Elimination of 4-n-Butoxyphenylacethydroxamic Acid (Bufexamac) in Man

A GLC determination showed that about 80% of a dose of bufexamac (125–500 mg.) can be recovered from urine after acid hydrolysis as 4-n-butoxyphenylacetic acid. Excretion is apparently complete within 24 hr. Not more than 1% of the dose is excreted as free bufexamac or 4-butoxyphenylacetic acid. Enzymic hydrolysis indicated that about 75% of the dose is excreted with the hydroxamic function intact and that the elimination of bufexamac is mainly by conjugation, probably with glucuronic acid. About 6% of the dose was recovered from urine as 4-butoxyphenylacetic acid glucuronide. Bufexamac is fairly rapidly absorbed and eliminated, the peak rate of excretion of total 4-butoxyphenylacetic acid occurring 3–6 hr. after dosage. 4-Butoxyphenylacetic acid glucuronide is less rapidly excreted, and the ratio of bufexamac conjugate to 4-butoxyphenylacetic acid glucuronide decreases steadily with time after dosage. The rate of excretion of total 4-butoxy-phenylacetic acid could not be interpreted as log-linear during the period (16 hr.) of the kinetic studies.