Chronic Pain: 2. The Case for Opiates
Daniel Brookoff; Hospital Practice, July 2000; 35(9); page 69.
Opioid medications allow us to treat chronic pain as aggressively as we would any pathogen, but we must first overcome ingrained misconceptions about patients' motivations for seeking treatment and about the addictive properties of the drugs. With controlled use, the newer sustained-release formulations give real hope for safe and sustained pain relief. Opioid analgesia is one of the most prolife therapies that we have to offer patients with cancer pain, and there is no reason to think that patients with other diseases are any less deserving of relief or that their pain is any less amenable to treatment..
Assessment of Pain
One of the main problems in assessing patients with chronic pain is that the physical examination and laboratory tests often do not provide the information necessary to gauge severity and assess outcomes. Various survey instruments and visual analogue scales that allow precise measurements of pain are available but used only rarely. Pain is generally assessed indirectly, which why it is so important to listen to--and believe--patients when they say that they are in pain.
Some physicians apparently have difficulty with that. Many of my patients with chronic pain have been refused treatment by previous caregivers who apparently believed that their pain was not real. Even after undergoing painful procedures and surgeries that failed to bring relief, some of these patients were labeled as drug-seekers when they continued to ask for help. They had to contend not only with the pain but also with feelings of frustration, isolation, and abandonment by those on whom they had most relied.
Treating Suffering as Well as Pain
The ultimate goal in treating chronic pain is for patients to reclaim control of their lives, and, to do that, they must be relieved of suffering as well as pain. Issues such as sadness over lost opportunities, guilt for being a burden to others, and feelings of inadequacy or abandonment contribute to the suffering of many patients with chronic pain and deserve attention. Ensuring that the patient obtains good psychological care is just as important as providing analgesic medications.
Unfortunately, many patients with chronic pain see referral to a psychologist as an invalidation of the physical nature of their pain. After years of hearing their disease or disorder referred to as functional or somatoform, they may need to be convinced that it is common for chronic pain to have an impact on many aspects of their lives, including their relationships with family and friends. In referring my patients for psychological assessment, I encourage them to recognize that psychological health is a vital aspect of well-being.
Initiation of Opioid Therapy
Opiate-naive patients are usually started with a short half-life drug (e.g., hydrocodone, hydromorphone, oxycodone, codeine, or morphine). Because of their rapid clearance, these drugs must be taken every three to four hours. For severe pain, the usual starting dose is 10 to 15 mg of hydrocodone or oxycodone, 2 to 4 mg of hydromorphone, 30 to 60 mg of codeine, or 15 to 30 mg of morphine.
The common strategy in treating chronic pain with opioid analgesics is to rely on "as-needed" intermittent dosing, but that does not usually provide sufficient coverage. As a result, the patient is subjected to periods of anxiety and pain that are not only unnecessary but also contribute to the patient's distrust of the physician's instructions.
The most feared side effect of opioid medications is respiratory depression. This does not occur, however, when the drugs are titrated against the patient's pain, probably because the pain signals activate respiratory centers in the brain that counterbalance depressive effects (Figure 1). In the event of an overdose, the activity of various brain centers is affected in an orderly, progressive fashion, with the cortex affected before the brainstem (see Figure 1, "Chronic Pain: 1. A New Disease?"). The patient will thus become unresponsive and obtunded before the opioid level is high enough to suppress the respiratory centers. One can be assured that a patient who is awake and complaining of pain is not in any imminent danger of respiratory depression.
If the source of pain is abruptly removed, an opioid dose that is well-tolerated can suddenly become sedating. That is clinically relevant when sending a patient taking opioids for an anesthetic or neurolytic procedure. Otherwise, respiratory depression rarely occurs. The main challenges of opioid therapy have to do with managing such common side effects as nausea, vomiting, itching, or somnolence. Although typically resolved within a few days to a week, they can be temporarily incapacitating.
Nausea occurs in 10% to 40% of patients treated with opioids. If they are getting good pain relief, there is no need to withdraw or reduce the medication. Antiemetics such as promethazine or prochlorperazine, both of which are available as pills and suppositories, are usually effective when used three to four times a day for a few days. If the nausea is primarily postprandial or related to bloating and early satiety, metoclopramide (10-20 mg tid) is the drug of choice. For some patients, antihistamines such as hydroxyzine are also useful as antiemetics. In refractory cases, low doses of haloperidol or olanzapine at bedtime can be very helpful.
Hives or itching may occur at the beginning of therapy with certain opioids as a result of their direct effect on mast cells. These problems are more commonly seen with the naturally occurring opiates (e.g., codeine or morphine) than with synthetics. Although hives and itching are not generally considered allergic reactions, relief can often be obtained with antihistamines. Patients with a positive history of such symptoms can be preemptively given a nonsedating antihistamine for the first week of opioid therapy.
The one common persistent side effect of opioid use is constipation, which is mediated by opioid receptors in the bowel. More than half of patients on sustained-release opioids experience constipation requiring specific therapy. It is important to get patients on a good bowel regimen as soon as possible and to teach them to adjust their bowel medications as needed. Many patients start out with a stool softener (e.g., docusate) and a mild fiber-based cathartic (e.g., senna). Osmotic laxatives such as milk of magnesia, polyethylene glycol, magnesium citrate, or lactulose will probably also be needed and may as well be started early. In contrast to stimulant laxatives, osmotic diuretics are safe and non-habit-forming. Patients have to find the dose that they can safely take nightly to produce a firm stool in the morning. Persistent constipation can be a serious problem requiring emergency treatment. I tell my patients to let me know if they have not had a bowel movement for at least three days. At that point, oral magnesium citrate or a sodium phosphate enema may be indicated.
Tolerance to Opioids
That most adverse side effects of opioids resolve on their own is an indication of growing tolerance with continued use. Tolerance can also be conferred by other factors. Severe pain, for example, allows patients to tolerate the sedative effects of opioids. Whether tolerance develops to the pain-relieving effects of opioids is a matter of controversy. Most of the data on opioid tolerance and physical dependence in humans involves subjects who were not in pain. Studies of patients with chronic pain who have taken opioids for a long time indicate that once the dose required for pain relief is established, it generally remains stable unless the underlying disease progresses.
Often, when a specific treatment or adjunctive therapy begins to work, patients who have been taking opioids for some time will begin to feel somnolent or sedated, or will not require rescue medications for long periods. That is the time to consider slowly tapering the long-acting pain medication.
Physical Dependence on Opioids
With long-term use of opioids, patients will experience physical symptoms (abdominal cramping, sweating, nausea, diarrhea, irritability) if the medication is abruptly withdrawn or the dose is markedly reduced. This type of physical dependence is not limited to opioids but can occur with other drugs such as antihypertensives and steroids. It is a medical condition and should not be taken as a sign of psychological or spiritual weakness. Withdrawal symptoms are easily avoided by using a tapering regimen when lowering the dose. This can nearly always be done, without discomfort, in an outpatient setting. When necessary, however, withdrawal symptoms can usually be relieved by slowing the taper or using small doses of clonidine or a benzodiazepine.
Treating Chronic Pain: Healing the Incurable
Opioids are usually reserved as a last resort for the treatment of pain, but it may be time to consider using them to rescue patients in severe pain who have not responded to disease-specific treatments or mild analgesics. Once some relief is achieved, adjuvant medications and nonpharmacologic or more aggressive approaches can be tried. In my experience, most treatments work better when there has been some initial pain relief.
Medical training places such a strong emphasis on curing disease that we sometimes do not pay as much attention as we should to patients who cannot be cured. This is particularly true of patients whose condition has not improved despite years of traditional therapy. Even if they cannot be cured, however, they can be healed. There may be no effective treatment for the underlying illness, but there is almost always an effective treatment for the pain.
One thing that I learned in medical school that is still true today is that it is very easy to become judgmental when faced with a patient whose suffering is difficult to understand. Unfounded assumptions are harmful and can rob a suffering patient of hope. With our current knowledge of how pain is generated and alleviated, it is both disrespectful to the patient and a breach of medical ethics not to provide what is clearly needed. When a patient in chronic pain seeks our help, the first question we should ask ourselves is not whether we should provide an analgesic but whether we can in good conscience leave that person in pain. To quote Marcia Angell, "Few things a doctor does are more important than relieving pain. . . pain is soul destroying. No patient should have to endure intense pain unnecessarily. The quality of mercy is essential to the practice of medicine; here, of all places, it should not be strained."
The Role of Opioids in Cancer Pain Management - M. Fukshansky, M. Are, A.W. Burton; Pain Practice, 5(1), page 43; 2005
Principles of Opioid Management of Pain - Joel Hochman and members of NFTP and PRN listServ; Summer 2006