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

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.