Title: Feprazone
CAS Registry Number: 30748-29-9
CAS Name: 4-(3-Methyl-2-butenyl)-1,2-diphenyl-3,5-pyrazolidinedione
Additional Names: 4-prenyl-1,2-diphenyl-3,5-pyrazolidinedione; 4-prenyl-1,2-diphenyl-3,5-dioxopyrazolidine; 4-(b-isoamylenyl)-1,2-diphenyl-3,5-pyrazolidinedione; 4-(2-isopentenyl)-1,2-diphenyl-3,5-pyrazolidinedione; phenylprenazone; prenazone
Manufacturers' Codes: DA-2370
Trademarks: Analud (Unifa); Methrazone (Boehringer, Ing.); Zepelin (De Angeli)
Molecular Formula: C20H20N2O2
Molecular Weight: 320.39
Percent Composition: C 74.98%, H 6.29%, N 8.74%, O 9.99%
Literature References: Non-steroidal anti-inflammatory drug. Prepn: S. Casadio, G. Pala, DE 2031238; eidem, US 3703528 (1971, 1972 both to Ist. De Angeli); Casadio et al., Arzneim.-Forsch. 22, 171 (1972). Series of articles on physical-chemical data, pharmacology, toxicology and clinical studies: ibid. 174-281. Toxicity data: C. Bianchi, G. Bonardi, ibid. 196.
Properties: Fine, white odorless and tasteless crystalline powder, mp 156.5° (ethanol). Very sol in acetone, chloroform, DMF; sparingly sol in acetonitrile, benzene, 10% NaOH. Slightly sol in ether, methanol, ethanol, cyclohexane. Practically insol in 10% HCl, 10% acetic acid, water. uv max (ethanol): 246 nm (log e 4.19); (pH 9-12 buffer): 264 nm (log e 4.322-4.326). pKa 5.09 ± 0.07. LD50 in male mice, rats (mg/kg): 408.8, 386.4 i.p.; 1067, >2000 orally (Bianchi, Bonardi).
Melting point: mp 156.5° (ethanol)
pKa: pKa 5.09 ± 0.07
Absorption maximum: uv max (ethanol): 246 nm (log e 4.19); (pH 9-12 buffer): 264 nm (log e 4.322-4.326)
Toxicity data: LD50 in male mice, rats (mg/kg): 408.8, 386.4 i.p.; 1067, >2000 orally (Bianchi, Bonardi)
Therap-Cat: Anti-inflammatory.
Keywords: Anti-inflammatory (Nonsteroidal); Pyrazolones.
Ferbam Ferredoxins Ferric Acetate, Basic Ferric Albuminate Ferric Ammonium Citrate

Systematic (IUPAC) name
Clinical data
AHFS/Drugs.com International Drug Names
Legal status  ?
ATC code M02AA16
PubChem CID 35455
ChemSpider 32612 YesY
KEGG D01305 YesY
Chemical data
Formula C20H20N2O2 
Mol. mass 320.385 g/mol
 YesY (what is this?)  (verify)

Feprazone (or prenazone) is a drug used for joint and muscular pain.[1]