Coffee interacts with some medications by changing the way your body absorbs them, ruining the medication’s effectiveness or causing toxic side effects.
ADHD stimulants
If you take prescription stimulants such as Adderall, Ritalin, or Concerta for ADHD, adding coffee can overstimulate your nervous system.
Since both coffee and these medications increase your brain function and heart rate, they can have amplified negative side effects such as jitteriness, increased heart rate, high blood pressure, and anxiety.
Thyroid medications
Drinking coffee, even just a single cup within an hour of taking your dose, can significantly decrease the amount of thyroid medication your body absorbs.
This will make your daily medications, like Levothyroxine (Synthroid), less effective at controlling your hormone levels and could leave you with uncontrolled thyroid symptoms.
Fluoroquinolone antibiotics
Some antibiotics can completely inhibit your body’s ability to metabolize caffeine. Antibiotics such as Ciprofloxacin (Cipro) or Levofloxacin (Levaquin) force your liver into taxi duty by blocking the normal pathway that would metabolize caffeine.
As a result, caffeine in your system can increase up to 3 times its normal level. So that one normal cup of coffee you just drank suddenly becomes a lethal dose, causing intense shakes, nausea, and insomnia.
Asthma bronchodilators
Theophylline and rescue inhalers like Albuterol are asthma medications used to relax your airway muscles and open your lungs.
Because they are chemically very similar to caffeine, coffee can cause an overdose-like effect of these drugs, making you feel dizzy, nauseous, and give you intense heart palpitations.
Melatonin supplements
OTC melatonin has become widely popular to help people fall asleep. However, coffee can drastically affect your sleep aid.
Caffeine inhibits the liver enzyme that breaks down melatonin. That means drinking coffee can increase the levels of your sleep hormone in your bloodstream by over 100%.
Having coffee later in the day if you’re taking supplements to regulate your sleep cycle (Melatonin, Natrol, Zarbee’s) can interrupt your sleep and leave you waking up with intense grogginess.
Osteoporosis drugs
Coffee can dramatically reduce how well your body absorbs osteoporosis drugs like Alendronate (Fosamax) or Risedronate (Actonel) by more than half. For these medications to work and actually strengthen your bones, you need to take them on a completely empty stomach with a full glass of plain water hours before your first cup of coffee.
Antidepressants and antipsychotics
Certain psychiatric drugs are metabolized by the same liver enzymes that break down caffeine. When a medication such as antidepressant Fluvoxamine (Luvox) or antipsychotic Clozapine (Clozaril) inhibits those enzymes, caffeine can accumulate in your body, leading to insomnia.
Coffee can also bind to these medications in your gut and prevent them from being absorbed.
Blood pressure medications
Coffee increases heart rate and constricts blood vessels naturally. Beta blockers such as Metoprolol or Propranolol are blood pressure medications designed to help lower blood pressure and calm a heart that feels like it’s racing.
Drinking coffee will work against the function of your medication, making your heart work overtime.
Cold and allergy decongestants
Most OTC cold and sinus medications contain strong decongestants such as Pseudoephedrine (Sudafed) to relieve congestion. Since pseudoephedrine is a CNS stimulant, when you add it to your coffee, you essentially double up on stimulants.
This can cause your blood pressure to skyrocket, putting unnecessary strain on your heart and making you feel extremely anxious, jittery, or paranoid as if you’ve had too many cups of coffee.
Blood thinners (anticoagulants)
Maintaining a finely tuned chemical balance within your bloodstream is necessary when taking daily medication to prevent life-threatening blood clots.
Blood thinners such as Warfarin (Coumadin) or the newer varieties such as Rivaroxaban (Xarelto) allow your blood to flow just right, but caffeine alone can decrease your blood’s clotting ability.
By consuming coffee daily along with your prescription blood thinner, you put yourself at a higher risk for bleeding internally and bruising way too easily from small injuries.
Sources: Please see here for a complete listing of all sources that were consulted in the preparation of this article.