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Flufenamic acid is a non-steroidal anti-inflammatory drug.
Proprietary names.Achless; Ansatin; Arlef; Dignodolin; Fullsafe; Meralen; Paraflu; Parlef; Rheuma Lindofluid; Sastridex; Surika; Tecramine.
2-[[3-(Trifluoromethyl)phenyl]amino]benzoic acid
A pale yellow crystalline powder. M.p. 124° to 125°, with resolidification and remelting at 134° to 136°. Practically insoluble in water; soluble 1 in 4 of ethanol, 1 in 7 of chloroform and 1 in 3 of ether.
Dissociation Constant.pKa3.9.
Partition Coefficient.Log P(octanol/water), 5.2.
Thin-layer Chromatography.System TA—Rf 96; system TE—Rf 18; system TG—Rf 37; system TAE—Rf 84; system TAJ—Rf 55; system TAK—Rf 78; system TAL—Rf 95. (Chromic acid solution, blue.)
Gas Chromatography.System GA—RI 1950; system GD—RRT of methyl derivative 1.26 (relative to n-C16H34); system GL—flufenamic acid-Me RI 1875, M (OH-)-Me2 RI 2115.
High Performance Liquid Chromatography.System HD—k 19.7; system HV—RRT 1.00 (relative to meclofenamic acid); system HX—RI 671; system HY—RI 667.
Ultraviolet Spectrum.Methanol—288 nm (A11=593a), 339 nm.
Infra-red Spectrum.Principal peaks at wavenumbers 1115, 1176, 1653, 1284, 1265, 1600 cm-1 (KBr disk). Five polymorphic forms occur.
Mass Spectrum.Principal ions at m/z 263, 281, 166, 92, 145, 167, 235, 139; flufenamic acid-Me m/z 263, 295, 235, 166, 264, 92; M (OH-)-Me2m/z 325, 293, 278, 250, 223, 202.
Quantification High performance liquid chromatography.In plasma: flufenamic acid and mefenamic acid, limit of detection 1 mg/L, UV detection—C. K. Lin et al., J. Pharm. Sci., 1980, 69, 95–97. In urine: flufenamic acid, mefenamic acid and tolfenamic acid, limit of detection for flufenamic acid about 3.5 ng, UV detection—E. Mikami et al., J.Chromatogr. B. Biomed. Sci. Appl., 2000, 744, 81–89.
Disposition in the Body.Readily absorbed after oral administration. Metabolised by hydroxylation and glucuronic acid conjugation. About 50% of a dose is excreted in the urine in 72 h and about 36% is eliminated in the faeces. The material excreted in the urine consists mainly of conjugated flufenamic acid and free and conjugated 4'-hydroxyflufenamic acid with smaller amounts of the 5'-hydroxy and dihydroxy derivatives.
Therapeutic concentration Following oral administration of 200 mg three times daily for 4 days to 10 subjects, plasma concentrations of 0.3 to 17 mg/L (mean 6.4) were reported 2 h after the morning dose [R. A. Buchanan et al., Curr. Ther. Res., 1969, 11, 533–538].
Half-life.Plasma half-life, about 3 h.
Protein binding.In plasma, extensively bound.
Dose.400 to 600 mg daily.
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