Medically Approved

Is your morning coffee messing with your medications?

Man drinking coffee at breakfast table

Caffeine can interfere with some medications and even make side effects worse. A pharmacist explains why — and what to do about it.  

Kim Robinson

By Kim Robinson

If you’ve ever seen one of those “But first, coffee” mugs, you know that some people take their caffeine very seriously. Whether it’s the jet fuel that gets you through your day or a once-in-a-while treat, caffeine is an important part of many people’s lives.  

But what if your favorite coffee brew (or tea) negatively affects your medical treatment? It turns out that caffeine can interact with some common medications. It could potentially make a medication less effective — or even bring on unpleasant symptoms or side effects. 

But don’t despair just yet, caffeine lovers. We called upon Joy Alonzo, PharmD, to explain how caffeine affects the body and which medications it interacts with. She’s a clinical assistant professor in the department of pharmacy practice at Texas A&M University in College Station.  

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What kind of impact does caffeine have on the body in general? 

Alonzo: First off, let’s go over what caffeine is. It’s a natural ingredient in the plants we use to make some of our favorite fixes: Coffee, tea and chocolate. And it can be added to other foods and drinks, too. 

When you eat or drink something that contains caffeine, it enters your bloodstream. It then travels to your brain and central nervous system, where it acts as a stimulant. That means it can boost your energy and mood and make your brain more alert. A moderate intake of caffeine can even help prevent weight gain and enhance cognitive function and attention span.   

According to the U.S. Food and Drug Administration, a maximum of 400 mg of caffeine a day is the amount that’s generally thought of as safe for a healthy adult. That’s about 4 cups of coffee or 8 cups of green tea.  

Be aware that it can take up to 10 hours for your body to break down caffeine and stop experiencing its effects. 

What are some medications that interact poorly with caffeine? 

Alonzo: The medications that can interact with caffeine come from 3 main classes: antibiotics, estrogen-containing medications and medications that slow blood clotting, such as anticoagulants and antiplatelets.  

Certain types of antibiotics known as quinolones can interact with caffeine. Examples include ciprofloxacin and levofloxacin. These antibiotics are broken down by the same pathway in the body as caffeine. Taking these antibiotics together with caffeine may increase the side effects of both. You might experience jitteriness, headaches, increased heart rate and other side effects. 

Birth control pills and other medications that add the hormone estrogen to your body (such as Premarin®) can interfere with caffeine, too. That’s because estrogen hinders the breakdown of caffeine. So it can cause increased side effects associated with too much caffeine — namely insomnia, anxiousness, nausea and headaches.  

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Some common medications that slow blood clotting include aspirin, ibuprofen, naproxen, clopidogrel (Plavix®), warfarin (Coumadin®), rivaroxaban (Xarelto®) and apixaban (Eliquis®).

These medications are often prescribed after a person has had a heart attack or blood clot, or if they have experienced a prolonged irregular heartbeat (called arrhythmia). Caffeine itself can slow blood clotting. So if you’re taking any of these medications, it may increase the chance that you’ll experience serious bleeding or bruising.  

Consuming a lot of caffeine may also worsen symptoms of anxiety and depression, including nervousness, restlessness, irritability and insomnia. And this can make treatment of those conditions less effective. (Here, we’ve answered your top questions about treatments for anxiety and depression.) 

Do I have to give up caffeine and coffee completely? 

Alonzo: Certainly not. But if you’re taking any of the medications mentioned above, cutting back may be best. (And there are always decaf options, too.) Talk to your doctor or pharmacist about your caffeine intake, as well as any adverse symptoms you’re experiencing.  

What about medications that contain caffeine? 

Alonzo: You’ll most often see caffeine used in medications to treat headaches and migraines. You can find it combined with other medications such as acetaminophen, aspirin, magnesium hydroxide and salicylamide (such as Excedrin Migraine®, PainAid® or Levacet®). 

If you’re taking any medication that contains caffeine, whether it’s over the counter or by prescription, be very cautious. Limit your caffeine intake to compensate, and monitor for signs and symptoms that indicate you may have taken too much. 

Caffeine is so ingrained in our culture that it can be easy to forget just how big of an impact it has on our bodies. If you’re taking any of the medications above, or if you’re just concerned about your intake, talk to your doctor about how you can indulge safely.  

Before you pour yourself another cup of joe, download our free prescription discount card, which can be used at pharmacies nationwide.  

Additional source
How much caffeine is safe:
 U.S. Food and Drug Administration