Coffee Interactions

Studies cited in the FDA label show coffee (and orange juice) reduce alendronate bioavailability by approximately 60%. Given the drug's already minuscule baseline absorption of ~0.6%, this drop can render the dose therapeutically ineffective.

Coffee, including espresso and instant coffee, can reduce levothyroxine absorption by roughly 25 to 55 percent when consumed at the same time as the tablet. Chlorogenic acids and tannins in coffee appear to bind levothyroxine and the acidic environment may also alter dissolution and gastric emptying.

Ciprofloxacin is a potent inhibitor of CYP1A2, the enzyme that metabolizes caffeine. Co-administration can reduce caffeine clearance by 30% to 50% and prolong its half-life, leading to higher plasma caffeine levels, jitteriness, insomnia, palpitations, tremor, and (rarely) seizures.

Coffee contains chlorogenic acid and other polyphenols with galloyl groups that chelate non-heme iron in the gut lumen, forming insoluble complexes. A cup of coffee taken with a meal can reduce non-heme iron absorption by roughly 39% to 60%.

Sertraline modestly inhibits CYP1A2-mediated caffeine metabolism, raising caffeine plasma levels and prolonging its half-life. Caffeine can also worsen the anxiety, insomnia, jitteriness, and palpitations that sertraline is often prescribed to treat, blunting the clinical response.

Many antidepressants (especially fluvoxamine, fluoxetine, sertraline, duloxetine) inhibit CYP1A2 to varying degrees and slow caffeine clearance, while caffeine itself can worsen the anxiety, insomnia, tremor, and tachycardia that antidepressants are often prescribed to treat. MAOIs add a risk of caffeine-induced hypertensive episodes.

Caffeine in coffee acutely raises heart rate and blood pressure, which can counteract the heart-rate and blood-pressure-lowering effects of propranolol, a non-selective beta-blocker. Propranolol may also slow caffeine clearance modestly, increasing caffeine exposure.

Some early studies suggested coffee contains compounds with antithiamine activity, but follow-up work showed chlorogenic and caffeic acids are not active antithiamine agents under physiological conditions. Heavy coffee or tea intake on a marginal thiamine diet can still modestly worsen thiamine status.