One in five individuals who try heroin will develop an addiction to opioids. Why are some individuals more susceptible to opioid addiction than others? And why do some individuals respond differently than others to treatment?
Methadone is one type of medication-assisted treatment that has shown success in treating opioid addiction. However, the effectiveness of methadone as a treatment depends on proper dosage. Determining proper dosage is complicated because studies have shown that effective and ineffective dosages overlap; therefore, dosages must be adjusted and readjusted for each person.
Research has shown that genetic factors contribute to opioid addiction, with scientists estimating that genes explain about 60% of the variability in risk of opioid addiction in the population. Researchers hypothesize that the effectiveness of a methadone dose is at least partly determined by genetics, but existing studies have yet to agree on what the link might be. Understanding this genetic link could not only help treatment providers prescribe the proper dose for a given patient but also enhance our understanding of genetic variants behind opioid addiction risk.
As principal investigator, I recently received a supplement on an existing grant from the National Institutes of Health (NIH) to study genetic contributions to methadone dosing among more than 500 people in methadone maintenance treatment. This will be the largest such study to date.
The methadone dose study complements other studies we are conducting with our partners at Case Western Reserve University, Icahn School of Medicine at Mount Sinai, and Washington University to uncover both genetic and epigenetic factors associated with opioid addiction. One of these study uses postmortem brains from people who overdosed on opioids and matched control brains. We will identify differences in gene regulation between opioid-addicted and control brain samples and then connect them to underlying genetic variants.
These studies and our partnership with Stanley Weiss at Rutgers University provide an exciting opportunity to identify genetic variants associated with effective methadone dosing, lay the groundwork for more comprehensive assessments of the biology driving patient differences in effective methadone dosing, and further our understanding of the genetic risks of opioid addiction.
RTI is conducting innovative research in the understanding, treatment, prevention, and intervention of opioid abuse. To learn more, visit RTI’s Opioid Research webpage.