Combination May Make Risk Greater

The word has been out for some time that higher-than-recommended-doses of acetaminophen (eg, Tylenol) can lead to liver damage, and that combining it with excess alcohol can make matters even worse. Now it emerges that combining large amounts of caffeine with acetaminophen can likewise prove dangerous. People can obtain high doses from not only the caffeine in strong coffee and energy drinks, but also by taking too many medications that combine caffeine with acetaminophen, such as certain Midol products or Excedrin brand drugs. These drugs often pack as much or more caffeine than a strong cup of coffee.

CAFFEINE BOOSTS PRODUCTION OF TOXIC BYPRODUCTS

At the University of Washington in Seattle, medicinal chemist Sidney D. Nelson, PhD, and his colleagues tested the effects of large amounts of acetaminophen and caffeine (approximately 20 8-ounce cups). They found that the combination produced triple the amount of a toxic byproduct that the body normally creates when breaking down acetaminophen. This same toxin is responsible for liver damage or failure from chronically combining acetaminophen with drinking alcohol (Tylenol’s label, for example, warns consumers of three or more drinks daily). Important to note: What’s acceptable for one person can be excessive for another, due to differing physiological responses.

Earlier research in lab animals had similarly demonstrated that high doses of caffeine increased the severity of acetaminophen-related liver damage. Because studies have taken place only in the lab and not in people (which is tricky to do for ethical reasons), the exact toxic threshold has not been established. Average doses of caffeine ingested either in caffeinated drinks (such as coffee) or in medications, such as many over-the-counter products, ranges from 200 to 300 mg depending on what the product is, its strength and how much is ingested. The average amount of caffeine in a normal 8-ounce cup of coffee is about 100 mg — and there’s more in a “stronger” cup, an espresso-type drink or 12 ounces instead of 8.

BETTER SAFE THAN SORRY: MODERATE CAFFEINE INTAKE

Dr. Nelson points out that moderate doses of caffeine actually enhance the pain-relieving effects of acetaminophen, and the two are commonly used together in combination drugs (such as Midol Menstrual Complete, Midol PMS and Midol Teen or Excedrin Extra Strength, Excedrin QuickTabs, Excedrin Migraine, Excedrin Sinus Headache and Excedrin Tension Headache). These products are generally safe and effective when taken infrequently and as directed. Correspondingly, drinking a few cups of coffee or consuming a similar amount of caffeine from other sources is not known to increase the risk of liver damage from acetaminophen.

However, one should limit caffeine intake when taking drugs for headache or migraine pain. A maximum would be four grams of acetaminophen in a 24-hour period in divided doses not to exceed one gram every six hours, says Dr. Nelson. It would be safer to take no more than 500 to 650 mg every six hours, as that relieves symptoms for most people.

Problems arise with excessive intake. Dr. Nelson says that in general, people should look for acetaminophen as an ingredient in many cold, flu and other medications, and avoid taking acetaminophen in addition to those products. In Dr. Nelson’s study, it was very high concentrations of caffeine (the equivalent of about 20 cups of coffee) that tripled the amount of the toxic liver metabolite of acetaminophen. So the good news is that you don’t have to sacrifice your coffee or cola or refrain from taking acetaminophen… but if you take them together, monitor your intake. This is especially important if you also drink large amounts of alcohol.