Frusemide antagonises exercise-induced but not histamine-induced bronchospasm

Area of Science:

• Pharmacology
• Respiratory Medicine
• Pulmonary Physiology

Background:

• Frusemide (a loop diuretic) has demonstrated efficacy in antagonizing exercise-induced bronchospasm.
• This effect was hypothesized to result from the blockade of chloride channels in the bronchial epithelium.

Purpose of the Study:

• To investigate whether frusemide non-specifically antagonizes bronchospasm.
• To test the hypothesis that frusemide's bronchodilatory effects extend to stimuli other than exercise.

Main Methods:

• Ten healthy subjects (aged 22-35 years) inhaled either 30 mg of nebulized frusemide or its vehicle (water at pH 9.1).
• Bronchial reactivity was assessed using inhaled histamine challenges, measuring the provocative dose of histamine causing a 20% fall in FEV1 (PD20).

Main Results:

• The geometric mean histamine PD20 after vehicle inhalation was 0.6 mumol.
• The geometric mean histamine PD20 after frusemide inhalation was 0.45 mumol.
• The difference in PD20 between control and frusemide groups was not statistically significant, indicating no significant change in bronchial reactivity.

Conclusions:

• Nebulized frusemide does not antagonize histamine-induced bronchospasm.
• The observed effect of frusemide on exercise-induced bronchospasm may be stimulus-specific and not a general bronchodilatory action.