A Cochrane review [Abstract] 1 included 5 studies with a total of 226 subjects examining the topical administration of the short-acting sodium channel blocker, amiloride, compared to placebo. In 3 studies over 6 months, there was a significant difference found in the difference in relative change in FVC in favour of placebo (WMD -1.51%, 95% CI -2.77 to -0.25), although heterogeneity was evident (I2 =92%). A two-week study demonstrated that hypertonic saline with amiloride pre-treatment did not result in a significant improvement in respiratory function or mucus clearance, in contrast to pre-treatment with placebo. There were no significant differences identified in other clinically relevant outcomes.
Comment: The quality of evidence is downgraded by study quality (unclear allocation concealment) and by inconsistency (variability in results across studies).
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