A study of the duration of the bronchodilator effect of 12 micrograms and 24 micrograms of inhaled formoterol and 200 micrograms inhaled salbutamol in asthma.

Formoterol is a new catecholamine analogue for which a longer duration of action is claimed. We studied the bronchodilator action of 12 micrograms and 24 micrograms of inhaled formoterol compared to 200 micrograms of inhaled salbutamol and placebo, in seven patients (mean age 59.3 yr) with moderate asthma. The adjusted mean peak rise in FEV1 was +0.331 each for salbutamol, 12 micrograms formoterol and 24 micrograms formoterol, all being significantly greater than that of placebo (+0.161; P less than 0.01). The duration of action was calculated in two ways. When calculating the time for the group mean FEV1 to return to baseline, the values were: for placebo, 3.1 h; salbutamol, 4.2 h; 12 micrograms formoterol, 6.8 h; and 24 micrograms formoterol, 11.2 h. When taking the times for each treatment at which individual FEV1 values returned to baseline and then calculating the adjusted mean time for each treatment group, the durations of action were: placebo, 3.5 h; salbutamol, 3.9 h; 12 micrograms formoterol, 5.9 h; and 24 micrograms formoterol, 8.1 h (24 micrograms formoterol compared to placebo, P = 0.02 and to 200 micrograms salbutamol, P = 0.03). The second method of calculation is nearer to a patient's approach in treating their asthma (i.e. taking an extra dose when needed), and may be a more realistic method of assessing duration of action. Formoterol is an effective bronchodilator, and the 24 micrograms dose should be assessed in the treatment of nocturnal asthma. In this group of older asthmatics with a degree of fixed airflow obstruction, we suggest that doses should be taken 8 hourly.