Intravenous procaine in the treatment of Ménière's disease

Drugs in the treatment of tinnitus

Many drugs and some foods can cause or aggravate tinnitus in some patients. These substances should be identified and withdrawn. Tinnitus may be improved by the treatment of associated conditions, infections, or hearing loss with appropriate drugs--hypotensives, antibiotics, vasodilators, fluoride or thyroxine. Intravenous lignocaine can temporarily reduce or abolish tinnitus in many patients but can aggravate existing tinnitus in some and may have no effect on others. Analogy with pain of central origin suggests that the beneficial effects of lignocaine (lidocaine) may be due to its anticonvulsant action. Lignocaine is used as a test to distinguish between different mechanisms of tinnitus and to predict responses to oral anticonvulsants. Dramatic responses with lignocaine are usually associated with cochlear hearing loss and often with comparable though less marked responses to oral anticonvulsants. Patients who do not benefit from lignocaine do not respond to oral anticonvulsants. The action of anticonvulsants is often potentiated by tricyclic antidepressants. The majority of patients who respond to lignocaine can also have their tinnitus effectively masked, as predicted, on a tinnitus synthesizer. A small proportion respond to masking and not to lignocaine and a small proportion to lignocaine and not to masking. Beneficial effects of masking and anticonvulsants are cumulative. Anticonvulsants may also produce subjective improvement in clarity, improved tolerance of hearing aids and increased masking benefit when a hearing aid is worn.

Pharmakotherapie des akuten Tinnitus

Hypoxia/ischemia may play an important role in the pathogenesis of sensorineural tinnitus due to the characteristics of the cochlear blood supply. In addition, hypoxia modulates molecular processes both in the acute and chronic forms of tinnitus. Transcription factor HIF-1 (hypoxia-inducible factor) may play a key role in the cells' adaptation to hypoxia and ischemia, while under hypoxic/ischemic conditions, HIF-1 induces changes in the gene expression which may contribute to the remodeling of particular structures within the cochlea. Disturbances in the cochlear blood supply may result in membrane changes, perineural edema, inflammation, disturbances in ion homeostasis and in the formation of reactive oxygen species. Thus, the pharmacotherapy of acute tinnitus may be aimed at the improvement of cochlear blood supply and the prevention of acute processes leading to cell damage. Pharmacotherapies with colloidal plasma substitutes, vasodilators, calcium antagonists, procaine, and cortisone have been described in the literature and are discussed here. Many of the pharmacological treatments have not been validated in double blind studies. Although it is impossible to deduce the cause of tinnitus from a drug's efficiency, there is some evidence that it can be effectively suppressed by improving blood supply, at least at certain stages. The aim is to achieve an improved pharmacotherapy by means of sophisticated diagnostic instruments for classifying particular types of tinnitus.

Lidocaine test in patients with tinnitus: rationale of accomplishment and relation to the treatment with carbamazepine

OBJECTIVES

There is strong evidence in the literature about the effect of local anesthetics such as lidocaine in controlling tinnitus; these agents act by stabilizing hair cell membrane and cochlear nerve fibers. However, the effect of intravenous lidocaine is transient, and its oral analog (tocainide) does not have the same efficacy for long-term treatment in patients with tinnitus. Some oral anti-epileptic drugs (carbamazepine, for instance) have been used alternatively in several studies. The aim of this work is to evaluate the response to intravenous lidocaine in patients with intractable tinnitus and the effect of oral carbamazepine in long-term maintenance of tinnitus relief.

PATIENTS AND METHODS

We studied prospectively 50 patients (28 females and 22 males; mean age 50.9 years) who underwent the lidocaine test, performed by a 3-min intravenous infusion of 2% lidocaine chloridrate. The patients who experienced any relief after the test started treatment with oral carbamazepine in ascending dosages (50-600 mg/day).

RESULTS

The results were classified as tinnitus abolition (18%), marked relief (32%), partial relief (26%), unchanged (22%), or worsening (2%). The lidocaine test showed favorable results in 76% of patients, especially those with bilateral tinnitus (P < 0.001). Afterwards, 50% of patients treated with carbamazepine maintained the improvement of tinnitus (P = 0.0034).

CONCLUSION

The authors conclude that intravenous lidocaine is effective in reducing intractable tinnitus and that there is a close association between lidocaine and oral carbamazepine effects. Therefore, carbamazepine can be used for the treatment of tinnitus when the patient achieves improvement of symptom after the lidocaine test.

Changes in auditory evoked responses during intravenous lidocaine

Auditory evoked responses in 21 cases with tinnitus were recorded before and after the administration of intravenous lidocaine. A dosage of 1 mg/kg body weight was diluted with 20% glucose (20 ml) and administered intravenously over a one-min period. The loudness of tinnitus was evaluated during electrocochleography (ECochG) or auditory brain-stem response (ABR) recordings using a score between 0 and 11. The stimulus sound was a tone burst in a frequency that corresponded to the pitch of tinnitus. AP latency on ECochG and the inter peak latency (IPL) of wave I-III and wave III-V on ABR were prolonged momentarily and tinnitus was reduced. These findings reveal that the sites of action for lidocaine are both the inner ear and the brain-stem.

Trial of flecainide acetate in the management of tinnitus

A two-phase trial of flecainide acetate in the management of tinnitus has been carried out in 22 patients with severe long-term tinnitus resistant to other treatments. Although 5 (23%) patients reported some limited benefit the results are not conclusive but suggest that, for such patients, flecainide deserves a place as a drug worth considering as a last resort, with the prospect of it occasionally giving a worthwhile degree of relief.

A comparison of the effects of eighth nerve section with lidocaine on tinnitus

The success rate of eighth nerve section in abolishing tinnitus is disappointing and the results generally unpredictable. A comparison of the effects of a bolus intravenous injection of lidocaine with the effects of nerve section is reported: it presents some evidence that the response to lidocaine may be of value in selecting patients for nerve section, and further it may shed some light on the site of action of lidocaine in suppressing tinnitus.

An electrocochleographic study of the effects of lignocaine on patients with tinnitus

Twenty patients complaining of tinnitus were investigated by extra tympanic electrocochleography (ECochG). Baseline ECochG recordings were carried out, followed by sequential recording after injections first of saline, as a control, and then after lignocaine in the dosage 1.5 mg/kg body weight. Significant improvement in the tinnitus was seen in 13 patients after lignocaine compared with only 3 patients after saline. A statistically significant reduction in the amplitude of the action potential was seen after the lignocaine injection. Our results confirm the views of Melding et al. that the effect of lignocaine is on the neuronal activity of the auditory pathway.

Melanin capacity to accumulate drugs in the internal ear. A study on lidocaine, bupivacaine and chlorpromazine

The distribution and retention of labelled lidocaine, bupivacaine, and chlorpromazine to melanin in the internal ear after intravenous and intraperitoneal injection were examined by whole-body autoradiography. Both young pigmented hooded rats and albino rats were studied. In the pigmented rats chlorpromazine showed the greatest accumulation, which was more pronounced in the cochlea than in the vestibular portion. The other two substances were evenly distributed in the internal ear. After a single injection of chlorpromazine and of bupivacaine these substances were still bound to the melanin of the internal ear after 14 days, which was the longest survival time. Lidocaine, on the other hand, had disappeared after only 4 days. Strong uptake and retention of the three substances were observed in the eyes of pigmented animals. In albino animals there was very weak, transient uptake in the internal ear of chlorpromazine and bupivacaine, but not of lidocaine. In studies in vitro on isolated bovine eye melanin there was considerably greater adsorption of chlorpromazine than of lidocaine and bupivacaine. An uptake was noted in the human eye in experiments in vitro. Clinical tests revealed no acute or late damage to hearing or sight after large doses of lidocaine. The participation of melanin in different basal labyrinthine functions such as the energy transfer mechanism and the sound protective mechanism is discussed in the light of the results obtained. Further, the theory is put forward that the melanin affinity of certain substances can be of both therapeutic and ototoxic importance.

The use of intravenous lignocaine in the diagnosis and treatment of tinnitus

The effect of intravenous lignocaine upon the symptom of tinnitus has been assessed in seventy-eight patients and the results correlated with associated hearing loss. Lignocaine appears to be highly effective in suppressing tinnitus in patients with presumed damage or degeneration of the Organ of Corti and is less effective in other groups. It is postulated that tinnitus in patients with Organ of Corti damage is the result of abnormal hyperactivity in the auditory pathway following deafferentation.

[Medical treatment in Menière's disease (author's transl)]

They are different methods of medical treatment in Menière's disease. 1. The dehydration of the hydrops by diet, diuretics, hypertonic solutions and glycerol. 2. Improvement of the blood supply by carbon dioxide, by myotropic and neurotropic vasodilators or by decreasing the blood viscosity and by medical or surgical paralysis of the sympathetic nerve. The optimistic results seen by acupuncture or neural therapy are not confirmed. - Experimental and double blind studies with betahistin (vasomotal) showed a significant effect in improving the blood circulation of the inner ear and the symptoms of Menière's disease. 3. Sedatives especially neuroleptics and tranquilizers were successful only by suppressing the symptoms, but are not a causal treatment. The same mechanism is supposed for procain and lidocain. 4. Partial destruction of the inner ear has been produced by local application of anesthetics or ototoxic antibiotics. These methods succeed in relieving vertigo and save the hearing in most cases.

Accumulation of 14C-lidocaine in the inner ear. Preliminary clinical experience utilizing intravenous lidocaine in the treatment of severe tinnitus

Clinical experience has demonstrated that intravenously administered local anaesthetics have a mitigating effect on severe tinnitus. In an attempt to gain some insight into the mechanism of this effect, autoradiography of the inner ear of young pigmented rats was performed after intravenous injection of 14C-lidocaine. Some accumulation of lidocaine was found in the modiolus, but almost none in the stria vascularis. A large accumulation was observed in other melanincontaining tissues, such as the hair follicles and uvea. The in vitro accumulation of 14C-labelled lidocaine adsorbed on melanin granules was low (12%) as compared with that of other drugs, such as kanamycin (89%) and chloroquine (85%). These autoradiographic results indicate that lidocaine has an effect upon the inner ear, in addition to its previously demonstrated effect on the CNS.