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S-carboxymethylcysteine for glue ear


Clinical bottom line

The use of S-carboxymethylcysteine resulted in 35% cure rates compared with 17% with placebo in seven studies with 282 children and 146 ears. The NNT was 5.5 (3.8 to 9.8).


RA Moore et al. S-carboxymethylcysteine in the treatment of glue ear: quantitative systematic review. BMC Family Practice 2001 2:3 ( )


The Cochrane Library, MEDLINE, PUBMED and EMBASE were searched to June 2001 for papers with the words "S-carboxymethylcysteine", "Carbocysteine", "S-CMC" and "mucodyne" as free text terms, and reviews sought for papers. Any language was accepted. Included trials had to be randomised comparisons of S-carboxymethylcysteine (any dose or duration) in glue ear in children under 16 years, and have a placebo comparison.

Outcomes of interest (including adverse effects) were for children, or failing that for individual ears, which could be interpreted as saving a child from an operation for grommet insertion. Ideally this would be a tympanogram type B becoming type A. Where this was not available (because several studies were quite old) we chose outcomes which would today influence the making of the clinical decision not to operate. Definitions used were:


Information was available for 283 children and 146 ears. S-carboxymethylcysteine was given as a syrup or linctus at various doses (sometimes age-related) for periods as little as 10 or 15 days, but other studies used it for between one and three months. Only two studies individually showed statistical benefit of treatment over placebo. Most studies, except one very small one, were above the line of equality (Figure 1).

Figure 1: S-carboxymethylcysteine and placebo for glue ear in children (blue) and ears (yellow)

Successful outcomes were obtained in 17% of children given placebo and in 35% of children given S-carboxymethylcysteine. The combined data had a number-needed-to-treat of 5.5 (95% confidence interval 3.8 to 9.8). This means that for every five or six children treated with S-carboxymethylcysteine over one to three months, one will not undergo surgery for grommet insertion who would have done had they been given placebo.

Sensitivity analysis was carried out by ears and children, by trial quality and size, without making much difference to the result. Only one adverse effect was reported in the seven trials.


S-carboxymethylcysteine appears to be moderately successful in treating children with glue ear. The outcome chosen was one that would result (in the UK in 2000) in a child avoiding surgery. Health economic analysis based on these data suggest that using S-carboxymethylcysteine would be cost saving if the NNT was below 15.

[ see: Phillips CJ, Burrell A, Moore RA, Bates GJ, Commins D. Mucodyne: the economics of preventing surgery for grommets. J Med Econ 1999, 2: 167-176. ]