A medicament characterized in that (A) a compound represented by the formula (I):its pharmaceutically acceptable salt, or a solvate thereof,whereinP is hydrogen or a group to form a prodrug；A1 is CR1AR1B, S or O；A2 is CR2AR2B, S or O；A3 is CR3AR3B, S or O；A4 is each independently CR4AR4B, S or O；the number of hetero atoms among atoms constituting the ring which consists of A1, A2, A3, A4, nitrogen atom adjacent to A1 and carbon atom adjacent to A4 is 1 or 2；R1A and R1B are each independently hydrogen, halogen, alkyl or the like；R2A and R2B are each independently hydrogen, halogen, alkyl, or the like；R3A and R3B are each independently hydrogen, halogen, alkyl, or the like；R4A are each independently hydrogen, halogen, alkyl, or the like；R4B are each independently hydrogen, halogen, alkyl, or the like；R3A and R3B may be taken together with an adjacent carbon atom to form non-aromatic carbocycle or non-aromatic heterocycle；n is any integer of 1 to 2； andR1 isor the like,is combined with (B) compound(s) having an anti-influenza activity, its pharmaceutically acceptable salt or a solvate thereof and/or an antibody having anti-influenza activity, is useful for treating or preventing influenza.
