Because the pain process is complex, there are many types of pain drugs that provide relief by acting through a variety of physiological mechanisms. Thus, effective medication for nerve pain will likely have a different mechanism of action than arthritis pain medication.
- Nonsteroidal anti-inflammatory drugs (NSAIDs) act on substances in the body that can cause inflammation, pain, and fever.
- Corticosteroids are often administered as an injection at the site of musculoskeletal injuries. They exert powerful anti-inflammatory effects. They can also be taken orally to relieve pain from, for example, arthritis.
- Acetaminophen increases the body’s pain threshold, but it has little effect on inflammation.
- Opioids, also known as narcotic analgesics, modify pain messages in the brain.
- Muscle relaxants reduce pain from tense muscle groups, most likely through sedative action in the central nervous system.
- Anti-anxiety drugs work on pain in three ways: they reduce anxiety, they relax muscles, and they help patients cope with discomfort.
- Some antidepressants, particularly the tricyclics, may reduce pain transmission through the spinal cord.
- Some anticonvulsant drugs also relieve the pain of neuropathies, possibly by stabilizing nerve cells.
Pain medications can be broadly classified into two categories: prescription and nonprescription. In the latter category are several mild anti-inflammatory drugs (ibuprofen, naproxen), as well as acetaminophen. These are mainly meant for use with short-term, acute pain — menstrual cramps, tension headaches, minor sprains — what are known colloquially as “everyday aches and pains.”
Over-the-counter pain relievers, especially acetaminophen, are also sometimes used to treat chronic pain, such as that seen in arthritis. These drugs also lower fever and are often used for that purpose.
The prescription arsenal against pain is extensive. It also includes some NSAIDs more powerful than their over-the-counter cousins as well as opioid analgesics. And then there are some unconventional analgesics – drugs which were not originally developed as pain-relievers, but which were found to have pain-relieving properties in certain conditions. For example, fibromyalgia pain medications include an antiseizure drug and an antidepressant (duloxetine hydrochloride [Cymbalta]).
One major difference between anti-inflammatories and opioid analgesics is that the former have a “ceiling effect” — that is, continuous dose escalation does not provide concomitant escalation in pain relief. One reason opioids are so useful in the treatment of chronic pain is that as tolerance to a dose develops, the dose can be raised. In fact, there is no limit to how high opioid dosing can go -– keeping in mind that higher doses can be associated with unpleasant and/or even dangerous side effects.