July/August 2018

The Role of Polypharmacy in Swallowing — Its Implications for Clinicians
By Lisa Milliken, MA, CCC-SLP
Today's Geriatric Medicine
Vol. 11 No. 4 P. 14

Medications can add a significant risk of dysphagia, based on several methods of action that may affect all phases of swallowing. One author shared that the Physician's Desk Reference lists dysphagia as a side effect for more than 160 medications.1 Many of these pose a more significant risk than others to the swallowing process.

The risk increases in people older than 65, secondary to several factors. First, there are age-related pharmacokinetic and pharmacodynamic changes that affect drug sensitivity. For example, the clinician might see marked side effects of a medication taken by a 70-year old patient that they do not see in a 45-year-old person. The clinical picture becomes more complicated due to the fact that older people tend to have multiple comorbidities for which they are taking several medications. Thus, while a single medication might induce dysphagia symptoms, the increased number of medications places that person at a higher risk of drug-to-drug interactions or drug-to-disease interactions.2,3 All of these combined factors lead to a higher incidence of adverse drug reactions in the elder population.4,5

We commonly meet older clients who are taking five or more medications for a variety of conditions and symptoms. And those are our healthy patients. Yet once they have one or more chronic diseases, that list can begin to grow exponentially.

Knowing how medications affect a client's functional status is critical. Since the origin of dysphagia is often found to be secondary to the effects of medications, the clinician must quickly recognize the methods of action for each of the client's medications and consider the adverse drug events (ADEs) of each drug as well as the risk of drug-to-drug interactions.

Aging Affects Drug Sensitivity
Age-related changes result in increased side effects of medications in older people. Due to pharmacokinetic changes, there is a reduction in renal and hepatic clearance, which leads to an increase in the volume of distribution of lipid-soluble drugs (prolonging the half-life). Likewise, pharmacodynamic changes often increase the sensitivity to several classes of drugs such as anticoagulants and cardiovascular and psychotropic drugs.6 These age-related changes in the kidneys, liver, and other organs will influence the way many medications work. And drugs that act on the central nervous system (CNS) will have a greater impact in older people, based on changes in the blood-brain barrier.

To complicate the clinical picture, the older person's nutritional status, multiple chronic diseases, and functional and cognitive deficits are other age-related factors that may have an impact on drug therapy. In general, older clients will often have a loss of muscle mass, so the percentage of their body fat increases and body water decreases. Cardiac output also decreases in older people. Kidney function gradually declines, and the effectiveness of the immune system decreases. These changes will often require a decrease in the dose of some medications to optimize their benefits and avoid toxicity and adverse reactions. These normal physiologic changes that occur with aging affect the way drugs work within the body.

While working with older clients in the long term care and short-term rehab settings, clinicians see higher rates of cognitive decline from the actions of medications. Such factors are significant to decisions regarding treatment approaches and compensatory strategies. Working with the interdisciplinary team members is critical—to include ongoing monitoring and reporting as well as accurate documentation and completion of clinical approaches.

ADEs and Drug-to-Drug Interactions in Older People
The prevalence of ADEs in older people is a real concern. In a 2012 study, older patients taking five or more medications were almost four times as likely to be hospitalized from ADEs than were younger subjects.7 And the rates of ADEs in skilled nursing facility residents have been found to be twice as high in patients taking nine or more medications.8 Common drug classes associated with ADEs most frequently include cardiovascular medications, anticoagulants, NSAIDs, diuretics, antibiotics, anticonvulsants, benzodiazepines, and hypoglycemic medications.

Similarly, drug-to-drug interactions are also higher in elders.9,10 In a prospective cohort study of hospitalized older adults taking five or more medications, the prevalence of a potential drug-drug interaction was 80%. Older people taking five to nine medications had a 50% probability of drug interaction risk, and the risk for patients taking 20 or more medications increased to a 100% probability of drug interaction risk.9

To further complicate matters, older people taking multiple medications often suffer from nutritional problems as well. One study found that 50% of older patients taking 10 or more medications were found to be malnourished or at risk of malnourishment.11 Polypharmacy has also been associated with a reduced intake of fiber and fat-soluble and B vitamins and minerals, and is associated with an increased intake of cholesterol, glucose, and sodium.12

How Medications Can Affect Swallowing
With this understanding of the complex effects of medications with older people, we can specifically consider how medications might affect the swallowing process.

Medications acting on the CNS can cause dysphagia by decreasing the level of arousal; directing suppression of the brain stem swallowing function; inducing movement disorders, a neuromuscular blockade, and myopathy; impairing oropharyngeal sensation; and disturbing the production and flow of salivation.1,13

Medications that affect the central neurotransmitter activity and depress the CNS may affect the anticipatory phase by causing a mental status change, leading to confusion or sedating the patients; this in turn may impair their ability to visually recognize food or to coordinate the motor acts to self-feed.1 CNS neurotransmitters histamine, dopamine, acetylcholine, and gamma-aminobutyric acid can depress the CNS and have an adverse effect by causing a mental status change, impairing cognition, decreasing awareness and voluntary muscle control, and sedating the patients. Therefore, anticonvulsants, benzodiazepines, narcotics, and skeletal muscle relaxants place the patient at risk for dysphagia.14

Medications inhibiting salivary flow may directly lead to the onset of dysphagia. The secretion and flow of saliva is a critical factor for all phases of the swallow, starting at the oral-prep and oral stages. The lubrication from the saliva continues to play a key role in the early esophageal stage and through the upper digestive tract. Since there are more than 400 medications listing xerostomia as a side effect, we see a high number of older people with dysphagia secondary to the fact that they often take two or more medications from this list. Some of the many medications on this list are those with anticholinergic properties that block acetylcholine in the central and the peripheral nervous system.15

Other actions of medications can affect the autonomic gastrointestinal motility, including changes to gastric emptying, decreased lower esophageal sphincter function, and the onset of esophagitis and stomatitis. Similar gastrointestinal effects of medications include those that affect appetite, taste, and smell. For example, antipsychotics and antihistamines inhibit acetylcholine to affect autonomic motility, and multiple drug classes produce side effects of altered smell and taste or changes in appetite.1,16

Anticholinergic Properties
It's commonly known that the peripheral effects of anticholinergics include constipation, dry mouth, dry eyes, tachycardia, and urinary retention. And the CNS effects of these drugs with anticholinergic properties include agitation, confusion, delirium, falls, hallucinations, and cognitive dysfunction.17

Specifically related to dysphagia, anticholinergics can cause or contribute to the following:

• lower esophageal sphincter relaxation, thus exacerbating gastroesophageal reflux disorder;

• mucous membrane dryness (mouth, nose), resulting in difficulty in forming a bolus or initiating a swallow;

• abnormal peristalsis, due to the anticholinergic effect on the smooth visceral muscle of the esophagus;

• severe oral-motor muscle weakness and slurred speech;

• impaired attention and cognitive decline, decreasing attention to food and voluntary movements of the preoral and oral stages; and

• deglutitive inhibition, due to the anticholinergic effects on esophageal striated and smooth muscles of the esophagus.1,18

Many drugs prescribed for older people have anticholinergic properties, to include some antidepressants, muscle relaxants, antispasmodics, antihistamines, and tricyclic antidepressants. Medications in these drug classes often have strong anticholinergic effects and older patients are particularly susceptible to these effects, which can reach toxicity levels more quickly, especially when the person is taking more than one medication with these properties.

The Effect of Antipsychotics on Swallowing
Medications in the antipsychotic drug class seem to have one of the longest lists of the most debilitating side effects. And while these medications can be most helpful for specific psychiatric disorders such as schizophrenia, they have also been widely prescribed for other conditions such as dementia and anxiety disorders, resulting in greater harm than good. The side effects significant to the swallowing process include the anticholinergic effects already described as well as extrapyramidal disturbances, also known as parkinsonism symptoms. Examples would include tardive dyskinesia, bradykinesia, muscle rigidity, akathisia, and dystonia. Tardive dyskinesia can significantly hinder preoral and oral stages of the swallow to include great difficulty with mastication and delay the oral onset of the swallow.19

To further understand the effects of antipsychotics on swallowing, consider the case study presented of a 79-year-old male with Alzheimer's disease who was initially given Haldol and thioridazine for his aggressive behaviors and then changed to loxapine, a typical antipsychotic agent. After a week, the patient started choking and became congested. The modified barium swallow study revealed moderate-severe oral pharyngeal dysphagia, characterized by reduced mastication, tongue pumping, defective tongue range of motion, reduced tongue base movement (likely due to muscle rigidity), reduced bolus control, delayed initiation of pharyngeal swallow, reduced laryngeal movement, pooling of residue in valleculae and pyriforms after the swallow with penetration on this residue, and silent aspiration on thin liquids. The repeat study, more than two weeks after medication was discontinued, showed significant improvements.20

Medications Affecting the Gastrointestinal System
Medications can contribute to dysphagia by affecting appetite, taste, and smell. They can also cause significant xerostomia and mucositis. A number of medications might also induce esophageal injury and mucosal injury, especially with the elder population. All of these drug effects are considered to be those contributing to dysphagia via the gastrointestinal system.

Medication-induced esophagitis has often been referred to as pill esophagitis and is often caused by antibiotics, potassium chloride formulations, NSAIDs, bisphosphonates, quinidine, and other sources such as aspirin, iron-containing products, and vitamin C products.

More than 70 frequently used medications have been implicated in esophageal injury and medication-induced esophagitis. Some factors that increase this risk include geriatric age, increased anatomic and motility abnormalities, decreased saliva production, ingestion of medication while supine, inadequate fluid intake while ingesting drugs, and consuming a higher number of medications. Geriatric patients also have a greater prevalence of cardiac enlargement with concomitant compression of the midesophagus.21,22

Other Significant Drug Classes
The list of medications that contribute to swallowing dysfunction is extensive. In addition to those already discussed, the higher-risk drug classes also include many other drug classes such as benzodiazepines, antidepressants, neuromuscular blocking agents, high-dose corticosteroids, and narcotics, to name a few. Of course, the degree of effects from these drugs on swallowing is most significant when they are prescribed for people older than 65.

The Role of the Health Care Provider
Elders have an increased risk of dysphagia from the effects of numerous medications. These drugs can affect multiple elements of swallowing, which can cause numerous issues that might trigger dysphagia from the preoral phase to the esophageal phase of dysphagia.

Clinicians should be aware of which drugs frequently cause problems with elders and maintain an accurate medication summary for each client's prescriptions. From that point, the practitioner should know the side effect profile for each medication and disease process that a client may have and be aware of which might increase risk of certain drug-drug interactions. Optimal treatments can then be planned; compensatory strategies, education, and supportive plans of care should be considered. Health care team members should also communicate any adverse effects to the prescribing physician where applicable.

When addressing medication-induced esophagitis, the offending agent should be discontinued. If it's not possible to discontinue the agent, dysphagia management strategies may include assuring that the medication is taken with adequate amounts of fluid, that the drug is ingested in an upright position, that the drug is taken at least 30 minutes before sleeping, and that the offending agents and other medications are spaced to allow for recovery time between doses.23

The clinician's most important role is to constantly review the list of prescriptions for all clients, talk with them about specific side effects they might be experiencing, and educate them regarding their medications' potential to cause dysphagia and what they can do to decrease the risks.

— Lisa Milliken, MA, CCC-SLP, is a speech language pathologist and serves as an education specialist for Select Rehabilitation.

References
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