Pain Medications and Cancer

Pain Medications Cancer

Reviewed By:
Mark Oren, M.D., FACP


Analgesics are a class of medications used to block pain. They either stop pain signals from going to the brain or alter the brain’s interpretation of those signals. In both cases, analgesics prevent the brain from processing pain signals, yet do not rely on anesthesia or loss of consciousness to achieve their pain-killing effect.

Analgesics are frequently used to control pain in cancer patients, particularly those with advanced forms of the disease. There are two primary types of analgesics:

  • Non-narcotic analgesics. Also known as non-opioids, these drugs are milder forms of painkillers that include acetaminophen, the most commonly used over-the-counter non-narcotic analgesic.  There are other drugs that are not technically part of the analgesic family, but are nonetheless considered analgesics in practice. These include aspirin and ibuprofen.
  • Narcotic analgesics. Also known as opioids, these drugs are stronger analgesics that are used when pain signals are too severe to be controlled by non-narcotic analgesics. Examples include morphine and codeine and these analgesics are available only by prescription.

In most cases, patients who experience pain can have their discomfort relieved by an analgesic or a combination of analgesics. Patients may need to try different combinations before discovering a therapy that works well for them.

About pain medications & cancer

Analgesics are medications that prevent the body from feeling pain. They do this by either stopping pain signals from going to the brain or altering the brain’s interpretation of those signals. Analgesics are often used to alleviate pain in cancer patients.

Cancer pain is either acute or chronic. Pain is a signal to the body that tissue is being injured in some way. It is often severe, but usually lasts a relatively short period of time. On the other hand, chronic pain (also referred to as “persistent pain”) lasts for longer periods of time. It may range from mild to severe. Chronic pain is sometimes marked by episodes of breakthrough pain, which is a moderate to severe pain that is felt for a short period of time. This may happen several times a day in some cases, and can be felt even by patients whose pain medication is usually effective. Cancer pain may be caused by the disease itself or its various treatments. It is important to note that not all cancer patients will experience pain and the actual pain can vary significantly.

There are two forms of analgesic pain medications used to treat cancer pain: narcotic and non-narcotic. Both types may be used by cancer patients, particularly when the disease is advanced and causing significant pain. Some drugs that are not technically part of the analgesic family are nonetheless treated as such for the purpose of therapy. This includes aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs).

Pain medications can be administered in several ways. Contrary to popular belief, analgesics are administered by injection only in relatively rare instances, and are more typically administered in ways that patients may find less uncomfortable. The following methods are used to deliver the medicine:

  • Oral. Delivered in liquid or pill form.

  • Suppository. Medicine that is inserted into the rectum in a solid form. It is absorbed into the body as the suppository dissolves.
  • Continuous infusion

    • Pump. Known as patient-controlled analgesia (PCA), it allows a patient to push a button that delivers a preset dose of medication.

    • Skin patch. A bandage-like patch applied to the skin that gradually and continuously releases medicine over a period of time. Newer transdermal patches may use a weak electrical current to release the medication.
  • Injection into a vein

    • Subcutaneous. Needle placed just under the skin.

    • Intravenous. Needle placed into a vein.

    • Intrathecal. Needle placed into fluid around the spinal cord.

    • Epidural. Needle placed into space around the spinal cord.

Patients who have chronic pain should receive pain medications regularly according to a planned schedule. This schedule is recommended even if it requires waking the patient. The drugs are most effective if patients do not experience any pain before the next dose is administered. Patients should consult their physician if their treatment regime is not properly controlling their pain.

Types and differences of pain medications

Pain medications are available in one of two primary forms:

  • Non-narcotic analgesics. Milder forms of the painkiller that include acetaminophen, the most commonly used over-the-counter (OTC) non-narcotic analgesic. These drugs work by preventing the production of prostaglandins, a substance that sensitizes pain receptors as a means of stimulating pain and inflammation. By interfering with the role of prostaglandins, a patient’s perception of pain is reduced.  Acetaminophen is found in hundreds of OTC medications. Aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs) are not technically analgesics. However, because they share many of the same properties, they are treated as such for the purpose of therapy. Examples of non-narcotic analgesics include:

    • Acetaminophen
    • Aspirin
    • Magnesium salicylate
    • Ibuprofen

  • Narcotic analgesics (opioids). Stronger analgesics that are used when pain signals are too severe to be controlled by non-narcotic analgesics. These drugs work on the central nervous system to relieve pain. In some cases, they are also given just before or during surgery to help increase the effectiveness of anesthesia. Examples of narcotic analgesics include morphine and codeine. These drugs are available only by physician prescription and the dosage level is closely controlled. The treating physician will determine the lowest dosage level that will relieve the patient’s pain. With monitoring, the dosage can be adjusted as necessary.

    Narcotic analgesics include the following:

    • Anileridine
    • Buprenorphine
    • Butorphanol
    • Codeine
    • Hydrocodone
    • Hydromorphone
    • Levorphanol
    • Meperidine
    • Methadone
    • Morphine
    • Nalbuphine
    • Opium injection
    • Oxycodone
    • Oxymorphone
    • Pentazocine
    • Propoxyphene

      In some cases, a narcotic analgesic may be used in combination with a non-narcotic analgesic to increase the painkilling effect. Such combinations may also have the benefit of requiring a lower amount of each drug to be effective.

Conditions of concern with pain medications

Certain medical conditions may affect the use of individual analgesics and analgesic combinations. Patients should inform their physician if they have any of the following conditions:

  • Anemia
  • Asthma, allergies and history of nasal polyps
  • Brain disease or head injury
  • Colitis
  • Emotional problems or mental illness
  • Emphysema or other chronic lung disease
  • Enlarged prostate or problems with urination
  • Gallbladder disease or gallstones
  • Gout
  • Heart disease
  • Hemophilia or other bleeding problems
  • History of alcohol and/or other drug abuse
  • History of convulsions (seizures)
  • Kidney or liver disease
  • Overactive or underactive thyroid
  • Stomach ulcer or other stomach problems
  • Vitamin K deficiency

The Food and Drug Administration is considering label changes for some painkillers, including acetaminophen and nonsteroidal anti-inflammatory drugs (NSAIDs). Prolonged use of acetaminophen may cause liver damage, especially when taken in large amounts or while drinking alcohol. NSAID warnings may be revised in further detail to describe potential gastrointestinal bleeding with their use. In addition, cancer patients who undergo chemotherapy are usually prohibited from taking NSAIDs because they can slow blood clotting. The use of analgesics will be determined by the physicians on the patient’s cancer care team.

Potential side effects of pain medications

When pain medications are used in moderation and according to a physician’s orders, they can provide comprehensive relief from cancer pain. However, these drugs can have some side effects, especially when taken in large doses or for extended periods of time.

Over time, a patient can build up a tolerance to narcotic analgesics. This means that the patient will need to take more of the drug to obtain the same pain-relieving effect. In addition, narcotic analgesics can become habit-forming and cause mental or physical dependence in the patient. This dependence can be difficult to eliminate and may result in withdrawal symptoms when the drug is no longer provided to the patient.

Patients who stop taking narcotic analgesics may find that their body goes through a period of adjustment as it withdraws from the drug. For this reason, patients should never stop taking these analgesics unless instructed by their physician. Side effects associated with withdrawal from narcotic analgesics include:

  • Body aches
  • Gastrointestinal problems including stomach cramps, nausea, vomiting or diarrhea
  • Fever with shivering, trembling or goose bumps
  • Increased sweating
  • Loss of appetite
  • Nervousness, restlessness or irritability
  • Runny nose or sneezing
  • Shivering or trembling
  • Stomach cramps
  • Trouble sleeping
  • Weakness

Although non-narcotic analgesics do not cause dependence, they may trigger other side effects in some patients, especially if taken in large doses. For example, large doses of non–narcotic analgesics can cause internal bleeding or damage to the liver.

There have been a number of studies examining the role of analgesics in both the prevention and cause of certain cancers. In particular, analgesics have been studied in relation to prostate cancer and breast cancer. To date, no conclusive evidence exists to connect analgesics with increased risk for or prevention of cancer.

Drug or other interactions

Before using pain medications, cancer patients should inform their physician if they have ever had an allergic reaction to any narcotic analgesic, acetaminophen, aspirin or other salicylates (such as methyl salicylate). Patients should also tell their physician if they have ever had a reaction to any of the following drugs:

  • Diclofenac
  • Diflunisal
  • Etodolac
  • Fenoprofen
  • Floctafenine
  • Flurbiprofen, oral
  • Indomethacin
  • Ketoprofen
  • Ketorolac
  • Meclofenamate
  • Mefenamic acid
  • Nabumetone
  • Naproxen
  • Oxaprozin
  • Oxyphenbutazone
  • Phenylbutazone
  • Piroxicam
  • Sulindac
  • Suprofen
  • Tenoxicam
  • Tiaprofenic acid
  • Tolmetin
  • Zomepirac

Use of prescription and non-prescription analgesics that contain a narcotic, aspirin or other salicylate may cause an overdose when combined with analgesics used to treat pain. Other medications that can impact treatment with analgesics include:

  • Anticoagulants
  • Anti-inflammatories
  • Antidepressants
  • Central nervous system depressants
  • Diarrhea medicine
  • Oral anti-diabetics
  • Urinary alkalizers

Patients taking analgesics should consult their physicians before taking additional prescriptions, over-the-counter medications, nutritional supplements or herbal medications. Patients should also report any allergies to other substances such as foods, preservatives or dyes. Alcohol and other central nervous system (CNS) depressants should not be used with analgesics. Examples of CNS depressants include:

  • Anesthetics
  • Antihistamines or other hay fever or allergy medications
  • Anti-seizure medications
  • Barbiturates
  • Cold medications
  • Muscle relaxants
  • Prescription pain medications
  • Sedatives, tranquilizers or sleeping pills

Other medications that may adversely interact with analgesics include:

  • Carbamazepine
  • Phenobarbital
  • Phenytoin
  • Rifampin
  • Sulfinpyrazone
  • Vitamin supplements

Symptoms of analgesic overdose

Symptoms of overdose can be similar to the medication’s side effects, but are usually more severe. An overdose of narcotic or non-narcotic pain medications is potentially life-threatening. Patients who are using analgesics and exhibit these symptoms should contact their physicians immediately:

  • Cold, clammy skin
  • Convulsions (seizures)
  • Low blood pressure (hypotension)
  • Ringing or buzzing in the ears or hearing loss
  • Severe anxiety, nervousness or restlessness
  • Severe dizziness or confusion
  • Severe drowsiness
  • Severe weakness
  • Shortness of breath or breathing problems

Pregnancy use issues

Women who are pregnant should approach using pain medications with caution. For example, while studies in humans have not conclusively shown that aspirin can cause birth defects, they have been found to cause birth defects in animal studies. There have been reports of low birth weight and possibly death in newborn human babies whose mothers took large amounts of aspirin late in pregnancy. Women should not take aspirin during the last three months of pregnancy without a physician’s approval. Too much aspirin late in pregnancy has also been associated with:

  • Bleeding problems in the fetus before or during delivery
  • Increase in length of pregnancy
  • Prolonged labor
  • Severe bleeding in the mother before, during or after delivery

Narcotic analgesics have been shown to produce birth defects in animals, but this has not been confirmed in people. However, mothers who use too much of a narcotic during pregnancy risk creating a drug dependency in the fetus. The newborn baby may suffer withdrawal symptoms. Narcotic analgesics can also cause breathing problems in the newborn baby if the mother takes the medication just prior to or during delivery.

Some analgesics (such as acetaminophen, aspirin, caffeine, codeine, butorphanol, meperidine, morphine, opium and propoxyphene) have been shown to pass into breast milk. It is not known if others (such as dihydrocodeine, hydrocodone, oxycodone and pentazocine) pass into breast milk.

Child use issues with pain medications

Children and teens with fever or other viral infections (especially flu or chickenpox) should not take aspirin because it may cause a serious illness known as Reye’s syndrome. In addition, children may be more vulnerable to the side effects of aspirin than adults.

Children who use narcotic analgesics may experience breathing problems, or unusual excitability or restlessness.

Elderly use issues

Elderly patients may be more susceptible to side effects associated with analgesics, particularly breathing problems.

Questions for your doctor

Preparing questions in advance can help patients have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions about pain medications:

  1. What type of analgesic is best for my pain?

  2. How will I receive the analgesic?

  3. Do I have any medical conditions that prevent me from taking analgesics?

  4. Will analgesics interfere with any of my cancer treatments?

  5. Are there medications I should not take while I am on this analgesic?

  6. What are the risks associated with this drug?

  7. Will the analgesic cause any serious side effects?

  8. What steps will be taken if my pain does not improve with this drug?

  9. How will I know if I am becoming dependent on a drug?

  10. What will be done if I do become dependent on a narcotic drug?
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