Chronic Pain Management in the Elderly

Chronic pain often ushers humans into senescence. Up to one half of community-dwelling elders and 45% to 80% of nursing home residents complain of pain.¹ Many elderly patients can anticipate 30 or more years of pain unless health care providers find answers to their problems. Used properly, pharmacotherapy is among the safest, most effective ways to treat pain.

Complications and Concerns

The severity of pain is difficult to quantify because of its inherent subjectivity. This difficulty is magnified with elderly patients who are unable or unwilling to express themselves. Visual analogue scales are commonplace, but chronic pain patients' perception that their pain is "off the scale" often limits the utility of these scales. Measuring resumption of function (ie, ability to rise, work, and sleep, or interest in hobbies) is often more telling.² When patients are cognitively impaired, caregiver input, previous pain documentation, or clinician observation must serve as proxy to estimate pain intensity, frequency, duration, and location, as well as precipitating factors, interventions that have worked or failed in the past, and previous side effects.

Pharmacists are well aware of the concerns of geriatric pharmacy: polypharmacy, altered pharmacokinetics and pharmacodynamics, and adverse events. Polypharmacy is not limited to prescription medications; this population uses OTC medications extensively.

Treatment Expectations

Often, patients have unrealistic expectations, considering pain to be an unrelievable consequence of aging, or expecting total relief when it is not possible. Their tenacious hold on myths (Table 1) may impede appropriate care. Good patient?clinician communication should promote patient autonomy.

Clinicians should prescribe the agent(s) that probably will provide the most relief with the fewest adverse events, titrating a low starting dose slowly upward. Patients and family members want to know the risks, benefits, and costs of each therapy, and their preferences should drive therapy to some extent. Doses should be scheduled, dispelling the myth that medication should be reserved for severe pain.

Step by Step

Acetaminophen

The World Health Organization advocates a stepwise approach to pain. Acetaminophen is effective for mildto- moderate pain. It generally is less toxic than the nonsteroidal antiinflammatory drugs (NSAIDs), although excessive short- or long-term doses increase the hepatotoxicity risk.¹ The recommended maximum dose of 4 g/day, at face value, appears to be a significant amount of acetaminophen (12 regular-strength dosages), but acetaminophen also is common in many combination products. Daily intake can accidentally exceed 4 g easily. Chronic use, especially in the elderly, should not exceed 2.6 g/day. Preexisting hepatic insufficiency or ethanol abuse dictates reducing the maximum daily dose by 50% to 75%.³

NSAIDs

NSAIDs (excluding the cyclooxygenase- 2 [COX-2] inhibitors) also relieve mild-to-moderate pain, especially musculoskeletal or inflammatory pain. At a certain point (unique for every patient), increasing the dose will not improve analgesia. Patients who fail to respond to a particular NSAID may respond to a different NSAID.

The elderly are at highest risk for the most serious NSAID-related adverse effects: gastrointestinal (GI) and renal toxicity.1 On average, 1 in 1200 patients (16,000 people in the United States annually) taking NSAIDs for at least 2 months will die needlessly from GI complications. Renal toxicity occurs less frequently than GI toxicity, but it is a concern. The most common NSAID-induced renal toxicity is acute reversible renal failure; it is followed by impaired electrolyte and water excretion, acute interstitial nephritis, and nephropathy.¹

The American Geriatrics Society's Guidelines for the Treatment of Persistent Pain do not recommend traditional NSAIDs as first-line treatment in the elderly, preferring COX-2 inhibitors. If an NSAID must be used, the guidelines recommend using a proton pump inhibitor to avoid gastric toxicity; this can be a costly intervention.⁴

COX-2 Inhibitors

The COX-2 inhibitors tend to cause fewer GI adverse events and affect coagulation minimally.⁵ Their longterm renal effects, however, are similar to those of the traditional NSAIDs. Edema and blood pressure increases have been observed, generally within the first few weeks of treatment initiation. Celecoxib is a sulfonamide, contraindicated in sulfa-allergic individuals. The liquid formulation of rofecoxib may be helpful for elders with dysphagia.

Opioids

For moderate-to-severe pain, opioids are a practical choice for elderly patients. Many prescribers often avoid these agents, fearing addiction. Inevitably, patients maintained on opioids will develop physical dependence and tolerance. The only real implication of this problem is that, if the need for the drug ends, doses must be tapered over days to weeks. True addiction (drug craving and continued use despite known harms) rarely occurs in older patients with persistent pain.

Not all opioids are appropriate for the elderly. Meperidine's renally cleared metabolite, normeperidine, can accumulate and cause seizures or delirium?especially as renal function declines.¹ Methadone's variable halflife makes it a poor choice.^6,7 Fentanyl generally is reserved for opioid-tolerant patients, especially those suffering from malignancies. Absorption varies with the patient's skin condition.

A brief warning about propoxyphene is in order. For 30 years, researchers have known that propoxyphene is a poor choice for elders, yet it endures. Its efficacy equals that of aspirin or acetaminophen alone.3 Propoxyphene and its metabolite, norpropoxyphene, can accumulate in patients with renal disease. Conventional dialysis removes neither. Excess norpropoxyphene can cause cardiotoxicity? a nonopioid effect not reversible by naloxone?as well as neuroexcitatory effects, respiratory depression, and ataxia or dizziness.⁸

Often, another opioid must be selected. Conversion is inexact at best, but general equivalencies can be found in Table 2.⁶

Short-acting, less-potent opioids (codeine, hydrocodone, oxycodone) are good starting drugs.⁹ If they are effective, most guidelines recommend switching patients to long-acting, regularly dosed opioids, reserving short-acting opioids for breakthrough pain. In reality, some patients prefer short-acting agents so that they can manage the side effects, and some patients prefer to dose themselves only when they have pain.

Other Agents

Adjuvant drugs are useful, especially in neuropathic pain. Tricyclic antidepressants and certain anticonvulsant medications, such as gabapentin and topiramate, have been used to manage neuropathic pain.³ These medications, however, often cause intolerable anticholinergic and cardiovascular side effects.

Managing Side Effects

Side effects may deter some patients from using opioids, but they need not do so.⁶ In anticipation, clinicians should discuss possible side effects and management plans with patients.

Sedation often occurs upon starting and increasing doses. Tolerance usually develops in a few days, so agents should be given a sufficient trial period. After that trial period, switching to a different opioid may provide relief and fewer adverse effects.

The question as to whether a patient should drive poses a dilemma, because a negative response will almost certainly lead to poor compliance. Most studies indicate that chronic opioid use does not impair driving skills. Driving should be restricted as follows:

• For 4 to 5 days after starting or increasing the dose of opioids
• If patients feel sedated
• After drinking alcohol while taking opioids
• After taking OTC antihistamines10

Older patients also should be cautioned about the possibility of falling. Giving the drug after a meal may prevent nausea and vomiting, side effects that often subside after a few days to weeks. No tolerance develops for constipation, and stool softeners alone are inadequate, so a stimulant should be given periodically. Dietary measures often are helpful.

Summary

Pain management for elderly patients can be frustrating. Polypharmacy frequently is the rule, not the exception. Scheduling doses, avoiding combination products, counseling carefully, and anticipating side effects can mean the difference between pain control and constant agony.

Ms. Wick is a senior clinical research pharmacist at the National Cancer Institute, National Institutes of Health. Dr. Zanni is a health systems consultant. The views expressed are those of the authors and not those of the National Cancer Institute.

For a list of references, send a stamped, self-addressed envelope to: References Department, Attn. D. Ryan, Pharmacy Times, 241 Forsgate Drive, Jamesburg, NJ 08831; or send an e-mail request to: dryan@mwc.com.