone follows one of two routes: maintenance or withdrawal management. [23] Methadone maintenance therapy (MMT) usually takes place in outpatient settings. It is usually prescribed as a single daily dose medication for those who wish to abstain from illicit opioid use. Treatment models for MMT differ. It is not uncommon for treatment recipients to be administered methadone in a specialized clinic, where they are observed for around 15–20 minutes post-dosing, to reduce the risk of diversion of medication. [24]

The duration of methadone treatment programs ranges from a few months to years. Given opioid dependence is characteristically a chronic relapsing/remitting disorder, MMT may be lifelong. The length of time a person remains in treatment depends on a number of factors. While starting doses may be adjusted based on the amount of opioids reportedly used, most clinical guidelines suggest doses start low (e.g., at doses not exceeding 40 mg daily) and are incremented gradually. [10] [25] It has been found that doses of 40 mg per day were sufficient to help control the withdrawal symptoms but not enough to curb the cravings for the drug. Doses of 80 to 100 mg per day have shown higher rates of success in patients and less illicit heroin use during the maintenance therapy. [26] However, higher doses do put a patient more at risk for overdose than a moderately low dose (e.g. 20 mg/day). [12]

Methadone maintenance has been shown to reduce the transmission of bloodborne viruses associated with opioid injection, such as hepatitis B and C, and/or HIV. [10] The principal goals of methadone maintenance are to relieve opioid cravings, suppress the abstinence syndrome, and block the euphoric effects associated with opioids.

Chronic methadone dosing will eventually lead to neuroadaptation, characterised by tolerance and dependence. However, when used correctly in treatment, maintenance therapy is medically safe, non-sedating, and can provide a slow recovery from opioid addiction. [10] Methadone has been widely used for pregnant women addicted to opioids. [10]

Pain

Methadone is used as an analgesic in chronic pain, often in rotation with other opioids. [27] [28] Due to its activity at the NMDA receptor, it may be more effective against neuropathic pain; for the same reason, tolerance to the analgesic effects may be less than that of other opioids. [29] [30]

Adverse effects

Table from the 2010 ISCD study ranking various drugs (legal and illegal) based on statements by drug-harm experts. Methadone was found to be the 12th overall most dangerous drug. HarmCausedByDrugsTable.svg
Table from the 2010 ISCD study ranking various drugs (legal and illegal) based on statements by drug-harm experts. Methadone was found to be the 12th overall most dangerous drug.
Addiction experts in psychiatry, chemistry, pharmacology, forensic science, epidemiology, and the police and legal services engaged in delphic analysis regarding 20 popular recreational drugs. Street methadone was ranked 4th in dependence, 5th in physical harm, and 5th in social harm. Rational harm assessment of drugs radar plot.svg
Addiction experts in psychiatry, chemistry, pharmacology, forensic science, epidemiology, and the police and legal services engaged in delphic analysis regarding 20 popular recreational drugs. Street methadone was ranked 4th in dependence, 5th in physical harm, and 5th in social harm.

Adverse effects of methadone include: [33]

Withdrawal symptoms

Methadone withdrawal symptoms are reported as being significantly more protracted than withdrawal from opioids with shorter half-lives.

When used for opioid maintenance therapy, Methadone is generally administered as an oral liquid. Methadone has been implicated in contributing to significant tooth decay. Methadone causes dry mouth, reducing the protective role of saliva in preventing decay. Other putative mechanisms of methadone-related tooth decay include craving for carbohydrates related to opioids, poor dental care, and a general decrease in personal hygiene. These factors, combined with sedation, have been linked to the causation of extensive dental damage. [39] [40]

Physical symptoms

Cognitive symptoms

Black box warning

Methadone has the following U.S. FDA black box warning: [43]

Overdose

Most people who overdose on methadone show some of the following symptoms:

The respiratory depression of an overdose can be treated with naloxone. [42] Naloxone is preferred to the newer, longer-acting antagonist naltrexone. Despite methadone's much longer duration of action compared to heroin and other shorter-acting agonists and the need for repeat doses of the antagonist naloxone, it is still used for overdose therapy. As naltrexone has a longer half-life, it is more difficult to titrate. If too large a dose of the opioid antagonist is given to a dependent person, it will result in withdrawal symptoms (possibly severe). When using naloxone, the naloxone will be quickly eliminated and the withdrawal will be short-lived. Doses of naltrexone take longer to be eliminated from the person's system. A common problem in treating methadone overdoses is that given the short action of naloxone (versus the extremely longer-acting methadone), a dosage of naloxone given to a methadone-overdosed person will initially work to bring the person out of overdose, but once the naloxone wears off, if no further naloxone is administered, the person can go right back into overdose (based upon time and dosage of the methadone ingested).

Tolerance and dependence

As with other opioid medications, tolerance and dependence usually develop with repeated doses. There is some clinical evidence that tolerance to analgesia is less with methadone compared to other opioids; this may be due to its activity at the NMDA receptor. Tolerance to the different physiological effects of methadone varies; tolerance to analgesic properties may or may not develop quickly, but tolerance to euphoria usually develops rapidly, whereas tolerance to constipation, sedation, and respiratory depression develops slowly (if ever). [48]

Driving

Methadone treatment may impair driving ability. [49] Drug abusers had significantly more involvement in serious crashes than non-abusers in a study by the University of Queensland. In the study of a group of 220 drug abusers, most of them poly-drug abusers, 17 were involved in crashes killing people, compared with a control group of other people randomly selected having no involvement in fatal crashes. [50] However, there have been multiple studies verifying the ability of methadone maintenance patients to drive. [51] In the UK, persons who are prescribed oral methadone can continue to drive after they have satisfactorily completed an independent medical examination which will include a urine screen for drugs. The license will be issued for 12 months at a time and even then, only following a favourable assessment from their own doctor. [52] Individuals who are prescribed methadone for either IV or IM administration cannot drive in the UK, mainly due to the increased sedation effects that this route of use can cause.

Mortality

In the United States, deaths linked to methadone more than quadrupled in the five-year period between 1999 and 2004. According to the U.S. National Center for Health Statistics, [53] as well as a 2006 series in the Charleston Gazette (West Virginia), [54] medical examiners listed methadone as contributing to 3,849 deaths in 2004. That number was up from 790 in 1999. Approximately 82 percent of those deaths were listed as accidental, and most deaths involved combinations of methadone with other drugs (especially benzodiazepines).

Although deaths from methadone are on the rise[ needs update ], methadone-associated deaths are not being caused primarily by methadone intended for methadone treatment programs, according to a panel of experts convened by the Substance Abuse and Mental Health Services Administration, which released a report titled "Methadone-Associated Mortality, Report of a National Assessment". The consensus report concludes that "although the data remains incomplete, National Assessment meeting participants concurred that methadone tablets or Diskets distributed through channels other than opioid treatment programs most likely are the central factors in methadone-associated mortality." [55]

In 2006, the U.S. Food and Drug Administration issued a caution about methadone, titled "Methadone Use for Pain Control May Result in Death." The FDA also revised the drug's package insert. The change deleted previous information about the usual adult dosage. The Charleston Gazette reported, "The old language about the 'usual adult dose' was potentially deadly, according to pain specialists." [56]

Pharmacology

Receptor binding affinities of isomers of methadone [57] [58]
Compound Affinities (Ki Tooltip Inhibitor constant, in nM)Ratios
MOR Tooltip μ-Opioid receptor DOR Tooltip δ-Opioid receptor KOR Tooltip κ-Opioid receptor SERT Tooltip Serotonin transporter NET Tooltip Norepinephrine transporter NMDAR Tooltip N-Methyl-D-aspartate receptorM:D:KSERT:NET
Racemic methadone1.74354051,4002592,500–8,3001:256:2381:5
Dextromethadone 19.79601,37099212,7002,600–7,4001:49:701:13
Levomethadone 0.9453711,86014.17022,800–3,4001:393:19681:50

Methadone acts by binding to the μ-opioid receptor, but also has some affinity for the NMDA receptor, an ionotropic glutamate receptor. Methadone is metabolized by CYP3A4, CYP2B6, CYP2D6, and is a substrate, or in this case target, for the P-glycoprotein efflux protein, a protein which helps pump foreign substances out of cells, in the intestines and brain. The bioavailability and elimination half-life of methadone are subject to substantial interindividual variability. Its main route of administration is oral. Adverse effects include sedation, hypoventilation, constipation, and miosis, in addition to tolerance, dependence, and withdrawal difficulties. The withdrawal period can be much more prolonged than with other opioids, spanning anywhere from two weeks to several months.

The metabolic half-life of methadone differs from its duration of action. The metabolic half-life is 8 to 59 hours (approximately 24 hours for opioid-tolerant people, and 55 hours for opioid-naive people), as opposed to a half-life of 1 to 5 hours for morphine. [12] The length of the half-life of methadone allows for the exhibition of respiratory depressant effects for an extended duration of time in opioid-naive people. [12]

Methadone at therapeutic concentrations is known to prolong the QTc interval, which indicates that the heart muscle repolarizes more slowly. This QTc prolongation tends to increase the risk of torsades de pointes (TdP), a heart rhythm disturbance that can lead to syncope or sudden death. In a large observational study in Sweden, methadone was associated with a particularly high incidence of TdP, especially in younger patients. The incidence of TdP was 41.9 cases per 100,000 users of methadone in the 18-64 year old age group. [59] In this study of TdP, methadone was the highest-risk drug in the 18-64 year-old group, with the sole exception of the antiarrhythmic drug amiodarone, which was associated with 66.5 cases of TdP per 100,000 amiodarone users. [59] The high incidence of TdP in amiodarone-treated patients may indicate correlation and not causation because amiodarone is often prescribed to patients with preexisting heart conditions that independently increase the risk of TdP. Methadone likely causes cardiac arrhythmias (such as TdP) via two mechanisms. [60] Like many other cardiotoxic drugs, methadone blocks the hERG K+ channel. The two enantiomers of methadone inhibit hERG channels with different potency. Dextromethadone, which is less potent as an opioid, is more potent at blocking the hERG channel with an IC50 of ~12 μM. Levomethadone has a lower affinity, with an IC50 of ~29 μM at the hERG channel. [60] Methadone is also known to block the Nav1.5 voltage-gated Na+ channel (SCN5A) with an IC50 of ~10 μM, which is similar to the local anesthetic bupivacaine. Both enantiomers of methadone block the Nav1.5 channel with similar affinities. [60] Bupivacaine is especially cardiotoxic among local anesthetics, and it is believed to act via this same sodium channel. Plasma concentrations of methadone in recovering addicts can reach 4 μM during therapy, so the actions of methadone at both the hERG potassium channel and the Nav1.5 sodium channel are possibly clinically relevant in producing cardiac side effects. [60] This also suggests that levomethadone is not completely free of cardiac toxicity.

Mechanism of action

Levomethadone (the R-(–)-methadone enantiomer) is a μ-opioid receptor agonist with higher intrinsic activity than morphine, but lower affinity. [61] Dextromethadone (the S-(+)-methadone enantiomer) has a much lower affinity to the μ-opioid receptor than levomethadone. Both enantiomers bind to the glutamatergic NMDA (N-methyl-D-aspartate) receptor, acting as noncompetitive antagonists. Methadone has been shown to reduce neuropathic pain in rat models, primarily through NMDA receptor antagonism.[ citation needed ] NMDA antagonists such as dextromethorphan, ketamine, tiletamine and ibogaine are being studied for their role in decreasing the development of tolerance to opioids and as possible for eliminating addiction/tolerance/withdrawal,[ citation needed ] possibly by disrupting memory circuitry. Acting as an NMDA antagonist may be one mechanism by which methadone decreases craving for opioids and tolerance, and has been proposed as a possible mechanism for its distinguished efficacy regarding the treatment of neuropathic pain.[ citation needed ] Methadone also acted as a potent, noncompetitive α3β4 neuronal nicotinic acetylcholine receptor antagonist in rat receptors, expressed in human embryonic kidney cell lines. [62]

Metabolism

Methadone has a slow metabolism and very high fat solubility, making it longer lasting than morphine-based drugs. Methadone has a typical elimination half-life of 15 to 60 hours with a mean of around 22. However, metabolism rates vary greatly between individuals, up to a factor of 100, [63] [64] ranging from as few as 4 hours to as many as 130 hours, [65] or even 190 hours. [66] This variability is apparently due to genetic variability in the production of the associated cytochrome enzymes CYP3A4, CYP2B6 and CYP2D6. Many substances can also induce, inhibit or compete with these enzymes further affecting (sometimes dangerously) methadone half-life. A longer half-life frequently allows for administration only once a day in opioid withdrawal management and maintenance programs. People who metabolize methadone rapidly, on the other hand, may require twice daily dosing to obtain sufficient symptom alleviation while avoiding excessive peaks and troughs in their blood concentrations and associated effects. [65] This can also allow lower total doses in some such people. The analgesic activity is shorter than the pharmacological half-life; dosing for pain control usually requires multiple doses per day normally dividing daily dosage for administration at 8-hour intervals. [67]

The main metabolic pathway involves N-demethylation by CYP3A4 in the liver and intestine to give 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP). [6] [68] This inactive product, as well as the inactive 2-ethyl-5-methyl-3,3-diphenyl-1-pyrroline (EMDP), produced by a second N-demethylation, are detectable in the urine of those taking methadone.

Route of administration

The most common route of administration at a methadone clinic is in a racemic oral solution, though in Germany, only the R enantiomer (the L optical isomer) has traditionally been used, as it is responsible for most of the desired opioid effects. [65] The single-isomer form is becoming less common due to the higher production costs.

Methadone is available in traditional pills, sublingual tablets, and two different formulations designed for the person to drink. Drinkable forms include ready-to-dispense liquid (sold in the United States as Methadose), and Diskets (known on the street as "wafers" or "biscuits") tablets which are dispersible in water for oral administration, used similarly to Alka-Seltzer. The liquid form is the most common as it allows for smaller dose changes. Methadone is almost as effective when administered orally as by injection. Oral medication is usually preferable because it offers safety, and simplicity and represents a step away from injection-based drug abuse in those recovering from addiction. U.S. federal regulations require the oral form in addiction treatment programs. [69] Injecting methadone pills can cause collapsed veins, bruising, swelling, and possibly other harmful effects. Methadone pills often contain talc that, when injected, produces a swarm of tiny solid particles in the blood, causing numerous minor blood clots. [70] [71] These particles cannot be filtered out before injection, and will accumulate in the body over time, especially in the lungs and eyes, producing various complications such as pulmonary hypertension, an irreversible and progressive disease. [72] [73] [74] The formulation sold under the brand name Methadose (flavored liquid suspension for oral dosing, commonly used for maintenance purposes) should not be injected either. [75]

Information leaflets included in packs of UK methadone tablets state that the tablets are for oral use only and that use by any other route can cause serious harm. In addition to this warning, additives have now been included in the tablet formulation to make the use of them by the IV route more difficult. [76]

Methadone is also available in ampoules with strength of 50mg/ml & 10mg/ml for IV/IM/SC use in the UK. [77] Prescribing the injectable formulation was more common in the 90s with prescribers reporting that up to 9-10% of all methadone prescription were for ampoules. This practice is much less common nowadays [78]

Chemistry

Detection in biological fluids

Methadone and its major metabolite, 2-ethylidene-1,5-dimethyl-3,3-diphenylpyrrolidine (EDDP), are often measured in urine as part of a drug abuse testing program, in plasma or serum to confirm a diagnosis of poisoning in hospitalized victims, or in whole blood to assist in a forensic investigation of a traffic or other criminal violation or a case of sudden death. Methadone usage history is considered in interpreting the results as a chronic user can develop tolerance to doses that would incapacitate an opioid-naïve individual. Chronic users often have high methadone and EDDP baseline values. [79]

Conformation

The protonated form of methadone takes on an extended conformation, while the free base is more compact. In particular, it was found that there is an interaction between the tertiary amine and the carbonyl carbon of the ketone function (R3N ••• >C=O) that limits the molecule's conformation freedom, though the distance (291 pm by X-ray) is far too long to represent a true chemical bond. However, it does represent the initial trajectory of attack of an amine on a carbonyl group and was an important piece of experimental evidence for the proposal of the Bürgi–Dunitz angle for carbonyl addition reactions. [80]

History

40 mg of methadone Methadone 40mg.jpg
40 mg of methadone

Methadone was developed in 1937 in Germany by scientists working for I.G. Farbenindustrie AG at the Farbwerke Hoechst who were looking for a synthetic opioid that could be created with readily available precursors, to solve Germany's opium and morphine shortage problem. [81] [82] On 11 September 1941 Bockmühl and Ehrhart filed an application for a patent for a synthetic substance they called Hoechst 10820 or Polamidon (a name still in regular use in Germany) [83] and whose structure had little relation to morphine or other "true opiates" such as diamorphine (Heroin), desomorphine (Permonid), nicomorphine (Vilan), codeine, dihydrocodeine, oxymorphone (Opana), hydromorphone (Dilaudid), oxycodone (OxyContin), hydrocodone (Dicodid), and other closely related opium alkaloid derivatives and analogues. [84] It was brought to market in 1943 and was widely used by the German army during WWII as a substitute for morphine. [81]

In the 1930s, pethidine (meperidine) went into production in Germany; however, the production of methadone, then being developed under the designation Hoechst 10820, was not carried forward because of side effects discovered in the early research. [85] After the war, all German patents, trade names, and research records were requisitioned and expropriated by the Allies. The records on the research work of the I.G. Farbenkonzern at the Farbwerke Hoechst were confiscated by the U.S. Department of Commerce Intelligence, investigated by a Technical Industrial Committee of the U.S. Department of State and then brought to the US. [81] The report published by the committee noted that while methadone itself was potentially addictive, it produced "considerably" less euphoria, sedation, and respiratory depression than morphine at equianalgesic doses and was thus interesting as a commercial drug. The same report also compared methadone to pethidine. German researchers reported that methadone was capable of producing strong morphine-like physical dependence, which is characterized by opioid withdrawal symptoms which are lesser in severity and intensity compared to morphine, but methadone was associated with a considerably prolonged or protracted withdrawal syndrome when compared to morphine. [48] [81] Morphine produced higher rates of self-administration and reinforcing behaviour in both human and animal subjects when compared to both methadone and pethidine. In comparison to equianalgesic doses of pethidine (Demerol), methadone was shown to produce less euphoria, but higher rates of constipation, and roughly equal levels of respiratory depression and sedation. [81]

In the early 1950s, methadone (most times the racemic HCl salts mixture) was also investigated for use as an antitussive. [86]

Isomethadone, noracymethadol, LAAM, and normethadone were first developed in Germany, the United Kingdom, Belgium, Austria, Canada, and the United States in the thirty or so years after the 1937 discovery of pethidine, the first synthetic opioid used in medicine. These synthetic opioids have increased length and depth of satiating any opiate cravings and generate very strong analgesic effects due to their long metabolic half-life and strong receptor affinity at the mu-opioid receptor sites. Therefore, they impart much of the satiating and anti-addictive effects of methadone by suppressing drug cravings. [87]

It was only in 1947 that the drug was given the generic name "methadone" by the Council on Pharmacy and Chemistry of the American Medical Association. Since the patent rights of the I.G. Farbenkonzern and Farbwerke Hoechst were no longer protected, each pharmaceutical company interested in the formula could buy the rights for the commercial production of methadone for just one dollar (MOLL 1990).

Methadone was introduced into the United States in 1947 by Eli Lilly and Company as an analgesic under the trade name Dolophine. [81] An urban myth later arose that Nazi leader Adolf Hitler ordered the manufacture of methadone or that the brand name 'Dolophine' was named after him, probably based on the similarity of "doloph" with "Adolph". (The pejorative term "adolphine" would appear in the early 1970s. [88] [89] ) However, the name "Dolophine" was a contraction of "Dolo" from the Latin word dolor (pain), and finis, the Latin word for "end". Therefore, Dolophine literally means "pain end". [90]

Methadone was studied as a treatment for opioid addiction at the Addiction Research Center of the Narcotics Farm in Lexington, Kentucky in the 1950s, and by Rockefeller University physicians Robert Dole and Marie Nyswander in the 1960s in New York City. [91] By 1976, methadone clinics had opened in cities including Chicago, New York, and New Haven, with some 38,000 patients treated in New York City alone. [91] [92]

Society and culture

Brand names

Brand names include Dolophine, Symoron, Amidone, Methadose, Physeptone, Metadon, Metadol, Metadol-D, Heptanon and Heptadon among others.

Economics

In the US, generic methadone tablets are inexpensive, with retail prices ranging from $0.25 to $2.50 per defined daily dose. [93]

Methadone maintenance clinics in the US may be covered by private insurance, Medicaid, or Medicare. [94] Medicare covers methadone under the prescription drug benefit, Medicare Part D, when it is prescribed for pain, but not when it is used for opioid dependence treatment because it cannot be dispensed in a retail pharmacy for this purpose. [95] In California methadone maintenance treatment is covered under the medical benefit. Patients' eligibility for methadone maintenance treatment is most often contingent on them being enrolled in substance abuse counseling. People on methadone maintenance in the US either have to pay cash or if covered by insurance must complete a pre-determined number of hours per month in therapeutic groups or counseling. [96] The United States Department of Veteran's Affairs (VA) Alcohol and Drug Dependence Rehabilitation Program offers methadone services to eligible veterans enrolled in the VA health care system. [97]

Methadone maintenance treatment (MMT) cost analyses often compare the cost of clinic visits versus the overall societal costs of illicit opioid use. [98] [99] A preliminary cost analysis conducted in 2016 by the US Department of Defense determined that methadone treatment, which includes psychosocial and support services, may cost an average of $126.00 per week or $6,552.00 per year. [100] The average cost for one full year of methadone maintenance treatment is approximately $4,700 per patient, whereas one full year of imprisonment costs approximately $24,000 per person. [101]

Regulation

United States and Canada

Methadone is a Schedule I controlled substance in Canada and Schedule II in the United States, with an ACSCN of 9250 and a 2014 annual aggregate manufacturing quota of 31,875 kilos for sale. Methadone intermediate is also controlled, under ACSCN 9226 also under Schedule II, with a quota of 38,875 kilos. In most countries of the world, methadone is similarly restricted. The salts of methadone in use are the hydrobromide (free base conversion ratio 0.793), hydrochloride (0.894), and HCl monohydrate (0.850). [102] Methadone is also regulated internationally as a Schedule I controlled substance under the United Nations Single Convention on Narcotic Drugs of 1961. [103] [104]

Methadone clinics

In the United States, prescription of methadone requires intensive monitoring and must be obtained in-person from an Opioid Treatment Program—colloquially known as a 'methadone clinic'—when prescribed for opioid use disorder (OUD). [26] According to federal laws, methadone cannot be prescribed by a doctor and obtained from a pharmacy to treat addiction. Because of its long half-life, methadone is almost invariably prescribed to be taken in a single daily dose. At nearly all methadone clinics in the US, patients must visit a clinic to receive and take their dose under the supervision of a nurse. Both patients who are new to methadone treatment and high-risk patients—such as those who are using drugs and alcohol, including cannabis in some states—must visit the clinic daily. [105] [106]

Other countries

In Russia, methadone treatment is illegal. In 2008, the Chief Sanitary Inspector of Russia Gennadiy Onishchenko, claimed that Russian health officials were not convinced of methadone's efficacy in treating heroin and/or opioid addiction. Instead of replacement therapy and gradual reduction of illicit drug use, Russian doctors encouraged immediate cessation and withdrawal. People who use drugs were generally given sedatives and non-opioid analgesics to cope with withdrawal symptoms. [107] Brazilian footballer assistant Robson Oliveira was arrested in 2019 upon arriving in Russia with methadone tablets sold legally in other countries for what was considered drug trafficking under Russian law. [108]

As of 2015, China had the largest methadone maintenance treatment program with over 250,000 people in over 650 clinics in 27 provinces. [109]

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Oxycodone, sold under the brand name Roxicodone and OxyContin among others, is a semi-synthetic opioid used medically for treatment of moderate to severe pain. It is highly addictive and is a commonly abused drug. It is usually taken by mouth, and is available in immediate-release and controlled-release formulations. Onset of pain relief typically begins within fifteen minutes and lasts for up to six hours with the immediate-release formulation. In the United Kingdom, it is available by injection. Combination products are also available with paracetamol (acetaminophen), ibuprofen, naloxone, naltrexone, and aspirin.

<span class="mw-page-title-main">Naloxone</span> Opioid receptor antagonist

Naloxone is an opioid antagonist: a medication used to reverse or reduce the effects of opioids. For example, it is used to restore breathing after an opioid overdose. It is also known as Narcan. Effects begin within two minutes when given intravenously, five minutes when injected into a muscle, and ten minutes as a nasal spray. Naloxone blocks the effects of opioids for 30 to 90 minutes.

<span class="mw-page-title-main">Hydromorphone</span> Opioid medication used for pain relief

Hydromorphone, also known as dihydromorphinone, and sold under the brand name Dilaudid among others, is a morphinan opioid used to treat moderate to severe pain. Typically, long-term use is only recommended for pain due to cancer. It may be used by mouth or by injection into a vein, muscle, or under the skin. Effects generally begin within half an hour and last for up to five hours. A 2016 Cochrane review found little difference in benefit between hydromorphone and other opioids for cancer pain.

<span class="mw-page-title-main">Opioid</span> Psychoactive chemical

Opioids are a class of drugs that derive from, or mimic, natural substances found in the opium poppy plant. Opioids work in the brain to produce a variety of effects, including pain relief. As a class of substances, they act on opioid receptors to produce morphine-like effects.

<span class="mw-page-title-main">Opioid use disorder</span> Medical condition

Opioid use disorder (OUD) is a substance use disorder characterized by cravings for opioids, continued use despite physical and/or psychological deterioration, increased tolerance with use, and withdrawal symptoms after discontinuing opioids. Opioid withdrawal symptoms include nausea, muscle aches, diarrhea, trouble sleeping, agitation, and a low mood. Addiction and dependence are important components of opioid use disorder.

<span class="mw-page-title-main">Buprenorphine</span> Opioid used to treat pain & opioid use disorder

Buprenorphine, sold under the brand name Subutex among others, is an opioid used to treat opioid use disorder, acute pain, and chronic pain. It can be used under the tongue (sublingual), in the cheek (buccal), by injection, as a skin patch (transdermal), or as an implant. For opioid use disorder, the patient must have moderate opioid withdrawal symptoms before buprenorphine can be administered under direct observation of a health-care provider.

<span class="mw-page-title-main">Naltrexone</span> Medication

Naltrexone, sold under the brand name Revia among others, is a medication primarily used to manage alcohol use or opioid use disorder by reducing cravings and feelings of euphoria associated with substance use disorder. It has also been found effective in the treatment of other addictions and may be used for them off-label. An opioid-dependent person should not receive naltrexone before detoxification. It is taken orally or by injection into a muscle. Effects begin within 30 minutes, though a decreased desire for opioids may take a few weeks to occur.

<span class="mw-page-title-main">Opioid antagonist</span> Receptor antagonist that acts on one or more of the opioid receptors

An opioid antagonist, or opioid receptor antagonist, is a receptor antagonist that acts on one or more of the opioid receptors.

Opioid-induced hyperalgesia (OIH) or opioid-induced abnormal pain sensitivity, also called paradoxical hyperalgesia, is an uncommon condition of generalized pain caused by the long-term use of high dosages of opioids such as morphine, oxycodone, and methadone. OIH is not necessarily confined to the original affected site. This means that if the person was originally taking opioids due to lower back pain, when OIH appears, the person may experience pain in the entire body, instead of just in the lower back. Over time, individuals taking opioids can also develop an increasing sensitivity to noxious stimuli, even evolving a painful response to previously non-noxious stimuli (allodynia). This means that if the person originally felt pain from twisting or from sitting too long, the person might now additionally experience pain from a light touch or from raindrops falling on the skin.

Drug detoxification is variously construed or interpreted as a type of "medical" intervention or technique in regards to a physical dependence mediated by a drug; as well as the process and experience of a withdrawal syndrome or any of the treatments for acute drug overdose (toxidrome). The first definition however, in relation to substance dependence and its treatment is arguably a misnomer and even directly contradictory since withdrawal is neither contingent upon nor alleviated through biological excretion or clearance of the drug. In fact, excretion of a given drug from the body is one of the very processes that leads to withdrawal since the syndrome arises largely due to the cessation itself and the drug being absent from the body; especially the blood plasma, not from ‘leftover toxins’ or traces of the drug still being in the system.

<span class="mw-page-title-main">RB-101</span> Chemical compound

RB-101 is a drug that acts as an enkephalinase inhibitor, which is used in scientific research.

An equianalgesic chart is a conversion chart that lists equivalent doses of analgesics. Equianalgesic charts are used for calculation of an equivalent dose between different analgesics. Tables of this general type are also available for NSAIDs, benzodiazepines, depressants, stimulants, anticholinergics and others.

<span class="mw-page-title-main">Opioid overdose</span> Toxicity due to excessive consumption of opioids

An opioid overdose is toxicity due to excessive consumption of opioids, such as morphine, codeine, heroin, fentanyl, tramadol, and methadone. This preventable pathology can be fatal if it leads to respiratory depression, a lethal condition that can cause hypoxia from slow and shallow breathing. Other symptoms include small pupils and unconsciousness; however, its onset can depend on the method of ingestion, the dosage and individual risk factors. Although there were over 110,000 deaths in 2017 due to opioids, individuals who survived also faced adverse complications, including permanent brain damage.

<span class="mw-page-title-main">Opiate</span> Substance derived from opium

An opiate is an alkaloid substance derived from opium. It differs from the similar term opioid in that the latter is used to designate all substances, both natural and synthetic, that bind to opioid receptors in the brain. Opiates are alkaloid compounds naturally found in the opium poppy plant Papaver somniferum. The psychoactive compounds found in the opium plant include morphine, codeine, and thebaine. Opiates have long been used for a variety of medical conditions, with evidence of opiate trade and use for pain relief as early as the eighth century AD. Most opiates are considered drugs with moderate to high abuse potential and are listed on various "Substance-Control Schedules" under the Uniform Controlled Substances Act of the United States of America.

<span class="mw-page-title-main">Buprenorphine/naloxone</span> Opioid treatment

Buprenorphine/naloxone, sold under the brand name Suboxone among others, is a fixed-dose combination medication that includes buprenorphine and naloxone. It is used to treat opioid use disorder, and reduces the mortality of opioid use disorder by 50%. It relieves cravings to use and withdrawal symptoms. Buprenorphine/­naloxone is available for use in two different forms, under the tongue or in the cheek.

<span class="mw-page-title-main">Harris Isbell</span> American pharmacologist

Harris Isbell was an American pharmacologist and the director of research for the NIMH Addiction Research Center at the Public Health Service Hospital in Lexington, Kentucky from 1945 to 1963. He did extensive research on the physical and psychological effects of various drugs on humans. Early work investigated aspects of physical dependence with opiates and barbiturates, while later work investigated psychedelic drugs, including LSD. The research was extensively reported in academic journals such as the Journal of Pharmacology and Experimental Therapeutics, Psychopharmacologia, and the A.M.A. Archives of Neurology and Psychiatry.

Clinical Opiate Withdrawal Scale (COWS) is a method used by registered practitioners to measure the severity of a patient's opioid withdrawal symptoms. This method consists of a series of 11 topics each comprising 4 - 5 common symptoms experienced by a patient undergoing opioid withdrawal. In each topic a rank is given depending on what the patient responds to. Generally, 0 is considered to be no symptom shown and 4 or 5 is considered to be the most common and severe symptom shown. These results are then added up and a final diagnosis is made based on the value obtained. This test is crucial as it allows the practitioner to assess the physiological and psychological behaviours of the patient as well as the severity of each symptom during the duration of the examination. The results are grouped into 3 categories of mild, moderately severe and severe. Mild consists of 5 to 12 points, moderately severe consists of 13 to 24 points and anything above 36 points is severe and requires direct medical attention.

<span class="mw-page-title-main">Opioid withdrawal</span> Withdrawal symptoms of opiates

Opioid withdrawal is a set of symptoms arising from the sudden cessation or reduction of opioids where previous usage has been heavy and prolonged. Signs and symptoms of withdrawal can include drug craving, anxiety, restless legs syndrome, nausea, vomiting, diarrhea, sweating, and an elevated heart rate. Opioid use triggers a rapid adaptation in cellular signaling pathways that, when reduced or stopped, can cause adverse physiological effects. All opioids, both recreational drugs and medications, when reduced or stopped, can lead to opioid withdrawal symptoms. When withdrawal symptoms are due to recreational opioid use, the term opioid use disorder is used, whereas when due to prescribed medications, the term prescription opioid use disorder is used. Opioid withdrawal can be managed by the use of opioid replacement therapy, while symptoms may be relieved by the use of medications such as lofexidine and clonidine.

Opioid agonist therapy (OAT) is a treatment in which prescribed opioid agonists are given to patients who live with Opioid use disorder (OUD). In the case of methadone maintenance treatment (MMT), methadone is used to treat dependence on heroin or other opioids, and is administered on an ongoing basis.

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