Caffeine is a potent pain killer. The relief it delivers to nociception, that is, pain perception, results from at least two distinct mechanisms: 1. Caffeine delivers pain relief by exerting so-called “peripheral action,” that is, relief at the site of an injury. In doing so, it acts directly on muscle tissue, relieving pain by repairing tissue damage and reducing inflammation; 2. Caffeine also has profound CNS effects that block the central processing of pain signals in the brain and that increase the effectiveness of the body’s natural pain killing mechanisms.
In addition to reducing pain on its own, caffeine in even low doses has been shown to magnify the pain killing power of aspirin and ibuprophen and even of narcotic analgesics.[i] That is the reason that caffeine is an active ingredient in over the counter pain killers like Excedrin Extra Strength, in prescription pain killers like Darvon Compound-65, and in narcotic pain killers like Percodan. Leading caffeine researchers Jan Snel and Monicque M. Lorist state that the studies of caffeine alone and in combination with other pain killers show that “different pain states can, to different degrees, be mediated by different mechanisms that may be caffeine-sensitive.”[ii] This means that there are several different mechanisms that enable caffeine to relieve pain of different kinds and differing intensities. Snel and Lorist add that caffeine’s power to alleviate intense pain suggests that the neural mechanisms that cause this pain are “directly sensitive to caffeine.”
One creative study, using a 200 mg caffeine pill, found that caffeine by itself was a potent pain reliever for muscle pain. Conducted by Daniel E. Myers, D.D.S., associate professor in the department of oral medicine and pathology at the University of Pittsburgh School of Dental Medicine, this experiment measured the effects of caffeine on “ischemic muscle contraction pain,” that is, the intense pain (such as that experienced during a heart attack) caused by blocking the flow of blood to an area of the body. Each participant in the study was given either a 200mg caffeine pill or a placebo. One hour later, subjects raised their arms to drain the blood and blood pressure cuffs were attached to prevent blood flow back into the arm. The participants then did wrist curls while holding a small weight, activity which would give rise to ischemic muscle pain. The subjects were then asked to rate pain levels after 15, 30, and 45 seconds of wrist curl exercises. At 15 seconds, the mean pain rating of those who had taken caffeine was half that of those who had taken a placebo! A similar profile but less pronounced pattern of effects was found at 30 seconds and 45 seconds. Myers attributes the pain killing power of caffeine in his study and in over-the-counter and prescription medications to its action in blocking adenosine receptors in muscles, concluding that caffeine alone delivers considerable analgesic efficiency and that the “implication is that there is a rationale for the use of caffeine in the treatment of muscle pain when blood flow is reduced.” [iii]
As we have noted, caffeine alone is a strong analgesic. But there have been relatively few studies of the effects of caffeine alone on pain in human beings. Most scientists have concentrated on examining caffeine’s use as an adjuvant, or added ingredient, in preparations of drugs like acetaminophen, acetaminophen and aspirin combinations, and ibuprophen. A thorough review of these studies was published in Pharmacological Reviews in 1993. It concluded that caffeine potentiated the pain relief of other analgesics, especially of ibuprophen, to a significant degree[BAW1] in postpartum pain, post-surgical pain following a dental extraction, and headache pain.[iv] Another metastudy reviewing 30 pain studies in which caffeine was used in combination with non-steroidal anti-inflammatory drugs (NSAIDs) to treat postpartum, dental, and headache pain, found that the addition of 65mg to 200 mg of caffeine (the amount in about 1/2 cup to about a 1 1/3 cups of filter drip coffee) resulted in a clear increase in the power of the NSAIDS to relieve pain.[v]
Caffeine has an especially powerful effect in relieving tension headaches. A landmark 2001 study, conducted by Dr. Seymour Diamond and Dr. Frederick G. Freitag of Chicago’s Diamond Headache clinic, tested hundreds of people who suffer from severe tension headaches at least three times a month.[vi] The researchers split participants into four groups, which were given either 400 mg of ibuprophen alone, 400 mg of ibuprophen combined with 200mg caffeine, 200 mg of caffeine alone, or a placebo. Amazingly, caffeine alone delivered as much pain relief as the ibuprophen, completely eliminating the headaches in nearly 2/3 of the participants! (In other studies, as little as 130mg of caffeine was effective at relieving headache pain. [vii]) Caffeine also worked faster, ending the headaches a half-hour quicker than the ibuprophen. However, the best results were achieved with the combination of caffeine and ibuprophen, which stopped the headaches in nearly ¾ of the participants. The combination of caffeine and ibuprophen also worked much longer, providing an extra four hours of pain relief as compared with ibuprophen alone. So, if your doctor is aware of these facts, perhaps he might be telling you, “Take 200mg of caffeine—and call me in the morning!”
How Caffeine Kills Pain
Scientists speculate that caffeine’s analgesic power arises from three different mechanisms:
- Blockade of “peripheral pronociceptive actions of adenosine,” which means that caffeine interferes with a neurotransmitter that is responsible for carrying pain signals from a specific area of the body to the brain (for example, caffeine could prevent adenosine’s ability to activate a nerve ending and block its ability to signal pain);[viii]
- Activation of “central noradrenergic [adrenalin] pathways that constitute an endogenous pain suppressing system,” which means that caffeine stimulates the body’s own pain killing mechanism; and
- Central nervous system (CNS) stimulation, which means that, caffeine’s overall stimulating effects somehow change the way pain signals are processed in a way that reduces pain.[ix],[x]
As has been known to physicians for nearly 500 years, caffeine also has a special power to relieve migraine headaches. Coffee was one of the earliest pharmacological remedies used against migraines, and caffeine has been a therapeutic ingredient in some modern migraine medicines for decades. In the 1970’s the theory arose that caffeine alleviates migraines by constricting cranial blood vessels. In the late 1990’s, it was discovered that, even though caffeine does constrict these blood vessels, its ability to relieve migraines is unrelated to this action and depends instead on its effects on the neurotransmitter serotonin. It turns out that migraines are not caused by vascular engorgement, but rather by a disorder of the serotonin system. This discovery helped explain why bad moods so often precede or accompany migraines. Caffeine has the power to help restore the balance of the serotonin system, and this is the key to its ability to relieve migraines. One lesson we can learn from this is that it is not always important to know why caffeine does what it does in order to get the benefits of using it. After all, people were using caffeine to treat migraines hundreds of years before anyone had ever heard of the serotonin system. You don’t have to know why it works—but you do have to know how to use it.
One additional statement that we found interesting was made by Jan Snel and Monique Lorist, leading caffeine researchers. They comment that “the positive effect of caffeine on lowering sensitivity to pain,” combined with the ways in which caffeine intensifies our sense perceptions, “may mean that caffeine…may form a major contribution to the enjoyment of life.”[xi]
Stopping Migraines in Their Tracks
Caffeine does more than mask the pain of migraines. It actually changes the course of the migraine headache. Left untreated, migraines typically progress into more intense headache pain and nausea. Many people find that by taking a 200mg caffeine pill at the first sign of migraine, followed by a 100mg supplement every few hours if necessary, they actually stop the migraine in its tracks and prevent it from developing into a full blown episode. The only way to find out if caffeine can do this for you is to try it for yourself.
[i] Sawynok, J., and TL Yaksh, “Caffeine as an analgesic adjuvant: a review of pharmacology and mechanism of action,” Pharmacological Review, 1993: 45 (1):43-85.
[ii] J Snel and MM Lorist, “Caffeine and Information Processing” in Pleasure and Quality of Life, ed. D. Warburton and Sherwood, Chichester: John Wiley & Sons, 1996, p. 107.
[iii] Daniel E. Meyers, “High-Dose Caffeine May Be Effective Pain Reliever,” Headache, November, 1997.
[iv] Sawynok, J., and TL Yaksh, “Caffeine as an analgesic adjuvant: a review of pharmacology and mechanism of action,” Pharmacological Review, 1993: 45 (1):43-85.
[v] Laska, EM, et al, “”Caffeine as an analgesic adjuvant. Journal of the American Medical Association, 251:1711-1718,
[vi] Dr. Seymour Diamond and Dr. Frederick G. Freitag, Current Pain and Headache Reports (vol 5, p 472) [October, 2001]
[vii] Avery Ward, et al, “The analgesic effects of caffeine in headache,” (1991) Pain, 44:151-155.
[viii] J Snel and MM Lorist, “Caffeine and Information Processing” in Pleasure and Quality of Life, ed. D. Warburton and Sherwood, Chichester: John Wiley & Sons, 1996, p. 107.
[ix] Sawynok, J., and TL Yaksh, “Caffeine as an analgesic adjuvant: a review of pharmacology and mechanism of action,” Pharmacological Review, 1993: 45 (1):43-85.
[x] “Sawynok and Yaksh point out that, on its own, caffeine may contribute to amelioration of pain. This may be caused by peripheral action at the level of a local injury or actions within the CNS by modifying nociceptive processing….” TE Graham, “Caffeine and Exercise: Metabolism, Endurance, and Performance,” Sports Medicine, 2001, 31(11):785-807( p. 790).
[xi] J Snel and MM Lorist, “Caffeine and Information Processing” in Pleasure and Quality of Life, ed. D. Warburton and Sherwood, Chichester: John Wiley & Sons, 1996, p. 114.