Lawrence Oh1,3, Nick Di Girolamo3, Stephanie Watson2,3
Purpose: To conduct a systematic review of the literature on the role of N-Acetyl-Cysteine (NAC) for ocular therapeutics. In order to determine the mechanism of action, current applications and safety profile of topical NAC for ophthalmic use.
Methods: A search of peer-refereed papers was performed in the MEDLINE, EMBASE and Cochrane library databases until December 2015 using the following key words: n-acetylcysteine, acetylcysteine, cysteine, acetyl, NAC, ocular burns, topical, ocular surface, cornea, ophthalmic use. A total of 89 relevant papers were identified.
Results: 12 in vitro, 16 in vivo and 9 clinical studies were identified. NAC has potent antioxidant, anti-inflammatory and mucolytic properties due to its thiol-groups and ability to inhibit the inflammatory cascade. These unique properties contribute to the diverse applications of NAC, including its steroid-sparing potential. Topical NAC was found to improve the healing rates of following ocular surface injury and provide symptomatic relief in penetrating ocular disorders and corneal epithelial defects. In clinical studies, these include chemical injuries resulting in ulcerations, dry eyes, and Meibomian gland dysfunction. A range of doses were investigated, with efficacy evident with 5-10% topical NAC applied four times daily. Corneal ulceration was a rare adverse effect of topical NAC and tended to occur with higher concentrations in in-vitro studies. When used as an adjunct to dexamethasone, lower haze scores were seen in post-LASEK surgery.
Conclusion: NAC has anti-oxidant, anti-inflammatory and mucolytic properties. Evidence from 12 in vitro, 16 in vivo and 9 clinical studies support its role in healing the ocular surface.