A pharmaceutical composition comprises: a) 5 wt% to 95 wt% of a HC1 salt*xH2O of Compound (1) by the weight of the pharmaceutical composition, wherein x is from 0 to 3 and b) 5 wt% to 95 wt% of a filler by the weight of the pharmaceutical composition. Another pharmaceutical composition comprises: a) 1 mg/mL to 20 mg/mL of Compound (1) in water and b) 0.01 M to 0.1 M of a pharmaceutically acceptable pH modifier. A method of preparing a pharmaceutical composition, comprising providing a mixture of Compound (1) that includes the HC1 salt*xH2O of Compound (1) and the filler. Another method of preparing a pharmaceutical composition comprises mixing the HC1 salt*xH2O of Compound (1) and the pH modifier to form 1 mg/mL to 20 mg/mL of Compound (1) in water. Methods of reducing the amount of influenza viruses, inhibiting the replication of influenza viruses, and treating influenza each independently employ such pharmaceutical compositions.
