Primer on Pain Medications

The sensation of pain is the body's way of alerting us that something harmful is happening. Pain signals are sent from the site of the problem to the brain via the spinal cord. Pain medications, or "analgesics," block the pain signals from reaching the brain; they do not usually treat the problem causing the pain.

Opioids

There are several different classes of pain medications. Opioids (narcotics) are the most commonly used pain medication for BMT patients. Opioids are all chemical relatives of morphine and include morphine, codeine, hydromorphone (Dilaudid), oxycodone (Roxicodone), meperidine (Demerol), fentanyl (Sublimaze) and methadone (Dolophine). They can be taken in pill or liquid form or through an injection into a vein, muscle, spinal cord or under the skin. They may also be administered via a skin patch.

In most cases opioids are administered to BMT patients via an injection into their Hickman-type catheter, a painless method of injecting drugs directly into the patient's bloodstream. Injecting opioids directly into the bloodstream is preferable to administering the drug orally, since two-thirds of the drug dosage is lost in the liver before reaching the bloodstream when opioids are taken orally.

Opioids are commonly used to treat the pain associated with mouth sores (mucositis), graft-versus-host disease and tumors. They're also used to control discomfort following surgical procedures such as lung biopsies, changing of Hickman-type catheters or to calm patients in advance of uncomfortable procedures such as bone marrow aspirates.

Side effects of opioids vary according to the medication being used. Approximately 20 percent of patients who take morphine experience some initial itching, nausea and/or vomiting. These side effects are not allergies to the drug and usually diminish with continued use. Medications such as Compazine, Torecan, Reglan, Ativan or droperidol are often used in conjunction with morphine to control the nausea and vomiting, and Benadryl or Atarax helps control the itching.

Meperidine (Demerol) is a weaker opioid than morphine and provides only short-term relief. While less useful as a pain medication, it's often used to prevent or relieve the chills and shaking that can occur when amphotericin (an anti-fungal medication) or platelet transfusions are given. At higher dosages and with prolonged use, meperidine can cause agitation, irritability and/or convulsions.

All opioids can cause constipation. Laxatives such as Ducolax or Senekot that stimulate contractions of the bowel are often used to relieve this problem. Laxatives such as Colace that merely soften the stool but don't stimulate contractions in the bowel are less effective.

Opioids can also cause temporary confusion, hallucinations or depression. This can be resolved by reducing the dosage.

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)

Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) are a second type of pain medication sometimes used to treat BMT patients. NSAIDs provide pain relief from tissue injury as well as nerve damage. However, they are usually not the pain medication of choice for BMT patients due to a variety of significant side effects. NSAIDs can interfere with normal platelet production, cause gastric irritation and bleeding and, in high dosages, may be toxic to the liver and kidneys. Motrin and aspirin are two examples of NSAIDs.

Certain problems, such as cyclosporine-induced headaches, are sometimes better managed by NSAIDs than opioids. Use of NSAIDs is only appropriate after a patient's bone marrow has engrafted, and then only under close supervision by a doctor and pharmacist.

Tricyclic Anti-Depressants

Anti-depressants historically have been used to treat depression but can be effective in treating pain in BMT patients as well. The dosage of anti-depressant required to provide pain relief is generally lower than the dosage required to treat depression. However, it may take several days before the anti-depressant is effective.

Anti-depressants are believed to suppress the normal activity of bone marrow, and thus are seldom used during transplant. Other possible side effects include sedation, changes in blood pressure, hallucinations or disorientation, restlessness, muscle spasms, blurred vision, nausea, vomiting, itching and constipation. These side effects are usually only seen at high dosages.

Anti-Convulsants

Anti-convulsants such as clonazepam (Klonopin) and phenytoin (Dilantin) are sometimes useful in relieving pain caused by nerve irritation. Anti-convulsants can cause sleepiness, reduced coordination, low blood pressure, involuntary eye movements or confusion.

Other Pain Medications

Acetaminophen (Tylenol) is commonly used to treat minor pain experienced by BMT patients. Acetaminophen is an NSAID, but unlike aspirin, it does not interfere with blood clotting and is therefore safe in the BMT setting. It can, however, mask a fever and is often discontinued if the presence of fever is suspected and monitoring the patient's temperature is important.

Local anesthetics such as lidocaine are often used to numb areas prior to uncomfortable procedures such as bone marrow aspirates. In the United States, they are usually injected into the skin and tissues around the area where the procedure will take place. In Europe, the anesthesia is often applied via a skin patch known as Eutectic Mixture of Local Anesthetics (EMLA). EMLA will soon be available in the United States.

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