disclosed are pyridazine derivatives represented by formula i or pharmaceutically acceptable salts or hydrates thereof , pharmaceutical compositions comprising the compounds , methods of treating and / or preventing diseases or disorders associated with viral infections in patients using the compounds , and the use of the compounds in preparing the medicaments for treating and / or preventing diseases or disorders associated with viral infections . the compounds represented by formula i have antiviral activity , especially anti - microrna viral activity . symbols in the compounds represented are described in the specification .