Drugs in the treatment of tinnitus

Review of Pharmacotherapy for Tinnitus

Various medications are currently used in the treatment of tinnitus, including anesthetics, antiarrhythmics, anticonvulsants, antidepressants, antihistamines, antipsychotics, anxiolytics, calcium channel blockers, cholinergic antagonists, NMDA antagonists, muscle relaxants, vasodilators, and vitamins. To date, however, no medications have been specifically approved to treat tinnitus by the US Food and Drug Administration (FDA). In addition, medicines used to treat other diseases, as well as foods and other ingested materials, can result in unwanted tinnitus. These include alcohol, antineoplastic chemotherapeutic agents and heavy metals, antimetabolites, antitumor agents, antibiotics, caffeine, cocaine, marijuana, nonnarcotic analgesics and antipyretics, ototoxic antibiotics and diuretics, oral contraceptives, quinine and chloroquine, and salicylates. This review, therefore, describes the medications currently used to treat tinnitus, including their mechanisms of action, therapeutic effects, dosages, and side-effects. In addition, this review describes the medications, foods, and other ingested agents that can induce unwanted tinnitus, as well as their mechanisms of action.

Pathophysiology of Tinnitus

The hypothesis is presented that certain forms of tinnitus are related to abnormal phase-locking of discharges in groups of auditory nerve fibers. Recent developments in auditory neurophysiology have shown that neural coding of the temporal pattern of sounds plays an important role in the analysis of complex sounds. In addition, it has been demonstrated that when some other cranial nerves are damaged, artificial synapses can occur between individual nerve fibers such that ephaptic transmission between nerve fibers is facilitated. Such “crosstalk” between auditory nerve fibers is assumed to result in phase-locking of the spontaneous activity of groups of neurons which in the absence of external sounds creates a neural pattern that resembles that evoked by sounds.

Anticonvulsants for tinnitus

BACKGROUND

Tinnitus is the perception of sound or noise in the absence of an external or internal acoustic stimulation. It is a common and potentially distressing symptom for which no adequate therapy exists.

OBJECTIVES

To assess the effectiveness of anticonvulsants in patients with chronic tinnitus.

SEARCH STRATEGY

We searched the Cochrane Ear, Nose and Throat Disorders Group Specialised Register, CENTRAL (2010, Issue 2), MEDLINE, EMBASE, bibliographies and additional sources for published and unpublished trials. The date of the most recent search was 26 May 2010.

SELECTION CRITERIA

We selected randomised controlled trials in patients with chronic tinnitus comparing orally administered anticonvulsants with placebo. The primary outcome was improvement in tinnitus measured with validated questionnaires. Secondary outcomes were improvement in tinnitus measured with self-assessment scores, improvement in global well-being or accompanying symptoms, and adverse drug effects.

DATA COLLECTION AND ANALYSIS

Three authors assessed risk of bias and extracted data independently.

MAIN RESULTS

Seven trials (453 patients) were included in this review. These studies investigated four different anticonvulsants: gabapentin, carbamazepine, lamotrigine and flunarizine. The risk of bias of most studies was 'high' or 'unclear'. Three studies included a validated questionnaire (primary outcome). None of them showed a significant positive effect of anticonvulsants. One study showed a significant negative effect of gabapentin compared to placebo with an increase in Tinnitus Questionnaire (TQ) score of 18.4 points (standardised mean difference (SMD) 0.82, 95% confidence interval (CI) 0.07 to 1.58). A second study showed a positive, non-significant effect of gabapentin with a difference compared to placebo of 2.4 points on the Tinnitus Handicap Inventory (THI) (SMD -0.11, 95% CI -0.48 to 0.25). When the data from these two studies are pooled no effect of gabapentin is found (SMD 0.07, 95% CI -0.26 to 0.40). A third study reported no differences on the THI after treatment with gabapentin compared to placebo (exact numbers could not be extracted from the article).A meta-analysis of 'any positive effect' (yes versus no) based on a self-assessment score (secondary outcome) showed a small favourable effect of anticonvulsants (RD 14%, 95% CI 6% to 22%). A meta-analysis of 'near or total eradication of tinnitus annoyance' showed no effect of anticonvulsants (risk difference (RD) 4%, 95% CI -2% to 11%). Side effects of the anticonvulsants used were experienced by 18% of patients.

AUTHORS' CONCLUSIONS

Current evidence regarding the effectiveness of anticonvulsants in patients with tinnitus has significant risk of bias. There is no evidence from studies performed so far to show that anticonvulsants have a large positive effect in the treatment of tinnitus but a small effect (of doubtful clinical significance) has been demonstrated.

A review of evidence in support of a role for 5-HT in the perception of tinnitus

Tinnitus is a debilitating condition from which some 0.5-1% of the population of the Western world suffer sufficiently badly as to interfere with their normal working and leisure life. There is no satisfactory treatment at the present time and the uncertainty surrounding the mechanism of its generation makes it difficult to devise an effective cure. After much debate, the consensus of opinion amongst researchers regarding its site of origin is that it is primarily a central nervous system pathology although there certainly exists a class of patients whose tinnitus is peripherally based. In this paper, we provide some speculative ideas on how an initial auditory insult can be translated into central neurological substrates that represent tinnitus. Plastic changes arising from sensory deprivation trigger a change in synaptology and neurotransmission with a consequent change in receptor configuration. From neuroanatomical considerations and analogies with other clinical conditions, we postulate the involvement of serotonin (5-HT) in these plastic changes and consider the evidence available from the use of serotonergic drugs in different conditions. A possible relationship between 5-HT and lidocaine is also discussed.

The influence of training on tinnitus perception: an evaluation 12 months after tinnitus management training

Sixty-five subjects were reviewed 12 months after tinnitus management training, which had been comprised variously of information, relaxation training and a therapeutic noise strategy. Seventy-four per cent of subjects reported increased habituation to tinnitus (n = 48), 65% reported reduced tinnitus annoyance (n = 42), and 52% reported an increased ability to cope with tinnitus (n = 34). Twenty-five per cent of subjects reported deterioration in coping ability (n = 16), 23% reported reduced habituation to tinnitus (n = 15) and 8% reported increased tinnitus-related annoyance (n = 5). None of the management strategies were found to be significantly more effective than others in facilitating improved coping or habituation to tinnitus. Subjects who reported reduced coping and habituation to tinnitus experienced greater levels of general life stress than subjects who reported increased habituation and coping ability. The use of relaxation therapies as applied in this study did not appear to influence the level of tinnitus distress or the level of life stress. Thirty-seven per cent of subjects given long-term low-level white noise (LTWN) stimulation reported benefit. However, LTWN stimulation did not significantly alter tinnitus awareness or the minimum masking level (MML) of tinnitus. Long-term low-level white noise stimulation appeared to influence cognitive reaction to tinnitus rather than its physical perception. Subjects who initially had low ability to cope with tinnitus and preferred a more active coping style reported significantly greater benefit from LTWN stimulation than subjects whose primary approach to coping was to regulate the emotional impact of tinnitus.

Patients' reports of the effect of alcohol on tinnitus

One hundred chronic sufferers attending a tinnitus outpatient clinic completed self-report questionnaires assessing the quantity of alcohol they consumed weekly and its effect on tinnitus. The results showed a mixed effect of alcohol on tinnitus with 22% of the sample reporting that drinking worsened tinnitus, 62% reporting no effect of alcohol on tinnitus and 16% reporting that alcohol improved tinnitus. The reported effect of alcohol on tinnitus significantly influenced the reported change in the level of alcohol intake since tinnitus onset, with significantly more units of alcohol being consumed by those sufferers who reported that alcohol improved their tinnitus. However, for the sample as a whole, drinking behaviour was not significantly different to that of the general population.

Zinc in the management of tinnitus. Placebo-controlled trial

To assess any possible beneficial effect from zinc on tinnitus we performed a placebo-controlled, randomized, double-blind investigation. Forty-eight patients with tinnitus were randomized to either placebo or the administration of zinc sulfate as sustained-release tablets of 22 mg Zn++ (Zinklet). The tablets were administered three times daily for 8 weeks. Every week the patients stated the severity of tinnitus on a number scale from 0 to 10. The levels of zinc and albumin in serum were determined both before and after treatment. Of 48 patients with tinnitus, hypozincemia was found in only one patient. The zinc level increased significantly in the patients treated with zinc. We could not demonstrate any beneficial effect from zinc on tinnitus. One of the essential reasons for this finding could be that the zinc levels in serum were in the normal range previous to treatment.

Treatment of depressed tinnitus patients with nortriptyline

Patients disabled by tinnitus show a high prevalence of major depression. Furthermore, tinnitus produces patterns of disability similar to those produced by major depression. To explore further this link between tinnitus and depression, and to investigate the efficacy of treating depression in the treatment of tinnitus, a single-blind, placebo-washout, nonrandomized pilot study of the tricyclic antidepressant nortriptyline (hydrochloride) was undertaken in disabled tinnitus patients who also met diagnostic criteria for major depression. Nineteen patients began the study, two responded to placebo, and two dropped out prior to completion. Fourteen considered their tinnitus improved, and 12 chose to continue taking nortriptyline after the study. Depression severity decreased, on the average, by 65% (p less than .0001). Tinnitus loudness measured by audiometric matching decreased by a mean of 10 dB or 50% (p less than .02). Self-reports of tinnitus loudness and severity, somatic and psychologic symptoms, and psychosocial dysfunction all showed significant improvement with treatment. These results suggest that what initially appears to be an irreversible otologic disability in these patients may be in large part a reversible psychiatric disability.

Long-term effects of psychological treatment of tinnitus

Twenty patients with severe tinnitus who had undergone behavioural treatment, including applied relaxation and perceptual restructuring, were re-assessed 9 months after completion of treatment. Among the self-recorded variables, tinnitus loudness, discomfort from tinnitus, depression, and irritation, discomfort from tinnitus was the only variable which was still significantly reduced. As part of the 9-month follow-up assessment, the patients' recall of the loudness and discomfort from their tinnitus was studied. Correlations between original recordings and recall data were low.