[Research in rheological properties of four types of ophthalmic preparations].

This study is prepared to provide the basis of rheological parameters for the additional quality standard of ophthalmic gels, the rheological properties of the ophthalmic gels and the other three types of ophthalmic preparations. The medicines were compared through the study of the rheological properties for four types of ophthalmic preparations. The cone-plate rheometer was used to determine the dynamic and steady rheological parameters of four types of ophthalmic preparations. The similarities and differences of the measured results were analyzed to summarize the rheological indexes and parameters which are applied to distinguish the ophthalmic gels and the other types of ophthalmic preparations. 1 The elastic modulus should be greater than the viscous modulus for the ophthalmic gels in the range of the linear viscoelastic region. 2 The ophthalmic gels should be shear thinning non-Newtonian fluid with a certain yield stress and thixotropy. 3 The dynamic viscosity of the ophthalmic gels should be greater than 0.5 Pa·S at the temperature of 25 ℃ with the 50 s-1 shear rate. The typical rheological indexes and parameters of the ophthalmic gels were proposed in this article. The determination methods are simple and feasible. The rheological indexes and parameters have an important significance in the prescription design, production technology and quality control of the ophthalmic gels.