A Cochrane review [Abstract] 1 included 11 studies with 1 021 patients. Five studies (n=883) compared inhaled mannitol with placebo. One of the studies was of cross-over design and the others were parallel group trials. Only one 12-month trial (n=461) provided results for exacerbations and demonstrated an advantage for mannitol in terms of time to first exacerbation (median 165 versus 124 days for mannitol and placebo respectively; HR 0.78, 95% CI 0.63 to 0.96). Number of days on antibiotics for bronchiectasis exacerbations was significantly better with mannitol (RR 0.76, 95% CI 0.58 to 1.00). Exacerbation rate per year was not significantly different between mannitol and placebo (RR 0.92 95% CI 0.78 to 1.08). Inhaled mannitol did not appear to cause many adverse events.
Two small cross-over studies (n=25) compared inhaled mannitol to no treatment. Data from these studies were inconclusive.
Four studies (n=113) compared hypertonic saline versus isotonic saline. Three of the four studies were cross-over design and one was a 12-month parallel group trial. On most outcomes there were conflicting results, and it is not possible to draw robust conclusions for this comparison.
Comment: The quality of evidence is downgraded by imprecise results (few patients for each comparison) and study limitations (selective outcome reporting).
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