Opioid analgesics provide symptomatic relief of pain, but the underlying disease remains. The clinician must weigh the benefits against any potential risk to the patient, which may be quite different in an acute versus chronic disease.
Acutely, opioids will reduce the intensity of pain; physical signs (e.g., abdominal rigidity) generally will remain. Relief of pain can facilitate history taking, examination, and the patient's ability to tolerate diagnostic procedures. Patients should not be evaluated inadequately because of the physician's unwillingness to prescribe narcotics, or over concerns of obscuring the progression of underlying disease.
The problems that arise in the relief of pain associated with chronic conditions are more complex. Repeated daily administration of opioid analgesics eventually will produce tolerance and some degree of physical dependence. The degree will depend on the particular drug, the frequency of administration, and the quantity administered. The decision to control any chronic symptom, especially pain, by the repeated administration of an opioid must be made carefully. When pain is due to chronic nonmalignant disease, measures other than opioid drugs should be employed if possible. Such measures include the use of NSAIDs, local nerve blocks, antidepressant drugs, electrical stimulation, acupuncture, hypnosis, or behavioral modification. However, highly selected subpopulations of chronic nonmalignant pain patients can be maintained adequately on opioids for extended periods of time.
In the usual doses, morphine-like drugs relieve suffering by altering the emotional component of the painful experience, as well as by producing analgesia. Control of pain, especially chronic pain, must include attention to both psychological factors and the social impact of the illness that sometimes play dominant roles in determining the suffering experienced by the patient. In addition to emotional support, the physician also must consider the substantial variability in the patient's capacity to tolerate pain and the response to opioids. Some patients may require considerably more than the average dose of a drug to experience any relief from pain; others may require dosing at shorter intervals. Some clinicians, out of an exaggerated concern for the possibility of inducing addiction, prescribe initial doses of opioids that are too small or given too infrequently to alleviate pain and then respond to the patient's continued complaints with an even more exaggerated concern about drug dependence. Infants and children may receive inadequate treatment for pain than are adults owing to communication difficulties, lack of familiarity with appropriate pain assessment methodologies, and inexperience with the use of strong opioids in children.
PAIN OF TERMINAL ILLNESS AND CANCER PAIN Opioids are not indicated in all cases of terminal illness, but the analgesia, tranquility, and even euphoria afforded by the use of opi-oids can make the final days far less distressing for the patient and family. Although physical dependence and tolerance may develop, this possibility should in no way prevent physicians from fulfilling their primary obligation to ease the patient's discomfort. The physician should not wait until the pain becomes agonizing. This sometimes may entail the regular use of opioid analgesics in substantial doses. Such patients, while they may be physically dependent, are not "addicts" even though they require large doses on a regular basis (see Chapter 23).
Most experts in pain management recommend that opioids be administered at sufficiently short, fixed intervals so that pain is continually under control and patients do not dread its return. Less drug is needed to prevent the recurrence of pain than to relieve it. Morphine remains the opioid of choice in most of these situations, and the route and dose should be adjusted to the needs of the individual patient. Oral morphine is adequate in most situations. Sustained-release preparations of oral morphine and oxycodone are available that can be administered at 8-, 12- or 24-hour intervals
(morphine) or 8- to 12-hour intervals (oxycodone). Superior control of pain often can be achieved with fewer side effects using the same daily dose; a decrease in the fluctuation of plasma concentrations of morphine may be partially responsible.
Constipation is exceedingly common with opioids, and stool softeners and laxatives should be initiated early. Amphetamines have demonstrable mood-elevating and analgesic effects and enhance opioid-induced analgesia. However, not all terminal patients require the euphoriant effects of amphetamine, and some experience side effects, such as anorexia. Although tolerance does develop to oral opioids, many patients obtain relief from the same dosage for weeks or months. In cases where one opioid loses effectiveness, switching to another may improve pain relief. "Cross-tolerance" among opioids exists, but cross-tolerance among related ^-receptor agonists is not complete.
For a complete Bibliographical listing see Goodman & Gilman's The Pharmacological Basis of Therapeutics, 11th ed., or Goodman & Gilman Online at www.accessmedicine.com.
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