Inhaled
furosemide prevents the obstructive response to several bronchoconstrictor stimuli in
asthma. To verify whether this protective effect is also shared by other
loop diuretics, we investigated the effect of inhaled
piretanide on the bronchial obstructive response to ultrasonically nebulized distilled water (UNW) in ten patients with moderate, stable
asthma. In a randomized, single-blind dose-response study, each subject performed an UNW test immediately after nebulization of different doses of
piretanide between 12 and 48 mg or placebo. The effect of a single 40-mg dose of inhaled
furosemide was also investigated in six subjects.
Piretanide caused a significant, dose-dependent increase in UNW PD20 with respect to placebo, corresponding to 0.6 +/- 0.2 doubling doses (mean +/- SE) after 12 mg, 1.3 +/- 0.2 after 24 mg, and 2.0 +/- 0.2 after 48 mg, and had a remarkable
diuretic effect; 40 mg of
furosemide increased UNW PD20 by 2.3 +/- 0.3 doubling doses (p < 0.01), but showed only a modest
diuretic activity. These data indicate that inhaled
piretanide is as effective as
furosemide in preventing UNW-induced
asthma, and this effect is unrelated to their
diuretic potency.