Diclofenac (INN; see trade names[1] below) is a nonsteroidal anti-inflammatory drug (NSAID) taken or applied to reduce inflammation and as an analgesic reducing pain in certain conditions. It is supplied as or contained in medications under a variety of trade names.

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| Trade names | Aclonac, Cataflam, Voltaren, see trade names[1] |
| AHFS/Drugs.com | monograph |
| MedlinePlus | a689002 |
| Pregnancy category |
AU: C US: C (Risk not ruled out) in 1st and 2nd trimester, D in 3rd trimester |
| Legal status |
AU: S2 (Pharmacy only) – S4 UK: POM (Prescription only) (P for topical formulation) ℞-only in most preparations/countries, limited OTC in some countries, manufacture and veterinary use is banned in India, Nepal, and Pakistan due to imminent extinction of local vultures |
| Routes of administration |
oral, rectal, intramuscular, intravenous (renal- and gallstones), topical |
| Protein binding | More than 99% |
| Metabolism | hepatic, oxidative, primarily by CYP2C9, also by CYP2C8, CYP3A4, as well as conjugative by glucuronidation (UGT2B7) and sulfation;[2] no active metabolites exist |
| Biological half-life | 1.2-2 hr (35% of the drug enters enterohepatic recirculation) |
| Excretion | 40% biliary 60% urine |
| CAS Number | 15307-86-5 |
| ATC code | D11AX18 M01AB05, M02AA15, S01BC03 |
| PubChem | CID: 3033 |
| IUPHAR/BPS | 2714 |
| DrugBank | DB00586 |
| ChemSpider | 2925 |
| UNII | 144O8QL0L1 |
| KEGG | D07816 |
| ChEBI | CHEBI:47381 |
| ChEMBL | CHEMBL139 |
| PDB ligand ID | DIF (PDBe, RCSB PDB) |
| Formula | C14H11Cl2NO2 |
| Molecular mass | 296.148 g/mol |
| SMILES[show] | |
| InChI[show] | |