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The metabolism of l-bunolol, a new beta-blocking drug, was studied in man after single oral 3-mg doses of 3H-labeled compound. Absorption from the gut was rapid and virtually complete. Peak levels of bunolol and of dihydrobunolol, an active metabolite, were observed at 1 hr. Excretion of the administered radioactivity was mainly into the urine (78% in 4 days), with only 3% appearing in the feces. Bunolol, bunolol glucuronide, bunolol sulfate, dihydrobunolol, and dihydrobunolol glucuronide were identified and quantified in the plasma. These compounds represented 82% of the radioactivity in plasma at 30 min and 55% at 24 hr. Plasma half-lives (+/-S.D.) were estimated to be 6.1 +/- 0.3 hr for bunolol, 9.1 +/- 1.9 hr for bunolol glucuronide, 17.4 +/- 2.5 hr for bunolol sulfate, 7.1 +/- 0.5 hr for dihydrobunolol, and 7.7 +/- 0.8 hr for dihydrobunolol glucuronide.

1. Two 14C-labelled preparations of 3-(hydroxymethyl)-8-methoxychromone were used to study the absorption, tissue distribution and excretion of isotope after oral administration to rats (20 mg/kg).2. 14C, presumably from the labelled hydroxymethyl side-chain, was eliminated extensively as 14CC2. This excretion was triphasic; kinetic constants were calculated for each phase.3. The major excretion route was via the kidney although significant quantities of isotope were excreted with the faeces. Isotope did not accumulate in tissues.2. London: Academic Press.8. New York: J. Wiley & Sons, Inc.