Drug prescribing for older adults

Optimizing drug therapy is an essential part of caring for an older person.

The process of prescribing a medication is complex and includes:

  • deciding that a drug is indicated,
  • choosing the best drug,
  • determining a dose and schedule appropriate for the patient’s physiologic status,
  • monitoring for effectiveness and toxicity,
  • educating the patient about expected side effects, and
  • indications for seeking consultation.

Avoidable adverse drug events (ADEs) are the serious consequences of inappropriate drug prescribing. The possibility of an ADE should always be borne in mind when evaluating an older adult individual; any new symptom should be considered drug-related until proven otherwise.

Prescribing for older patients presents unique challenges.

  • Premarketing drug trials often exclude geriatric patients and
  • approved doses may not be appropriate for older adults
  • Many medications need to be used with special caution because of age-related changes in pharmacokinetics (ie, absorption, distribution, metabolism, and excretion) and pharmacodynamics (the physiologic effects of the drug).

Particular care must be taken in determining drug doses when prescribing for older adults.

  • increased volume of distribution may result from the proportional increase in body fat relative to skeletal muscle with aging.
  • Decreased drug clearance may result from the natural decline in renal function with age, even in the absence of renal disease
  • decreased clearance prolong drug half-lives and lead to increased plasma drug concentrations in older people.

As examples,

  • the volume of distribution for diazepam is increased, and
  • the clearance rate for lithium is reduced, in older adults.
  • The same dose of either medication would lead to higher plasma concentrations in an older, compared with younger, patient.

Hepatic function also declines with advancing age, and age-related changes in hepatic function may account for significant variability in drug metabolism among older adults

Especially when polypharmacy is a factor, decreasing hepatic function may lead to adverse drug reactions (ADRs).

MEDICATION USE BY OLDER ADULT

Medications (prescription, over-the-counter, and herbal preparations) are widely used by older adults.

Prescription medications — 

A survey in the United States à At least one prescription medication was used by 87 percent. Five or more prescription medications were used by 36 percent, and 38 percent used over-the-counter medications.

Herbal and dietary supplements — 

Use of herbal or dietary supplements (eg, ginseng, ginkgo biloba extract, and glucosamine) by older adults has been increasing

Herbal medicines may interact with prescribed drug therapies and lead to adverse events

Examples à ginkgo biloba extract taken with warfarin, causing an increased risk of bleeding, and St. John’s wort taken with serotonin-reuptake inhibitors, increasing the risk of serotonin syndrome in older adults

QUALITY MEASURES OF DRUG PRESCRIBIN

Multiple factors contribute to the appropriateness and overall quality of drug prescribing.

  • avoidance of inappropriate medications,
  • appropriate use of indicated medications,
  • monitoring for side effects and drug levels,
  • avoidance of drug-drug interactions, and i
  • involvement of the patient and integration of patient values.

POLYPHARMACY

Polypharmacy is defined simply as the use of multiple medications by a patient. The precise minimum number of medications used to define “polypharmacy” is variable, but generally ranges from 5 to 10

The issue of polypharmacy is of particular concern in older people who, compared with younger individuals, tend to have more disease conditions for which therapies are prescribed.

The use of greater numbers of drug therapies has been independently associated with an increased risk for an adverse drug event (ADE), irrespective of age, and increased risk of hospital admission

There are multiple reasons why older adults are especially impacted by polypharmacy:

●Older individuals are at greater risk for ADEs due to metabolic changes and decreased drug clearance associated with aging; this risk is compounded by increasing numbers of drugs used.

●Polypharmacy increases the potential for drug-drug interactions and for prescription of potentially inappropriate medications

●Use of multiple medications can lead to problems with adherence in older adults

INAPPROPRIATE MEDICATIONS

Anticholinergic activity — 

Anticholinergic medications are associated with multiple adverse effects to which older individuals are particularly susceptible.

Adverse effects associated with anticholinergic use in older adults include memory impairment, confusion, hallucinations, dry mouth, blurred vision, constipation, nausea, urinary retention, impaired sweating, and tachycardia. A

 Anticholinergics can precipitate acute glaucoma episode in patients with narrow angle glaucoma and acute urinary retention in patients with benign prostatic hypertrophy.

the risk of dementia and Alzheimer’s disease increased in a dose-response relationship with use of anticholinergic drug classes (primarily first-generation antihistamines, tricyclic antidepressants, and bladder antimuscarinics)

Beers criteria — developed by an expert consensus panel in 1991

  • most widely cited criteria used to assess inappropriate drug prescribing
  • The criteria are a list of medications considered potentially inappropriate for use in older patients, mostly due to high risk for adverse events.
  • Medications are grouped into five categories:
    • those potentially inappropriate in most older adults,
    • those that should typically be avoided in older adults with certain conditions,
    • drugs to use with caution,
    • drug-drug interactions, and
    • drug dose adjustment based on kidney function.

The criteria have been repeatedly updated, most recently in 2019 à Selected changes

●Avoid the concurrent use of opioids with either benzodiazepines or gabapentinoids, due to the increased risk of overdose and severe sedation-related adverse events such as respiratory depression and death.

Use caution when prescribing trimethoprim-sulfamethoxazole in patients who are taking an (ACE) inhibitor or (ARB), and who have decreased creatinine clearance, to avoid hyperkalemia.

●Use caution when recommending aspirin for primary prevention of cardiovascular disease or colorectal cancer in patients age 70 or older (down from previous threshold of 80 years or older), due to increased risk of bleeding.

UNDERUTILIZATION OF APPROPRIATE MEDICATION

Much attention has been paid to over-prescribing for older adults; under-prescribing appropriate medications is also of concern.

Prescribing strategies that seek to simply limit the overall number of drugs prescribed to older adults in the name of improving quality of care may be seriously misdirected.

START (Screening Tool to Alert doctors to the Right Treatment) is a set of 22 validated criteria, developed by a consensus process involving experts in geriatric pharmacotherapy, aimed to identify potential prescribing omissions in older hospitalized patients

Medication effectiveness — Studies of drug effectiveness specifically often exclude the geriatric population due to concerns with comorbidities and side effects, causing difficulty in interpretation of study results. Therefore, the benefit of treatment for older adults, especially for preventive purposes, may not be established or may not be recognized by prescribing clinicians. As an example, in a study of statin use for secondary prevention in patients over age 66, the likelihood of being prescribed statin therapy declined 6.4 percent for every year of age; overall, only 19 percent of patients in this high-risk population had been prescribed a statin [76].

Dose availability — Older individuals often require lower than usual doses of medications, especially at initiation. If medications are not readily available in prescribed doses, the need to split tablets may make it more difficult for patients to take beneficial drug therapy

ADVERSE DRUG EVENTS

 coexisting medical problems, memory issues, and use of multiple prescribed and non-prescribed medications.

Compared with younger adults, ADR-related hospitalizations in older adults are more common and are more likely to be preventable.

A 2017 systematic review and meta-analysis of 42 studies of hospitalizations among adults 60 years of age and older, conducted in 21 countries àmean prevalence of ADR-related hospitalizations of 8.7 percent à (NSAIDs) being the most commonly implicated class of medications.

Prescribing cascades — 

Prescribing cascades occur when an adverse drug effect is misdiagnosed as a new medical condition, and treated with a potentially unnecessary drug

●One of the best recognized examples of a prescribing cascade relates to the initiation of anti-Parkinson therapy for symptoms arising from use of drugs such as antipsychotics or metoclopramide. The anti-Parkinson drugs can then lead to new symptoms, including orthostatic hypotension and delirium.

Populations at higher risk — Certain patient groups are at higher risk for ADEs

Renal impairment — 

For patients with stable renal function, creatinine clearance can be estimated according to published formulas which factor age into the calculation. àCockcroft-Gault formula à Creatinine clearance = (140-age) x (BW in Kg )/S. creatinine  x 72

Practical recommendations to reduce medical errors

●Maintain an accurate list of all medications that a patient is currently using. This list should include the drug name (generic and brand), dose, frequency, route, and indication.

●Advise periodic “brown-bag check-ups.” Instruct patients to bring all pill bottles to each medical visit; bottles should be checked against the medication list.

●Patients should be made aware of potential drug confusions: sound-alike names, look-alike pills, and combination medications.

●Medication organizers that are filled by the patient, family member, or caregiver can facilitate compliance with drug regimens.

A STEPWISE APPROACH TO PRESCRIBING

Review current drug therapy — Periodic evaluation of a patient’s drug regimen is an essential component of medical care for an older person. Such a review may indicate the need for changes to prescribed drug therapy. These changes may include

  • discontinuing a therapy prescribed for an indication that no longer exists,
  • substituting a therapy with a potentially safer agent,
  • changing a drug dose, or
  • adding a new medication

Discontinue unnecessary therapy — Clinicians are often reluctant to stop medications, especially if they did not initiate the treatment and the patient seems to be tolerating the therapy.

It is reasonable to gradually taper off most medications to minimize withdrawal reactions and to allow symptom monitoring, unless dangerous signs or symptoms indicate a need for abrupt medication withdrawal.

Certain common drugs require tapering, including beta blockers, opioids, barbiturates, clonidine, gabapentin, and antidepressants.

Consider adverse drug events for any new symptom — Before adding a new therapy to the patient’s drug regimen, clinicians should carefully consider whether the development of a new medical condition could be the presentation of an atypical ADE to an existing drug therapy.

Consider nonpharmacologic approaches — Some conditions in older adults may be amenable to lifestyle modification in lieu of pharmacotherapy.

The Trial of Nonpharmacologic Interventions in the Elderly (TONE) demonstrated that weight loss and reduced sodium intake could allow discontinuation of antihypertensive medication in about 40 percent of the intervention group

Care in the use of common drugs — Some commonly prescribed drugs may result in increased toxicity in older adults. As an example, numerous studies have documented adverse events associated with nonsteroidal anti-inflammatory drug (NSAID) use, including gastrointestinal bleeding, renal impairment

Reduce the dose — Many ADEs are dose-related.

prescribing of the newer atypical antipsychotic therapies (eg, olanzapine, risperidone, and quetiapine) and the development of parkinsonism in older adults. Relative to those dispensed a low dose, those dispensed a high dose were more than twice as likely to develop parkinsonism

Simplify the dosing schedule — When multiple medications are required, greater regimen complexity will increase the likelihood of poor compliance or confusion with dosing.

Prescribe beneficial therapy — The fewer-the-better approach to drug therapy in older adults is often not the best response to optimizing drug regimens. Avoiding medications with known benefits to minimize the number of drugs prescribed is inappropriate. Patients must be informed about the reason to initiate a new medication and what the expected benefits are.

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