Ototoxicity
Ototoxicity is generally a structural damage to the inner ear by exposure to certain drugs or chemical agents. There are approximately 200 prescriptions and over-the-counter drugs identified as potentially ototoxic. The consequence of ototoxicity could be structural and/or functional, permanent or temporary, cochlear or vestibular specific, depending upon type of drug and drug action. Among all the ototoxic drugs, aminoglycoside antibiotics and antineoplastic (chemotherapeutic) medications are identified as potentially more ototoxic. The frequent use of ototoxic drugs in health care system has direct impacts on the occurrence of hearing loss.
General symptoms of ototoxicity could be divided into cochlear and vestibular ototoxicity. Cochlear ototoxicity mainly includes symptoms such as tinnitus, hearing loss, and difficulty in understanding speech in noise. Vestibulotoxicity can result in conditions associated with disequilibrium, instability of the visual field and vertigo. Symptoms of ototoxicity can present immediately after single course of treatment or can be delayed for several days and months, which signifies the importance of audiological monitoring.
Ototoxicity more often occurs along with nephrotoxicity. Typically, nephrotoxicity is monitored through drug dosage, peak plasma concentration or peak serum levels of ototoxic agents in blood. However, various studies have reported poor correlation of ototoxicity with drug dosage, peak serum levels and other toxicities. The only way to detect ototoxicity is by assessing auditory and vestibular function directly.
Early Identification and prevention
The general presentation of ototoxic hearing loss starts from higher frequencies and spreads towards lower frequencies. Due to the gradual nature of ototoxicity, unfortunately, hearing loss may go unnoticed by patient until it has advanced enough to cause obvious hearing and communication problems, signifying that hearing loss in speech frequencies has already occurred. Similarly, by the time patient complains of dizziness, significant vestibular damage has already occurred.
Communication ability is a central quality-of-life issue for patients with life-threatening illnesses requiring treatment with ototoxic drugs. Thus, early identification of hearing loss and balance problems is of paramount importance to prevent or minimize permanent impairment and therefore improve quality of life post treatment.
Implementation of initial baseline and periodic hearing monitoring can improve treatment outcome by identifying and minimizing hearing loss progression. It also provides physician the opportunity to monitor or adjust the therapeutic treatment in order to minimize or prevent permanent hearing loss warranting rehabilitation.
From rehabilitation point of view, early identification and monitoring of ototoxicity provides audiologists’ opportunities to counsel patients and families regarding ototoxicity induced hearing loss, tinnitus, dizziness and its consequences on communication. It also provides an opportunity to plan the rehabilitation program during and after the treatment.
Conclusion
Although benefits of early detection and monitoring of ototoxicity are well known, there are not many programs implemented in health care system, which are dedicated to ototoxicity identification and monitoring. There may be various reasons for it ranging right from unawareness of such programs within the healthcare fraternity to practical problems like cost and lack of facilities for monitoring. Early identification and monitoring for ototoxicity is a cost effective, efficient and invaluable program that helps preserve patient’s quality of life and should be implemented in all health care sectors where patients are treated with ototoxic drugs. With continuous efforts from health care professionals involved in patient undergoing ototoxic treatment, monitoring of ototoxicity through periodic audiological assessment is possible.
For better hearing health, anyone who takes medications or on treatment for heart, blood pressure, diabetes, kidneys and cancer should arrange for regular audiological monitoring either by requesting the physician or directly contacting nearest audiology clinic.
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