The present invention provides a pharmaceutical composition comprising a compound represented by formula (1): or N-[3-((4aS,5R,7aS)-2-amino-5-methyl-4a,5,7,7a-tetrahydro-4H-furo[3,4-d] [1,3]thiazin-7a-yl)-4-fluorophenyl]-5-difluoromethylpyrazine-2-carboxamide, or a pharmaceutically acceptable salt of the foregoing, and a salt of a compound having a C12-22 saturated aliphatic hydrocarbon group.