Etofenamate-d₄is intended for use as an internal standard for the quantification of etofenamate by GC- or LC-MS. Etofenamate is a non-steroidal anti-inflammatory drug (NSAID) and diethylene glycol ester form of flufenamic acid that has anti-inflammatory and analgesic activities.^1,2It inhibits lipoxygenase isolated from guinea pig leukocytes (IC₅₀= 5.3 μM) and the production of prostaglandin E₂in stimulated rat peritoneal macrophages.²In vivo, etofenamate reduces acetic acid-induced vascular permeability in mice and UV-induced erythema in guinea pigs in a dose-dependent manner at doses ranging from 40-320 and 5-20 mg/kg, respectively.¹Etofenamate (40 mg/kg per day for 21 days) inhibits inflammation in a rat model of adjuvant-induced arthritis. It also decreases the pain response in a silver nitrate-induced rat model of arthritis and the acetic acid-induced writhing test in mice, indicating analgesic activity. Formulations containing etofenamate have been used in the treatment of osteoarthritis.

1.Nakamura, H., Motoyoshi, S., Imazu, C., et al.Anti-inflammatory, analgesic and anti-pyretic activities of a non-steroidal anti-inflammatory drug, etofenamate, in experimental animalsNihon Yakurigaku Zasshi.80(2)125-135(1982) 2.Nakamura, H., Motoyoshi, S., Ishii, K., et al.The mode of anti-inflammatory action of a topical non-steroidal anti-inflammatory drug, etofenamateNihon Yakurigaku Zasshi.89(1)15-24(1987)