Nepafenac
[CAS 78281-72-8]

Identification

• Classification: Biochemical >> Inhibitor >> Neuronal signaling >> COX inhibitor
• Name: Nepafenac
• Synonyms: 2-Amino-3-benzoylbenzeneacetamide
• Molecular Formula: C₁₅H₁₄N₂O₂
• Molecular Weight: 254.28
• CAS Registry Number: 78281-72-8
• EC Number: 682-241-7
• SMILES: C1=CC=C(C=C1)C(=O)C2=CC=CC(=C2N)CC(=O)N

Properties

• Density: 1.3±0.1 g/cm³ Calc.^*
• Boiling point: 562.5±50.0 °C 760 mmHg (Calc.)^*
• Flash point: 294.0±30.1 °C (Calc.)^*
• Solubility: DMSO: 32 mg/mL (Expl.)
• Index of refraction: 1.641 (Calc.)^*

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS09 Warning
• Risk Statements: H400
• Safety Statements: P273-P391-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Acute hazardous to the aquatic environment	Aquatic Acute	1	H400
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Acute toxicity	Acute Tox.	4	H332
Acute toxicity	Acute Tox.	4	H302
Reproductive toxicity	Repr.	2	H361
Chronic hazardous to the aquatic environment	Aquatic Chronic	2	H411
Acute toxicity	Acute Tox.	2	H300

Discovery and Applications

Nepafenac is a nonsteroidal anti-inflammatory drug (NSAID) designed for ophthalmic use, primarily to reduce pain and inflammation associated with cataract surgery and other ocular procedures. It is chemically distinct among NSAIDs because it functions as a prodrug that is activated within ocular tissues.

NSAIDs act by inhibiting cyclooxygenase (COX) enzymes, which are responsible for converting arachidonic acid into prostaglandins. Prostaglandins are key mediators of inflammation, pain, and fever. By reducing prostaglandin synthesis, NSAIDs alleviate inflammatory responses. Nepafenac follows this general mechanism but differs in that it is administered in an inactive form that undergoes biotransformation in the eye.

Nepafenac is a neutral amide prodrug that efficiently penetrates the cornea due to its relatively lipophilic and non-ionized structure. After topical administration, it diffuses through ocular tissues and is converted by intraocular hydrolases into its active metabolite, amfenac. Amfenac is the pharmacologically active NSAID that inhibits COX enzymes, particularly COX-2, thereby reducing prostaglandin production in ocular tissues.

The prodrug design of nepafenac is important because direct administration of polar NSAIDs often results in poor corneal penetration. By masking the acidic functionality in a neutral amide form, nepafenac achieves enhanced ocular bioavailability. Once inside the eye, enzymatic hydrolysis restores the active acidic NSAID form at the site of action.

Structurally, nepafenac contains an aromatic system with a nitrogen-containing heterocycle-like amide linkage, along with hydrophobic aromatic substituents. These features contribute to its lipophilicity, enabling efficient transport across lipid-rich biological membranes such as the corneal epithelium.

The active metabolite, amfenac, contains a free carboxylic acid group that is essential for cyclooxygenase inhibition. Like other arylacetic acid NSAIDs, amfenac binds to the COX active site and blocks access of arachidonic acid, thereby suppressing prostaglandin synthesis. This inhibition reduces ocular inflammation, pain, and postoperative discomfort.

Clinically, nepafenac is used as an ophthalmic suspension or solution, often administered prior to and following cataract surgery. It helps prevent and treat postoperative inflammation and may also reduce the risk of cystoid macular edema, a complication involving fluid accumulation in the retina.

Compared with other ophthalmic NSAIDs such as ketorolac or bromfenac, nepafenac’s prodrug strategy provides enhanced corneal penetration and sustained intraocular activity. This makes it particularly effective in achieving therapeutic concentrations within deeper ocular tissues.

From a pharmacokinetic perspective, nepafenac is rapidly absorbed through the cornea and converted to amfenac in the iris-ciliary body and retina. The localized activation minimizes systemic exposure and reduces the risk of systemic NSAID-related side effects.

Structurally related NSAIDs and prostaglandin analogs such as misoprostol and latanoprost acid highlight the broader therapeutic importance of modulating prostaglandin pathways in ophthalmology, either by inhibiting their synthesis or mimicking their activity.

Overall, nepafenac is an ophthalmic NSAID prodrug that is converted to amfenac in ocular tissues, where it inhibits cyclooxygenase enzymes and reduces prostaglandin-mediated inflammation. Its significance lies in its enhanced ocular penetration, targeted activation, and effectiveness in managing postoperative eye inflammation.

References

2026. Thermal load management in photorefractive keratectomy: a comprehensive review of cooling strategies. Graefe's archive for clinical and experimental ophthalmology = Albrecht von Graefes Archiv fur klinische und experimentelle Ophthalmologie.
DOI: 10.1007/s00417-025-07114-y

2026. Management of Ocular Diseases Using Nanocrystal-based Formulations. Nanocrystals.
DOI: 10.1007/978-3-032-10238-6_9