Out of the approximately 20,000 genes in the human genome, a number of genes have been described to have an important effect on how individuals respond to medications. This is the focus of the field of pharmacogenomics (PGx). For example, variants in the genes VKORC1 and CYP2C9 are known to influence the required dose of warfarin, the most commonly used anticoagulant in the world. Importantly, some of the genes of PGx relevance, including the gene VKORC1, show extensive geographic differentiation in allele frequencies, and this has implications at the population level. In collaboration with Dr. Guilherme Suarez-Kurtz, from the Brazilian Instituto Nacional de Cancer (Rio de Janeiro), we carried out the first genome-wide association study (GWAS) of stable warfarin dosing in Brazilians (Parra et al. 2015. Pharmacogenomics 16:1-11). I have also collaborated with researchers from Mexico and Brazil in the characterization of polymorphisms of PGx relevance in these two regions (Bonifaz-Peña et al. 2014. PLoS One 9: e112640). More recently, in collaboration with the research group of Dr. Michel Naslavski, from the University of Sao Paulo, we carried out a detailed characterization of pharmacogenomic variants in a Brazilian cohort of elderly individuals based on whole-genome sequencing data (Bertholim-Nasciben et al. 2023. Frontiers in Pharmacology 14:1178715).