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Abstract
1. After inhalation of doses of 3H-albuterol (84 and 220 μg) by humans, plasma radioactivity reached a max. after 2 and 4 h, respectively.
2. About 72% of the inhaled dose was excreted within 24 h in urine and a similar urinary excretion pattern was obtained with both dosages. From the excretion pattern of the unchanged drug in urine a half-life of 3.8 h and an elimination constant of 0.18 h−1 for albuterol were calc.
3. Approx. 28% dose was excreted as unchanged albuterol, 40% as a major urinary metabolite and 4% as a minor metabolite. The major metabolite could be converted to an albuterol-like compound by acid hydrolysis but not enzymically (Glusulase).
4. These results show that albuterol as an aerosol is readily absorbed, and is excreted mainly in the urine as the free drug and at least two metabolites.