Comparative study of inhaled amiloride and inhaled furosemide in exercise-induced asthma

Abstract

Background: Certain diuretics such as furosemide, when inhaled, have been found to be useful in preventing Exercise-Induced Asthma (EIA).

Study objective: To assess the possible preventive effect of inhaled amiloride in EIA.

Design: A double blind, randomized, cross-over study comparing the effect of inhaled amiloride, inhaled furosemide and placebo in EIA.

Patients: Sixteen asthmatic patients (8 males and 8 females) with an average age of 21 years (range 9-31) who presented a FEV1 decrease of over 15% in a previous free-running exercise test.

Interventions: Solutions were inhaled with a Hudson nebulizer connected to an oxygen source in different days before exercise testing. A Vitalograph Compact (Ohmeda, England) spirometer was used and FEV1 was obtained at baseline, three minutes after solution inhalation, immediately after exercise and then every 5 min. until 20 minutes post-exercise. The changes in FEV1 percentages (FEV1%) and the mean FEV1 decreases expressed as percentages for each solution were compared.

Results: Inhaled furosemide diminished the fall in the FEV1 at every time after exercise. The maximum decrease in mean FEV1 was at 5 minutes post-exercise and was 11 +/- 7% with furosemide, 24 +/- 14% (p < 0.01) with amiloride and 19 +/- 12% (p < 0.05) with placebo. Amiloride administration resulted in a slight but significative increase in the FEV1 fall (p < 0.01 when compared with placebo).

Conclusions: Amiloride is not useful to protect EIA whereas Furosemide does it. These differences results may be related to the differents mechanisms of action of the two diuretics.