Long-term beta2 bronchodilator therapy and the question of tolerance.

maximum percent increase for each patient after the test drug on each of the three days. On day 1, the response of the FEV, to fenoterol was better than that to ephedrine to a highly significant degree ( P < 0.01) at all times from one to six hours (Fig 1) . This degree of difference was found at two, three. and four hours on day 45, and only at three and four hours on day 90 (Fig 2). The responses of the FEF,,.,, to fenoterol and ephedrine differed to a similar degree. The specific conductance (Caw/VL) increased by 83 percent two hours after fenoterol on day 1, and 88 percent on day 45. However. on day 90, the maximum increase was less (74 percent) and later (three hours). By contrast, the maximum response to ephedrine was higher (25 percent) on day 90 than on day 1 (16 percent). The differences between the response of the c a w / V ~ to the two drugs were highly significant on day 1 and 2, 3, and 5 hours, but by day 90 were only moderately significant ( P < .05) at one, two, and three hours. The median duration of action (ie, FEV, remaining more than 15 percent above baseline) for fenoterol was 0 001 I