SNPs from intron 1, but none in the 5′ flanking region. 29, 30 Xuei et al. genotyped 18 SNPs including one in the proximal 5′ region (−6 kb). 41 A recent study used a haplotype-based approach to predict response to naltrexone treatment based on 10 OPRM1 tag SNPs but was limited to the proximal 5′ region (−11 kb).42 Haplotype-based analysis is generally considered more powerful than single-marker analysis and may help to determine if a specific polymorphism occurs on a common genetic background.
