Provided are intravenous pharmaceutical compositions comprising the antiviral agent { 8-fluoro-2-[4-(3-methoxyphenyl)piperazin-1-yl]-3-[2-methoxy-5-(trifluoromethyl)phenyl]-3,4-dihydroquinazolin-4-yl} acetic acid (letermovir) and at least one excipient selected from the cyclodextrins, lysine, and arginine. The inclusion of at least one of a cyclodextrin, lysine, and arginine is to stabilise the active pharmaceutical ingredient.