Penetration enhancers for topical drug delivery to the ocular posterior segment—a systematic review

Zubair Ahmed, Abhinav Thareja

Research output: Contribution to journalReview articlepeer-review

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There is an unmet clinical need for eye drop formulations to efficiently treat the diseases of the posterior ocular segment by non-invasive topical administration. Here, we systematically reviewed the literature on ocular penetration enhancers and their ability to transfer drugs to the posterior segment of the eye in experimental studies. Our aim was to assess which penetration enhancer is the most efficient at delivering drugs to the posterior segment of the eye, when topically applied. We conducted a comprehensive search in three electronic databases (Ovid Embase, Ovid MEDLINE, and PubMed) to identify all the relevant manuscripts reported on ocular penetration enhancers based on the PRISMA guidelines. We identified 6540 records from our primary database search and filtered them per our inclusion/exclusion criteria to select a final list of 14 articles for qualitative synthesis. Of these, 11 studies used cell penetrating peptides (CPPs), 2 used chitosan, and 1 used benzalkonium chloride (BAC) as the penetration enhancer. Cationic and amphipathic CPPs, transactivator of transcription (TAT), and penetratin can be inferred to be the best among all the
identified penetration enhancers for drug delivery to the fundus oculi via topical eye drop instillation. Further high-quality experimental studies are required to ascertain their quantitative efficacy.
Original languageEnglish
Article number276
Number of pages17
Issue number2
Publication statusPublished - 18 Feb 2021

Bibliographical note

Funding Information:
This project is funded by the European Union?s Horizon 2020 research and innovation programme under the Marie Sk?odowska?Curie Actions grant agreement N? 813440 (ORBITAL? Ocular Research by Integrated Training And Learning).

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Copyright 2021 Elsevier B.V., All rights reserved.


  • Neuroprotection
  • Penetration enhancers
  • Posterior segment
  • Retina
  • Retinal ganglion cells
  • Topical drug delivery

ASJC Scopus subject areas

  • Pharmaceutical Science


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