Having New Side Effects? Check Your Caffeine Intake

caffeine drug side effects
  • A cup or two of caffeine is unlikely to be dangerous
  • Larger servings can interact with many common medications, like antidepressants and antibiotics
  • Some drugs can enhance the effects of caffeine

You’ve probably seen someone holding a mug or wearing a T-shirt that reads “Don’t talk to me until I’ve had my coffee.” Though lighthearted, the statement refers to something that many of us may forget: caffeine, an active ingredient in coffee, tea, chocolate and other foods and drinks is, in fact, a psychoactive stimulant drug. Unless you’re consuming exceptionally large servings of caffeine (upwards of 5 to 10 cups of coffee a day), you’re unlikely to overdose on the substance. Nonetheless, fewer servings can, in some cases, interact with the drugs and supplements you’re taking to decrease their efficacy or exacerbate their side effects.

“Caffeine is a stimulant, or an ‘upper’ type of drug. It’s best known for promoting wakefulness and increasing energy, but it also causes increases in both heart rate and blood pressure that can produce unwanted side effects,” says Kelly Johnson-Arbor, MD, a toxicologist and co-medical director of the National Capital Poison Center.. “Caffeine can be problematic when taken with other medications that affect heart rate and blood pressure.” She adds that many drugs, such as asthma inhalers, use ingredients that can raise blood pressure levels. 

Drugs That Contain Caffeine

Many drugs, including those available over-the-counter (OTC), contain caffeine. The amounts of caffeine found in many of these drugs are about the same as in a cup of coffee or less. If you’ve been consuming caffeinated food or drinks before taking the drug, the effects are cumulative and can raise your heart rate, make you jittery or contribute to difficulty sleeping.

For example, Cafergot (ergotamine tartrate and caffeine) is a prescription migraine drug. The caffeine helps constrict blood vessels to treat migraines, but it’s important to recognize if you’re using this drug, one tablet has about the same amount of caffeine as an 8 oz cup of coffee (91mgs of caffeine).

Some OTC pain killers also harbor caffeine. Examples are Bayer Select Maximum Strength Headache Pain Relief (acetaminophen and caffeine), Excedrin (acetaminophen, aspirin and caffeine) and Midol Complete (acetaminophen, pyrilamine and caffeine).

Herbal supplements and powders that promise to enhance your workout or help you lose weight often contain caffeine, or ingredients that can similarly raise your heart rate. Some formulations of Hydroxycut, such as Hydroxycut Max for Women, have more caffeine than 16 oz of coffee (182mgs of caffeine).

Other Ways Caffeine Can Mess With Your Medications

“Caffeine use may affect the liver’s ability to adequately break down other drugs and can lead to toxic effects,” says Johnson-Arbor.

The enzyme CYP1A is responsible for metabolizing caffeine, as are several other drugs, including the antipsychotic Clozaril (clozapine), the muscle relaxant Flexeril (cyclobenzaprine), the antidepressant Tofranil (imipramine), the antiarrhythmic Mexitil (mexiletine) and the bronchodilator Theo 24 (theophylline). In one case study, a man who had been taking clozapine for years started drinking about four 12 oz cans of the energy drink Red Bull a day (about 440mgs of caffeine) and ended up in the hospital with life-threatening clozapine toxicity. Doctors suspected that the large amounts of caffeine prevented the body from breaking down clozapine, so it stayed in his body longer and built up to toxic levels as he continued taking it. He experienced cognitive and acute respiratory symptoms and kidney failure.

Some other drugs, including common quinolone antibiotics such as Cipro (ciprofloxacin) and Floxin (ofloxacin), and the antidepressant Luvox (fluvoxamine) inhibit CYP1A activity, meaning caffeine may stay in your body longer, making you jittery and anxious or causing sleep disturbances.

Caffeine can also reduce the efficacy of some drugs, for reasons that are not yet fully understood. A review of studies on caffeine suggests that anti-seizure medications, especially Topamax (topiramate), can lose efficacy when combined with caffeine.

Caffeine is so ubiquitous that we may forget that it’s a drug. About 85% of Americans consume at least one caffeinated beverage every day. In most cases, this amount is harmless and even unlikely to interact with your drugs and supplements.  However, if you’re starting a new drug or if you recently upped your caffeine intake, it’s important to discuss the stimulant with your doctor, so you’re aware of any potential side effects.

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