The present invention is directed to an aqueous pharmaceutical composition, particularly an aqueous ophthalmic composition, suitable as an injection, particularly an intravitreal injection. The composition includes a biologic therapeutic agent (e.g., an isolated monoclonal antibody that specifically binds to a C5 protein) that tends to raise the viscosity of the composition and a guanidine and/or guanidine derivative (e.g., L-arginine) that tends to lower the viscosity of the composition.