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Skeletal formula of diclofenamide
Space-filling model of diclofenamide
Clinical data
AHFS/Drugs.com International Drug Names
MedlinePlus a601233
ATC code
Pharmacokinetic data
Protein binding 55%
CAS Number
PubChem CID
ECHA InfoCard 100.004.037 Edit this at Wikidata
Chemical and physical data
Formula C6H6Cl2N2O4S2
Molar mass 305.16 g/mol
3D model (JSmol)
Melting point 228.5 °C (443.3 °F)
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Diclofenamide (or dichlorphenamide) is a sulfonamide and a carbonic anhydrase inhibitor of the meta-disulfamoylbenzene class.


Diclofenamide was approved in the United States in 1958 as Daranide to treat glaucoma,[1][2][3] Subsequently, it was found effective in cases of therapy-resistant epilepsy.[4] In 2015, the medication was approved in the US under the name Keveyis as an orphan drug for the treatment of primary hypokalemic and hyperkalemic periodic paralysis.[1][5]


In 2001, diclofenamide had a U.S. list price of $50 for a bottle of 100 pills, and was approved for glaucoma. Merck discontinued diclofenamide when better glaucoma drugs were developed. In 2010, Sun Pharmaceutical Industries bought the rights. In 2015, the F.D.A. approved it as an orphan drug, with 7-year exclusive marketing rights, for periodic paralysis, which the company estimates affects 5,000 people in the U.S. In 2016, Strongbridge Biopharma acquired Sun, which raised the price to $15,001 for 100 pills. The cost of treatment would range from $109,500 to $219,000 a year. Sun gives the drug free to patients who don't have insurance.[5]


  1. ^ a b "Dichlorphenaide (Keveyis) for Periodic Paralysis". The Medical Letter. April 16, 2016. Retrieved December 19, 2017. 
  2. ^ International Drug Names: Diclofenamide
  3. ^ Kanski, J. J. (1968). "Carbonic anhydrase inhibitors and osmotic agents in glaucoma. Carbonic anhydrase inhibitors". The British journal of ophthalmology. 52 (8): 642–643. doi:10.1136/bjo.52.8.642. PMC 506660Freely accessible. PMID 5724852. 
  4. ^ Rucquoy, M.; Sorel, L. (1978). "Diclofenamide in the treatment of therapy-resistant epilepsy". Acta Neurologica Belgica. 78 (3): 174–182. PMID 352085. 
  5. ^ a b This old drug was free. Now it’s $109,500 a year. By Carolyn Y. Johnson, Washington Post, December 18, 2017