What Are Ototoxic Medications?

Ototoxicity is poisoning to the ear that takes place from exposure to harmful chemicals. The resulting consequence is temporary or permanent damage to the inner ear, which leads to hearing loss, tinnitus, dizziness, or balance problems.

There are many types of ototoxic substances including: over the counter medications, prescription drugs, and environmental chemicals. Generally speaking, ototoxic medications are most commonly used to treat or prevent severe illness. Although they can be effective in treating life threatening diseases, their lasting side effects can be permanent. With proper monitoring of the signs and symptoms of ototoxicity, individuals can hope for the best possible outcome. In circumstances where permanent damage occurs, seeking rehabilitative treatment options from an audiologist can help improve an individual’s quality of life.

What Is an Ototoxic Drug?

Ototoxic drugs are medications known to cause damage to the inner ear. Ototoxicity literally translates to: oto=ear; toxicity=poisoning. More specifically, ototoxicity can cause temporary or permanent damage to the hearing and/or vestibular (balance) organs. Disturbances in the hearing and vestibular organs can result in: hearing loss, tinnitus, dizziness, or balance problems. Generally ototoxic medications are utilized to treat severe, life-threatening illnesses.

The U.S. Food and Drug Administration is not required to examine the function of inner ear structures when releasing new drugs on the market. Ototoxic drugs are often only discovered after enough people suffer the signs and symptoms of ototoxicity, in addition to their health care professionals being able to identify the connection between these side effects and the medication. This was the case for specific ototoxic medications such as: aspirin, quinine, antibiotic streptomycin, and most recently in some chemotherapeutic drugs.

Ototoxic medications are often utilized in the hope of preventing or stopping severe illness. Some examples include but are not limited to:

  • aminoglycoside antibiotics (e.g. gentamicin)
  • cancer chemotherapy drugs (e.g. cisplatin and carboplatin)
  • salicylate pain relievers (aspirin, used for pain relief and to treat heart conditions)
  • quinine (to treat malaria)
  • loop diuretics (to treat certain heart and kidney conditions).

What Happens in Ototoxicity?

In a healthy inner ear, there are cell bodies with tiny hair cell attachments. These hair cells move back and forth in response to sound vibrations or movements, and are responsible for relaying sensory information along the vestibulo-cochlear (hearing and balance) nerve to the brain. When these hair cells become fractured, broken, or damaged, they are unable to move appropriately to send information to the brain. When an ototoxic drug attacks the inner ear, it ultimately damages these sensory hair cells, or the hearing and balance nerves themselves. The resulting consequences can lead to temporary or permanent damage to an individual’s hearing and/or balance. Depending on the portion of the inner ear damaged, the signs and symptoms can vary.

What Are the Signs & Symptoms of Ototoxicity?

The signs and symptoms of ototoxicity can vary depending on the structures that are most damaged. Cochlear Toxicity (i.e. damage to the inner ear cochlea) symptoms range from tinnitus (noises in the ears) to total hearing loss, depending upon the individual. Symptoms may also include one-sided or two-sided hearing loss and constant or fluctuating tinnitus. The form of toxin in addition to the duration and dosage of the medication can have a significant impact.

Vestibulotoxicity (i.e. damage to the inner ear balance organ) symptoms range from mild imbalance or dizziness, to total incapacitation. There are several factors that can impact the symptoms of a vestibular or balance loss including: if one or both ears are impacted, the degree of damage, the onset of damage (rapid or slow), and how long ago the damage occurred. A vestibulotoxic loss that is slow and one-sided might not result in any symptoms at all. Whereas a rapid onset loss can produce vertigo (sensation of spinning), vomiting, and nystagmus (eye jerking). These symptoms can make a person feel bed ridden and unable to perform activities of daily living.

How Is Ototoxicity Diagnosed?

In order to properly diagnose ototoxicity, a thorough case history must be obtained. This includes providing information on the medications taken, dosage, and duration. In addition, noise exposure history is also informative, as individual’s taking ototoxic medications are more susceptible to damage from noise exposure.

A comprehensive hearing test should be conducted before and after taking a known ototoxic medication. If changes in hearing, tinnitus, or balance are noted throughout treatment, a hearing test may also be performed to monitor changes. A diagnostic hearing test should include:

  • Pure tone audiometry
  • Ultra-high frequency audiometry
  • Speech descrimination testing
  • Distortion product otoacoustic emissions (DPOAEs): an objective test that measures the outer hair cell function of the inner ear. DPOAEs can be useful in detecting changes in the inner hair cells prior to when the patient might notice changes in their hearing.

How Is Ototoxicity Treated?

At the present moment there is not a treatment to cure ototoxicity. However, open and honest communication with your healthcare professionals is essential in achieving the most favorable outcome. In some instances, there may be a possibility of altering the medication dosage to help ease or reduce the severity of the ototoxic side effects. In some instances this is not possible, as ototoxic medications are often used for life-threatening, severe circumstances. Thankfully, there are resources and solutions to help ease the burden of hearing loss caused by ototoxicity.

What Can Help With Hearing Loss?

Hearing aids can be an excellent solution for individuals who suffer from hearing loss resulting from ototoxicity. The goal of a hearing aid is to provide amplification specific to an individual’s hearing loss. Hearing aids do not restore hearing to normal, however they provide access to speech sounds to make conversation more accessible. This in return improves communication, eases the burden of listening fatigue, and improves overall quality of life.

In some instances, ototoxicity may lead to greater degrees of hearing loss. Individuals who experience severe to profound hearing loss as a result of ototoxicity may consider cochlear implants. A cochlear implant is different from a hearing aid, in that it is a surgically implanted device designed for individuals who are no longer receiving benefit from traditional hearing aids. In order to be considered for a cochlear implant, comprehensive testing is performed by an audiologist to assess candidacy.

Communication strategies are also beneficial for individuals who have hearing loss, wear hearing aids, or cochlear implants. A few useful tips for effective communication include: gaining the individual’s attention prior to talking, visual cues (speaking face to face), and providing context. Additionally, rephrasing a comment can be more beneficial than repeating the same misunderstood comment a second time.

Ototoxicity: What Else Should I Know?

Being informed and educated on the medications you are taking can equip you with confidence in being proactive if you observe changes in your health or adverse side effects. Many health care professionals are aware of known ototoxic medications and will schedule baseline and post treatment testing. Following through on these tests is important to gather data on the status of your hearing prior to taking the medication. Monitoring your hearing and/or balance symptoms during treatment is also important. Please communicate with your doctor if you notice sudden changes!  Even if you don’t feel there is a significant loss after taking an ototoxic medication, it is essential to complete your hearing test post treatment. In general, the sooner hearing loss is identified and treated, the better the outcomes patients tend to have.

Ototoxic medications are often used to help patients treat life threatening illness, however they can have lasting effects on an individual’s hearing and/or balance. Depending on which medication, dose, and duration of exposure, the side effects can vary. Scheduling a baseline and post treatment hearing test with an audiologist is imperative to monitor changes in your hearing and/or balance.

Being keenly aware of changes in your hearing, tinnitus, and balance are important if you are taking a known ototoxic medication. An open and honest conversation with your doctor may allow for changes to be made to your medication if appropriate. If changes are unable to be made to alter the course in your medication, please consider seeking care from an audiologist. With the help of an audiologist, there are treatment options available to help improve your quality of life and ease the burden of hearing loss and/or dizziness.

Dr. Sarah Fontaine

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Dr. Sarah Fontaine

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