CLINICAL POTENTIAL OF INHALED DIURETICS IN ASTHMA

Inhaled furosemide (frusemide), a loop diuretic which inhibits the Na+/2Cl-/K+ cotransport system, has been shown to inhibit asthma provoked by several bronchial stimuli known to induce mediator release from inflammatory cells. Although other loop diuretics with greater diuretic potency (e.g. bumetanide, piretanide and torasemide) have been tested, furosemide provides the widest and most effective antiasthma activity. Inhaled acetazolamide, a selective inhibitor of carbonic anhydrase, may have a similar protective profile. The relative antiasthma activity of these agents seems to be unrelated to their diuretic potency, but is likely to be linked to their pharmacokinetic characteristics. The underlying mechanisms of antiasthma activity are probably a reduction of mediator release from inflammatory cells and a modulation of bronchoconstriction mediated by sensory nerve activation. Whether this observation will lead to the development of a new class of antiasthma compounds or will be a research tool for the study of asthma pathophysiology remains to be determined.