Pharmacology and Aging

Commonly used drugs
Trends in pharmaceutical sales reflect the management of chronic illnesses in an aging population. More than three billion prescriptions were dispensed in 2001. Six of the top 10 drugs prescribed in 2001 were used to treat age-related chronic conditions such as cardiovascular disease, pain associated with arthritis, depression, and postmenopausal hormone replacement. Oral complications associated with these and many other prescription medications are extremely common (Table 2).52

Xerostomia, the most common drug-induced oral side effect, is associated with approximately 600 different prescription and over-thecounter (OTC) preparations in 26 different categories (Table 3).53 Xerostomia is not an inevitable result of aging.54 If medications are the etiology, consultation with the person’s physician is warranted to determine if there are alternatives that do not produce oral dryness. Drugs that produce xerostomia increase a person’s risk of developing dental caries. The potential for developing rampant decay is great in individuals who experience both drug-induced vomiting and xerostomia. A daily fluoride regimen in custom trays is advised for such patients.34

Adverse drug reactions
The incidence of adverse drug reactions in older adults is two to three times higher than in young adults. Adverse drug reactions are common in older adults due to the physiological changes that occur with aging, the diseases they experience, and changes in their diet.55 Common gastrointestinal changes that lead to the malabsorption of drugs include delayed gastric emptying, reduced visceral blood flow, decreased intestinal motility, and increased transit time. Changes in hepatic and renal function serve to reduce drug metabolism and excretion. Changes in body mass, such as increased adipose tissue and loss of skeletal muscle, can affect the storage of drugs.9 Poor nutrition, common in older adults, also increases the potential for adverse drug reactions. Drugs may increase the need for certain nutrients by increasing metabolism and competing for certain receptor sites. Many drugs must be taken with food or should not be taken with milk or grapefruit juice. The dental hygienist can alert a patient about potential adverse drug reactions and how to prevent them.

Drugs frequently associated with adverse reactions in older adults include NSAIDs, digoxin, systemic corticosteroids, diuretics, betablockers, methyldopa, clonidine, benzodiazepines, and calcium channel blockers. The adverse conditions associated with these drugs are delirium, falls, depression, urinary incontinence, and constipation.12, 56

Polypharmacy issues
The older adult consumes approximately one-third of all prescription and OTC drugs. The average person aged 65 and older takes three or more medications daily and nearly 14 different prescriptions per year.56 Polypharmacy is an additional contributing factor to adverse drug reactions. Many older adults lack understanding due to a cognitive, sensory, or functional impairment or have not been properly educated by their health care providers about the negative outcomes of drug interactions related to poor compliance with a regimen and the impact of OTC drugs with their prescribed medications.6

Older adult patients who become confused when several drugs with various dosages often do not follow drug regimens. Other issues related to non-compliance include the belief that medications should only be taken as needed to relieve symptoms or financial constraints. As the number of prescribed medications increases, compliance with taking these medications tends to decrease. Polypharmacy increases the likelihood of drug interactions. Therefore, adverse drug reactions are the most common reason for hospital admissions among older adults. To further complicate matters, many OTC drugs (i.e., analgesics, antacids, and antihistamines), herbs, and vitamin/nutritional supplements are not viewed as medicines by the patient and are not reported to health care professionals during history-taking. With this in mind, it is essential to ask patients what medications they are taking in each of these categories.6,56

Adverse reactions also can occur when an individual sees multiple physicians and receives multiple drugs for the same medical condition or takes multiple medications from more than one pharmacy. Lastly, adverse drug reactions are likely if a person abuses alcohol.57