The quality of evidence is downgraded by study limitations (unclear allocation concealment and blinding), and by imprecise results (few patients and outcome events).
A Cochrane review [Abstract] 1 included 10 studies with a total of 623 subjects of all ages (900 ears). One study compared active treatments with no treatment, 3 compared active treatments with water or saline, and all 10 studies compared two or more active treatments. Studied interventions included oil-based treatments (triethanolamine polypeptide, almond oil, benzocaine, chlorobutanol), water-based treatments (docusate sodium, carbamide peroxide, phenazone, choline salicylate, urea peroxide, potassium carbonate), other active comparators (e.g. saline or water alone) and no treatment.
The proportion of ears with complete clearance of ear wax was higher in active treatment group compared with no treatment after 5 days of treatment (22% vs. 5%; RR 4.09, 95% CI 1.00 to 16.80; 1 study, n=73, 117 ears; NNTB = 8). No difference was observed between active treatment group and water or saline group (RR 1.47, 95% CI 0.79 to 2.75; 3 studies, n=213, 257 ears). There was no difference when sterile water was compared to no treatment for 5 days (RR 4.00, 95% CI 0.91 to 17.62; 1 study, n=48, 76 ears). Several single studies evaluated 'head-to-head' comparisons between 2 active treatments, but no differences between treatments were observed. There was no difference in effect between oil-based and non-oil-based active treatments (RR 0.85, 95% CI 0.48 to 1.49; 4 studies, n=195, 225 ears).
There were no serious adverse effects reported in any of the 10 studies. No evidence of a significant difference in the number of adverse effects between the different types of ear drops was observed.
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