KUWAIT CITY, Oct 29: Your morning cup of coffee might do more than wake you up – it could also affect how your body processes certain medications, potentially reducing their effectiveness or increasing side effects, according to experts.

For many people, the day doesn’t begin until the first sip of coffee. While the beverage is comforting, energising, and widely consumed globally, caffeine can interact with medications in ways that go far beyond a simple energy boost. Tea contains caffeine too, but usually in lower concentrations and with less pronounced effects.

Dipa Kamdar, Senior Lecturer in Pharmacy Practice at Kingston University, highlights five common types of medications that may be affected by coffee.

1. Cold and Flu Medicines: Caffeine is a stimulant that speeds up the central nervous system. Pseudoephedrine, a decongestant found in cold and flu medications such as Sudafed, is also a stimulant. Taken together, the combined effect can lead to jitters, restlessness, headaches, rapid heart rate, and insomnia.

Some cold remedies already contain caffeine, which can further amplify these effects. Studies suggest that combining caffeine with pseudoephedrine may also raise blood sugar and body temperature, a concern for people with diabetes. Stimulant effects are also noted when caffeine interacts with ADHD medications like amphetamines or asthma drugs such as theophylline, increasing the risk of rapid heartbeat and sleep disruption.

2. Thyroid Medication: Levothyroxine, the standard treatment for an underactive thyroid, is highly sensitive to timing. Drinking coffee too soon after taking levothyroxine can reduce absorption by up to 50 percent. Caffeine accelerates gut motility, giving the drug less time to be absorbed, and may bind to it in the stomach, lowering bioavailability. Tablet forms are more affected than liquid formulations.

If absorption is impaired, symptoms of hypothyroidism—including fatigue, weight gain, and constipation—can return. The same timing considerations apply to osteoporosis medications called bisphosphonates, including alendronate and risedronate, which require an empty stomach and a 30–60 minute wait before food or drink.

3. Antidepressants and Antipsychotics: The interaction between caffeine and mental health medications can be complex. Selective serotonin reuptake inhibitors (SSRIs), such as sertraline and citalopram, may bind with caffeine in the stomach, reducing absorption and potentially diminishing effectiveness.

Older tricyclic antidepressants (TCAs), including amitriptyline and imipramine, are metabolized by the liver enzyme CYP1A2, which also processes caffeine. Competition between the two can slow drug breakdown, increasing side effects or prolonging caffeine’s stimulant effects. Clozapine, an antipsychotic, is similarly processed by CYP1A2. Research shows that drinking two to three cups of coffee can increase clozapine blood levels by up to 97 percent, raising risks such as drowsiness, confusion, or more serious complications.

4. Painkillers: Some over-the-counter painkillers, including those containing aspirin or paracetamol, include added caffeine. Coffee can accelerate stomach emptying and increase acidity, speeding up drug absorption. While this may help some medications work faster, it can also raise the risk of side effects such as stomach irritation or bleeding, particularly when combined with other sources of caffeine.

5. Heart Medications: Caffeine can temporarily raise blood pressure and heart rate for three to four hours after consumption. For patients taking blood pressure medication or drugs controlling irregular heart rhythms, caffeine may counteract the intended effects. People with heart conditions do not necessarily need to avoid coffee, but monitoring symptoms and moderating intake—or switching to decaf—may be advisable.

Guidance for Safe Use: Experts recommend taking levothyroxine or bisphosphonates on an empty stomach with water and waiting 30–60 minutes before drinking coffee or eating. Caution is advised with cold remedies, asthma treatments, and ADHD medications due to caffeine’s stimulant effects.

Patients on antidepressants, antipsychotics, or heart medications are encouraged to discuss caffeine consumption with their healthcare provider. Reducing intake or opting for decaffeinated options can help prevent side effects like restlessness, insomnia, or heart palpitations.

“Everyone metabolizes caffeine differently,” Kamdar noted. “Some people tolerate multiple cups with no issues, while others may experience side effects from just one. Paying attention to how your body responds and consulting your pharmacist or doctor can prevent weeks of reduced treatment effectiveness and ensure you enjoy your coffee safely.”