Metabolism of alpha-methylfluorene-2-acetic acid (cicloprofen): isolation and identification of metabolites from rat urine.

1. Four metabolites of alpha-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.