Pharmaceutical Research

, 35:234 | Cite as

Perspectives on Physicochemical and In Vitro Profiling of Ophthalmic Ointments

  • Quanying Bao
  • Diane J. BurgessEmail author
Expert Review
Part of the following topical collections:
  1. Ophthalmic Drug Discovery and Development


Ophthalmic ointments are unique in that they combine features of topical drug delivery, the ophthalmic route and ointment (semisolid) formulations. Accordingly, these complex formulations are challenging to develop and evaluate and therefore it is critically important to understand their physicochemical properties as well as their in vitro drug release characteristics. Previous reports on the characterization of ophthalmic ointments are very limited. Although there are FDA guidance documents and USP monographs covering some aspects of semisolid formulations, there are no FDA guidance documents nor any USP monographs for ophthalmic ointments. This review summarizes the physicochemical and in vitro profiling methods that have been previously reported for ophthalmic ointments. Specifically, insight is provided into physicochemical characterization (rheological parameters, drug content and content uniformity, and particle size of the API in the finished ointments) as well as important considerations (membranes, release media, method comparison, release kinetics and discriminatory ability) in in vitro release testing (IVRT) method development for ophthalmic ointments.

Graphical Abstract

Summary of the physicochemcial profiling and in vitro drug release testing (IVRT) for ophthalmic ointments.

Key words

discriminatory ability in vitro release testing ophthalmic ointment particle size rheology semisolid topical 



Active pharmaceutical ingredient


Cellulose acetate


Design of Experiments


Franz diffusion cell


Fourier-transform infrared


Storage modulus


Loss modulus


In vitro release testing


Mixed cellulose ester






Polarized light microscopy




Polyvinylidene fluoride


Powder X-ray Diffraction

Q1/Q2 equivalent

Qualitative and quantitative sameness


Reference listed drug


Sodium dodecyl sulfate


US pharmacopeia


Vertical diffusion cell


Acknowledgements and Disclosures

Funding for this project was made possible by a Food and Drug Administration grant (1U01FD005177–01). The views expressed in this review do not reflect the official policies of the U.S. Food and Drug Administration or the U.S. Department of Health and Human Services; nor does any mention of trade names, commercial practices, or organization imply endorsement by the United States Government. Dissolution equipment support from Sotax Corporation is highly appreciated. The authors are grateful to Dr. Louis Tisinger (application specialist, Agilent Technologies) and Mr. Keegan A. McHose (product specialist, Agilent Technologies) for FTIR-imaging test support.


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© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Department of Pharmaceutical Sciences, School of PharmacyUniversity of ConnecticutStorrsUSA

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