Metabolism of α-Methylfluorene-2-acetic acid (Cicloprofen): Isolation and Identification of Metabolites from Rat Urine

1. Four metabolites of α-methylfluorene-2-acetic acid (cicloprofen) have been isolated from rat urine and identified as the 7-hydroxy, 9-hydroxy, 7,9-dihydroxy and 9-hydroxy-9-methoxy derivatives of cicloprofen. 2. 7-Hydroxy cicloprofen was the major metabolite, contributing 47% of the total radioactivity excreted in rat urine. The other three metabolites each contributed approx. 10% of the radioactivity in urine. There was little unchanged drug excreted in urine (2.6%); at least three other minor metabolites have not been identified. 3. A metabolic pathway for the formation of the 9-hydroxy-9-methoxy metabolite of cicloprofen is proposed.