Cancer Pain : Opioids

by National Cancer Institute

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Opioids

Opioids are very effective for the relief of moderate to severe pain. Many patients with cancer pain, however, become tolerant to opioids during long-term therapy. Therefore, increasing doses may be needed to continue to relieve pain. A patient's tolerance of an opioid or physical dependence on it is not the same as addiction ( psychological dependence). Mistaken concerns about addiction can result in undertreating pain.

Types of Opioids

There are several types of opioids. Morphine is the most commonly used opioid in cancer pain management. Other commonly used opioids include hydromorphone, oxycodone, methadone, and fentanyl. The availability of several different opioids allows the doctor flexibility in prescribing a medication regimen that will meet individual patient needs.

Guidelines for Giving Opioids

Most patients with cancer pain will need to receive pain medication on a fixed schedule to manage the pain and prevent it from getting worse. The doctor will prescribe a dose of the opioid medication that can be taken as needed along with the regular fixed-schedule opioid to control pain that occurs between the scheduled doses. The amount of time between doses depends on which opioid the doctor prescribes. The correct dose is the amount of opioid that controls pain with the fewest side effects. The goal is to achieve a good balance between pain relief and side effects by gradually adjusting the dose. If opioid tolerance does occur, it can be overcome by increasing the dose or changing to another opioid, especially if higher doses are needed.

Occasionally, doses may need to be decreased or stopped. This may occur when patients become pain free because of cancer treatments such as nerve blocks or radiation therapy. The doctor may also decrease the dose when the patient experiences opioid-related sedation along with good pain control.

Medications for pain may be given in several ways. When the patient has a working stomach and intestines, the preferred method is by mouth, since medications given orally are convenient and usually inexpensive. When patients cannot take medications by mouth, other less invasive methods may be used, such as rectally or through medication patches placed on the skin. Intravenous methods are used only when simpler, less demanding, and less costly methods are inappropriate, ineffective, or unacceptable to the patient. Patient-controlled analgesia (PCA) pumps may be used to determine the opioid dose when starting opioid therapy. Once the pain is controlled, the doctor may prescribe regular opioid doses based on the amount the patient required when using the PCA pump. Intraspinal administration of opioids combined with a local anesthetic may be helpful for some patients who have uncontrollable pain.

Side Effects of Opioids

Patients should be watched closely for side effects of opioids. The most common side effects of opioids include nausea, sleepiness, and constipation. The doctor should discuss the side effects with patients before starting opioid treatment. Sleepiness and nausea are usually experienced when opioid treatment is started and tend to improve within a few days. Other side effects of opioid treatment include vomiting, difficulty in thinking clearly, problems with breathing, gradual overdose, and problems with sexual function.

Opioids slow down the muscle contractions and movement in the stomach and intestines resulting in hard stools. The key to effective prevention of constipation is to be sure the patient receives plenty of fluids to keep the stool soft. The doctor should prescribe a regular stool softener at the beginning of opioid treatment. If the patient does not respond to the stool softener, the doctor may prescribe additional laxatives.

Patients should talk to their doctor about side effects that become too bothersome or severe. Because there are differences between individual patients in the degree to which opioids may cause side effects, severe or continuing problems should be reported to the doctor. The doctor may decrease the dose of the opioid, switch to a different opioid, or switch the way the opioid is given (for example intravenous or injection rather than by mouth) to attempt to decrease the side effects. (Refer to the PDQ summaries on Gastrointestinal Complications 1, Nausea and Vomiting 2, Nutrition in Cancer Care 3, and Sexuality and Reproductive Issues 4 for more information about coping with these side effects.)

Drugs Used with Pain Medications

Other drugs may be given at the same time as the pain medication. This is done to increase the effectiveness of the pain medication, treat symptoms, and relieve specific types of pain. These drugs include antidepressants, anticonvulsants, local anesthetics, corticosteroids, bisphosphonates, and stimulants. There are great differences in how patients respond to these drugs. Side effects are common and should be reported to the doctor. Certain bisphosphonates given for bone pain are linked to a risk of bone loss after dental work. Patients taking bisphosphonates should check with their doctor before having dental work done.

Physical and Psychosocial Interventions

Noninvasive physical and psychological methods can be used along with drugs and other treatments to manage pain during all phases of cancer treatment. The effectiveness of the pain interventions depends on the patient's participation in treatment and his or her ability to tell the health care provider which methods work best to relieve pain.

Physical Interventions

Weakness, muscle wasting, and muscle/bone pain may be treated with heat (a hot pack or heating pad); cold (flexible ice packs); massage, pressure, and vibration (to improve relaxation); exercise (to strengthen weak muscles, loosen stiff joints, help restore coordination and balance, and strengthen the heart); changing the position of the patient; restricting the movement of painful areas or broken bones; stimulation; controlled low-voltage electrical stimulation; or acupuncture.

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