[Clinical and electrophysiological investigations of the influence of phenytoin natrium on tinnitus].
Anticonvulsant drugs like Carbamazepine and Phenytoin natrium (PHT) have been used for suppressing the tinnitus. In this paper, a clinical experience was reported, in that 100 patients with tinnitus were treated with intravenous administration of PHT, and the influence of PHT on auditory systems in the guinea pig investigated in detail electrophysiological examinations was also reported. The results are summarised as follows: 1. Clinical evaluation in the treatment of tinnitus (1) Of the 100 patients, more than 70% were well responded. (2) Pith match, loudness balance test correlated closely with the suppression of tinnitus. (3) Side effects were found in 5%, but there were all mild enough to be well tolerated. 2. Experimental evaluation in the guinea pig (1) In intravenous administration of PHT, latency and amplitude of each waveform peak in ABR were prolonged and decreased. As for the latency, waves III and IV were most prominently affected. The results may indicated that PHT works in the upper brain stem predominantly and effects also to the cochlear nucleus and cochlear nerve. (2) The amplitude of N1 in AP was depressed and its latency was slightly prolonged. These phenomena related closely with change of wave I in ABR. This may indicate that PHT can directly suppress the cochlear nerve. (3) Even at the dose that apparently influenced ABR and N1 in AP, no obvious change was observed on amplitudes in CM and EP, that may indicate PHT cannot affect on hair cells at this dose or it cannot proceed to the cochlea. (4) These changes were considered to be direct effect of PHT on auditory systems, since they were not correlated with change in the circulatory system. (5) In the perilymphatic perfusion of PHT, amplitudes in EP and CM were depressed slightly at the beginning of the perfusion. Changes in EP preceded those in CM. The results may indicate that PHT effects directly on the stria vascularis and secondarily on CM. (6) In this perfusion, no obvious change was found in AP. Nevertheless, the amplitude of N1 in AP increased over the initial level after the perfusion corresponding to the recovery of EP in some animals. The results may indicate that PHT cannot work directly on hair cells nor cochlear nerve and that the suppression of efferent inhibitory neurons can increase AP potentials. (7) PHT works on the large part of auditory pathway without cochlea, as a role of inhibitor. Considering antitinnitic effect of PHT, tinnitus bases on unusual excitement of the auditory pathway.
Tatemoto
K
K
Department of Otolaryngology, Kyoto Prefectural University of Medicine.
D000328:Adult; D000368:Aged; D000818:Animals; D001933:Brain Stem / Q000502:physiology; D003055:Cochlear Microphonic Potentials / Q000187:drug effects; D004341:Drug Evaluation; D005072:Evoked Potentials, Auditory / Q000187:drug effects*; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D008297:Male; D008875:Middle Aged; D010672:Phenytoin / Q000494:pharmacology / Q000627:therapeutic use*; D014012:Tinnitus / Q000188:drug therapy*
D010672:Phenytoin