|Why Is Caffeine in My Pain Reliever? A Pharmacist Answers|
by Daniel P. Hays, Pharm.D., B.C.P.S.
Q. Why is caffeine added to some over-the-counter pain medication? (If I take it too close to bedtime, it keeps me awake!)
A. Headaches are often the result of dilated, or swollen, blood vessels putting pressure on your nerves. Caffeine is a potent vasoconstrictor—it will squeeze some of the blood vessels, taking the pressure off and decreasing the pain.
Caffeine also increases the body’s ability to absorb the pain-relieving portion of the medication, though we’re not quite sure why. One of the side effects, of course, is that it can perk you up, causing you to be unable to sleep at night.
Adenosine sometimes works by balancing out a feel-good chemical called dopamine. So when caffeine stops adenosine from working, that feel-good chemical increases. Caffeine may also increase the amount of epinephrine, also known as adrenaline, in your body.
If you’ve ever drunk to much coffee, you may be familiar with the jitters, your heart racing, frequent trips to the bathroom and an upset stomach. These are all side effects of caffeine blocking adenosine. As with all drugs, too much of a good thing is a bad thing!
Last updated and/or approved: September 2010. Original article appeared in fall 2006 former print magazine. Bio current as of that issue. This general health-care information is not meant as individual advice. Please see our disclaimer.