The statistics on medication usage among elderly patients in the US are eye-opening: more than one-third of prescriptions drugs used in the US are taken by elderly patients; the ambulatory elderly fill between 9-13 prescriptions a year (including new prescriptions and refills); the average elderly patient is taking more than five prescription medications; the average nursing home patient is taking seven medications.
The increased risk for adverse drug-drug interactions that accompanies high levels of polypharmacy among this patient population, coupled with the physiological changes associated with aging that can affect pharmacokinetics and pharmacodynamics, should lead physicians to exercise caution when prescribing pharmacotherapy for their elderly patients.
In fact, said Aubrey Knight, MD, FAAFP, during his presentation, “Polypharmacy in the Elderly: To Prescribe or Not to Prescribe,” Saturday at the 2010 AAFP Scientific Assembly, given what we know about the effects of polypharmacy in the elderly patient, any symptom in an elderly patient should be considered a drug side effect until proved otherwise. He reminded the audience to heed Osler’s dictum that “a medication is a poison with a desirable side effect” and advised that physicians “consider medication as a possible problem, and not just as the solution” when prescribing medications for elderly patients with multiple chronic conditions.
Knight reviewed a litany of pharmacokinetic and pharmacodynamic effects associated with aging that can lead to adverse outcomes, including:
The effect on volume of drug distribution caused by the decrease in total body water and increase in total body fat commonly seen in elderly patients (which can lead to increased serum levels of water-soluble drugs and an increased half-life for fat-soluble drugs)
The increase in body fat among elderly patients (up to about age 70) can lead to higher circulating levels of tricyclic antidepressants and antipsychotic drugs
The decrease in lean body mass after age 70 can lead to increased digoxin concentration
Oxidative metabolism through the cytochrome P450 system decreases with aging, leading to decreased clearance of drugs
Decreased hepatic and renal blood flow, resulting in altered plasma half-lives of an array of medications
Knight recommended consulting the Beers Criteria for Potentially Inappropriate Medication Use in the Elderly, first published by Beers and colleagues in 1997 in the Archives of Internal Medicine
and updated in 2003. Described by Knight as more of a “cautionary guide, as opposed to a ‘never use’ list,” it identifies nearly 50 medications and medication classes that are potentially harmful when used in patients who are over the age of 65. The complete updated Beers criteria is available here
. An interactive list of the medications included in the Beers criteria is available here
. Additional information on the Beers list medications is available here
The "prescribing cascade" and nursing home residents
With more than 15% of hospitalizations involving elderly patients caused by or related to adverse drugs reactions, and the increased risk of drug-drug interactions or adverse drug reactions associated with polypharmacy, Knight noted it is especially important to be aware of what he called “the prescribing cascade” with elderly patients, wherein the side effects from one prescription medication beget a prescription to counteract them, which leads to more side effects, and still another prescription, and so on and so forth.
This is especially common among nursing home residents, whom Knight said are prescribed more medications than patients in any other setting. In particular, he noted that certain drugs such as antibiotics and PPIs are overprescribed in this population. He said that studies have shown that more than half of nursing home residents had experienced an adverse drug reaction, and that patients who are taking nine or more medications are 2.3 times more likely to experience an adverse drug reaction. Guidelines for effective medication management and monitoring in this population call for physicians to prescribe only medications that are clinically necessary to treat the patient’s assessed conditions; to consider non-pharmacologic interventions, where appropriate; to minimize risks for adverse consequences; and to re-evaluate the patient’s medication regimen when there is a change in the patient’s condition. “Analyze the problem; don’t just treat the symptom,” monitor for continued need and effectiveness, and “consider the patient’s age and co-morbidities when choosing the medication and dose,” Knight said.
When treating elderly inpatients, physicians should anticipate a 50% risk of adverse drug reactions (ADR) among patients who are on five or more medications, and weigh the use of high-risk/low-benefit drugs against the increased possibility of ADRs. The care team should also conduct a thorough medication review at admission and discharge to avoid polypharmacy.
Start low and go slow: Principles for managing medications in elderly patients
Knight offered several take-home points to aid physicians for who manage patients with multiple chronic conditions:
Perform a complete “brown bag” review of all of the patient’s medications, including OTC drugs and supplements
Be cautious with new drugs for which there is less-than-robust data regarding use in elderly patients
Keep the medication regimen as simple as possible to promote adherence
Discontinue the use of drug when possible if the benefit is unclear or if observed side effects could be due to that drug
Consider if the benefit of the 7th or 8th drug is sufficient to justify the cost, increase in complexity of regimen, and risk of side effects
When selecting and titrating medication doses: start low, and go slow!
HCPLive wants to know:
What best practices do you recommend when prescribing medications in elderly patients?
Do you consult the Beers List or other medication reaction/interaction tools?
What online resources have you found to be useful when managing prescription drug therapy in elderly patients?