Caffeine is one of the world’s most consumed psychostimulants (compounds that stimulate brain activity). It can be found in coffee beans, teas, cocoa, and energy drinks.
Despite its widespread use, caffeine can interact with certain medications, affecting how they work, how long they last in the body, and how your body absorbs them.
Drug interactions between caffeine and other medications can lead to increased side effects and toxicity, make a medication less effective, or cause unexpected health complications.
Blood-thinning medications like aspirin, Plavix (clopidogrel), and warfarin (brands like Coumadin and Jantoven) prevent blood from clotting. A healthcare provider might recommend blood thinners if you have heart or blood conditions like stroke or to reduce the risk of blood clots after surgery.
One of the most common side effects of blood thinners is bleeding. Just like blood thinners, caffeine might slow blood clotting. Taking caffeine with these medications might increase your risk of bruising and bleeding.
Some studies show that caffeine can modestly increase how fast blood thinners like aspirin are absorbed and how much is available to the body, making the bleeding side effect more pronounced.
Sudafed (pseudoephedrine) is a medication that treats stuffy or blocked noses caused by colds or allergies.
Just like caffeine, pseudoephedrine is a stimulant. When used together, the medications can produce a two-fold effect, making you feel more jittery, restless, and irritable.
Some studies also show that combining pseudoephedrine with caffeine can raise blood sugar and increase body temperature, which may be dangerous for people living with diabetes.
It’s best to avoid caffeine while using pseudoephedrine or space them about 5-6 hours apart.
Birth control pills or oral contraceptives like Micronor (norethindrone) or Sprintec (norgestimate/ethinyl estradiol) are medications taken by mouth to prevent pregnancy.
Research has shown that using oral contraceptives can double the half-life of caffeine, making caffeine last twice as long. Since the caffeine effect lingers longer than normal, you may experience heightened symptoms like insomnia, restlessness, or stomach discomfort.
Lexapro (escitalopram), Elavil (amitriptyline), and Tofranil (imipramine) are common medications prescribed to treat symptoms of depression.
Research reveals that caffeine forms a complex with escitalopram when used together. This complex lowers the amount of escitalopram available to act in the body, which may reduce its effectiveness.
Caffeine may increase the amount of imipramine concentration in the brain, which may result in increased antidepressant effects.
Other studies found that caffeine can increase the concentration of amitriptyline in the blood by slowing down its elimination from the body. This can increase the risk of side effects such as constipation, dizziness, dry mouth, and sleepiness.
Antibiotics are medicines that kill or inhibit the growth of bacteria. Your healthcare provider may prescribe them to treat conditions like strep throat, urinary tract infections (UTIs), and pneumonia.
Research shows that caffeine inhibits the action of some antibiotics, such as Avelox (moxifloxacin), Noroxin (norfloxacin), Cipro (ciprofloxacin), and Chloromycetin (chloramphenicol). Caffeine can make these medications less effective at fighting infections.
Theochron (theophylline) is a medication used to manage severe asthma and chronic obstructive pulmonary disease (COPD).
Caffeine and theophylline are stimulants in the same class of drugs: methylxanthines. When used together, caffeine may heighten the side effects of theophylline, such as headache, tremors, vomiting, insomnia, and increased blood pressure and heart rate.
It is recommended that people taking theophylline be cautious about consuming foods or drinks with high caffeine content, as this combination may increase the risk of side effects.
Zanaflex (tizanidine) is a medication used to relieve muscle spasms. It is commonly prescribed to treat conditions like multiple sclerosis (MS), spinal cord injury, or stroke.
Tizanidine and caffeine are both metabolized by the same enzyme, CYP1A2. Taking them together can increase the risk of tizanidine side effects, such as low blood pressure, which can lead to falls and fractures.
Synthroid (levothyroxine) is a medication used to treat hypothyroidism, a condition where the thyroid gland does not produce enough thyroid hormone.
Caffeine can slow down the absorption of levothyroxine, potentially lowering the effectiveness of levothyroxine in managing hypothyroidism. This interaction is especially prominent when both medications are taken within an hour of each other.
It is recommended to wait at least four hours between consuming caffeine and taking levothyroxine to minimize this interaction.
Caffeine may not directly interact with medications used to lower blood pressure, but it may blunt their effects, especially when consumed in high amounts.
Two types of blood pressure-lowering medications affected by this interaction are beta-blockers (propranolol, known as Inderal) and diuretics (furosemide, known as Lasix). Research has found that caffeine can oppose these medications, reducing their effectiveness in lowering blood pressure.
Risedronate (brands like Actonel and Atelvia) and Fosamax (alendronate) are medications used to treat and prevent osteoporosis.
Coffee and other caffeine-containing beverages can decrease the absorption of oral osteoporosis medications like risedronate and alendronate, rendering them less effective.
Studies also show that high concentrations of caffeine can interfere with calcium absorption, which supports bone health. People prone to osteoporosis should avoid caffeine altogether.
Galantamine, rivastigmine, and donepezil are approved for management of mild to moderate Alzheimer’s.
To effectively treat memory decline, Alzheimer’s treatments must cross the blood-brain barrier (BBB) to reach the brain, where they can exert their effects. Caffeine can prevent the opening of BBB, making it harder for these medications to get to the brain.
Methotrexate is a medication used to treat psoriasis, especially forms that other treatments cannot manage. It may also be prescribed to treat certain types of cancer, such as breast and lung cancer and leukemia.
Caffeine has been found to reduce the beneficial effects of methotrexate, particularly its anti-inflammatory action. This may be due to caffeine’s antagonistic effect on adenosine receptors, which methotrexate also targets.
However, other studies have found that caffeine may improve the action of methotrexate, so it’s best to consult with a physician before using this combination.
Caffeine is generally safe and well-tolerated, especially when consuming less than 400 milligrams per day.
Caffeine may interact with medications like warfarin, levothyroxine, and theophylline, potentially heightening the side effects or performance of the medication.
If you regularly consume caffeine and are starting a new medication or have an underlying health condition, it’s best to consult your healthcare provider about potential interactions.
You should also see your healthcare provider if you are experiencing any side effects, such as increased restlessness, agitation, insomnia, hallucination, or any other unusual symptoms.
Here are some ways you can cut back or limit caffeine if you’re taking medications that may interact with it:
- To prevent withdrawal symptoms, gradually reduce your daily caffeine intake (e.g., if you consume four cups of caffeinated drinks, reduce it to two)
- Switch caffeinated tea or coffee for the decaffeinated version
- Avoid consuming caffeine at night and within 5-6 hours of taking your medication
- For teas with caffeine, brew for less time to reduce the caffeine
- Seek professional guidance if reducing caffeine feels overwhelming
Caffeine can be part of a healthy diet for most people. However, it can pose health risks depending on your current medications, certain medical conditions, and age.
If you are a caffeine lover, it is best to talk to your healthcare provider or pharmacist about how caffeine may interact with your medication before you start taking it.
Contact your healthcare provider if you experience any of the following symptoms while using caffeine and any medication: increased restlessness, sleep disturbances, rapid heart rate, anxiety, jitters, or heart palpitations.
