The present Invention relates to pharmaceutical compositions of (3S,11aR)-N-[(2,4-difluorophenyl)methyl]-2,3,5,7,11,11a-hexahydro-6-hydroxy-3-methyl-5,7-dioxo-oxazolo[3,2-a]pyrido[1,2-d]pyrazine-8-carboxamide, useful in the treatment or prevention of Human Immunodeficiency Virus (HIV) infections.