Management with Drugs
Basic Principles of Cancer Pain Management
Acetaminophen and NSAIDs
Opioids
Types of Opioids
Guidelines for Giving Opioids
Side Effects of Opioids
Drugs Used with Pain Medications
Basic Principles of Cancer Pain Management
The World Health Organization developed a 3-step approach for pain
management based on the severity of the pain:
- For mild to moderate pain, the doctor may prescribe a Step 1 pain medication such as aspirin, acetaminophen, or a nonsteroidal
anti-inflammatory drug (NSAID). Patients should be monitored for side
effects, especially those caused by NSAIDs, such as kidney, heart and blood vessel, or stomach and intestinal problems.
- When pain lasts or increases, the doctor may change the prescription to a
Step 2 or Step 3 pain medication. Most patients with cancer -related pain
will need a Step 2 or Step 3 medication. The doctor may skip Step 1
medications if the patient initially has moderate to severe pain.
- At each step, the doctor may prescribe additional drugs or treatments (for
example, radiation therapy).
- The patient should take doses regularly, "by mouth, by the clock" (at
scheduled times), to maintain a constant level of the drug in the body;
this will help prevent recurrence of pain. If the patient is unable to
swallow, the drugs are given by other routes (for example, by infusion or injection).
- The doctor may prescribe additional doses of drug that can be taken as
needed for pain that occurs between scheduled doses of drug.
- The doctor will adjust the pain medication regimen for each patient's
individual circumstances and physical condition.
Acetaminophen and NSAIDs
NSAIDs are effective for relief of mild pain. They may be given with opioids for the relief of moderate to severe pain. Acetaminophen also relieves pain,
although it does not have the anti-inflammatory effect that aspirin and NSAIDs
do. Patients, especially older patients, who are taking acetaminophen or
NSAIDs should be closely monitored for side effects.
Aspirin should not be given to children to treat pain.
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, fentanyl, and tramadol. 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. Unless there are problems such as a blocked bowel or diarrhea, patients will usually be given a regimen to follow to prevent constipation and information on how to manage bowel health while taking opioids.
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, Nausea and Vomiting, Nutrition in Cancer Care,
and Sexuality and Reproductive Issues 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.
The use of bisphosphonates may cause severe and sometimes disabling pain in the bones, joints, and/or muscles. This pain may develop after these drugs are used for days, months, or years, as compared with the fever, chills, and discomfort that may occur when intravenous bisphosphonates are first given. If severe muscle or bone pain develops, bisphosphonate therapy may need to be stopped.
The use of bisphosphonates is also linked to the risk of bisphosphonate-associated osteonecrosis (BON). See the PDQ summary on Oral Complications of Chemotherapy and Head/Neck Radiation for more information on BON.
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