In patient 5 it was noted after 6 hours (1 hour after the cumulative dose of 228 \Lg of formoterol), in patient 4 after 4 hours (2 hours after a cumulative dose of 84 jig of formoterol), and finally, in patient 9 after 6 hours (2 hours after a cumulative dose of 180 fig of formoterol). However, in patients 4 and 5 the basal serum potassium values on the formoterol day were 0.2 to 0.3 mmol’L lower than the corresponding values on the salbutamol day. The mean reduction in serum potassium amounted to 0.14 mmol’L after salbutamol and 0.38 mmol*L_l after formoterol.
This is obviously much less than the mean reductions seen by Scheinin et al 30 minutes after inhalation of 2,400 |xg of salbutamol or 2,400 |xg of fenoterol, which amounted to 0.67 mmol-L and 1.13 mmol’L, respectively. However, the cumulative doses in that study were given over a time span of 60 minutes and no further reduction in serum potassium levels took place afterwards. There was a certain degree of compensatory increase in the serum potassium concentrations, but 3 hours after the last dose of bronchodilator, they were still approximately 10 percent below the basal values. Haalboom et al showed a reduction of potassium level averaging 0.9 mmoHL”l, 30 minutes after inhalation of 2,400 \ig of fenoterol, but no further reduction took place subsequently.