NEW ORLEANS—In the treatment of cancer pain, physicians often withhold adequate analgesia out of fears that are largely unfounded in this population. As a result, cancer pain often robs patients of the opportunity “to see life as good” in their final days, Dr. Daniel Brookoff said at a cancer update, sponsored by the Ochsner Medical Foundation and the American Cancer Society.
He described the visceral pain of cancer as being “like an alarm clock that you cannot turn off,” making it seem meaningless, cyclical, and irreversible. “It is a different chemical event and produces stronger autonomic and affective responses than somatic pain,” said Dr. Brookoff, associate director of the Transitional and Internal Medicine Program, Methodist Hospital, Memphis, and a specialist in pain management.
Involvement of the limbic system in the processing of chronic visceral pain may explain the emotionality connected with visceral pain, he said. It gives a physiologic explanation for why certain types of visceral pain cause patients to “lose control” while the same patients can tolerate severe somatic pain, such as from an incision.
It also provides a neurochemical explanation of why anxiolytics and antidepressants can be useful components of pain treatment, he added.
Physicians often lack understanding of cancer pain and wrongly err on the side of caution, he said. Contrary to what many physicians believe, cancer patients do not become “addicted,” defined as the compulsive use of a drug despite its harmful effects.
A Simple Definition of Abuse
“If a patient who has been precluded from living life fully by a medical problem is using a medication to get back into life, then he is using it appropriately; it is making him normal, not ‘high.’ If that patient is using medications to escape existential problems, then he is abusing drugs. The physician may be called upon to determine the difference,” Dr. Brookoff said.
The development of tolerance—by which higher and higher doses are needed to achieve the same effect—is another misunderstood area, he said. “It is not true that if you give a strong drug now, you will need more later,” he said, noting that physicians often hold back because they don’t want to use up their analgesic armamentarium too soon.
“If a patient tolerates 200 mg of morphine(Drug information on morphine), does this mean something is wrong? No, it just means the patient has a lot of pain and needs this much drug to neutralize it,” he said. When a patient’s pain worsens, it usually means the disease has spread or the patient’s activity level has increased as analgesia has provided relief.
Other barriers to adequate pain control include lack of knowledge and also fear of the DEA (Drug Enforcement Agency). Dr. Brookoff assured the physicians that while the DEA is watchful of abuse, the agency does not want to interfere with the healing of patients.
“The more tools you put in the pain tool box, the better job you can do in treating the cancer patient,” he said. “But first the physician must try to assess the pain, which involves listening to our patients and believing them.”
The measurement of pain should take into account the patient’s report of the sensation of pain (by pain diaries and numerical scales), functional status at home, emotional state during office visits, and use of analgesics.
Opioids are the mainstays of treatment. Moderate pain is usually treated with codeine, hydrocodone(Drug information on hydrocodone), or oxy-codone, usually in combination with acetaminophen or aspirin(Drug information on aspirin). For severe pain, morphine, hydromorphone(Drug information on hydromorphone), levorphanol (Levo-Dromoran), methadone(Drug information on methadone), and fentanyl(Drug information on fentanyl) are customarily used.
Oxycodone(Drug information on oxycodone) has been re-formulated in a controlled-release, higher-dose preparation (Oxy-contin) that may cause fewer side effects, making it particularly useful, Dr. Brookoff said.
For continuous pain, a controlled-release opioid with dosing every 8 to 12 hours is highly recommended, once the patient has responded to the short-acting opioid and the side effects are manageable. “Percocet [5 mg oxycodone, 325 mg acetaminophen] may last only 2 hours for the patient in bad pain, although the package insert says 6 hours,” Dr. Brookoff said. “But with controlled-release opioids, about 90% of cancer patients can be made comfortable.”
Along with the long-acting opioids, patients should be supplied with a rescue drug for breakthrough pain. The consumption of the rescue drug should guide dosage adjustments of the primary analgesic. “But there is really no ceiling for opiates. You can usually increase the dose safely,” he pointed out.
Controlling Side Effects
Side effects of opioids can be troublesome but many will resolve with continued use of the drug. Nausea can be controlled with scheduled antiemetic doses. Itching can be relieved by antihistamines. Somnolence usually lessens over time or with decreased dosage. Constipation is essentially the only side effect to which the patient does not develop tolerance; therefore, the patient should be taught a good bowel regimen.
Once opioids have accomplished some measure of pain relief, other pain management approaches can be added to enhance the effect. Tricyclic antidepressants provide good augmentation, especially amitriptyline(Drug information on amitriptyline), imipramine(Drug information on imipramine), and doxepin.
Most of the pain relief of antidepressants is related to their effect on norepinephrine(Drug information on norepinephrine) rather than on serotonin; therefore, the tricyclics are a better choice than selective serotonin reuptake inhibitors (SSRIs) for cancer pain. For the depressed patient with chronic pain, the combination of an SSRI in the morning and a tricyclic at bedtime can be efficacious.
Neurogenic Pain Syndromes
Anticonvulsant and antiarrhythmic medications may help treat neuropathic pain. For a variety of neurogenic syndromes, mexiletine(Drug information on mexiletine) (Mexitil) can help, largely by stabilizing nerve cell membranes and by inhibiting the release of substance P in the central nervous system. Carbamazepine(Drug information on carbamazepine) or gabapentin(Drug information on gabapentin) (Neurontin) may also be useful in neurogenic pain syndromes, he said.
Benzodiazepines are more controversial for chronic pain, although alprazolam(Drug information on alprazolam) (Xanax) has shown analgesic properties independent of its sedative effects. The antihistamine hydroxyzine(Drug information on hydroxyzine), as well as clonidine(Drug information on clonidine) and propranolol(Drug information on propranolol), may also be useful adjuncts.
Psychological approaches to pain management, as well as spiritual counseling, should be made available to all patients, Dr. Brookoff said, because they can decrease the perception of pain and diminish pain-related distress.
