Genetic Makeup May Help Explain Methadone Overdoses

 

 Genetic variations that affect how quickly people metabolize the synthetic drug methadone have been identified. Methadone is a prescription drug used to treat pain. Methadone is also used to treat addiction to narcotic drugs used for pain relief and heroin. Although methadone is a narcotic pain reliever, if it remains in the body for too long, it can be deadly. 

Dr. Evan Kharasch from Washington University School of Medicine stated that, “A person’s genetic makeup influences how an enzyme in the liver metabolizes methadone. This explains why some people can have very high levels of methadone in their blood – high enough to trigger a potential overdose – even if they have received the same dose of the drug as others who are not affected the same way.” The researchers have concluded that if genetic testing is used prior to patients being prescribed methadone that the findings could help prevent and reduce some of the 5,000 deaths that occur in the United States each year due to methadone overdoses. In figuring out why people metabolize methadone differently and how exactly a person’s genetic makeup affected that process, blood samples were analyzed from healthy volunteers to determine their genetic makeup and then gave them methadone and observed how quickly it cleared from their bodies. This experiment allowed the researchers to pinpoint genetic sub-types that affect methadone metabolism. 

The results from the experiment showed that variations in a gene that influences how methadone clears in the liver had a major effect on how long the drug stayed in the body. The researchers also found that the genetic variants were more likely to affect metabolism of methadone in liquid or pill form than intravenous methadone. To primary doctors, that finding is important because they may be more likely to prescribe the oral form and may or may not be familiar with the difficulties in using methadone to treat pain. I found this interesting because if tests are done prior to prescribing patients the narcotic pain reliever, overdoses due to the drug can be prevented and the overall amount of deaths per year due to overdoses can decrease.

In addition, the study also found that, African-Americans were more likely to have the gene variant associated with slower methadone metabolism and less likely to have the gene variant associated with faster methadone metabolism. They believe that, that is why African-Americans and Caucasian patients typically clear methadone at different rates, because African-Americans were more likely than Caucasians to have higher methadone levels in the blood despite receiving the same amounts of the drug.

Original Article