|(A;G)||2.5||stronger cravings for alcohol. if alcoholic, naltrexone treatment 2x more successful|
Carriers of at least one rs1799971(G) allele appear to have stronger cravings for alcohol than carriers of two rs1799971(A) alleles, and are thus hypothesized to be more at higher risk for alcoholism. [PMID 17207095]
Among 200+ alcoholics treated with naltrexone, rs1799971(G) carriers receiving the drug (even without behavioral intervention) had an increased percentage of days abstinent (p = .07) and a decreased percentage of heavy drinking days (p = .04) if treated with naltrexone vs. placebo, whereas rs1799971(A;A) homozygotes showed no medication differences. Upon treatment with naltrexone, 87% of rs1799971(G) carriers had a good clinical outcome, compared with only 55% of individuals with the (A;A) genotype (odds ratio, 5.75, CI: 1.88-17.54)[PMID 18250251]
This SNP may also influence the response to opioids such as heroin, codeine or morphine. A 2015 meta-analysis (totaling 5,902 patients) concluded that the carriers of a rs1799971(G) allele consumed more opioids for analgesia (SMD = -0.17, CI:-0.25, -0.10, p < 0.00001), but still reported higher pain scores (p = 0.002) and less nausea and vomiting (odds ratio 1.30, CI:1.08-1.55, p= 0.005) than homozygous (A;A) patients during the first 24 hour, but not 48 hour, postoperative period.[PMID 25794200]
A study of 200 Chinese heroin addicts found increased frequency for the rs1799971(G) allele compared to non-addicts (40% vs 29%) [PMID 11338173]; but another study of Han Chinese addicts found no difference [PMID 11933204].
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