Coanalgesics are a varied group of medications that can provide additive pain relief when they are added to nonsteroidal anti-inflammatory drugs (NSAIDs) or opioids (American Pain Society [APS], 2008). They can have independent analgesic activity for some painful complaints, and they can counteract select adverse effects of analgesics (APS, 2008). This group of medications was developed to treat a wide variety of conditions, such as seizures or muscle spasms, and was originally intended for symptom control of the various conditions. However, in many cases, patients reported pain relief when these medications were prescribed for them, leading health care providers to consider their additional application for pain relief.
Medications that are considered to be coanalgesic for pain management include the following:
■ Muscle relaxants
■ Topical agents
■ A^-methyl-D-aspartate (NMDA) receptor blockers
■ Alpha-2 adrenergic agonists
■ Antispasmodic agents
Although these medications were not developed for pain control, they have been used for adjunct pain relief and are found to be effective. For some medications, such as gabapentin, pregabalin, and duloxetine, the unapproved use for pain management became so prevalent that the manufacturers sought and received Food and Drug Administration (FDA) approval for the pain management indication. Many patients with neuropathic pain benefit greatly from the addition of one or more of these agents to help decrease pain. Because many patients with chronic pain are depressed, the use of antidepressants has improved the quality of pain relief and enhanced sleep for many of these patients.
When the World Health Organization (WHO) ladder was developed with medication choices for pain management (see Chapter 3), the focus was on dividing different types of opioid medications. However, the ladder also includes adjuvant medications, or coanalgesics, on each step of the ladder. The broad classes of these medications are listed on the ladder steps, but no specific medications are listed (Dalton & Youngblood, 2000).
Trying to group these medications into a single class, coanalge-sics, is difficult. They all have such different mechanisms of action and application. These medications can enhance the effect of opioids or other medication that are being used for pain relief, or they can stand alone as single agent pain relievers (APS, 2008). Some of the benefits of using these medications include the following:
■ Enhance pain relief
■ Allow lower doses of opioids (opioid sparing effect)
■ Manage refractory pain
■ Reduce side effects of opioids related to opioid sparing (APS, 2008) Commonly used coanalgesics include the following:
■ ibuprofen or naproxen
■ gabapentin and pregabalin
■ Topical lidocaine and capsaicin
■ cyclobenzaprine, carisoprodol, metaxalone
No matter which medication is selected or combined with another pain medication, each patient's comorbidities and related treatments need to be assessed and evaluated before adding a new medication to the pain management medication regimen. The following sections of the chapter will discuss different classes of coanalgesic that can be used for additional pain relief.
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