The proportion of variation explained by the significant haplotypes we identified.

In accordance with the inclusion steps of haplotypes in each analysis of plasma concentration of R-methadone and S-methadone, we list the chromosome and linkage disequilibrium (LD) block where the haplotypes are located. A haplotype which contributed a higher increment of model R2 was included earlier in a sequential order. Univariate R2 and model R2 of the significant haplotypes are provided in the final two columns.