SNPs have been identified that influence the response to morphine.
- A meta-analysis of 5,000 patients concluded that the A118G SNP, rs1799971, in the OPRM1 gene does influence the perception of pain relief from morphine.
- A study of 145 Italian patients found that pain relief variability from morphine treatment was significantly (p<0.0001) associated with polymorphisms in both the ABCB1 and OPRM1 genes. Combining the extreme genotypes of both genes, the association between patient polymorphism and pain relief improved (p<0.00001), allowing the detection of three groups: strong responders, responders, and non-responders, with sensitivity close to 100% and specificity more than 70%.[PMID 17898703]