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Clinical data
Trade namesCatalin
ATCvet code
  • 1,5-Dioxo-4H-pyrido[3,2-a]phenoxazine-3-carboxylic acid
CAS Number
PubChem CID
CompTox Dashboard (EPA)
ECHA InfoCard100.012.612 Edit this at Wikidata
Chemical and physical data
Molar mass308.249 g·mol−1
3D model (JSmol)
  • C1=CC=C2C(=C1)N=C3C(=CC(=O)C4=C3C(=O)C=C(N4)C(=O)O)O2
  • InChI=1S/C16H8N2O5/c19-9-5-8(16(21)22)18-14-10(20)6-12-15(13(9)14)17-7-3-1-2-4-11(7)23-12/h1-6H,(H,18,19)(H,21,22)

Pirenoxine (abbreviated PRX, trade name Catalin) is a medication used in the possible treatment and prevention of cataracts.

A report in the journal Inorganic Chemistry showed that in liquid solutions pirenoxine could cause decreased cloudiness of a crystallin solution produced to mimic the environment of the eye. Pirenoxine interacts with selenite or calcium ions that have been proven as factors leading to the formation of lens cataract.[1]

Pirenoxine reduces the cloudiness of the lens solution containing calcium by 38% and reduced the cloudiness of the selenite solution by 11%.[2]

“...there are not any proctored studies that prove the utility of these drops. In Canada and in the U.S. they are considered homeopathic—probably do no harm but doubtful that they will have any protective value."[3]


  1. ^ Liao JH, Chen CS, Hu CC, Chen WT, Wang SP, Lin IL, et al. (January 2011). "Ditopic complexation of selenite anions or calcium cations by pirenoxine: an implication for anti-cataractogenesis". Inorganic Chemistry. 50 (1): 365–77. doi:10.1021/ic102151p. PMID 21138325.
  2. ^ Staff, R. O. "Can Chinese Drop Clear Cataracts?". www.reviewofoptometry.com. Retrieved 2022-07-15.
  3. ^ Can Catalin Eye Drops Protect Eyes From Cataracts? Answered by Jeffrey Whitman MD OCS on Febr. 21, 2014 on the website of the American Academy of Ophthalmology.