Antagonism of fenoterol against beta-blocking drugs bunitrolol and practolol in asthmatics

In 4 X 10 young white male histamine-sensitive asthmatics without bronchitis or emphysema, the antagonism of fenoterol (40 mug) to bunitrolol (2.5 and 5 mg) or practolol (20 and 30 mg) was tested in an open comparative trial. Pulse frequency and several physiological parameters were determined before and after histamine challenge test, after injection of beta-blocking drug and after injection of fenotrolol. All groups were found to be equally sensitive to histamine. Bunitrolol and practolol were found to have no influence on histamine effect. It was also found that bunitrolol in the dosages tested is a much more potent beta-blocking drug in the bronchi compared to practolol in the dosages tested were equivalent. beta-Blockade of practolol (20 or 30 mg) could completely be antagonized by 40 mug fenoterol; this dosage was not sufficient to antagonize 2.5 or 5 mg bunitrolol.