Glycerol lidocaine eardrops for the treatment of acute abacterial otitis externa

Inflammations of the external auditory canal number among the most frequently occurring ear-nose-throat diseases. For local treatment, substances from various groups of active ingredients are used as combinations and as single-agent drugs, e.g. antibiotics, glucocorticoids or analgesics [1]. In the case of acute otitis externa, treatment measures focus on the reduction of pain and swelling. The study described here investigates the efficacy and safety of glycerol lidocaine eardrops for the treatment of acute abacterial otitis externa (CAS No. for glycerol: 56-81-5, lidocaine-HCl: 73-78-9). In this double-blind, three-arm study, 105 patients diagnosed with acute abacterial otitis externa were included and randomized to receive either glycerol eardrops, glycerol eardrops with 0.5% lidocaine, or glycerol eardrops with 2% lidocaine for seven days. The primary outcome parameter was the change of the five typical clinical symptoms, earache, itching, otorrhea, hearing impairment, and "clogged ear" at Visit 2 (Day 7) based on the initial examination on Day 0. Both therapy groups treated with a combination of glycerol and lidocaine exhibited definite improvement in overall symptoms after seven days. This improvement differed from the mild reduction of symptoms under treatment with glycerol eardrops alone. Overall improvement of symptoms, expressed by the area under the curve of the baseline-adjusted symptom sum score, yielded a mean value of 10.95 (standard deviation 27.4) for the morning survey of the groups receiving eardrops containing only glycerol; in comparison, for eardrops containing glycerol and 2% lidocaine it was 15.71 (+/- 23.6) and for glycerol with 0.5% lidocaine, 23.16 (+/- 19.4). No severe adverse events occurred. Five adverse events were documented during the clinical investigation, none of which was considered by the investigators to be related to the study medication. Local therapy with glycerol lidocaine eardrops is a safe, and cost-effective treatment for the widely spread clinical picture of acute abacterial otitis externa. The advantage regarding efficacy of this combination compared with glycerol eardrops must be demonstrated in an adequately powered clinical trial.