Transtympanic pilocarpine in tinnitus.

In 48 patients who had neurosensory hypoacusia and whose main complaint was tinnitus, a 1% pilocarpine solution or a 2% carbachol Isopto solution was placed in the tympanic cavity by means of a No. 26 pencil-tipped lumbar puncture needle through the front quadrant of the eardrum. Patients were chosen without regard for age, gender, or topographical damage of the acoustic pathway. Evaluation of the drug's effect was performed audiometrically by masking with the minimum intensity of the pure sound or narrow band that most closely resembled the patients' own noises. The results of this medical therapy were positive and ranged from complete annulment to attenuation of the tinnitus, which was confirmed by audiometric masking 30 minutes after the intratympanic injection. These positive results reached 50% and would have been higher if the several cases submitted by accident insurance companies and cases of presbyacusia were discarded. The unsatisfactory element of the study was the short-term effect of the therapy, which usually lasted no more than 12-72 hours. Tinnitus reappeared in all patients at its original intensity. The best results involved the use of carbachol as compared with pilocarpine. The decision to replace pilocarpine with carbachol was based on the idea that the inhibitory cholinergic efferent pathways are damaged before the afferent pathways. The use of pilocarpine depends on efficient cholinergic functioning, as its activity is as an indirect agonist (i.e., to annul the cholinesterase enzyme).