THE DRUGS
LIDOCAINE (lignocaine, xylocaine)
The only consistently tinnitus reducing or alleviating drug has been Lidocaine. This was first observed by Barany (1935). This is a drug with local anaesthetic, anti-arrhythmic and anticonvulsive properties. The effect of this on tinnitus has been studied by many especially Shea et al. (1981), Emmett and Shea (1984). Unfortunately this can only be administered intravenously for tinnitus suppression. Its effect lasts between some minutes and some hours and can have unacceptable side effects.
Although the intravenous injection of lidocaine is seldom used in treatment at present, it provides fertile grounds for research into its mechanism of action. Research using lidocaine so far indicates that it has effects upon central auditory pathways as well as on the cochlea.

Iontophoresis of lidocaine through the skin of the external auditory canal was used in the past with no apparent benefit.

Although intratympanic lidocaine injection was advocated by Sakata and Umeda (1976), Coles et al (1992) in their study did not find support for this and the complication of vertigo was very common. It is still used in some centres.
Lidocaine is one of the group of cardiac arrythmic or membrane stabiliser drugs. In the same class there are drugs that can be taken orally:

Tocainide hydrochloride (Tonacard) 400mg tablets.
Flecainide Acetate (Tambocor) 100mg tablets.
Mexiletine (Mexilin) 100mg tablets.

Although these drugs were found to be quite effective in tinnitus alleviation they cannot be used in patients with a variety of health problems including heart disease. When used, co-operation with the cardiologist is required. Emmett and Shea concluded that due to lack of tolerance of the drug's adverse effects, which include cardiovascular problems and blood dyscrasias, there usefulness is not supported. Clinical use of these drugs has been virtually abandoned.
ANTIEPILEPTIC (anticonvulsant) DRUGS WITH MEMBRANE STABILISING PROPERTIES
It is likely these drugs were trialled because the anticonvulsant property of lidocaine inspired investigation into the effect of anticonvulsant drugs on tinnitus. The following were tried:
Amylobarbitone sodium
Phenitoine sodium
Sodium valporate
Primidone
Although some patients benefited from these drugs, they had undesirable side effects and therefore are seldom used.
BENZODIAZEPINES WITH ANTICONVULSANT PROPERTIES
Carbamazepine (Tegretol) 100-200mg tablets.
The studies of Goodhill (1981) gave promising results, however later studies (Goodey 1981, Lechtenberg and Schulman 1984) did not support these levels of effectiveness and the unpleasant side effects of gastrointestinal distress, drowsiness and unsteadiness limit its usefulness.
Clonazepam (Rivotril) 500micrograms tablets.
Lechtenberg and Schulman found clonazepam to have promising effect in comparison with other benzodiazepines such as diazepam, flurazepam and oxazepam. Recently Bumby and Stephens (1997) in a double-blind placebo controlled crossover pilot study found significant reduction in the annoyance caused by tinnitus in comparison with cinnarizine and placebo. It was concluded that it would be helpful to use it in brief and intermittent courses when patients' tinnitus is very troublesome and unresponsive to other management. The effect was explained in terms of the GABAergic effect of the drug on the excitability of auditory neural activity of the cochlea.

 

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