Described as a "first," interferon (IFN) caused sudden but reversiblehearing loss in 22 of 49 Japanese hepatitis patients, say theirphysicians. The auditory deficits recovered a week or two after IFNtherapy ended.Ear-and-throat specialists, led by otolaryngologist Yukihiko Kanda atthe Nagasaki University School of Medicine, reported in this week'sThe Lancet (issue of May 7), that "Ototoxicity of interferon has notpreviously been recorded."After encountering "a case of sudden sensorineural hearing loss duringinterferon therapy," Kanda and co-authors at six medical centersmounted a controlled clinical trial to confirm the unexpected IFN sideeffect. Of their 49-patient cohort treated for hepatitis B or C, 22received recombinant alpha IFN, including Roferon (Hoffmann-LaRoche) and Intron A (Schering Plough). The usual IFNa dose was 6million international units by intramuscular injection, first daily, thenthree times weekly, for 14 to 22 weeks.The remaining 27 patients got cell-cultured beta IFN, for six weeks _roughly half to a quarter the alpha duration.Of the beta group, 15 sustained auditory disability, including hearingloss in 11 and tinnitus (noises in the ears) in four. This compared withseven of the 22 treated with IFNa. The deficits seemed to correlate withcumulative doses of the drug.Only two of the 49 had to discontinue their hepatitis therapy because ofprogressive hearing loss.To justify blaming this side effect on IFN, the researchers point out thatthe frequency of auditory disability was unexpectedly high, apparentlydose-related, reversible with cessation, and without any other plausibleetiology. They suggest autoimmunity as a possible mechanism, andrecommend that all patients on long-term IFN regimens be monitoredfor auditory decrements."I've seen a lot of interferon side effects," Samuel Ronel, the founder,president and CEO of Interferon Sciences Inc. (ISI), told BioWorld,"but this is the first time I hear of hearing loss." Ronel, whose companyin New Brunswick, N.J., pioneered production of natural INF, added,"But nothing will surprise me; the drug is still in its infancy."A high-dose clinical study of ICI's Alferon-N in 20 patients byWashington D.C.-based Walter Reed Army Medical Center, Ronelsaid, "saw no psychoneurological toxicity."And a press spokesman for Schering Plough Corp., of Kenilworth, N.J., which markets Biogen's Intron A under license, told BioWorld that"rare occurrences of auditory deficits have been noted in the literature."He added that the product's package insert alerts physicians prescribinginterferon to this possible side effect.
-- David N. Leff Science Editor
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