DOSE UNIFORMITY OF OPHTHALMIC SUSPENSIONS

To quantify the rate of redispersion of three commercially available o pthalmic preparations as well as the drug content of single drops duri ng the course of emptying a full container of suspension eyedrops. Set ting: Department of Ophthalmology, University of Koln, and Department of Pharmaceutical Technology, University of Bonn, Germany. Methods: In a computer-controlled test apparatus used to simulate the shaking and dropping behavior oi humans under strictly reproducible conditions, w e studied the rate oi redispersion of three ophthalmic suspensions: 50 mg indomethacin, 50 mg prednisolone-21-acetate, and 50 mg dexamethaso ne in 5 mL aqueous fluid. The degree of shaking intensity essential fo r the redispersion of the ophthalmic suspensions was quantified in hea lthy persons and patients by an acceleration sensor. Results: The mean dose delivered and the coefficient oi variation of prednisolone were satisfactory, However, only 25% of the dexamethasone was available for administration; the rest remained in the bottle as a cake of sediment , Also, the variability oi the drug content between drops was unaccept ably high. The mean dose of indomethacin was adequate, but the between -drop variability was excessive. Conclusion: The dose uniformly oi sus pension eyedrops depends on their homogeneity immediately before admin istration. Among the formulation factors studied, particle size appear s to be the most important. The various redispersion rates of the thre e drugs underline their clinical profile.