Inhaled loop diuretics as potential new anti-asthmatic drugs.

The observation that changes in bronchial osmolarity can induce bronchoconstriction in asthma inspired the experimental studies which, unexpectedly, revealed that frusemide is an effective bronchoprotective agent against a variety of osmotic and non osmotic stimuli. Although the mechanism of this protective effect is not fully understood, studies in vivo and in vitro suggest that frusemide may inhibit the activation of different cell types induced by bronchoconstrictor stimuli. Other loop diuretics also exert bronchoprotective activity, but frusemide appears to be the more effective bronchoprotective agent of this family, regardless of their diuretic potency and lipid solubility. Despite the relatively large amount of experimental evidence, there is currently little information on the clinical effectiveness of frusemide in asthma and a long-term controlled study is currently in progress. The observations that treatment with a combination of inhaled acetylsalicylate and frusemide results in a markedly increased bronchoprotective effect compared to either drug alone, opens a new perspective in the possible clinical use of these drugs. Preliminary studies suggest that the association of these drugs is well tolerated and may result in a remarkable steroid sparing effect in patients with steroid dependent asthma, for whom a convenient alternative to long-term steroid therapy is not currently available.