Methadone, Methaqualone, and Propoxyphene

Methadone, methaqualone, and propoxyphene are often tested simply because they can be readily screened by many commercially available immunoassays. Methadone is used in the treatment of heroin addiction and chronic pain. Methadone does not metabolize to morphine or codeine, and thus will not be detected on the HHS 5 drug panel. As the use of methadone to treat chronic pain increases, MROs need to be aware of the potential safety risks associated with its use for individuals who may be working with machinery or in other potentially dangerous work environments. The Federal Motor Carrier Safety Administration still considers methadone a medically disqualifying medication for commercial motor vehicle drivers. Propoxyphene (Darvon) is prescribed with or without aspirin or acetaminophen for mild to moderate pain. Propoxyphene chemical structure is similar to methadone and it is approximately one-half to two-thirds as potent as codeine. Propoxyphene as parent drug is detected in the urine for only l to 2 days after use; however, when confirmation testing can detect norpropoxyphene, the primary metabolite, the detection window is approximately I week. Most of the individuals who test positive for methadone or propoxyphene will have a prescription or be in a methadone maintenance program. Methaqualone (Quaalude) had been prescribed as a sedative-hypnotic. Because of its high potential for abuse and the availability of newer, less toxic drugs like the benzodiazepines, its use was discontinued in 1983 and it is now a Schedule I drug. For some reasons many laboratories still include this drug in their panels despite the fact that there is little evidence to support that the drug is available on the illicit drug market, or that workplace urine specimens test positive for the drug.

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