Pharmacologic Interventions - Pain Management Strategies

Pain Management Strategies

Reducing pain to a “tolerable” level was once considered the goal of pain management. However, even patients who have described pain relief as adequate often report disturbed sleep and marked distress because of pain. In view of the harmful effects of pain and inadequate pain management, the goal of tolerable pain has been replaced by the goal of relieving the pain. Pain management strategies include both pharmacologic and nonpharmacologic ap-proaches. These approaches are selected on the basis of the pa-tient’s requirements and goals. Appropriate analgesic medications are used as prescribed. They are not considered a last resort to be used only when other pain relief measures fail. Any intervention is most successful if initiated before pain sensitization occurs, and the greatest success is usually achieved if several interventions are applied simultaneously.

PHARMACOLOGIC INTERVENTIONS

Managing a patient’s pain pharmacologically is accomplished in collaboration with the physician or other primary care provider, the patient, and often the family. The physician or nurse practi-tioner prescribes specific medications for pain or may insert an intravenous line for administering analgesic medications. Alter-natively, an anesthesiologist or nurse anesthetist may insert an epidural catheter for their administration. However, it is the nurse who maintains the analgesia, assesses its effectiveness, and reports if the intervention is ineffective or produces side effects.

The pharmacologic management of pain requires close col-laboration and effective communication among health care pro-viders. In the home setting, it is often the family who manages the patient’s pain and assesses the effectiveness of pharmacologic in-terventions, while it is the home care nurse who evaluates the ad-equacy of pain relief strategies and the family’s ability to manage the pain. The home care nurse reinforces teaching and ensures communication among the patient, family care providers, physi-cian, pharmacist, and other health care providers involved in the patient’s care.

Premedication Assessment

Before administering any medication, the nurse asks the patient about allergies to medications and the nature of any previous al-lergic responses. True allergic or anaphylactic responses to opi-oids are rare, but it is not uncommon for a patient to report an allergy to one of the opioids. On further examination, the nurse often learns that the extent of the allergy was “itching” or “nau-sea and vomiting.” These responses are not allergies; rather, they are side effects that, when necessary, can be managed while the patient’s pain is relieved. The patient’s description of responses or reactions should be documented and reported before admin-istering the medication.

The nurse obtains the patient’s medication history (eg, cur-rent, usual, or recent use of prescription or over-the-counter med-ications or herbal agents), along with a history of health problems. Certain medications or conditions may affect the analgesic med-ication’s effectiveness or the metabolism and excretion of anal-gesic agents. Before administering analgesic agents, the nurse should assess the patient’s pain status, including the intensity of current pain, changes in pain intensity after the previous dose of medication, and side effects of the medication.

Approaches for Using Analgesic Agents

Medications are most effective when the dose and interval be-tween doses are individualized to meet the patient’s needs. The only safe and effective way to administer analgesic medications is by asking the patient to rate the pain and by observing the re-sponse to medications.

BALANCED ANESTHESIA

Pharmacologic interventions are most effective when a multi-modal or balanced analgesia approach is used. Balanced analge-sia refers to use of more than one form of analgesia concurrentlyto obtain more pain relief with fewer side effects. Three general categories of analgesic agents are opioids, NSAIDs, and local anesthetics. These agents work by different mechanisms. Using two or three types of agents simultaneously can maximize pain re-lief while minimizing the potentially toxic effects of any one agent. When one agent is used alone, it usually must be used in a higher dose to be effective. In other words, although it might re-quire 15 mg morphine to relieve a certain pain, it may take only 8 mg morphine plus 30 mg ketorolac (an NSAID) to relieve the same pain.

PRO RE NATA (PRN)

In the past, the standard method used by most nurses and physi-cians in administering analgesia was to administer the analgesic pro re nata (PRN), or “as needed.” The standard practice was forthe nurse to wait for the patient to complain of pain and then ad-minister analgesia. As a result, many patients remained in pain because they did not know they needed to ask for medication or waited until the pain became intolerable.

By its very nature, the PRN approach to analgesia leaves the pa-tient sedated or in severe pain much of the time. To receive pain relief from an opioid analgesic, the serum level of that opioid must be maintained at a minimum therapeutic level (Fig. 13-8). By the time the patient complains of pain, the serum opioid level is below the therapeutic level. From the time the patient requests pain medication until the nurse administers the medication, the patient’s serum level continues to fall. The lower the serum opi-oid level, the more difficult it is to achieve the therapeutic level with the next dose. The only way to ensure significant periods of analgesia, using this method, is to give doses large enough to pro-duce periods of sedation.

PREVENTIVE APPROACH

Currently, a preventive approach to relieving pain by adminis-tering analgesic agents is considered the most effective strategy because a therapeutic serum level of medication is maintained. With the preventive approach, analgesic agents are administered at set intervals so that the medication acts before the pain be-comes severe and before the serum opioid level falls to a sub-therapeutic level.

Administering analgesic medication on a time basis, rather than on the basis of the patient’s report of pain, prevents the serum drug level from falling to subtherapeutic levels. An exam-ple of this would be giving the patient the prescribed morphine or the prescribed NSAID (ibuprofen) every 4 hours rather than waiting until the patient complains of pain. 

If the patient’s pain is likely to occur around the clock or for a great portion of a 24-hour period, a regular around-the-clock schedule of administering analgesia may be indicated. Even if the analgesic is prescribed PRN, it can be administered on a preventive basis before the patient is in severe pain, as long as the prescribed interval between doses is observed. The preventive approach reduces the peaks and troughs in the serum level and provides more pain relief for the patient with fewer adverse effects.

Smaller doses of medication are needed with the preventive approach because the pain does not escalate to a level of severe in-tensity. Thus, a preventive approach may result in the adminis-tration of less medication over a 24-hour period, thereby helping prevent tolerance to analgesic agents and decreasing the severity of side effects (eg, sedation and constipation). Better pain control can be achieved with a preventive approach, reducing the amount of time the patient spends in pain.

In using the preventive approach, the nurse assesses the patient for sedation before administering the next dose. The goal is to provide analgesia before the pain becomes severe. It would not be safe to medicate a patient (with an opioid) repeatedly if he or she was sedated or having no pain. It may be necessary to decrease the dosage of the opioid analgesic so that the patient receives pain relief with less sedation.

INDIVIDUALIZED DOSAGE

The dosage and the interval between doses should be based on the patient’s requirements rather than on an inflexible standard or routine. People metabolize and absorb medications at differ-ent rates and experience different levels of pain. Therefore, one dose of an opioid medication given at specified intervals may be effective for one patient but ineffective for another.

Because of the fear of promoting addiction or causing respira-tory depression, health care providers tend to prescribe and ad-minister inadequate dosages of opioid agents to treat acute pain or chronic pain in the terminally ill patient (Chart 13-5). How-ever, even prolonged administration of opioid agents is associatedwith an extremely low incidence (less than 1%) of addiction. Fur-thermore, small doses are not necessarily safe doses. For example, some patients receiving a relatively small dose (25 to 50 mg) of meperidine (Demerol) intramuscularly have experienced respira-tory depression, whereas other patients have not exhibited any se-dation or respiratory depression with very large doses of opioids.

Therefore, the effects of opioid analgesic medications must be monitored, especially when the first dose is given or when the dose is changed or given more frequently. The time, date, the pa-tient’s pain rating (scale of 0 to 10), the analgesic agent, other pain relief measures, side effects, and patient activity are recorded. When the first dose of an analgesic is administered, the nurse needs to record a pain rating score, blood pressure, and respira-tory and pulse rates (all of which are considered “vital signs”). If the pain has not decreased in 30 minutes (sooner if an intra-venous route is used) and the patient is reasonably alert and has a satisfactory respiratory status, blood pressure, and pulse rate, then some change in analgesia is indicated. Although the dose of analgesic medication is safe for this patient, it is ineffective in re-lieving the pain. Therefore, another dose of medication may be indicated. In such instances, the nurse consults with the physi-cian to determine what further action is warranted.

PATIENT-CONTROLLED ANALGESIA

Used to manage postoperative pain as well as chronic pain, patient-controlled analgesia (PCA) allows patients to control the ad-ministration of their own medication within predetermined safety limits. This approach can be used with oral analgesic agents as well as with continuous infusions of opioid analgesic agents by intra-venous, subcutaneous, or epidural routes. PCA can be used in the hospital or home setting.

The PCA pump permits the patient to self-administer contin-uous infusions of medication (basal rates) safely and to administer extra medication (bolus doses) with episodes of increased pain or painful activities. A PCA pump is electronically controlled by a timing device. Patients experiencing pain can administer small amounts of medication directly into their intravenous, sub-cutaneous, or epidural catheter by pressing a button. The pump then delivers a preset amount of medication.

The PCA pump also can be programmed to deliver a constant, background infusion of medication or basal rate and still allow the patient to administer additional bolus doses as needed. The timer can be programmed to prevent additional doses from being administered until a specified time period has elapsed (lock-out time) and until the first dose has had time to exert its maximal ef-fect. Even if the patient pushes the button multiple times in rapid succession, no additional doses are released. If another dose is re-quired at the end of the delay period, the button must be pushed again to receive the dose. Patients who are controlling their own opioid administration usually become sedated and stop pushing the button before any significant respiratory depression occurs. Nevertheless, assessing respiratory status remains a major role for the nurse.

A continuous infusion plus bolus doses may be effective with cancer patients who require large doses of analgesia, or for post-surgical patients. Although this allows more uninterrupted sleep, the risk of sedation increases, especially when the patient has min-imal or decreasing pain.

Patients who use PCA achieve better pain relief (Walder, Schafer, Henzi et al., 2001) and often require less pain medica-tion than those who are treated in the standard PRN fashion. Because the patient can maintain a near-constant level of med-ication, the periods of severe pain and sedation that occur with the traditional PRN regimen are avoided.

To initiate PCA or any analgesia used at home or in the hos-pital, it is important to avoid playing “catch-up.” Pain should be brought under control before PCA starts, often by the use of an initial, larger bolus dose or loading dose. Then, after control is achieved, the pump is programmed to deliver small doses of medication at a time. If the patient with severe pain has a low serum level of opioid analgesic because of an inadequate basal rate, it is difficult to regain control with the small doses available by pump. Before the PCA pump is used, repeated bolus doses of an intra-venous opioid may be administered as prescribed over a short time until the pain is relieved. Then PCA is initiated. If pain con-trol is not achieved with the maximal dose of medication pre-scribed, further prescriptions are obtained. The goal is to achieve a minimum therapeutic level of analgesia and to allow the patient to maintain that level by using the PCA pump. The patient is in-structed not to wait until the pain is severe before pushing the button to obtain a bolus dose. The patient is also reminded not to become so distracted by an activity or visitor that he or she for-gets to self-administer a prescribed dose of medication. One po-tential drawback to distraction is that a patient who is using a PCA pump may not self-administer any analgesia during the time of effective distraction. When distraction ends suddenly (eg, the movie ends or the visitors leave), the patient may be left without a therapeutic serum opioid level. When intermittent distraction is used for pain relief, a continuous low-level background infusion of opioid through the PCA pump may be prescribed so that when the distraction ends, it will not be necessary to try to catch up.

If PCA is to be used in the patient’s home, the patient and family are taught about the operation of the pump and the side effects of the medication and strategies to manage them.

Local Anesthetic Agents

Local anesthetics work by blocking nerve conduction when ap-plied directly to the nerve fibers. They can be applied directly to the site of injury (eg, a topical anesthetic spray for sunburn) or di-rectly to nerve fibers by injection or at the time of surgery. They can also be administered through an epidural catheter.

TOPICAL APPLICATION

Local anesthetic agents have been successful in reducing the pain associated with thoracic or upper abdominal surgery when in-jected by the surgeon intercostally. Local anesthetic agents are rapidly absorbed into the bloodstream, resulting in decreased availability at the surgical or injury site and an increased anes-thetic level in the blood, increasing the risk of toxicity. Therefore, a vasoconstrictive agent (eg, epinephrine or phenylephrine) is added to the anesthetic agent to decrease its systemic absorption and to maintain its concentration at the surgical or injury site.

A topical anesthetic agent known as eutectic mixture or emul-sion of local anesthetics, or EMLA cream, has been effective in preventing the pain associated with invasive procedures such as lumbar puncture or the insertion of intravenous lines. To be ef-fective, EMLA must be applied to the site 60 to 90 minutes be-fore the procedure.

INTRASPINAL ADMINISTRATION

Intermittent or continuous administration of local anesthetic agents through an epidural catheter has been used for years to produce anesthesia during surgery. Although the administration of local anesthetic agents in the spinal canal is still largely con-fined to acute pain, such as postoperative pain and pain associ-ated with labor and delivery, the epidural administration of local anesthetic agents for pain management is increasing.

A local anesthetic agent administered through an epidural catheter is applied directly to the nerve root. The anesthetic agent can be administered continuously in low doses, intermittently on a schedule, or on demand as the patient requires it, and is often combined with the epidural administration of opioids. Surgical patients treated with this combination experience fewer compli-cations after surgery, ambulate sooner, and have shorter hospital stays than patients receiving standard therapy (Correll, Viscusi, Grunwald et al., 2001).

Opioid Analgesic Agents

Opioids can be administered by various routes, including oral, in-travenous, subcutaneous, intraspinal, intranasal, rectal, and trans-dermal routes. The goal of administering opioids is to relieve pain and improve quality of life; therefore, the route of administration, dose, and frequency of administration are determined on an in-dividual basis. Factors that are considered in determining the route, dose, and frequency of medication include the character-istics of the pain (eg, its expected duration and severity), the overall status of the patient, the patient’s response to analgesic medications, and the patient’s report of pain. Although the oral route is usually preferred for administering opioids, oral opioids must be given frequently enough and in large enough doses to be effective. Opioid analgesic agents given orally may provide a more consistent serum level than those given intramuscularly.

If the patient is expected to require opioid analgesic agents at home, the patient’s and the family’s ability to administer opioids as prescribed is considered in planning. Steps are taken to ensure that the medication will be available to the patient. Many phar-macies, especially those in smaller rural areas or inner cities, may be reluctant to stock large amounts of opioids. Therefore, arrange-ments for obtaining these prescription medications must be made ahead of time.

With the administration of opioids by any route, side effects must be considered and anticipated. Anticipating side effects and taking steps to minimize them increase the likelihood that the pa-tient will receive adequate pain relief without interrupting ther-apy to treat these effects.

RESPIRATORY DEPRESSION AND SEDATION

Respiratory depression is the most serious adverse effect of opi-oid analgesic agents administered by intravenous, subcutaneous, or epidural routes. However, it is relatively rare because doses ad-ministered through these routes are small, and tolerance to respi-ratory depressant effects increases if the dose is increased slowly. The risk of respiratory depression increases with age and the con-comitant use of other opioids or other central nervous system de-pressants. The risk of respiratory depression also increases when the catheter is placed in the thoracic area and when the intra-abdominal or intrathoracic pressure is increased.

The patient receiving opioids by any route must be assessed fre-quently for changes in respiratory status. Specific notable changes are decreasing respiratory rate or shallow respirations. Despite the risks associated with their use, intravenous and epidural opioids are considered safe, with the risks related to epidural administra-tion no greater than those related to intravenous or other systemic routes of administration. Sedation, which may occur with any method of administering opioids, is likely to occur when opioid doses are increased. However, the patient often develops tolerance quickly, so that in a short time the patient is no longer sedated by the dose that initially caused sedation. Increasing the time between doses or reducing the dose temporarily, as prescribed, usually prevents deep sedation from occurring. The patient at risk for se-dation must be monitored closely for changes in respiratory sta-tus. The patient is also at risk for other problems associated with sedation and immobility. Therefore, the nurse must initiate strategies to prevent problems such as skin breakdown.

NAUSEA AND VOMITING

Nausea and vomiting frequently occur with opioid use. Usually these effects occur some hours after the initial injection. Patients, especially postoperative patients, may not think to tell the nurse that they are nauseated, particularly if the nausea is mild. How-ever, the patient receiving an opioid should be assessed for nau-sea and vomiting, which may be triggered by a position change and may be prevented by having the patient change positions slowly. Adequate hydration and the administration of antiemetic agents may decrease the incidence. Opioid-induced nausea and vomiting often subside within a few days.

CONSTIPATION

Constipation, a common side effect of opioid use, may become so severe that the patient is forced to choose between relief of pain and relief of constipation. This situation can occur in patients after surgery and in patients receiving large doses of opioids to treat cancer-related pain. Preventing constipation must be a high priority in all patients receiving opioids. Whenever a patient re-ceives opioids, a bowel regimen should begin at the same time. Tolerance to this side effect does not occur; rather, it persists even with long-term use of opioids.

Several strategies may help prevent and treat opioid-related constipation. Mild laxatives and a high intake of fluid and fiber may be effective in managing mild constipation. Unless con-traindicated, a mild laxative and a stool softener should be ad-ministered on a regular schedule. Continued severe constipation, however, often requires the use of a stimulating cathartic agent, such as senna derivatives (Senokot) or bisacodyl (Dulcolax). Oral laxatives and stool softeners may prevent constipation; rectal sup-positories may be used if oral agents fail (Plaisance & Ellis, 2002).

INADEQUATE PAIN RELIEF

One factor commonly associated with ineffective pain relief is an inadequate dose of opioid. This is most likely to occur when the caregiver underestimates the patient’s pain or the route of ad-ministration is changed without the differences in absorption and action being considered. Consequently, the patient receives doses too small to be effective and, possibly, too infrequently to relieve pain. For example, if opioid delivery is changed from the intra-venous route to the oral route, the oral dose must be approxi-mately three times greater than that given parenterally to provide relief. Because of differences in absorption of orally administered opioids among individuals, the patient must be assessed carefully to ensure that the pain is relieved.

Table 13-2 lists opioids and dosages that are equivalent to morphine. In general, no recalculation needs to be done when switching from one brand of an agent to another brand of the same medication, with the exception of extended-release oral morphine. Currently, three brands of extended-release morphine (MS Contin, Oramorph, Kadian) are commonly used by cancer patients. Although these agents come in the same dosage form and contain the same drug, they are not considered therapeuti-cally equivalent because they employ different release mecha-nisms. Patients who need to switch brands should be monitored carefully both for overdose and for inadequate pain relief.

OTHER EFFECTS OF OPIOIDS

During the health history, when asked about drug allergies, pa-tients with previous hospital experience (especially for surgery) may report that they are “allergic” to morphine. This report should be thoroughly investigated. Commonly, this “allergy” will be described as itching only. Pruritus (itching) is a frequent prob-lem associated with opioids administered through any route, but it is not an allergic reaction. Itching can be relieved by adminis-tering prescribed antihistamines. Epidurally administered opioids may also cause urinary retention or pruritus. The patient should be monitored and may require urinary catheterization. Small doses of naloxone may be prescribed to relieve these problems in patients who are receiving epidural opioids for the relief of acute postoperative pain.

A number of factors may influence the safety and effectiveness of opioid administration. Opioid analgesic agents are primarily metabolized by the liver and excreted by the kidney. Therefore, metabolism and excretion of analgesic medications will be im-paired in patients with liver or kidney disease, increasing the risk of cumulative or toxic effects. In addition, normeperidine, a metabolite of meperidine, may rapidly or unexpectedly accumu-late to toxic levels. This is more likely to occur in patients with impaired kidney function and may result in seizures in suscepti-ble patients.

Patients with untreated hypothyroidism are more susceptible to the analgesic effects and side effects of opioids. In contrast, pa-tients with hyperthyroidism may require larger doses for pain re-lief. Patients with a decreased respiratory reserve from disease or aging may be more susceptible to the depressant effects of opioids and must be carefully monitored for respiratory depression.

Dehydrated patients are at increased risk for the hypotensive effects of opioids. Patients who become hypotensive after the ad-ministration of an opioid should be kept recumbent and rehydrated unless fluids are contraindicated. Patients who are dehydrated are also more likely to experience nausea and vomiting with opioid use. Rehydration usually relieves these symptoms.

Patients receiving certain other medications, such as mono-amine oxidase (MAO) inhibitors, phenothiazines, or tricyclic antidepressants, may have an exaggerated response to the de-pressant effects of opioids. Patients taking these medications should receive small doses of opioids and must be monitored closely. Continued pain in these patients indicates that a thera-peutic level of the analgesic has not been achieved. The patient must be monitored for sedation even if an analgesic effect has not been obtained.

TOLERANCE AND ADDICTION

There is no maximum safe dosage of opioids, nor is there any eas-ily identifiable therapeutic serum level. Both the maximal safe dosage and therapeutic serum level are relative and individual. Tolerance (the need for increasing doses of opioids to achieve thesame therapeutic effect) will develop in almost all patients taking opioids over an extended period. Patients requiring opioids over a long term, especially cancer patients, will need increasing doses to relieve pain. After the first few weeks of therapy, the patient’s dosing requirements usually level off. Patients who become tol-erant to the analgesic effects of large doses of morphine may ob-tain pain relief by switching to a different opioid. Symptoms of physical dependence may occur when the opioids are discontin-ued; dependence often occurs with opioid tolerance and does not indicate an addiction.

Addiction is a behavioral pattern of substance use character-ized by a compulsion to take the drug primarily to experience its psychic effects. Fear that patients will become addicted or de-pendent on opioids has contributed to inadequate treatment of pain. This fear is commonly expressed by health care providers as well as patients and results from lack of knowledge about the low risk of addiction.

In an often-cited classic study (Porter & Jick, 1980) of more than 11,000 patients receiving opioids for a medical indication, only four patients without a history of substance abuse could be identified as becoming addicted. Addiction following therapeu-tic opioid administration is so negligible that it should not be a consideration when caring for the patient in pain. Thus, patients and health care providers should be dissuaded from withholding pain medication because of concerns about addiction.

Nonsteroidal Anti-inflammatory Drugs

NSAIDs are thought to decrease pain by inhibiting cyclo-oxygenase (COX), the rate-limiting enzyme involved in the production of prostaglandin from traumatized or inflamed tissues. There are two types of COX: COX-1 and COX-2. COX-1 is involved with mediating prostaglandin formation involved in the maintenance of physiologic functions. Some of the physiologic functions in-clude platelet aggregation through the provision of thromboxane precursors and increased gastric mucosal blood flow. This pre-vents ischemia and promotes mucosal integrity. Inhibition of COX-1 will result in gastric ulceration, bleeding, and renal dam-age. The second type, COX-2, mediates prostaglandin forma-tion that results in symptoms of pain, inflammation, and fever. Thus, inhibition of COX-2 is desirable. Newer NSAIDs such as celecoxib (Celebrex), rofecoxib (Vioxx), and valdecoxib (Bextra) are COX-2 inhibitors. Ibuprofen (Advil, Motrin), another NSAID, blocks both COX-1 and COX-2 and is effec-tive in relieving mild to moderate pain and has a low incidence of adverse effects. Aspirin, the oldest NSAID, also blocks COX-1 as well as COX-2; however, because it causes frequent and severe side effects, aspirin is infrequently used to treat significant acute or chronic pain.

NSAIDs are very helpful in treating arthritic diseases and may be especially powerful in treating cancer-related bone pain. They have been effectively combined with opioids to treat postopera-tive and other severe pain. The use of an NSAID with an opioid relieves pain more effectively than the opioid alone. In such cases, the patient may obtain pain relief with less opioid and fewer side effects. It has been shown that intraoperative administration of NSAIDs results in improved postoperative pain control follow-ing laparoscopic surgery and in some cases shorter hospital stays (McLaughlin, 1994).

A regimen of a fixed-dose, time-contingent NSAID (eg, every 4 hours) and a separately administered fluctuating dose of opioid may be effective in managing moderate to severe cancer pain. In more severe pain, the opioid dose will also be fixed, with an addi-tional fluctuating dose as needed for breakthrough pain (a sud-den increase in pain despite the administration of pain-relieving medications). These regimens result in better pain relief with fewer opioid-related side effects.

Most patients tolerate NSAIDs well. However, those with im-paired kidney function may require a smaller dose and must be monitored closely for side effects. Patients taking NSAIDs bruise easily because NSAIDs have some anticoagulant effect. More-over, they may displace other medications, such as warfarin (Coumadin), from serum proteins and increase their effects. High doses or prolonged use can irritate the stomach and in some cases result in gastrointestinal bleeding as well. Thus, monitoring the patient for gastrointestinal bleeding is indicated.

Gerontologic Considerations Related to Analgesic Agents

Physiologic changes in older adults require that analgesic agents be administered with caution. Drug interactions are more likely to occur in older adults because of the higher incidence of chronic illness and the increased use of prescription and over-the-counter medications. Although the elderly population is an extremely het-erogeneous group, differences in response to pain or medications by a patient in this 40-year span (60 to 100 years) are more likely to be due to chronic illness or other individual factors than age. Before administering opioid and nonopioid analgesic agents to elderly patients, the nurse needs to obtain a careful medication history to identify potential drug interactions.

Absorption and metabolism of medications are altered in elderly patients because of decreased liver, renal, and gastrointestinal func-tion. In addition, changes in body weight, protein stores, and dis-tribution of body fluid alter the distribution of medications in the body. As a result, medications are not metabolized as quickly and blood levels of the medication remain higher for a longer period. Elderly patients are more sensitive to medications and at an in-creased risk for drug toxicity (American Geriatrics Society, 1998).

Opioid and nonopioid analgesic medications can be given ef-fectively to elderly patients but must be used cautiously because of the increased susceptibility to depression of both the nervous and the respiratory systems. Although there is no reason to avoid opioids simply because a person is elderly, meperidine should be avoided because its active and neurotoxic metabolite, normeperi-dine, is more likely to accumulate in the elderly. In addition, be-cause of decreased binding of meperidine by plasma proteins, blood concentrations of the medication twice those found in younger patients may result.

In many cases, the initial dose of analgesic medication prescribed for an elderly patient may be the same as that for a younger person, or slightly smaller than the normal dose, but because of slowed me-tabolism and excretion related to aging, the safe interval for subse-quent doses may be longer (or prolonged). As always, the best guide to pain management and administration of analgesic agents in all patients regardless of age is what the patient says. The elderly pa-tient may obtain more pain relief for a longer time than a younger patient. As a result, smaller, less frequent doses may be required. The American Geriatrics Society (2002) has published clinical prac-tice guidelines for managing chronic pain in elderly patients.

Tricyclic Antidepressant Agents and Anticonvulsant Medications

Pain of neurologic origin (eg, causalgia, tumor impingement on a nerve, postherpetic neuralgia) is difficult to treat and in general is not responsive to opioid therapy. When these pain syndromes are accompanied by dysesthesia (burning or cutting pain), they may be responsive to a tricyclic antidepressant or an antiseizure agent. When indicated, tricyclic antidepressant agents, such as amitriptyline (Elavil) or imipramine (Tofranil), are prescribed in doses considerably smaller than those generally used for depres-sion. The patient needs to know that a therapeutic effect may not occur before 3 weeks. Antiseizure medications such as phenytoin (Dilantin) or carbamazepine (Tegretol) also are used in doses lower than those prescribed for seizure disorders. Because a vari-ety of medications can be tried, the nurse should be familiar with the possible side effects and should teach the patient and family how to recognize these effects.