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Adverse Drug Reactions: Issues and Answers for the Audiologist

Adverse Drug Reactions: Issues and Answers for the Audiologist
Robert M. DiSogra
March 15, 2004
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Audiology Associates of Freehold (NJ) and The School of Audiology
Pennsylvania College of Optometry
Elkins Park, PA


INTRODUCTION:

As audiologists, we're taught to recognize ototoxic medications that potentially cause hearing loss, tinnitus, and vestibular problems. Our test procedures and monitoring protocols have traditionally focused on a handful of chemotherapy drugs (i.e., Cisplatin), aminoglycosides (i.e., streptomycin) and loop diuretics (i.e. furosemide). However, many of our subjective test batteries require the patient to be conscious and alert, not drowsy or sedated! Yet many of us never look beyond ototoxic medications to determine if the patient's ongoing drug regimen might influence data collection (i.e., difficulty following/remembering directions) or data interpretation (i.e., abnormal ocular movements).

I propose that in the final analysis, if we are not aware and knowledgeable of the drug regimen the patient is following, we are potentially wasting significant time and money, and potentially gathering and reporting faulty results!

Patients sometimes decide not to reveal all of their medicines to us, as they may indeed believe that medicine "ABC" or pharmacologic or herbal agent "XYZ" has nothing whatsoever to do with hearing or balance issues. Sometimes they may be right, and other times -- perhaps not. As mentioned above, if the pharmacologic agent alters their level of consciousness, it may also alter their responses to behavioral and physiologic challenges.

Importantly, we are not only discussing prescription medicines.

With millions of people taking over-the-counter herbal medicines, we need the most accurate and up-to-date information about herbal medicines and supplements and their adverse effects too! This is why there is now Physician's Desk Reference for Herbal Medicines.

According to the 1999 JCAH Glossary of Terms, an adverse drug reaction (ADR) is "an undesired effect of a medication that either increases toxicity, decreases [the] desired therapeutic effect, or both."

INCIDENCE:

ADRs account for over 100,000 deaths per year in the USA. Only heart disease, cancer, lung disease and stroke claim more lives. Of that figure, 41% were admitted to the hospital because of an ADR and subsequently died. Approximately 3 out of every 1000 patients admitted to a hospital will die from an ADR!

The reader is directed to the September, 2001 Special Issue of Audiology Today (DiSogra, 2001) which lists over 300 drug reactions an audiologist should be interested in and over 1500 FDA approved medications that have one or more effects listed as "reported events" in clinical trials.

For herbals medicines, the March/April 2003 issue of Audiology Today (DiSogra, 2003) has the herbal medicine and associated botanicals list of side effects.

DRUG TOXICITY:

The US Food and Drug Administration (FDA) is the federal agency that regulates the investigation of drugs. The FDA's website (www.fda.gov) provides a wealth of information for the professional and the consumer. The Center for Drug Evaluation and Research (CDER) within the FDA, is the source for information on FDA approved drugs efficacy and safety (www.fda.gov/cder/).

When a new drug (Investigational New Drug or "IND") is being evaluated and introduced, there are specific steps the drug manufacturer must follow in the ''pre-clinical'' process before the drug is granted FDA approval. The overall time frame can be many years from IND status to final approval.

Animal studies are used to identify the pharmacokinetic, pharmacodynamic and toxicological properties of the drug. The drug's safety is determined studying the acute, subchronic and chronic toxicity of the drug, usually in several animal species. The lethal dose required to kill 50% or 90% of the laboratory animals must be determined in the initial toxicity data. Toxic symptoms and their time course must be documented. More than one administration route (oral, IV, IM etc) must also be evaluated.

FDA APPROVAL: HUMAN STUDIES:

There are four phases of drug research when human beings are used in FDA investigational studies. In all phases of human studies, informed consent must be given to protect the rights of participants in the study. Interestingly, some adverse side effects, such as tinnitus, depression, heartburn and headache cannot be evaluated in animals because of the subjective nature of these complaints.

Phase 1. After the FDA approves the study's protocols, 20 to 80 healthy male volunteers aged 18 to 45 will be given the investigational drug in small dosages until the first signs of toxicity appear. This will determine a safe, tolerated dose. Absorption, metabolism and excretion are monitored.

Phase 2. To determine the optimum dose-response range, approximately 80 - 100 patients (with the disorder for which the drug was intended) are evaluated. This phase allows the new drug to be compared to other drugs in randomized studies. Data from long term administration is also valuable in this phase. Adverse reactions are closely monitored.

Phase 3. Once safety and efficacy have been established, the third phase involves many physicians and hundreds or thousands of patients who are closely monitored to detect any side effects (or adverse reactions) previously not identified in the first two phases. Phase 3 may take many years.

Phase 4. This phase further evaluates a drug on "sub-populations" such as children, pregnant women and the elderly. In phase 4, difficult and intricate questions regarding ethics need to be addressed, such as exposing a fetus to the drug. Because of the larger number of participants in this phase, very low incidence side effects can be documented. For example, the incidence figure of a given side effect might be reported as "1 case in 5000" or 0.0002% or ''occasional'' or ''rarely." Side effects must be reported to the FDA every three months during the first year of phase 4, every six months in the second year and annually thereafter. Reported side effects must be included in the patient information brochure or advertising by the manufacturer. The FDA continually monitors the drug for unexpected adverse effects, injury and/or toxic or allergic reactions.

ADVERSE DRUG REACTIONS (ADRs):

When an undesired effect is reported by the patient or the clinical team during clinical trials, this is referred to as an adverse drug reaction (ADR). The term excludes non-therapeutic overdosage; such as accidental exposure or attempted suicide.

The FDA has established a monitoring program to alert physicians about serious and unexpected ADRs. The program, called MedWatch has a website to report ADRs: www.fda.gov/medwatch. MedWatch can also be contacted by calling 1-800-FDA-1088. MedWatch seeks input from all concerned parties.

There are four classifications of ADRs:



  1. Mild - requiring no antidote or prolonged hospitalization;

  2. Moderate - requiring a change, but not cessation, of a drug or need for special treatment;

  3. Severe - potentially life threatening requiring discontinuation; and

  4. Lethal - directly or indirectly contributes to the patient's death.

Estimates of 3% to 7% of all hospitalizations are the result of an ADR and some 20% of ADRs occurred during hospitalization. Estimates of lethal ADRs occurances are less than 1%. (Beers, 2000)

Incidence and severity can be patient related (age, sex, genetics, etc.) or drug-related (route of administration, duration, dosage, etc.). There is a greater severity of ADRs in the elderly. Other variables are patient compliance and prescribing errors.

Additional information on pharmacological management can be obtained from the on-line Merck Manual: www.merck.com/pubs/mmanual.

AUDIOLOGY AND ADRs:

The Physician's Desk Reference (PDR) lists all FDA approved drugs by manufacturer (www.pdr.net). Each PDR entry is extremely detailed. Because audiology as a profession, does not mandate biochemistry or organic chemistry as academic pre-requisites, alternate references for drug indications, dosage recommendations and side effects are useful. In some situations, it may be useful to speak with a pharmacist too. A useful website is www.rxlist.com. This website is in "plain" language and offers many hyperlinks to additional resources.

DRUG INDUCED OTOTOXICITY:

As audiologists, we are generally most concerned with ototoxicity. We know that aminoglycoside antibiotics (streptomycin, neomycin, kanamycin, amikacin, viomycin, vancomycin, gentamycin, tobramycin), diuretics (ethracrynic acid, furosemide), salycilates (aspirin) and other synthetic substitutes (quinine) can damage the cochlea or vestibular portion of the ear.

Possible sites of action for ototoxic damage include the sensory receptors, afferent and efferent nerve endings and the stria vascularis.

Ototoxic effects on the vestibular system include; vascular abnormalities, uncontrolled vasodilation and constriction and autoimmune dysfunction. Electrophysiologic changes, such as depressed cochlear microphonic and depressed or absent eighth nerve action potential responses, might also be attributed to ototoxic effects.

AUDIOMETRIC MONITORING FOR OTOTOXICITY:

Audiometric monitoring protocols are unique to each clinic, and arguably to the situation, patient and specific drug of concern. However, there are several published guidelines which can serve as references (Campbell and Durrant, 1993; ASHA, 1994; Vasquez and Mattucci, 2003). Audiometric monitoring of ototoxic medications should ideally commence before administration of the agent and should continue during and after cessation to monitor late onset hearing loss.

ADRs IN CLINICAL PRACTICE:

In clinical practice, the case history helps the audiologist determine which tests to perform to establish a diagnosis for the patient's auditory or vestibular complaint. Aside from the usual intake questions, the patient's drug history and current pharmacologic regimen needs to be established. As simple as this might sound, it can be a time-consuming and perhaps confusing event. Patients often have difficulty recalling the names of their medications, how long they've been taking them, and in some cases, why they are being taken. ''Was it Zantac or Xanax?" Some patients describe the color or size or shape of their drug, hoping we'll be able to quickly identify the name of ''the little white pill.''

I recommend all patients carry a wallet-sized card designed to list all medications, dosages, and family and physician contact names and phone numbers. For hospital-based audiology practices, this information is readily available in the patient's chart. As mentioned previously it is not unusual for patients to withhold the names of their medications because he/she has determined it has nothing to do with their hearing loss, dizziness or tinnitus complaints! When the appointment to see the audiologist is made, the scheduling person might mention "It will be important to bring a complete list of all your medications to the appointment."

PATIENT COMPLIANCE:

Patient compliance with a prescription drug is a key factor in accomplishing the desired outcome. Patients literally forget to take their medication(s) or they may be in denial of the illness, since taking the drug is a constant reminder they are not healthy. Other patient-related causes of non-compliance include misunderstanding instructions, low or no confidence in the drug's effectiveness, lessening of symptoms to varying degrees, concern for adverse side effects, apathy, cost of medications and physical difficulties such as swallowing problems, opening bottles and even getting the prescription filled! Improving doctor-patient and pharmacist-patient and nurse-patient relationships - based on trust - is the best way to insure compliance. Clarity of instructions, benefits and side effects should be made as simple as possible. As audiologists, we should review the medications and ask, ''Are you following the doctor's orders?"

HERBAL MEDICATIONS:

For many herbal medications, side effects are not well known or well documented. The reader is directed to Dietary Supplement Health and Education Act of 1994 (DSHEA) for more information (http://vm.cfsan.fda.gov/~dms/dietsupp.html).

VESTIBULAR CONCERNS:

Vestibular evaluations can be affected by any vestibular-ocular side effects. Because vestibular-ocular deficits are usually bilateral, the precision, velocity and latency of the response are important in the data analysis. Acuity is not an issue but can influence calibration (Gans, 2001). Of course, no medicines or drugs should be discontinued without prior (preferably written) consent from the treating or referring physician. Patients who can discontinue non-life sustaining medications for at least 24 to 48 hours before the vestibular test should do so. However, if a medication cannot be stopped and if there are known vestibular-ocular side effects, they must be documented. The decision to perform and interpret the vestibular battery may be a judgment call. What is in the patient's best interests will determine your outcome (i.e., task reliability, accuracy and even rescheduling) (Eckert, 2001).

INFORMING YOUR PATIENT:

Importantly, ADRs are reported side effects. Some side effects have a very low incidence. They might not occur in all (or any) of your patients. Nonetheless, as they relate to hearing loss, tinnitus and dizziness, they are topics for discussion between the audiologist and the patient, with presenting symptoms. Often, the patient may be relieved to know their tinnitus is very likely a side effect of their medication and not a manifestation of a tumor!

However, if the patient asks, "Should I stop taking my heart pill so the ringing in my ears can go away?" The appropriate answer may be, "That's a decision only your doctor can make after I tell him/her what we found today. In the meantime, don't make any changes."

GETTING TO KNOW YOUR LOCAL PHARMACIST

One enlightening experience you might consider, would be "shadowing" a pharmacist for a day. You will likely be amazed at the many similarities between their profession and audiology. I anticipate that your visit would be welcomed!

Pharmacists can be an important link to better patient management, especially when drug interactions are a concern. Pharmacists are generally more accessible than PCPs for quick and reliable, unscheduled consultations.

CONCLUSION:

ADRs can cause, mimic, alter (fluctuate) or exacerbate hearing loss, vestibular function or cognitive abilities. Audio-vestibular test accuracy and results can be directly affected, misinterpreted or mis-reported based on drugs, herbal remedies and other agents. A full chart listing of the patient's drug regimen and cross-referenced known ADRs is recommended. A solid relationship with a pharmacist is recommended. Wallet-sized drug information cards are recommended and can expedite information especially in an emergency.


REFERENCES:

American Speech-Language Hearing Association (ASHA). Audiologic management for individuals receiving cochleotoxic drug therapy. NOTE: Full text is available online at: www.asha.org/NR/rdonlyres/2724E51A-70C4-4118-9A50-D1794EBD26F0/0/18855_1.pdf

Beers, MH and Berkow, R., eds, The Merck Manual of Diagnosis and Therapy. Merck Research Laboratories, Whitehouse Station, NJ, 2000.

Campbell, CM and Durant, J, Audiologic monitoring for ototoxicity, Otolaryngologic Clinics of North America, Vol. 26, No. 5, 1993.

DiSogra, RM. Adverse herbal medicine reaction and audiology practice. Audiology Today, Mar/Apr 2003, Vo. 15, No. 2, pp.37 - 42.

DiSogra, RM. Adverse drug reactions and audiology practice. Audiology Today, Special Issue, September 2001.

DiSogra RM and Weir, K, The side effects of drugs on hearing, auditory perception and other related systems, Audiology Today, November/December, 1993.

Eckert, A., Director, Speech Pathology and Audiology and The Balance Center, JFK Medical Center, Edison, NJ, personal communication, 2001.

Gans, R. Director, American Institute of Balance, Clearwater, FL., personal communication, 2001.

Vasquez, R and Mattucci, KF. A proposed protocol for monitoring ototoxicity in patients who take cochleo- or vestibulotoxic drugs. ENT Journal, March 2003, VOL. 82, NO. 3.

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robert m disogra

Robert M. DiSogra

Dr. Robert M. DiSogra is a graduate of the PCO School of Audiology. He received his Masters Degree in Audiology from Hofstra University on Long Island in 1976 and a Bachelor's Degree in Speech Education (K-12) from St. John's University in NY in 1975.

Bob is a US Navy veteran and he attributes his transition from speech pathology to Audiology from his electronics/communications experiences in the Navy.

He has had his private practice for the past 18 years in Freheold, NJ. His teaching assignments include Pharmacology/Ototoxicity at PCO, graduate and undergraduate courses in Audiology at Rutger's University (NJ) and Kean College of NJ. He has also presented papers at the national meetings of AAA, ADA, ASHA, NHCA and other allied health organizations.



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