Pain keeps us out of trouble. When it isn't busy preventing injury, it's lessening it or reminding us to let it heal. But sometimes pain becomes a nuisance, like an alarm bell that keeps clanging away long after the fire dies out.
One way to mute this din is to cut the signal off at the source. That's ibuprofen's party trick: It stops banged-up cells from ginning up or sending out more prostaglandin. Ibuprofen belongs to a whole category of pain medicines called nonsteroidal anti-inflammatory drugs, or NSAIDs. NSAIDs also relieve the swelling and inflammation that can cause pain. NSAIDs include aspirin and naproxen sodium (aka Aleve) [sources: AHFS; McNicol].
Other analgesics ignore the pain signal but muffle the bell. Acetaminophen, aka Tylenol, works in the brain and central nervous system to deaden pain, although researchers do not fully grasp how it works [sources: AHFS; McNicol].
Both NSAIDs and acetaminophen belong to a category called non-opioid analgesics. Most non-opioid analgesics work by inhibiting cyclooxygenase (COX) or COX-2 enzymes, which kick off the process of converting arachidonic fatty acid found in cell walls into the prostaglandins that activate pain nerves. No prostaglandin means no nociceptor activation and therefore no pain [sources: AHFS; McNicol; Ricciotti and FitzGerald].
For more severe short-term pain, as after an operation, or long-term pain, many doctors turn to opioids. Opioid drugs plug into an existing network of receptors located in your brain, spinal cord and body. Under normal conditions, this system works with your body's naturally produced opioids to control all kinds of processes, including pain. Natural opiates, like morphine and codeine, as well as synthetic opioids, mimic the structure of these naturally occurring neurotransmitters and hijack the system. Like spies who knock out the guards and then man the gates, they keep out other signals, including those associated with pain. They also plug into the body's reward system, producing potentially addictive euphoric effects [sources: Encyclopaedia Britannica; Fine and Portenoy; NAABT].
More intense medical procedures, like surgery, involve general, regional or local anesthesia. General anesthesia involves a mixture of drugs that calms patients, keeps them unconscious, lessens or relieves their pain, relaxes their muscles or blocks their memories from forming. Regional anesthesia locks down sensation from a whole section of the body, e.g., from the waist down, while local anesthesia numbs a small portion, like a foot or spot of skin. This might seem highly localized but, again, the painkiller doesn't know where you hurt -- the person applying it does [sources: Encyclopaedia Britannica; Mayo Clinic].
Author's Note: How do painkillers know where you hurt?
It's strange that we dismiss other people's emotional and physical pain by telling them "it's all in your head." All pain is in our heads, but then so is everything else. What we consider as vision and sound amount to no more than mental interpretations of nerve signals transmitted by specialized tissues reacting to particular wavelengths of radiation. Of course, that's assuming that those signals are real and not imagined. Indeed, in the Cartesian sense, the only experience we can be confident of is that we think. For all we know, we are just brains in jars, or assemblages of thought free-floating in space.
- American Society of Health-System Pharmacists. "Acetaminophen." Jan. 15, 2014. (June 11, 2014)http://www.nlm.nih.gov/medlineplus/druginfo/meds/a681004.html
- American Society of Health-System Pharmacists. "Ibuprofen." May 27, 2014. (June 11, 2014) http://www.nlm.nih.gov/medlineplus/druginfo/meds/a682159.html
- The Cleveland Clinic Foundation. "Psychogenic Pain." 2009. (June 12, 2014) http://my.clevelandclinic.org/services/pain_management/hic_psychogenic_pain.aspx
- Craig, A. D. "Mapping Pain in the Brain." The Wellcome Trust. (June 11, 2014) http://www.wellcome.ac.uk/en/pain/microsite/science2.html
- Dafny, Nachum. "Pain Modulation." Neuroscience Online. University of Texas Medical School. (June 10, 2014) http://neuroscience.uth.tmc.edu/s2/chapter08.html
- Encyclopaedia Britannica. "Analgesic." (June 6, 2014) http://www.britannica.com/EBchecked/topic/22403/analgesic
- Encyclopaedia Britannica. "Anesthetic." (June 6, 2014) http://www.britannica.com/EBchecked/topic/24338/anesthetic
- Encyclopaedia Britannica. "Morphine." (June 6, 2014) http://www.britannica.com/EBchecked/topic/392758/morphine
- Encyclopaedia Britannica. "Pain." (June 6, 2014) http://www.britannica.com/EBchecked/topic/438450/pain
- Fine, P. and R. K. Portenoy. "Opioid Analgesia." New York: McGraw Hill. 2004. (June 6, 2014) http://www.stoppain.org/pcd/content/forpros/opioidbook.asp
- Mayo Clinic. "Anesthetic, General (Inhalation Route, Parenteral Route, Rectal Route)." Feb. 1, 2014. (June 11, 2014) http://www.mayoclinic.org/drugs-supplements/anesthetic-general-inhalation-route-parenteral-route-rectal-route/description/drg-20069931
- McNicol, Ewan. "How Does Acetaminophen Relieve Pain?" Tufts Journal. April 2008. (June 10, 2014) http://tuftsjournal.tufts.edu/2008/04/professor/01/
- Messlinger, K. "What is a Nociceptor?" The Anesthetist. Vol. 46, no. 2. Page 142. Feb. 1997. (June 10, 2014) http://www.ncbi.nlm.nih.gov/pubmed/9133176
- National Alliance of Advocates for Buprenorphine Treatment. "How Do Opioids Work in the Brain?" December 2008. (June 10, 2014) http://www.naabt.org/faq_answers.cfm?ID=6
- Purves, Dale, et al., eds. "Neuroscience." 2nd Ed. Sunderland (MA): Sinauer Associates. 2001.
- Ricciotti, Emanuela, and Garret FitzGerald. "Prostaglandins and Inflammation." Arteriosclerosis, Thrombosis and Vascular Biology. Vol. 31, no. 5. Page 986. May 2011 (June 11, 2014) http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3081099/
- Wood, John N., Simon Beggs and Liam J. Drew. "Sensing Damage." The Wellcome Trust. (June 10, 2014) http://www.wellcome.ac.uk/en/pain/microsite/science1.html
- Woolf C. J. and Q. Ma. "Nociceptors -- Noxious Stimulus Detectors." Neuron. Vol. 55, no. 3. Page 353. Aug. 2, 2007. (June 11, 2014) http://www.ncbi.nlm.nih.gov/pubmed/17678850