By Jennifer McInnish, AuD CCC-A
It is important for physicians to know that there are a number of ototoxic medicines that can cause hearing damage.
Ototoxicity is the cellular degeneration of cochlear and vestibular tissues, leading to functional deterioration. Ototoxic chemicals are classified as neurotoxicants, cochleotoxicants, or vestibulotoxicants based on the part of the ear they damage. They can reach the inner ear through the bloodstream and cause injury to inner ear and connected neural pathways. Neurotoxicants are ototoxic when they damage the nerve fibers that interfere with hearing and balance. Cochleotoxicants mainly affect the cochlear hair cells, the sensory receptors, and can impair the ability to hear. Vestibulotoxicants affect the hair cells on the spatial orientation and balance organs.
Over the past several decades, environmental and chemical toxins and more than 200 medications have been identified as ototoxic. Platinum-based chemotherapeutic agents and aminoglycoside antibiotics are the most common ototoxic medications linked to permanent auditory damage, while loop diuretics, macrolide antibiotics, and antimalarials are known to cause temporary symptoms. Patients affected by ototoxic drugs can experience hearing loss, tinnitus, hyperacusis, and occasionally vertigo.
The presentation of hearing loss symptoms varies widely among those receiving treatment with ototoxic medications. Research indicates several factors may influence a patient’s probability of experiencing hearing loss while receiving these treatment regimens. Such factors include but are not limited to the particular drug utilized, the dosage level, frequency of treatments, method of delivery, the patient’s age, hearing status at the time beginning of treatment, history of ototoxic drug treatment, and other risk factors including past and concurrent noise exposure. In addition, genetic factors also may contribute to individual vulnerability to ototoxicity.
The primary purpose of ototoxic monitoring is to provide feedback to the attending physician about the effects of the drug therapy on the patient’s auditory system, so the treatment team can then make any necessary adjustments to avoid further permanent damage to the auditory system. Results from regular auditory testing are also helpful in setting expectations for the patient and their family about the communication issues resulting from drug therapy.
Audiologic testing should be completed to detect changes in auditory function before the damage affects the speech frequency range and before the patient is aware of changes in hearing or experience other auditory symptoms. Therefore, it is important that patients who are treated with these medications be scheduled for auditory monitoring before, during, and after treatment, with the goals of early identification, prevention, and, if necessary, intervention.
According to the American Academy of Audiology’s position statement published in 2009, “audiologic monitoring for ototoxicity is primarily performed for two purposes: (1) early detection of changes to hearing status presumably attributed to a drug/treatment regimen so that changes in the drug regimen may be considered and (2) audiologic intervention when handicapping hearing impairment has occurred.” Intervention may include counseling, communication strategies, amplification, and assistive listening devices.
Permanent sensorineural hearing loss secondary to medication used to treat various infections and cancers is a risk for over four million people in the United States annually. The American Cancer Society reported that 1.7 million people would be diagnosed with cancer in 2017. While the five-year survival rate varies based on the type of cancer and other factors, that rate has steadily improved over the past 40 years. Based on data reported from 2005–2011, approximately 70% of cancer patients are now likely to survive. As an increasing number of cancer patients survive, there will be a greater need for audiologic intervention services to improve the patient’s communication and overall quality of life.
Jennifer McInnish, AuD CCC-A is a Clinical Audiologist in practice at Princeton Baptist Medical Center.