Polypharmacy in the Older Patient With Cancer
Mary E. Corcoran, RPh, CRPh
The plethora of medications taken by older patients with
cancer increases the risk of harmful drug interactions.
Background: Elderly patients -- those aged 65 years and over -- use more
medications than their younger counterparts and experience higher risks for polypharmacy,
drug interactions, adverse drug reactions, and noncompliance for this age-group.
Methods: The data on polypharmacy in the aged is reviewed, supplemented with
preliminary information from studies performed on elderly patients with cancer at our
institution.
Results: Polypharmacy occurs in ambulatory, extended care, and institutional
settings. Over-the-counter medications are underreported. The number of potential
drug-related problems is related to the total number of prescriptions. Methods for
evaluating the extent of polypharmacy include the "brown-bag" technique and
careful medication histories.
Conclusions: The risks of polypharmacy may be reduced with patient and physician
education, intervention, and drug monitoring. Further pharmacokinetic investigations of
anticancer medications are needed to recognize the potential for harmful drug
interactions, to understand their toxicity profiles, and to avoid the clinical
implications of drug interactions.
Introduction
The definition of polypharmacy has changed over the past decade. The earlier
interpretation -- the mixing of several drugs into one prescription -- has evolved to
refer to the concurrent use of several different medications, which can include more than
one medication from the same drug classification.1,2 The Healthy People 2000
Conference identified polypharmacy by older people with chronic health problems as the
principal safety issue in the coming years.3
The elderly population -- those 65 years of age and older -- comprises approximately
12% of the total population.4 The number of senior adults is projected to reach
39.3 million by the year 2010.3 Four out of five elderly people experience at
least one chronic illness and a vast array of symptoms.5 The likelihood that an
older individual will experience a chronic illness increases rapidly with age. Twice as
many medications are prescribed to patients over 65 years of age compared with younger
patients.6 The trend for multiple medications continues through 80 years of
age.7 The older population uses approximately 30% of all prescription
medications, along with an unknown percentage of nonprescription medications.4
Approximately three quarters of ambulatory seniors take at least one prescription
medication. The number of over-the-counter medications is not well documented. As the
elderly population increases and as researchers discover and test new medications to
prevent and treat medical problems such as cancer, polypharmacy will continue to flourish.
The complex treatment of cancer, coupled with the increased comorbidity in the older
patient, increases the potential for polypharmacy. According to the 1994 Surveillance,
Epidemiology, and End Results Program of the National Cancer Institute, over 50% of all
cancers occur in patients who are older than 65 years of age, and complex treatments may
involve multiple cytotoxic medications at near-toxic dosages. The simultaneous use of
several different medications is increasingly resulting in harmful drug interactions in
the older patient with cancer. The usefulness of a drug, its side effects, and any
potential interactions that could alter its toxicity or efficacy profile must be carefully
considered before being added to a medication regimen.
All medications used by an older patient should be reviewed before the addition of
systemic therapy to the cancer treatment.
In 1984, Simonson8 suggested seven features that identify medication misuse
and abuse: (1) medications that have no apparent indication, (2) duplicate medications,
(3) concurrent use of interacting medications, (4) contraindicated medications, (5)
inappropriate dosages, (6) drug therapy to treat adverse reactions, and (7) improvement
when the medication is discontinued. Polypharmacy may also be attributed to the fact that
medical advice is sought more often by older adults than by young adults. The elderly rely
on medications more than their younger counterparts to alleviate symptoms and/or disease
states. Nolan and O’Malley7 noted that 35% of office visits by those more
than 85 years of age resulted in prescriptions for three or more medications. The senior
adult is often targeted by the mass media in the promotion of new medications and
medications that are given over-the-counter status.
Until age 60 years, the incidence of invasive cancer is greater in women than in men.
This trend reverses for those age 60 and older, when the incidence becomes higher in men.9
On average, drugs are used more often by older women than older men.10 At our
center, a retrospective study is being conducted to evaluate sex specificity and
medication use in older patients. As an example, an analysis of 147 patients with cancer
shows that nonprescription medications are used more often by women with breast cancer
than by men with prostate cancer (Fig 1).
Arenas for Polypharmacy
The rate of prescribing medications is lower in the ambulatory community setting than
in the extended care facility or in the institutional setting.11 Two studies12,13
on the use of prescription and nonprescription drugs show that regardless of study
parameters, the categories of medications most frequently used in the elderly population
are similar (Table 1). Prescription medications for 218 older patients with cancer at our
center were ranked in order of frequency of medication prescribed (Table 2). Similarities
are apparent among the groups cited in these tables.
Shimp et al14 studied potential prescription and nonprescription
medication-related problems in noninstitutionalized elderly patients and concluded that
the number of potential drug-related problems was most strongly affected by the number of
prescription medications used. Frequent changes in medication regimens may confuse the
older patient about which medications to continue or discontinue. A change from a
brand-name drug to a generic drug may result in an elderly patient using both medications
concurrently, and alterations in the color, appearance, or size of capsules or tablets may
also confuse a patient who identifies medications by these traits.
A 1988 study by Carbonin et al15 analyzed drug use and adverse reactions in
41 medical and geriatric wards. Each patient used an average of 5.1 medications, and this
number increased with advancing age. The most common medications given during
hospitalization were cardiac glycosides, loop diuretics, cardiac medications, and
antiulcer medications. These medications are also reported on the top 10 medications in
the ambulatory setting (Table 1) and at our center (Table 2).
The primary reason for hospitalization of cancer patients is neutropenic fever. An
older cancer patient may require hospitalization due to additional side effects of
chemotherapy that would not be apparent in a younger cancer patient. Compared with their
younger counterparts, older patients with cancer generally have more comorbid conditions
that may be exacerbated by the chemotherapeutic regimen. For example, elderly cancer
patients with heart conditions may be receiving chemo-therapeutic agents (or dosages of
those agents) that affect function of the heart. In general, these patients are taking
medications to control their comorbid condition, and the additional volume of administered
fluid or medication may unbalance the homeostasis. These situations are usually rectified
prior to admission of chemotherapeutic medications, but complications can arise following
treatment. Another example is the high frequency of use of laxative or antidiarrheal
medication in the elder population. Laxatives coupled with chemotherapeutic agents that
have a laxative effect can cause dehydration and subsequent hospitalization in the older
person with cancer. These side effects may not be apparent immediately after chemotherapy
treatment but may be latent.
The phenomenon of treating with "natural" products advocated and sold by
health food stores may unintentionally harm the older person. The term "natural"
may imply "safe" to the elderly when in fact the product may not be safe, due to
its intrinsic nature, to the physical health of the older individual, or to other
medications being used for treatment. These "natural" products may interact with
prescribed medications and thus exacerbate existing health conditions. For example, iron
products inhibit the absorption of tetracyclines, quinolones, and antihypertensive agents.
When iron is given with thyroxine replacement therapy, the serum concentration of
thyrotropin (thyroid-stimulating hormone) increases and thus the signs and symptoms of
hypothyroidism are increased.16(p1074) As another example, calcium products
inactivate tetracycline and should not be given with antibiotics. Calcium should be used
cautiously in older patients using cardiac glycosides due to the interaction between these
two drug classifications. Arrhythmias may occur if these agents are taken concurrently.16(p1985)
"Alternative" therapies (eg, herbal products, food supplements, vitamins,
crystals, and religious beliefs) are widely publicized for the treatment and prevention of
cancer. A medication is defined as "any substance, other than food, that is used in
the prevention, diagnosis, alleviation, treatment, or cure of a disease."2
Based on this definition, most alternative therapies should be considered as medications.
The Food and Drug Administration does not regulate food supplements in the manner of
traditional medications. Ingredients do not need to be included on the label, and the
quality control required of traditional medication manufacturing is not mandatory in food
supplements. Therefore, "what you see" may not always be "what you
get." Nutritional claims can be stated on labels of food supplements without the
support of factual studies or proof. The effects of food supplements in conjunction with
chemotherapy regimens have not been adequately studied.
Antioxidants for the prevention of cancer are heavily promoted. They may control damage
to cells by holding cellular integrity and preventing the formation of free radicals.
Significant side effects may result from indiscriminate use of these agents by cancer
patients. For example, megadoses of vitamin C can cause the formation of kidney stones and
can acidify the urine. Methotrexate is an example of a chemotherapeutic agent that needs
an alkaline urine pH in order to be properly excreted. By acidifying the urine,
methotrexate may be retained and thus cause excess toxicity or damage to the renal
tubules. Several anticancer medications exert their cytotoxicity via the formation of free
radicals. For example, doxorubicin, an anthracycline,is used alone or in combination with
other chemotherapeutic agents in a variety of antitumor regimens. In theory, preventing
the formation of free radicals may inhibit the full potential of an important piece of the
treatment regimen, which could decrease the efficacy of the chemotherapeutic regimen.
Further studies are needed to evaluate the use of antioxidants in combination with
chemotherapeutic regimens.
Evaluation and Potentiation of Polypharmacy
Older patients with cancer are especially vulnerable to the risks associated with
polypharmacy. Their heightened use of drugs to treat cancers and increasing chronic
illnesses, the availability of nonprescription medications, the tendency to self-treat,
the prohibitive costs of some anticancer medications are among the various reasons that
can promote polypharmacy (Table 3).
The potential for adverse effects from the use of "natural" products by the
elderly population is enhanced when the patient fails to disclose all medication use to
the health professional. When medical histories are recorded, drug side effects,
interactions, and exacerbations of already apparent disease processes may be attributed to
other causes. The older patient may not perceive nonprescription products to be
medications and thus may use these products without the knowledge of possible drug
interactions. Of 218 older patients with cancer who were interviewed at our institute, 47%
were taking nonprescription items but did not report these products as medications on a
three-day medication history report. An average of 4.4 medications per patient was
reported: 3.2 were via prescription and 1.2 were nonprescription items taken on a daily
basis. Of the daily nonprescription items, 65.9% were classified as vitamins and
nutritional supplements, 25.4% as analgesics, 5% as laxatives, and 3.7% as antacids and
other (Figs 2A-B). Home remedies, nutritional supplements, vitamins, and alcohol can
potentially interact with prescribed medications as well as with each other.17
At least one half of the most commonly prescribed medications for the elderly have the
potential to interact with alcohol.18
Hoarding medications poses a potential risk for polypharmacy.19 "Saving
medication for later use" is a common explanation for not taking medications as
prescribed.20 The fixed income of many elderly people may prompt the need to
hoard medications. In addition, the policy of some health care coverage plans to limit the
number of prescriptions per month has also led to hoarding medications by chemotherapy
patients. Oral chemotherapeutic medications may be costly, and treatment may be repeated
twice a month. The potential for misuse occurs when only one prescription is filled with
the stipulation of a twice-monthly treatment. Patients may inadvertently use
chemotherapeutic medication incorrectly, which may result in medication overuse and the
risk of increased adverse reactions. Misuse can also be compounded by sharing medications
with friends and family members.
The increase in the number of chronic illnesses reported with advancing age may
increase the number of different physicians seen by the elderly population.14
Consequently, physicians may prescribe different medications to achieve the same
therapeutic endpoint. If the physicians do not have access to the primary medical record,
therapy may be initiated without the full scope of a patient’s medication history.
With each additional physician seen by the senior adult, the probability of duplicate
medications and other polypharmacy issues increases exponentially. The lack of a primary
care physician to orchestrate all physicians seen by one patient increases the possibility
of polypharmacy. Multiple prescribers for the senior adult are not limited to physicians,
however. Health food store personnel, pharmacists, dietitians, nurses, friends, and family
members may also influence the medication practices of the elder adult and may make
recommendations without full knowledge of the disease process, symptoms, or concomitant
illness experienced by the elder person.
Using multiple pharmacies to fill prescription medications also can add to the risk of
polypharmacy. Rather than using one pharmacy for all medications and thus developing a
convenient record of drug use, the older adult may patronize various pharmacies to find
the lowest cost for a medication. Several large drug store chains are linking pharmacies
via a common computer data base, thus providing access to a record of all prescriptions
filled by that chain. However, the record becomes unreliable and incomplete when the
patient uses different chains or sources.
The patient’s lack of knowledge concerning medications, as well as poor
understanding of the medical conditions for which the medications are prescribed, may also
lead to polypharmacy. Psychosocial aspects of the ability of the older adult to learn
about medications has been documented.21 The education of patients is vital to
the successful treatment of their medical condition. Lack of knowledge may or may not be
attributed to the information resources available to the elderly. Presentation of
information must correspond to the physical limitations of patients and their individual
education levels. Beyond 65 years of age, one in four people is affected by vision or
hearing loss or by significant tinnitus.22,23 Medication information is often
presented in small print, making it difficult to read by some older individuals. The
cognitive process may slow with advancing age and thus may correspond to a decline in
memory and learning procedures.24 In addition, the patient may not understand
the therapeutic endpoint of the therapy or why the medication is being given.
Consequences of Polypharmacy
Adverse Drug Reactions
Differences in study design and samples hinder the ability to draw conclusions from
reports of adverse drug reactions (ADRs) in the elderly hospitalized population. Drug
interactions are thought to be a leading cause of ADRs.25 The multitude of
medications prescribed to the elderly patient upon hospitalization potentiates the risk of
drug interactions. This may explain the assumption that ADRs are related to the age of the
individual, when in reality ADRs may be due to the severity of the presenting medical
problem (eg, congestive heart failure, an infectious process, or respiratory
difficulties). An exponential rather than linear increase in the incidence of ADRs is
observed with the addition of each drug to an existing regimen.7,26 Lipton et
al27 reported that 48% of 236 ambulatory patients experienced a drug
interaction, and only 2% of those reactions were clinically significant.
Common medications used by the elderly have been previously listed (Tables 1 and 2). It
is important to note that those medications most commonly cause ADRs in the senior
population with cancer (Table 4).15,28-30 Another factor that heightens ADR
risk in the elderly is inappropriate prescribing of medications. ADRs also may be the
result of changes in drug pharmacodynamics and pharmacokinetics in the senior adult, such
as decreased absorption,31 declining renal function,32 reduced liver
mass, and metabolic clearance of medications.33 The adverse effects may be
heightened by alterations in diet, exercise, sleeping patterns, and daily activities.
Intentional and unintentional change in drug doses may be made by the elderly patient.
If information on noncompliance is not reported by the patient to the prescriber,
increases or decreases in dosages of medications may result, with multiple possible
outcomes. The patient may be hospitalized with an ADR secondary to the improper dosage of
the medication rather than to the medication itself, which may result from both
subtherapeutic or supertherapeutic drug levels.
Cough and cold remedies may cause adverse effects in the older person with
hypertension, diabetes, and/or coronary artery disease. For example, cimetidine, recently
approved as a nonprescription agent, reduces the hepatic metabolism of some prescription
items such as warfarin, phenytoin, propranolol, theophylline, terfenadine, some tricyclic
antidepressants, and some benzodiazepines. By reducing hepatic metabolism, cimetidine
decreases elimination and increases blood concentrations of these medications, and
clinically important adverse effects can occur. The concomitant administration of
cimetidine with phenytoin and theophylline, for example, increases the side effects from
these medications.16(p2267) Discontinuation or irregular use of cimetidine may
result in subtherapeutic levels.
Drug Interactions
Table 5 summarizes some drugs that, either in vitro or in vivo, may interact with
commonly prescribed antitumor chemotherapeutic agents. The risk for deleterious drug
interactions increases with the addition of each anticancer medication to the drug
regimen. Research on anticancer drugs historically has reported the efficacy and safety of
single drugs but has not determined the effects on combined medications.34
Published drug interactions usually reference only one other drug, while several
medications may have the ability to potentiate one medication. Thus, determining which
medication is the cause of the interaction can be difficult, and the potential for
polypharmacy may continue if the cause of the interaction is not identified. Another
medication may be added to the regimen if the drug interaction causes a decrease in
response for the patient. An increase in response may also occur and cause the patient to
describe exacerbated side effects to medication that may result in hospitalization or an
addition of medication to the therapy. Additional medications may include not only
prescription medications, but also self-treatment by the older patient with
nonprescription products.
Medication Side Effects
Many of the side effects experienced by older patients can be uncomfortable but usually
do not warrant that the medication be stopped. However, treating these side effects
escalates the risk of polypharmacy. Using several medications simultaneously can become
cumbersome not only to the patient taking the medication, but also to the clinician
attempting to discover the reasons for prescribing those medications. Also, identifying
which medication is causing which problem may be difficult, since some medications have
the same indications and side effects. For example, narcotics and tricyclic
antidepressants are used in pain control, and both can cause constipation. An overlapping
of effects may occur with the concomitant administration of medication.
Cost
The costs associated with medications and with hospitalization due to medication use
may prohibit the older patient on a fixed income from purchasing essential medications.
The cost of oral chemotherapeutic agents such as cyclophosphamide and etoposide is
relatively high. Elderly patients on a fixed income may be able to afford medications that
are part of a chemotherapeutic regimen only by discontinuing other medications, and higher
medication costs have been linked to an increase in noncompliance. Medications that are
not essential may take priority over essential medications because the cost:benefit ratio
of each drug has not been clarified with the elder adult. Also, elderly patients may avoid
the cost of consulting a physician by accepting recommendations from individuals not
actively involved in treatment.
Insurance companies and the health care system’s resources are also responsible
for covering the mounting costs of additional drug therapies. Medication assistance
programs are available to the cancer patient to offset the financial burden of purchasing
chemotherapeutic agents. Information regarding these programs must be provided to the
patient and to the physician when discussing treatment in order to expedite a financial
benefit to the patient.
Noncompliance
The main reason for most outpatient treatment failure of drug treatment is
noncompliance, which can cause serious medical complications. Rates of noncompliance have
been estimated at 25% to 59% in the elderly.31 The average rate of
noncompliance in individuals with chronic diseases has been reported to be 50%.35-37
While noncompliance with medications correlates more strongly with the number of
medications given than with the age of the patient, the difficulty experienced by an
elderly person in interpreting the importance of a medication or the directions for use
may lead to noncompliance.
The knowledge base, cognition, hearing acuity, vision, memory, and physical condition
of the older patient may also affect compliance, and these may be single or additive in
nature. The elderly person who cannot open the bottle of medication or cannot travel to
purchase the medication may be regarded as noncompliant. Compliance also decreases when
the older patient does not understand the directions regarding the medication due to
hearing or vision loss or educational level. A patient who cannot take a medication as
prescribed (eg, due to swallowing difficulties) is also often regarded as noncompliant. If
the patient does not relate these difficulties to the physician, more medications may be
prescribed.
Medication scheduling may be an exacerbating factor in the development of
noncompliance. Following the directions of several different medications dispersed
throughout the day may be confusing to the older patient, and the amount of time spent
taking medications may affect the patient’s quality of life. For example, the
frequency of urination that soon follows the ingestion of diuretics may prevent the senior
adult from enjoying outdoor activities or traveling.
Dosages that are missed and taken at a later date or time can generate future medical
problems. Seniors may also try to "catch up" by taking two doses of a medication
to make up for one that was missed. This noncompliance can cause serious problems that may
lead to hospitalization. Also, chemotherapeutic medications used incorrectly may result in
hospitalization. Side effects such as nausea and vomiting, which would not be apparent at
lower doses, could be exacerbated if the patient tries to "catch up" missed
medications. Uncontrolled nausea and vomiting, dehydration, and hospitalization may
result. Gebhardt et al32 reported that 60% of older adults interviewed would
discontinue a prescription drug without consulting a physician if the medication did not
appear to be working.
Prevention of Polypharmacy
Recognizing polypharmacy is the first step toward its prevention. A comprehensive
baseline assessment of the older patient helps in recognizing situations where
polypharmacy may occur.33 A review of all aspects of the patient’s daily
life provides insight into physical, emotional, or educational situations and helps to
determine if polypharmacy has occurred.
A medication history is valuable tool in determining the extent of polypharmacy. An
effective evaluation incorporates questions about medication use that will allow the older
patient to expound on his or her experiences. Answers to open-ended questions provide more
insight into the medication habits of the senior adult than "yes" or
"no" answers. The medication history should include any adverse reactions or
allergies to medication.
The "brown bag" approach employed by Colt and Shapiro6 is also
useful in identifying and preventing polypharmacy. This approach is dependant on the
instructions given to the elderly person about the definition of a medication. The patient
brings all medication products -- prescription and nonprescription -- to the office visit.
The amount of medications remaining in a vial compared with the amount that should remain
can help to determine the extent of compliance. Multiple physician and pharmacy use can be
determined by the labels on the vials. Nonprescription medication use can be evaluated.
This approach provides information about possible drug interactions, actual prescribed
dosages of medications, and duplications of medications.
At our center, a three-day medication history provided by the older patient with cancer
is an additional tool to prevent polypharmacy. This record of the elder patient’s
daily medication use (dosage and scheduling), coupled with a check of the medications
brought to the visit, provides another measure of medication compliance in the older
cancer patient. Actual use of posttreatment antiemetics, antidiarrheals, or laxatives can
be captured on the three-day medication history. Any deviation on the use of medication
from that prescribed on the label is apparent. Preliminary assessment of the effectiveness
of these two tools to judge medication use has been promising. Twenty percent of patients
who completed the medication history and brought medications to the clinic visit were not
using medications in accordance with the indication on the label. The importance of
recording actual medication use has been shared with the elder patient in order to treat
symptoms of posttreatment nausea and/or vomiting associated with chemotherapy. Changes in
posttreatment antiemetics have been avoided when instruction on the importance of taking
medications has been provided.
Education regarding medication use is important in preventing polypharmacy in the older
patient. This medication information is provided at a level that is appropriate and
relevant to the individual senior is imperative. Patient involvement in treatment options
not only allows some control to the patients in the treatment plans but also may help to
prevent possible polypharmacy occurrences by their understanding the possible
ramifications of noncompliance. As an active partner, the patient can aid the physician in
the choice of medication for the disease process. For example, if fixed income is a
concern for the patient, the physician may be able to suggest lower-cost therapeutic
alternatives.
Simplification of drug regimens is another means by which the health care provider can
prevent polypharmacy. Single-day dosing schedules are possible for many medications and
may reduce the number of medications taken on a given day.38 One medication may
have many therapeutic indications and can therefore be used for a number of disease
states. Also, continued quality of life is an important consideration in scheduling oral
chemotherapeutic agents. For example, agents that cause nausea may be taken prior to
bedtime to prevent nausea during waking hours and may also reduce the use of antiemetic
agents during the day. The patient would avoid the side effects of antiemetic agents that
may affect current lifestyle, and the cost of use of these agents would be reduced.
A pharmacotherapy consultant is a good resource in preventing polypharmacy. Clinical
pharmacists can improve geriatric prescribing by physicians in the outpatient setting.27
Utilizing a clinical pharmacist in our institution has provided the opportunity to
minimize drug prescriptions and has improved medication scheduling, information on
cost-containment and medication use, and notification of medication use to the
patient’s primary physician (Fig 3).
Polypharmacy can best be prevented by changing prescription habits. Prescribing
medications without a found diagnosis intensifies the risk of polypharmacy. The benefit of
an additional medication to a therapeutic regimen must be weighed against the possible
problems that may result from the addition. The patient should be aware of the
benefit:risk ratio of each additional medication.
Communication among medication prescribers reduces the number of medications used. A
responsible party is designated to review all medications (both prescription and
nonprescription) taken by the senior patient to determine necessary and unnecessary
medications. A record of all medication use should be available to all practitioners. The
use of "as needed" medications should be kept to a minimum since antagonism or
synergism of daily medications can occur.
The outcomes of drug therapy are reviewed, and medications that have reached their
therapeutic endpoint or are not accomplishing the therapeutic endpoint are discontinued.
This information is shared with the patient to prevent the continued use of medications
past their usefulness.
The use of nondrug strategies may be effective in treating many symptoms experienced by
older patients. Health promotion for older patients is an important asset to their quality
of life. Exercise, nutrition, and a healthy lifestyle all decrease the need for
medications to treat symptoms.
Conclusions and Recommendations
Polypharmacy is defined as the concurrent use of several different medications,
including more than one medication from the same drug classification. Unnecessary and
excessive medications are used by the elderly population. The development of polypharmacy
is enhanced by factors such as lack of education concerning medications, a tendency toward
self-treatment, and multiple disease states, medications, prescribers, and sources for
medication. The consequences of polypharmacy involve ADRs, drug interactions, higher
medication costs, and noncompliance. Polypharmacy is often recognized after it has
occurred.
The key to the prevention of polypharmacy is to incorporate prevention methods prior to
its occurrence. Education of the medical community as well as the elderly population is an
effective prevention method. The use of the "essential medication only" premise
to medication treatment in the elderly population will also aid in the prevention of
polypharmacy. Cost factors, therapeutic endpoints, nondrug therapy through health
promotion, and communication among the older patient and all prescribers involved in
medical care are vital components to the main goal of decreased medication use in the
senior population with cancer.
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