Some lifesaving antibiotics may cause hearing loss and balance problems

Antibiotics, which treat bacterial infections, are essential, life-saving medicines. But just like any medication, they carry the risk of side effects.

When it comes to one potent class of antibiotics, known as aminoglycosides, these potential side effects include hearing loss, tinnitus and balance problems.

What are aminoglycosides?

Aminoglycosides are antibiotics that work by attaching to bacteria and disrupting their production of essential proteins. Without these proteins, the germ cannot survive, halting the spread of infection. Aminoglycosides are powerful drugs and routinely used in critical care settings (such as intensive care) to treat meningitis, sepsis, serious respiratory infections, and other life-threatening infections.

Aminoglycosides were developed in the 1940s. Though newer alternatives have been developed, aminoglycosides are still used because they are effective and inexpensive.

Which antibiotics can cause hearing loss?

Drugs used to combat infections, broadly known as antimicrobials, are more commonly associated with hearing problems than any other class of drugs, according to a comprehensive review of medical literature by researchers at the Medical University of South Carolina.

Of the microbials, aminoglycosides are well-known for hearing-related side effects.

Aminoglycosides and hearing loss

Some common aminoglycosides that are strongly associated with hearing-related effects are:

• Kanamycin (Kantrex)
• Amikacin (Amikin)
• Gentamicin (Garamycin)
• Neomycin
• Paromomycin (Humatin)
• Plazomicin (Zemdri)
• Streptomycin
• Tobramycin (Tobi)

While powerful against certain infections, aminoglycosides can damage the sensory cells in the inner ear that detect sound and motion. This is known as ototoxicity and can lead to permanent sensorineural hearing loss, dizziness  and tinnitus.

Depending on the specific drug, ototoxic effects of aminoglycosides can be one or both of the following:

• Vestibulotoxic: damaging the inner ear's vestibular system, causing dizziness, vertigo and balance issues
• Cochleotoxic: damaging the inner ear cells that detect sound, resulting in hearing impairment or tinnitus 

Anywhere from 20 to 60 percent of adults who are given aminoglycosides experience some degree of hearing loss, from mild to profound. It usually causes high-frequency hearing loss. At higher doses given over longer period of times, it may affect other ranges of hearing, such as low frequencies, and eventually cause complete deafness.

These antibiotics can also harm the kidneys. Because of these risks, aminoglycosides are usually reserved for serious infections, often given by IV in hospitals. Aminoglycosides come in other forms, such as pills and ear drops.

"These medications can be extremely effective for treating infections–they should be used when really needed, and avoided otherwise," said Dr. Andy Miller, an infectious disease specialist with the Hospital for Special Surgery in New York City.

Aminoglycoside ear drops like Cortisporin Otic can potentially harm your inner ear as well, causing hearing and balance problems. However, when used according to the recommended dosage and limiting treatment to a maximum of 10 days, the risk of systemic absorption and ototoxicity is much lower compared to when these drugs are taken orally or intravenously.

Still, experts usually favor other antibiotic ear drops over aminoglycoside ear drops, especially if your eardrum is damaged or if there's a higher risk of the drug getting into your bloodstream.

Research indicates that some people may be more genetically susceptible to the effects of aminoglycosides.

Hearing loss with other antimicrobials

Besides aminoglycosides, other antibiotics and antimicrobials have been linked to mild or temporary hearing problems. Permanent cases have been rarely reported. Though not a complete list, common examples include:

• azithromycin (Zithromax)
• clarithromycin (Biaxin)
• ketoconazole (Nizoral)
• minocycline (Minocin)
• ritonavir (Norvir)
• sulfamethoxazole
• vancomycin (Vancocin)

Note that, in many cases, people who reported hearing problems with these and other infection-fighting drugs may have been concurrently using other medications linked to hearing loss or tinnitus, such as nonsteroidal anti-inflammatory drugs (NSAIDs) used for pain relief.

Hearing loss: Undesirable but unavoidable side effect

As of right now, hearing loss and balance problems are considered unavoidable potential side effects to taking these life-saving antibiotics.

"Currently, it's accepted that the price that some patients have to pay for surviving a life-threatening bacterial infection is the loss of their ability to hear," said Dr. Peter Steyger, professor of otolaryngology, head and neck surgery at Oregon Health & Science University School of Medicine, in a 2015 news release. "The costs of this incalculable loss are borne by patients and society." 

Steyger's research team studied the effect of aminoglycosides on mice, finding that mice with severe infections were at greater risk of aminoglycoside-induced hearing loss than healthy mice given the same medications, according to the study. This suggests that inflammation caused by infection may increase the absorption rate, leading to a toxic level of medication in the ear.

NICU babies often receive aminoglycosides

Of particular concern are infants in neonatal intensive care units (NICU). Eighty percent of all infants admitted to the NICU receive aminoglycosides; that means each year 480,000 babies are at risk. The rate of hearing loss in babies who have been in the NICU is significantly higher than that of the general infant population, at 2 to 4 percent. In comparison, the rate of hearing loss in full-term infants from congenital causes is just 0.1 to 0.3 percent. 

What to do if you suspect you have hearing loss

If you've recently taken an aminoglycoside or another ototoxic drug, and are concerned you have hearing loss, don't wait to get an evaluation. Not only does it rob you of hearing those around you, untreated hearing loss is associated with a higher risk of physical and mental health dangers. A few examples include cognitive decline, depression and falling. Find a hearing care provider near you to make an appointment.

Note: This piece was medically reviewed by Dr. Patricia Weiser, a licensed pharmacist and medical writer. She obtained her Doctor of Pharmacy degree at the University of Pittsburgh.