Inhalation of the loop diuretic furosemide has been found to protect against challenges with bronchoconstrictive agents. OBJECTIVE: To determine if furosemide has any objective and/or subjective therapeutic effect on adult patients with acute exacerbations of asthma, above and beyond the effects of B2 agonists and oral glucocorticoids. METHODS: 35 adult patients with acute exacerbations of asthma were randomized and recruited into the study if they had a prior history of asthma, and <10 pack-year smoking history, had not received pre-hospital B2 agonists, were not pregnant, and had no sulfonamide allergy. A double blind study design was employed. One group received albuterol 5 mg with placebo and one group received albuterol 5 mg with furosemide 40 mg in their nebulizer. Both groups received prednisone 80 mg po. PEFRs were obtained before initiation of treatment and 30 and 60 minutes thereafter. A 10 point dyspnea scale was also employed at initiation of treatment and 30 and 60 minutes thereafter. Physicians were permitted to give rescue albuterol treatments as deemed necessary. RESULTS: There was no difference in the treatment arms with respect to PEFR, dyspnea score, or number of rescue albuterol treatments at 30 and 60 minutes. CONCLUSIONS: We found no statistical benefit to adding furosemide to a regimen consisting of prednisone and optimal doses of B2 agonist. We conclude that there is not a current role for furosemide in acute exacerbations of asthma.