A recent meta-analysis suggested a possible beneficial effect of carboxymethylcysteine (Mucodyne) in resolving otitis media with effusion (OME), but the methodology in several of the included trials was flawed. A double-blind randomised controlled trial (RCT) involving 163 patients (78 randomised to Mucodyne and 85 to placebo) was therefore performed. operative intervention or not. Of the 28 patients with resolved OME, 17 were in the Mucodyne group and 11 in the placebo group. Although it appeared that patients treated with Mucodyne were 1.68 times more likely to undergo resolution of OME than patients receiving placebo, this did not reach statistical significance. [Risk ratio of 1.68 (95% C.I., 0.74-3.37)]. chi2 test (df = 162) = 2.24 (P = 0.134). The absolute risk difference in the study was 8.5% (95% C.I., -3-20). We cannot exclude the possibility that Mucodyne is as beneficial as a 20% additional resolution of OME, or as harmful as a 3% decrease in the resolution of OME.