Disposition of zomepirac sodium in man

Five healthy male human subjects were administered 200 mg oral solution doses of zomepirac-14C sodium. Plasma and urine samples were analyzed for zomepirac, hydroxyzomepirac, and zomepirac glucuronide. Zomepirac was the major circulating compound, with zomepirac glucuronide and hydroxyzomepirac accounting for the remainder of the radioactivity. Elimination half-lives for zomepirac, zomepirac glucuronide, and hydroxyzomepirac were 7.6, 8.2, and 7.8 hours, respectively. The dose was completely recovered in the urine (95 per cent in 72 hours). Zomepirac glucuronide constituted up to 90 per cent of the urinary radioactivity, with zomepirac and hydroxyzomepirac about 5 per cent each. The urinary zomepirac was probably present as a result of hydrolysis of zomepirac glucuronide. The plasma clearance of zomepirac was 189 +/- 23 ml/min. The metabolites were cleared by the kidney at rates of 343 +/- 88 ml/min (zomepirac glucuronide) and 339 +/- 88 ml/min (hydroxyzomepirac). Thus, metabolic clearance appears to be the sole mode of zomepirac elimination. The metabolites are then rapidly cleared by the kidneys.