Preventing Adverse Drug Events in Older Adults

Todd Semla, MS, Pharm.D., BCPS, FCCP, AGS

The term adverse drug events (ADEs) encompasses both medication errors and adverse drug reactions (ADRs), either of  />which can result in unintended harmful outcomes. Medication errors are problems arising from human action or inaction, such as missing a dose, giving the wrong dose or incorrect administration. Adverse drug reactions are an unintended or exaggerated pharmacological response to a drug at its usual and appropriate dose. The term “side effects” refers to what are often considered milder and often tolerable forms of ADRs. For example, medication-induced stomach upset or sedation, which may be managed by taking the medication with food or at bedtime could be tolerated as a manageable side effect. However, when noxious effects cause serious temporary or even permanent harm, these are categorized as an ADR. Certain ADRs are anticipated and expected; hair loss from many agents of cancer chemotherapy is one example.</p>
<p>In the community, the ADE rate has been reported to be 50.1 per 1,000 person-years, and the preventable ADE rate to be 13.8 per 1,000 person-years. ADEs are estimated to be responsible for 5 percent to 28 percent of acute hospital admissions for older adults, with an estimate of approximately 100,000 emergency hospitalizations of older adults for ADEs annually in the United States. Two-thirds of ADEs are due to an unintentional overdose. The rate of ADEs in nursing homes ranges from 1.89 to 9.8 per 100 resident-months. Over half of these are judged to be preventable. It has been estimated that in the nursing home sector, for every dollar spent on medications, $1.33 is spent to manage ADEs.</p>
<p><strong>Why do adverse drug events happen?</strong></p>
<p>Multiple risk factors have been identified that place older patients at risk for ADEs.</p>
<li><em>The drugs themselves<strong>.</strong></em> Cardiovascular drugs, anticoagulants, insulin and sulfonylureas, opioids and drugs affecting the central nervous system such as anti-Parkinson drugs, sedative/hypnotics and antipsychotic agents are consistently associated with ADEs.  Many of these drugs require frequent monitoring due to their narrow therapeutic index.</li>
<li><em>The number of drugs.</em> As the number of drugs increases the probability of a drug-drug interaction increases in an exponential fashion. Types of ADEs arising from a drug-drug interaction are toxicity arising from the combination of drugs or one drug inactivating another, resulting in a therapeutic failure. Many drugs share a common pharmacologic effect such as sedation or lowering of blood pressure, which may or may not be its intended effect. The effects of taking multiple medications are cumulative and can increase the risk for a serious adverse reaction such as a fall, motor vehicle accident or change in mental status.</li>
<li><em>The number of prescribers and pharmacies</em>. Having more than one prescriber is not always avoidable, so patients need to inform each prescriber and pharmacy of <em>all</em> the other medications they are taking. Using more than one pharmacy may be economical but it limits the safeguard of computer-based drug-drug interaction screening programs since these programs do not communicate with one another across pharmacies and are only as reliable as the available data.</li>
<li><em>Multiple diseases and conditions.</em> Chronic conditions are more common and accumulate with age, which in turn leads to the prescribing of multiple drugs to treat multiple conditions. Older adults take between four and six prescription and nonprescription medications regularly, yet onset of an additional  condition such as heart failure can require treatment with as many as another four to six medications. Nursing home residents taking nine or more medications have a 2.33 times greater risk of an adverse drug reaction than those taking fewer than nine medications.</li>
<li><em>A previous adverse drug reaction</em>. A forgotten or undocumented ADR can happen again if the patient is re-exposed to the medication or takes a related medication with a similar chemical structure. </li>
<p>All of these risk factors intertwine. Multiple diseases requiring multiple prescribers and treatment with multiple medications, coupled with each medication’s inherent risk for adverse effects creates a scenario with elevated risk of ADEs. Also, the physiologic decline associated with aging and disease can alter a drug’s pharmacokinetics and pharmacodynamics, i.e., how the body processes, eliminates and reacts to a medication. The challenge is how to balance these risks while treating the intended condition without impairing the patient’s physical or mental function. ADEs are not unique to older adults and there is evidence to suggest that age itself is not a risk factor for ADEs; rather older adults, as a group, have a higher exposure to medications, placing them at greater risk.</p>
<p><strong>Can adverse events be predicted? Can they be prevented?</strong></p>
<p>An adverse drug event can be predicted with certainty if it is due to a foreseeable medication error, e.g., giving penicillin to a patient with a known penicillin allergy. Preventable ADEs are among the most serious consequences of inappropriate drug prescribing among older adults. The vast majority of ADEs experienced by older adults are considered to be predictable.  Cardiovascular drugs, diuretics, nonsteroidal anti-inflammatory drugs, hypoglycemic agents, antipsychotics and anticoagulants are the drug classes found to be most often associated with preventable ADEs. Regardless of the setting, errors most often occur at the time of prescribing or from inadequate monitoring of administration of the drugs.</p>
<p><strong>Tips to prevent adverse drug events: </strong></p>
<p>The responsibility belongs to patients, caregivers and health care professionals. </p>
<p><em>The patient or caregiver</em> <em>should:</em></p>
<li>View their pharmacist as a key person to communicate with for expertise in reviewing the patient’s medication list and assisting in medication management.</li>
<li>Question the need for taking any medication without a clear and warranted indication.  Ask the prescriber if it can safely be stopped.</li>
<li>Avoid medications with similar effects, other than the intended one.</li>
<li>Keep an up-to-date list of medications.</li>
<p><em>Prescribers should: </em></p>
<li>Take careful steps to avoid prescribing errors – even if e-prescribing.
<li>Write-out directions clearly; don’t abbreviate.</li>
<li>Re-read what’s been written or selected.</li>
<li>Adjust doses based on the patient’s renal and hepatic function, as well as other medications being taken.</li>
<li>Monitor for therapeutic benefit and adverse effects.</li>
<li>Avoid using one medication to treat the adverse effects of another.</li>
<li>Review all of a patient’s medications at least annually and before prescribing a new medication.</li>
<p>For more helpful tips, see Health & Aging at <a href=

Todd Semla, MS, Pharm.D., BCPS, FCCP, AGS is a clinical pharmacist with 35 years’ experience in geriatric pharmacotherapy. He is a National PBM Clinical Pharmacy Program Manager for the U.S. Department of Veterans Affairs and an Associate Professor, Clinical in the Departments of Medicine, Geriatrics Division, and Psychiatry and Behavioral Sciences, Northwestern University Feinberg School of Medicine, Chicago, IL. Dr. Semla’s opinions are his own and do not necessarily reflect those of the U.S. Government or the U.S. Department of Veterans Affairs.