30 Dec Medications used for Chronic Pain
Chronic pain affects more Americans than cancer, heart disease, and diabetes combined. According to the National Center for Health Statistics, 75 million Americans (1 in every 4) has some type of pain during the past week. In addition, chronic pain is the most common reason for long-term disability. Different types of medications are used to treat different kinds of pain. Each medication has a unique mechanism of action and side effects. Sometimes, the pain management specialist uses a combination of medicines to treat chronic pain.
Acetaminophen is the drug of choice for treating pain related to osteoarthritis. This medication works by inhibition of cyclooxygenase (COX) enzymes, with an effect on COX-2. In addition, inhibition of these enzymes prevents metabolism of arachidonic acid to prostaglandins, which is a byproduct converted to pro-inflammatory compounds. Taking too much Tylenol could damage your liver, especially if you drink alcohol. It is important to take this drug as prescribed and avoid alcohol when using it.
Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)
Aspirin, ibuprofen, naproxen, and ketoprofen are commonly prescribed nonsteroidal anti-inflammatory drugs. These drugs work by fighting inflammation and offering general pain relief. The mechanism of action of NSAIDs is the non-selective, reversible inhibition of the COX1 and COX2. Because NSAIDs can cause stomach problems, they increase the risk of bleeding.
Also called opioids, narcotic analgesics are used to treat chronic pain. These drugs work by binding to opioid receptors. Molecular signaling activates the receptors, which are present in the brainstem, thalamus, and limbic system. Because they cause drowsiness and impaired judgment, you should not drive or operate heavy machinery while taking these agents. Because of the risk for psychological and physical dependence, narcotic pain medicines are no often prescribed. Opioids can lead to constipation, so you should drink plenty of water and increase intake of fiber while taking them.
Antidepressants are used as adjuvant analgesics. While not formulated as pain medicines, they can help with the treatment of some types of chronic pan. Tricyclic antidepressants (amitriptyline and nortriptyline) and selective serotonin reuptake inhibitors (SSRIs) (Prozac, Paxil, Celexa) are the most commonly used agents. Side effects to these drugs include dizziness, drowsiness, constipation, weight gain/loss, and increased/decreased appetite.
For neuropathic pain, such as trigeminal neuralgia or diabetic neuropathy, pregabalin and gabapentin are often prescribed. These drugs are also adjuvant analgesics. These drugs are antagonists of voltage gated calcium 2 channels. They bond to alpha-2-delta to produce analgesic actions. Studies show that these drugs treat hyperalgesia and allodynia, and are effective for diabetic neuropathy, fibromyalgia, and post-herpetic neuralgia. Anticonvulsant side effects include constipation, drowsiness, and dizziness.
Topical analgesics are pain medications applied directly to the skin. These drugs are available as patches, lotions, and creams. While a few topical pain medicines are available over-the-counter, some require a doctor’s prescription. Aspercreme (trolamine salicylate), Lidoderm patches (lidocaine), and Zostrix (capsaicin) are examples of topical analgesics. Capsaicin is a potent exogenous agonist for certain receptors related to pain. Lidocaine works by numbing the region, and trolamine salicylate has anti-inflammatory properties. Side effects to topical agents include skin burning, rash, itching, and redness of the skin.
Some patients with back muscle spasms are prescribed muscle relaxants. Commonly used agents are Flexiril, Zanaflex, and Baclofen. These drugs are to be used with caution, as relaxing muscles can lead to further back injury.
American Chronic Pain Association. APCA Medications and Chronic Pain: Supplement 2007. Retrieved from: http://www.theacpa.org/documents/ACPA%20Meds%202007%20Final.pdf
Anand P & Bley K (2011). Topical capsaicin for pain management: therapeutic potential and mechanisms of action of the new high-concentration capsaicin 8% patch. Br J Anesth, 107(4), 490-502.
National Institute of Health (2016). Pain management. Retrieved from: https://report.nih.gov/nihfactsheets/ViewFactSheet.aspx?csid=57
Verma V, Singh N, & Jaggi AS (2014). Pregabalin in Neuropathic Pain: Evidences and Possible Mechanisms. Curr Neuropharmacol, 12(1), 44-56.