Pharmacotherapy Considerations

By Abimbola Farinde, PharmD, MS, CGP

Geriatrics is largely focused on the clinical, preventive, and social aspects of illness along with medication selection and ongoing management, which is integral for achieving positive therapeutic outcomes in the sensitive elder population.1 Medication is viewed as an important health care therapy that aids in preventing illness, disability, and death in the geriatric population and simultaneously offers the potential for improved quality of life.1

Currently, the term “elderly” refers to individuals aged 65 and older.1 It has been reported that less than 15% of the total US population was over the age of 65 in 2004, but by 2030, it is estimated that the percentage will increase to about 20%.2 The geriatric population, as a subset of the general population, utilizes a disproportionate amount of health care, especially services related to medication therapies, due to the presence of co-occurring health conditions.3

Elderly patients frequently experience multiple illnesses and take many drugs concurrently. For most physicians, the decision to initiate specific drug therapies in these patients generally involves an assessment of risks and benefits. The combination of altered drug activity, impaired homeostasis, and the use of multiple drugs can contribute to adverse drug reactions and has been found to be a frequent cause of hospitalization and morbidity3.

Prescribers must be cognizant of the physiological changes that occur in the elderly population and consider these changes when making drug selections.4 Age-related physiological changes that can impact drug pharmacokinetic variables in the elderly include the following5:

• absorption: increasing gastric pH, decreasing absorptive surface;

• distribution: decreasing total body water, lean body mass, and serum albumin;

• metabolism: decreasing hepatic mass and blood flow; and

• excretion: decreasing renal blood flow, glomerular filtration rate, and tubular secretion. 

The observed changes that occur with the aging process should be factored into subsequent therapeutic selections.

Increasing Adverse Drug Reactions
In the United States, the elderly population consumes about 30% of all prescribed medications. The presence of polypharmacy—the use of multiple medications that are not clinically indicated—is recognized as a significant contributing factor to adverse drug reactions in this population.6 According to Larson, the possibility of an adverse drug reaction among elderly patients is estimated at 6% among individuals taking two types of drugs, 50% among those taking five types, and 50% among those taking eight types.7

The potential for adverse outcomes in elderly patients can increase as the number of drug therapies rises. It is essential for physicians to routinely evaluate medication profiles to assess appropriateness, and monitoring patients for the development of adverse events must become a standard of clinical practice.8 Care team members must remain aware of the critical need for health care providers to recognize the necessary precautions and considerations related to prescribing medications in the geriatric population.

Recent studies have suggested that the level of potentially inappropriate medication use among the elderly population should raise concern. The Beers criteria published in 1997 provides specific information for determining inappropriate medication use in elderly patients.9,10

The American Geriatrics Society’s 2012 Updated Beers Criteria for Potentially Inappropriate Medication Use in Older Adults identify medications with risks that may be greater than their benefits for people aged 65 and older. Prescribing potentially inappropriate medications continues to be common among physicians for even the most vulnerable older adults despite evidence of poor outcomes. It is best for physicians to avoid prescribing inappropriate or high-risk drugs because they can increase the likelihood of medication-related problems and adverse drug events in older adults.11

Medication-related problems are common, costly occurrences in older adults, but such problems can be prevented through the application of the Beers criteria that suggest close monitoring of drug use and the application of interventions to decrease adverse drug events in older adults.12 Physicians must recognize that certain medications should be used with caution in older adults, and the updated Beer criteria provide guidelines for which medications are considered appropriate and inappropriate for this population.12

In treating chronic disease states, alleviating pain, and helping to improve overall quality of life, physicians must be aware of drug classes to avoid in treating patients with certain diseases and syndromes.13,14 The presence of age-related changes that can occur with drug disposition and pharmacokinetic responses can be used as predictors of whether an agent produces a therapeutic or a toxic effect.15,16 As a result of declining renal and liver function as well as diminished clearance, the potential for medication use and incidence of adverse drug reactions increase with advancing age. Another contributing factor is increased pharmacokinetic sensitivity of the elderly to drugs that may impact the central nervous system or cardiovascular system, sometimes causing irreversible damage.17,18

Assess the Possibilities
Adverse drug reactions can be divided into two categories: Type A (eg, dose dependent and predictable) and type B (eg, bizarre or idiosyncratic) in nature. Approximately 80% of adverse drug reactions are type A, and the drugs generally associated with this type of reaction in the elderly population are those with low therapeutic index and commonly used in this group, which may lead to hospitalization.19,20 Some of the most common medicines likely to be used in the elderly include anticoagulants, antibiotics, digoxin, diuretics, hypoglycemic agents, antineoplaistic agents, and nonsteroidal drugs.21

These medications contribute to approximately 60% of adverse drug reactions that potentially can lead to hospitalizations, and about 70% can occur in the hospital setting. Prior to the initiation of any of these medications, prescribers must assess therapeutic outcomes, the possibility of drug-drug interactions or drug-disease interaction, and/or therapy appropriateness.21

In clinical practice settings, there are general principles for prescribing to geriatric patients that clinicians can apply to ensure the selection of appropriate pharmacological interventions for their patients. First, a comprehensive care plan must be created that includes decisions on medication use, indication, appropriateness, and the integration of factors that affect health status, such as disability, cognition, comorbidities, social role, and psychological state.18 Ideally, therapeutic interventions should aim to address a patient’s functional, physical, psychological, and social health.

The assessment should provide a detailed description of the risks and benefits of prescribing a medication for a particular disease state or condition within the context of comorbidity and disability, and also should provide information on what types of assistance a patient may require to adhere to the medication regime.21,22

The following steps can help to broadly guide prescribing patterns in geriatric patients:

• Determine and assess the evidence of a drug therapy’s efficacy in elderly patients through analysis of clinical trial data with a focus on meaningful outcomes. If there is an absence of such evidence, an extrapolation of the trials from younger patients can be utilized.

• Determine the likelihood of adverse events in elderly patients if adverse drug reactions data are not properly described by clinical trials. Prescribers usually will need to rely on data from postmarketing surveillance. Consideration should be given to the increased occurrence of adverse drug reactions in elderly patients that can be exacerbated by multiple medications.

• Conduct a harm vs. benefit analysis with the patient, allowing for patient autonomy with treatment decisions.

• Select the dose-appropriate regimen, associated age-related disposition, and possible response to medications.

• Monitor elderly patients carefully because of the increased prevalence of adverse drug reactions. The assessment of function and quality-of-life outcomes can be more relevant than primary disease state outcomes as described in clinical trials.

Geriatric pharmacotherapy can be viewed as a doubled-edged sword because there is the potential to improve quality of life, but the increased use of drugs in this population also can increase the risk of adverse drug reactions and potentially cause increased morbidity and mortality.21,22 It is important for health care professionals, particularly prescribers, to ensure the safe management of medications in the elderly population through awareness of potential risk and continuous monitoring.23

The use of a large number of medications may continue to be a required aspect of the medical care of some geriatric patients, and sometimes educated guesses can be made on doses, safety, and effectiveness. Since many clinical trials do not include an adequate number of subjects who are aged 65 or older, caution must be exercised when medications are initiated to ensure that the potential for medication-related adverse effects is recognized, minimized, or prevented.

— Abimbola Farinde, PharmD, MS, CGP, is a pharmacist at Clear Lake Regional Medical Center in Webster, Texas.

References
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