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1 The metabolism of (+)‐, (‐)‐ and (±)‐salbutamol by sulphoconjugation was determined in vitro using human lung cytosol and bronchial epithelial BEAS‐2B cell homogenate. 2 For the lungs the intrinsic clearance (Vmax/Km) value for the pharmacologically active (‐)‐salbutamol (0.49 ± 0.32 ml min‐‐1 g‐1 protein) exceeded that of (+)‐salbutamol (0.046 ± 0.028 ml min‐1 g‐1 protein) by 11‐fold. This was mainly due to a difference in Km value, which was 16 times higher for (+)‐salbutamol (1300 ± 170 μM) than for (‐)‐salbutamol (83 ± 12 μM). 3 The stereoselectivity of sulphoconjugation of salbutamol was very similar in the BEAS‐2B cells, although the absolute activity was considerably lower. 4 The enzyme catalyzing this reaction both in the lungs and in the BEAS‐2B cells was the monoamine (M) form phenolsulphotransferase. 5 These observations emphasize that the smooth muscle of the bronchi most likely are exposed to considerably higher concentrations of the potentially toxic (+)‐enantiomer than of the bronchodilating (‐)‐enantiomer during therapy with (±)‐salbutamol.

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Clinical Pharmacology & Therapeutics (1996) 59, 171–171; doi: