TINNITUS: REDUCTION BY MELATONIN
Tinnitus is the perception of sound when it is otherwise externally quiet. It occurs as a result of a variety of conditions including allergies, a consequence of medications (e.g., aspirin) or a congenital defect and may accompany natural hearing loss that is observed during aging. Tinnitus is often caused by noiseinduced hearing impairment (71). When the health care professional can actually hear a sound emanating from the ear of a patient, it is referred to as objective tinnitus (72). Conversely, where no noise can be perceived by anyone other than the patient, it is referred to as subjective tinnitus (73). Interest in the potential use of melatonin to minimize tinnitus was initiated by observation of Rosenberg et al. (74) who found that melatonin, taken at a dose of 3 mg daily for 30 days, caused a perceptible reduction in tinnitus. The improvement was most obvious in patients with bilateral, as opposed to unilateral, tinnitus and in those whose sleep was disturbed because of tinnitus. Melatonin is also a sleep promoting agent, however, which may have reduced the perception of tinnitus. Due to their results, the authors suggested that melatonin should be included in the armamentarium of drugs useful in treating subjective tinnitus. A double-blind, placebo-controlled prospective study also showed that melatonin alleviated subjective tinnitus (75). In this study, melatonin (3 mg daily) was compared with the D2 dopamine receptor antagonist, sulpiride (50 mg daily), or combined with it with tinnitus perception being subjectively graded by the patients; the duration of treatment was 30 days. Using the subjective rating scale, sulpiride reduced tinnitus by 56%, melatonin lowered it by 40% and the combined treatment caused an 81% drop in subjective tinnitus. The visual analogue scale evaluation also indicated that the combination of drugs also was the best treatment to reduce tinnitus perception. In this study it was surmised that melatonin’s efficacy in limiting the perception of tinnitus stemmed from its ability to reduce the response to dopamine, possibly by inhibiting the release of the tissue biogenic amine which may be mediated by central-type benzodiazepine receptors (76). While Lopez-Gonzalez and coworkers (75) provide a logical flow diagram to illustrate how melatonin may impact tinnitus via a dopaminergic mechanism, the paper provides no direct support for this hypothesis. Similar findings using a combination of melatonin and sulodexide were observed in terms of reducing tinnitus. In the 34 patients receiving this treatment, the combination of drugs improved the quality of life and reduced the subjective evaluation of the severity of tinnitus (77). Sulodexide, a glycosaminoglycan, was used because of its ability to enhance the blood flow in the labyrinthine microcirculation. In a study that lacked a placebo-treated control group, melatonin also seemingly reduced the subjective interpretation of the severity of tinnitus in patients as assessed using the Tinnitus Handicap Inventory (78). In the same report, the effect of melatonin on sleep was estimated. As with the presumed reduction in tinnitus, melatonin also improved sleep quality as evaluated using the Pittsburgh Sleep Quality Index. There seemed to be some association between the improvements in sleep and tinnitus. The authors of this report feel melatonin may be a safe treatment for tinnitus, particularly in patients where the tinnitus is so severe it disturbs sleep.
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