Opioids, particularly heroin, are drugs with extremely high addictive potential [125]. Treatments for opioid dependence can vary from the typical use of methadone (opioid agonist) and buprenorphine (partial agonist) to even naltrexone (opioid antagonist). Response rates vary dramatically and the use of none of these is without risks [126]. One recent study of African-Americans found that for a variant, rs678849, in the gene encoding the delta opioid receptor (OPRD1), CC individuals had more positive urine tests (24 weeks post-treatment) if treated with buprenorphine but less positive tests when treated with methadone [127]. Another recent study implicates a functional variant (rs2760118) in the gene encoding the succinic semialdehyde dehydrogenase enzyme (ALDH5A1) in response to methadone maintenance with T allele carriers more likely to be non-responders [128].
