March/April 2018

Medication Monitor: Medication-Related Sensory Impairments
By Mark D. Coggins, PharmD, BCGP, FASCP
Today's Geriatric Medicine
Vol. 11 No. 2 P. 6

The use of all five senses—vision, hearing, taste, smell, and touch—allows humans to process everything occurring in the world around them.1 However, with increased age, sensory changes that can negatively impact an individual's quality of life often occur. Additionally, the use of certain medications can further impair senses, which can be especially troublesome for aging adults who generally have high rates of polypharmacy and increasing frailty. By recognizing the role medications play in sensory impairment and taking steps to minimize the use of these medications, health care professionals can help older adults live their lives to the fullest extent possible.

Vision
The risk of low vision (ie, where some usable vision remains) and blindness increases significantly with age, particularly in those over the age of 65.2,3 The most common age-related eye diseases include the following4:

• glaucoma, which leads to peripheral vision loss;
• age-related macular degeneration, which leads to central vision loss;
• diabetic retinopathy, which leads to a spotty field of vision;
• cataracts, which lead to blurring, clouding of images, sensitivity to light, and decreased contrast differentiation; and
• dry eye, which creates insufficient tear production, making vision-related activities more difficult.

A number of factors, including disease and medication use, can result in vision impairment and impact the overall health and well-being of older adults. Some of the potential negative impacts include the following2:

• increased risk of falls and fractures, leading to hospital or nursing home placement, increased disability, and premature death;
• increased risk of depression;
• increased difficulty identifying medications, which can lead to medication-related adverse events; and
• declines in activities of daily living.

Medications
Medications can impact vision in various ways, including the following:

• anticholinergic side effects that lead to blurred vision or changes in perception (eg, antihistamines, gastrointestinal medications, certain antidepressants, antipsychotics, and others)3-6;
• worsening glaucoma (eg, steroids, anticholinergics, and medications with anticholinergic side effects, sulfa-based medications, and others)3,6;
• contributing to or worsening macular degeneration (eg, phenylephrine, long-term NSAID use, niacin, quinine, and others)3,4;
• increasing cataract formation (eg, steroids, long-term NSAID use, antipsychotics, glaucoma medications, and others)3,4; and
• causing visual disturbances such as visual hallucinations (eg, as may occur with anticholinergic syndrome,5 benzodiazepines, and others6).

Visual abnormalities are among the first and most common signs of digoxin toxicity, occurring in 7% to 20% of adults who take the medication. Patients most frequently complain of decreased acuity, xanthopsia (yellow colored vision), chromatopsia (abnormal coloration of objects), photopsias (sparkles of light in the vision field), photophobia (light sensitivity), and blind spots near the center of the vision.7

Hearing Loss
Hearing loss occurs in 80% of people over the age of 85 and is the most common sensory deficit.8 It can lead to severe social and health-related problems. It's especially problematic in the elderly with hearing loss that impairs the exchange of information, thus significantly impacting everyday life, causing loneliness, isolation, dependence, and frustration, as well as communication disorders.8,9

When working with older adults, it's good practice to be mindful of symptoms of ototoxicity including the following9:

• tinnitus (ringing in the ears);
• hearing loss (bilateral or unilateral);
• dizziness;
• incoordination in movements;
• unsteadiness of gait; and
• oscillating or bouncing vision (vertigo).

Hearing loss may be partial or total; this depends upon the severity of damage to the hair cells lining the cochlea. Tinnitus may be described as roaring, clicking, hissing, or buzzing and may be soft or loud and high or low pitched; it often is one of the first symptoms of damage. Fall risk can increase as well, particularly among patients who experience dizziness, poor coordination, unsteady gait, or vertigo.9

Medications9
A number of medications are known to be ototoxic (cause damage to hearing). Medications can influence hearing; this underscores the need to minimize unnecessary medication use as an essential aspect of hearing function preservation. Additionally, it's important to remain mindful that medications causing ototoxic symptoms may need to be considered as a potential contributing factor if increased fall incidence is noted.

Consider the following tips to reduce the risk of ototoxicity:

• When possible, assess hearing before starting ototoxic medications and monitor over the course of treatment, as symptoms alone are not always reliable.
• Educate patients about medications known to be ototoxic.
• In some cases, early recognition of changes in hearing may prevent permanent damage, so encourage patients to immediately report to providers any changes in their hearing, especially when new medications are added or doses are increased.
• Remind patients that even over-the-counter medications such as aspirin and NSAIDs (eg, ibuprofen, naproxen) may be ototoxic.
• Routinely review medication profiles for ototoxic medications.
• Avoid using ototoxic medications in the elderly and others with existing hearing deficits when other effective alternatives are available.
• Many medication-related side effects are frequently dose related and/or related to duration of therapy, so using the lowest effective dose may minimize risk.
• Closely monitor blood levels of known ototoxic medications, such as aminoglycosides and vancomycin.
• When possible, avoid combination therapy of ototoxic medications with other ototoxic medications, which may further increase the risk of hearing loss.
• Suggest patients avoid exposure to loud noises when taking ototoxic medications, as this exposure may increase hearing damage.

When working with patients with hearing loss, techniques such as minimizing background noise and speaking in an appropriate tone can help increase the ease of older adults' interaction and participation in conversations.

Smell and Taste10
The senses of taste and smell serve several functions and allow for a full appreciation of the flavors of foods. Smell and taste begin the initial response for saliva formation and digestion. Deficits in taste and smell can adversely affect food choices and intake, especially in the elderly, which can contribute to weight loss, malnutrition, impaired immunity, mood change, and functional decline.

Secondary consequences to older adults' changes in taste and smell may be evidenced by patients increasing intake of sugar and/or salt to compensate, which can have serious adverse effects in patients with diabetes, hypertension, and other cardiovascular diseases.

Important terms associated with the loss of taste or smell include anosmia, a rare condition that refers to a complete loss of smell; hyposmia, which is a reduced sense of smell (represents most drug-induced smell disorders); ageusia, which describes a loss of taste; and hypogeusia, which indicates diminished taste.

Both old age and polypharmacy are risk factors for drug-induced taste disturbances, and as many as 11% of elderly individuals using multiple drugs report taste aberrations.11

Medications
Good nutritional support with zinc supplementation may reduce the possibility of the onset of drug-induced smell and taste disorders. It's not uncommon for patients to experience a metallic taste with some medications. Good oral hygiene coupled with prevention of dry mouth may reduce the incidence of taste disturbances. If a patient shows signs of such a disturbance, an early discontinuation of the offending drug may prevent complete loss or irreversible distortion of smell or taste. Note that while a number of orally given (systemic medications) can affect smell and taste, medications administered nasally are especially troublesome for many persons.10

Although this list is not comprehensive, common medications associated with taste or smell disturbances include the following10:

• angiotensin-converting enzyme inhibitors (notably captopril), which are among the medications most commonly associated with taste disturbances, including decreased sense of taste (hypogeusia) and a strongly metallic, bitter, or sweet taste;
• medications known to dry the oral cavity (eg, anticholinergics, antihistamines, and antidepressants);
• antibiotics (eg, penicillin, tetracycline, macrolides, and fluoroquinolones, among others);
• antiparkinsonian agents (levodopa/carbidopa);
• anticonvulsants (eg, carbamazepine, phenytoin); and
• antithyroid agents, cholesterol-lowering agents, blood pressure medications, and muscle relaxers.

Reminders
When prescribing medications for the elderly, it is important to begin with low doses and increase slowly because older adults can be especially sensitive to adverse events. Counseling patients about the potential side effects of the medications they are taking can help identify any subsequent serious problems more readily. If a change of condition occurs in a person who has experienced a recent medication addition or change, always consider the cause as being medication related until ruled otherwise.

— Mark D. Coggins, PharmD, BCGP, FASCP, is vice president of pharmacy services and medication management for Diversicare, which operates skilled nursing centers in 10 states. He was nationally recognized by the Commission for Certification in Geriatric Pharmacy with the 2010 Excellence in Geriatric Pharmacy Practice Award.

References
1. Groeger L. Making sense of the world, several senses at a time. Scientific American. February 28, 2012. https://www.scientificamerican.com/article/making-sense-world-sveral-senses-at-time/#

2. Aging and vision loss fact sheet. American Foundation for the Blind website. http://www.afb.org/section.aspx?SectionID=68&TopicID=320&DocumentID=3374

3. Quillen DA. Common causes of vision loss in elderly patients. Am Fam Physician. 1999;60(1):99-108.

4. Age-related eye diseases. National Eye Institute website. https://nei.nih.gov/healthyeyes/aging_eye

5. Coggins MD. Antihistamine risks. Aging Well. 2013;6(2):6-7.

6. Wade M. Medication-related visual hallucinations: what you need to know. EyeNet Magazine. March 2015. https://www.aao.org/eyenet/article/medication-related-visual-hallucinations-what-you-

7. Ocular side effects of medications. Richmond Eye Associates, P.C. website. http://www.richmondeye.com/ocular-side-effects-of-medications/

8. Walling AD, Dickson MD. Hearing loss in older adults. Am Fam Physician. 2012;85(12):1150-1156.

9. Coggins MD. Medication-related ototoxicity. Today's Geriatric Medicine. 2014;7(3):6-7.

10. Bromley SM. Smell and taste disorders: a primary care approach. Am Fam Physician. 2000;61(2):427-436, 438.

11. Arcavi L, Shahar A. Drug related taste disturbances: emphasis on the elderly. Harefuah. 2003;142(6):446-450, 484, 485.