Rethinking your morning coffee

photo of a woman standing by a window while holding a cup of coffee

Perhaps your morning beeline to the coffee pot got delayed, fueling a caffeine-withdrawal headache. But if your remedy for that involved washing down a couple of ibuprofen (Advil) or other anti-inflammatory pain reliever with your longed-for java, you unwittingly magnified the drug's effects, essentially increasing your dose. The culprit? Your now-empty mug of coffee.

While this scenario probably isn't — and shouldn't be — an everyday occurrence, it's a ready example of the way certain drugs and supplements can behave differently just by pairing them with coffee. The most widely consumed stimulant beverage in the world, coffee is a major source of caffeine. Up to 400 milligrams (mg) of caffeine a day is considered safe, but coffee can interact with many drugs by affecting the way they're absorbed, distributed through the body, processed, and excreted.

Caffeine in coffee can boost the effectiveness of over-the-counter pain relievers like acetaminophen and anti-inflammatory pain drugs, including aspirin and ibuprofen. However, for many other important medications, coffee can cause interactions that decrease their potency. For example, coffee — even decaf — may lower a medicine's absorption by making stomach contents more acidic. But caffeine is the main offender in most medication clashes, says Lina Matta, director of ambulatory pharmacy at Harvard-affiliated Brigham and Women's Hospital.

If you're taking medication for a chronic condition, that's reason enough to wake up to the ways coffee — and other sources of caffeine — can alter the way medicines work. "Caffeine can affect all of the phases of a drug's journey through the body, but for different reasons," Matta says. "It just depends on the drug."

Additional caffeine sources

Found naturally in the leaves, seeds, and fruits of more than 60 plants, caffeine is a stimulant that quickly gets into the brain — jolting us awake shortly after we down that morning cup. Coffee contains up to 100 mg of caffeine per 6-ounce cup, meaning the 20-ounce whopper you picked up at your local bistro may contain more than 300 mg of caffeine.

But coffee is far from the only fount of significant amounts of the stimulant. Other high-caffeine sources include

black or green teas, which contain 60 to 100 mg in 16 ounces
chocolate, which has 10 mg in each ounce of sweet, semisweet, or dark varieties, and 58 mg per ounce in unsweetened baking versions
cola, which contains about 45 mg in a 12-ounce drink.

Caffeine is also found in various energy drinks, candies, and snacks. It's sometimes added to over-the-counter pain relievers and cold medicines as well.

Problematic pairings

Coffee (or caffeine) doesn't affect the way all drugs work, but many common medications are vulnerable to the effects of one or both. Any of the following conditions might have you reaching for one of those drugs:

Cold or allergy. Over-the-counter remedies often contain decongestants such as pseudoephedrine (Sudafed), which is a stimulant. Paired with caffeine, these medications can produce a one-two punch, making you restless, jittery, and unable to sleep. Bear in mind that older allergy medications that typically make people sleepy, such as diphenhydramine (Benadryl), don't interact with coffee in this way.

Depression. Drinking coffee — especially in large amounts — can affect how your body processes selective serotonin reuptake inhibitors such as fluvoxamine (Luvox) and escitalopram (Lexapro) and tricyclic antidepressants such as amitriptyline and imipramine (Tofranil). But since not all antidepressants are vulnerable to these effects — which can reduce the amount of medication your body absorbs by about one-third — ask your doctor if you should take your antidepressant at a different time than your morning brew.

High blood pressure. Drinking coffee at the same time you take certain blood pressure medications, including the calcium-channel blocker verapamil (Verelan), can temporarily hamper their ability to relax blood vessels.

Asthma. An older bronchodilator, theophylline (Elixophyllin, Theo-24), relaxes the airways to allow more air to move in and out of the lungs. But its side effects, which include restlessness and irritability, can double up with caffeine's tendency to trigger the same issues. Coffee can also hamper the absorption of these asthma medications, leaving them less potent against symptoms such as wheezing and shortness of breath.

Osteoporosis. Drinking coffee with drugs to prevent or treat the bone-thinning condition, such as risedronate (Actonel, Atelvia), ibandronate, and alendronate (Fosamax), can render them less effective. But people prone to osteoporosis may want to avoid coffee altogether because it can hinder the absorption of vitamin D and calcium from foods, which support bone strength. "Some studies show that more than two to three cups of coffee — about 200 to 300 milligrams of caffeine — a day is associated with a sizable increase in fracture risk over 10 years," Matta says.

Anemia. Taking iron supplements with coffee can render the supplements between 50% and 90% less effective, Matta says.

Alzheimer's disease. Caffeine can thwart the effects of prescription drugs that might improve thinking abilities and ease other dementia symptoms, including donepezil (Aricept), rivastigmine (Exelon), and galantamine. "Coffee and other caffeine sources can tighten the blood-brain barrier, so some drugs that can normally cross it [and thus work on the brain] have a tougher time doing so," Matta explains.

Thyroid problems. Drinking coffee at the same time as taking levothyroxine (Synthroid) — which is prescribed for underactive thyroid — can dramatically reduce the medication's absorption, leaving it less effective against symptoms such as fatigue, weight gain, constipation, and sensitivity to cold.

Insomnia. For many people, a late night cup of coffee keeps them awake. But ironically, some people find that caffeine combined with a melatonin supplement or prescription zolpidem (Ambien, Edluar) can make them overly sedated, presumably by boosting the amount of brain melatonin.

Easy changes

The good news? To avoid coffee- or caffeine-related drug interactions, you don't have to give up your beloved morning routine. Just modify the timing, Matta says.

"I don't know of any drug that stops you from drinking coffee at all because you happen to be on that medication," she says. "When in doubt about potential interactions, just take your medications an hour before your coffee or two hours after."

Matta also suggests these strategies to keep medications working properly:

Track your caffeine. Heavy coffee drinkers — those who down more than three cups a day — are more likely to experience drug interactions. But most people won't have such issues if they consume 200 to 300 mg of caffeine a day or less.

Consider other caffeine sources. Keep an eye on more than your trail of empty coffee cups. If you gulp one diet cola after another on a daily basis, that can really add up too.

Stay alert for problems. If you notice your medication is working differently, or if you're experiencing new or unusual side effects, think back to your recent coffee or caffeine consumption — and cut back if necessary. If you're still not sure about what effects caffeine has on any of your medications, talk to your doctor or pharmacist.