Methadone - Similar Drugs

Similar Drugs

See also: Heroin-assisted Treatment and Buprenorphine

There are two methadone isomers that form the racemic mixture which is more common as it is cheaper to produce. The laevorotary isomer, which is isolated by several recrystalisations from racemic methadone, is more expensive to produce than the racemate. It is more potent at the opioid receptor than the racemic mixture and is marketed especially in continental Europe as an analgesic under the trade names Levo-Polamidone, Polamidone, Heptanone, Heptadone, Heptadon and others. It is used as the hydrochloride salt almost exclusively with some uncommon pharmaceuticals and research subjects consisting of the tartrate. The dextrorotary isomer d-methadone is not commercially available. It is devoid of opioid activity and it acts as an NMDA antagonist. It has been shown to be analgesic in experimental models of chronic pain. Clinical trials of d-methadone, to test its analgesic efficacy against neuropathic pain are in progress.

The closest chemical relative of methadone in clinical use is levo-α-acetylmethadol or LAAM. It has a longer duration of action (from 48 to 72 hours), permitting a reduction in frequency of use. In 1994, it was approved as a narcotic addiction treatment. In the Netherlands, like methadone and all other strong opioids, LAAM is a List I drug of the Opium Law, and in Schedule II of the United States Controlled Substances Act. LAAM has since been removed from the US and European markets due to reports of rare cardiac side effects.

Other drugs which are not structurally related to methadone are also used in maintenance treatment, particularly Subutex (buprenorphine) and Suboxone (buprenorphine combined with naloxone). In the NL, Switzerland, the UK and a few other European countries, however, not only buprenorphine and oral methadone but also injectable methadone and pharmaceutical diamorphine (heroin) or other opioids may be used for outpatient maintenance treatment of opiate addiction, and treatment is generally provided in much less heavily regulated environments than in the United States. In the United Kingdom, diamorphine is used extremely selectively and is not available on prescription to addicts; except in specialist trials which involved no more than 300 participants. A study from Austria indicated that slow release oral morphine (in the form of MS-Contin) under trade names Substitol-Retard and Compensan, provide better results than oral methadone, and studies of heroin maintenance have indicated that a low background dose of methadone combined with heroin maintenance may significantly improve outcomes for less-responsive patients. Since the late 90s in Austria, slow release oral morphine has been used alongside methadone and buprenorphine for OST and more recently it has been approved in Slovenia and Bulgaria, and it has gained approval in other EU nations including the United Kingdom, although its use is not as of yet not as widespread. The more attractive side effect profile of morphine compared to buprenorphine or methadone has led to the adoption of morphine as an OST treatment option, and currently in Vienna over 60 percent of substitution therapy utilizes slow release oral morphine. Illicit diversion has been a problem, but to the many proponents of the utilization of morphine for OST, the benefits far outweigh the costs, taking into account the much higher percentage of addicts who are "held" or, from another perspective, satisfied by this treatment option, as opposed to methadone and buprenorphine treated addicts, who are more likely to forgo their treatment and revert to using heroin etc., in many cases by selling their methadone or buprenorphine prescriptions to afford their opiate of choice. Driving impairment tests done in the Netherlands that have shown morphine to have the least negative effects on cognitive ability on a number of mental tasks also suggest morphines use in OST may allow for better psychological functioning and engagement in society. Other opiates such as dihydrocodeine in both extended-release and immediate-release form are also sometimes used for maintenance treatment as an alternative to methadone or buprenorphine in some European countries.

Another close relative of methadone is dextropropoxyphene, first marketed in 1957 under the trade name of Darvon. Oral analgesic potency is one-half to one-third that of codeine, with 65 mg approximately equivalent to about 600 mg of aspirin. Dextropropoxyphene is prescribed for relief of mild to moderate pain. Bulk dextropropoxyphene is in Schedule II of the United States Controlled Substances Act, while preparations containing it are in Schedule IV. More than 100 tons of dextropropoxyphene are produced in the United States annually, and more than 25 million prescriptions are written for the products. Since dextropropoxyphene produces relatively modest pain relief compared to other opioids but still produces severe respiratory depression at high doses, it is particularly dangerous when abused, as drug users may take dangerously high doses in an attempt to achieve narcotic effects. This narcotic is among the top 10 drugs reported by medical examiners in recreational drug use deaths. However, dextropropoxyphene is still prescribed for the short term relief of opiate withdrawal symptoms, particularly when the aim of treatment is to smooth detoxification to a drug free state rather than a switch to maintenance treatment.

Other analogues of methadone which are still in clinical use are dipipanone (Diconal) and dextromoramide (Palfium) which are shorter-lasting but considerably more effective as analgesics. In the 1980s and beginning of the 1990s, before pharmaceutical grade IV heroin treatment became available to heroin addicts, as either single drug replacement for street heroin, or to be used alongside prescribed methadone, oral dextromoramide was prescribed to heroin addicts instead, because even when taken orally it still produces a strong, so called "rush", without the need of IV administration and any of the risks involved with it. These drugs have a high potential for abuse and dependence and were notorious for being widely abused and sought after by drug addicts in the 1970s. They are still rarely used for the relief of severe pain in the treatment of terminal cancer or other serious medical conditions. Different nations within the EU have different regulations, and in some nations general practitioners have the legal right to maintain addicts with whatever they deem to be most efficacious in maintaining their health and well being.