A Pharmacist Breaks Down How Coffee Could Influence Your Medications

For many people, the day doesn’t truly begin until that first cup of coffee. It’s familiar, energizing, and ranks among the most popular drinks worldwide.

However, despite its comforting appeal, your morning coffee may not be as harmless as it seems—especially when combined with certain medications. It can alter how some drugs work, either by reducing their effectiveness or increasing the risk of side effects.

From cold remedies to antidepressants, caffeine’s influence on the body goes well beyond a temporary energy lift. While tea also contains caffeine, its lower levels generally don’t produce the same effects.

Here’s what you need to know about how coffee can interact with your medications—and how to protect your health.

1. Cold and Flu Medications

Caffeine acts as a stimulant, accelerating the central nervous system. Pseudoephedrine—a common decongestant found in cold and flu products like Sudafed—is also a stimulant. When both are taken together, their effects can intensify, potentially causing symptoms like nervousness, restlessness, headaches, rapid heartbeat, and difficulty sleeping.

Many cold remedies already include added caffeine, which can further heighten these risks. Some research also indicates that combining caffeine with pseudoephedrine may raise blood sugar levels and body temperature—especially important for individuals with diabetes.

Stimulant-related concerns also arise when caffeine is taken alongside ADHD medications like amphetamines, or asthma drugs such as theophylline, which has a chemical structure similar to caffeine. Using these together may increase the likelihood of side effects like a racing heart and trouble sleeping.

2. Thyroid Treatments

Levothyroxine, the common medication for an underactive thyroid, is very sensitive to timing—and having your morning coffee too soon after taking it can interfere. Research shows that drinking coffee shortly after levothyroxine can cut its absorption by up to 50%.

Caffeine speeds up gut motility, which means food and waste move faster through the digestive system, giving the medication less time to be absorbed. It may also bind to levothyroxine in the stomach, making it harder for the body to absorb. These factors reduce the drug’s bioavailability, meaning less of it reaches the bloodstream where it’s needed. This interaction occurs more often with tablet forms of levothyroxine and less with liquid versions.

If absorption decreases, symptoms of hypothyroidism—like fatigue, weight gain, and constipation—can reappear even if you’re taking the medication correctly.

Patients must take bisphosphonate osteoporosis medications, such as alendronate and risedronate, on an empty stomach and wait about 30-60 minutes before eating or drinking anything.

3. Medications for Depression and Psychosis

The way caffeine interacts with mental health medications can be quite complex.

Doctors commonly prescribe selective serotonin reuptake inhibitors (SSRIs), like sertraline and citalopram, to treat depression, anxiety, and other psychiatric disorders. Laboratory studies indicate that caffeine may bind with these drugs in the stomach, reducing their absorption and possibly decreasing their effectiveness.

Tricyclic antidepressants (TCAs), such as amitriptyline and imipramine, are older antidepressants that influence neurotransmitter levels in the brain. Although doctors prescribe TCAs less frequently today than SSRIs—due to their higher risk of side effects and overdose—the liver enzyme CYP1A2 metabolizes both TCAs and caffeine. When both substances compete for this enzyme, it can slow the metabolism of the medication, increasing side effects, or delay caffeine clearance, causing prolonged jitteriness or overstimulation.

Clozapine, an antipsychotic medication, is also metabolized by CYP1A2. Research has shown that consuming two to three cups of coffee can nearly double clozapine blood levels, raising the risk of side effects such as drowsiness, confusion, or more severe complications.

4. Analgesics

Certain over-the-counter painkillers, like those with aspirin or paracetamol, often contain added caffeine. Coffee can speed up the absorption of these medications by accelerating stomach emptying and increasing stomach acidity, which enhances absorption for drugs like aspirin.

While this may help painkillers take effect more quickly, it can also increase the risk of side effects such as stomach irritation or bleeding, especially when combined with other caffeine sources. Although no serious incidents have been reported, experts still advise exercising caution.

5. Cardiovascular Drugs

Caffeine can cause a temporary increase in blood pressure and heart rate, usually lasting three to four hours after consumption. For individuals on blood pressure medications or drugs that regulate irregular heart rhythms (arrhythmias), this effect may reduce the medication’s effectiveness.

This doesn’t mean those with heart conditions need to avoid coffee entirely, but they should pay attention to how it impacts their symptoms and consider cutting back or switching to decaf if necessary.

What steps can you take?

Coffee might be a daily staple for you, but it’s also a powerful chemical that can affect how your body absorbs medication. Here’s how to prevent it from causing issues.

Take levothyroxine or bisphosphonates on an empty stomach with water, then wait 30-60 minutes before having coffee or breakfast.

Use caution with cold and flu medicines, asthma drugs, and ADHD treatments, since caffeine can increase side effects.

If you take antidepressants, antipsychotics, or blood pressure medications, talk to your doctor about your caffeine consumption.

If you notice side effects like restlessness, insomnia, or heart palpitations, consider cutting back or switching to decaf.

Since everyone processes caffeine differently—some tolerate three cups easily, while others react to just one—pay attention to how your body reacts and consult your pharmacist or doctor if something feels off.

Whenever you’re unsure if your medication and coffee go well together, don’t hesitate to ask a healthcare professional. A quick conversation could prevent weeks of side effects or reduced medication effectiveness, letting you enjoy your coffee worry-free.

Read the original article on: Sciencealert

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