Drug-food/beverage/nutrient interactions

Drugs can interact with foods, beverages, and nutrients in several ways. Sometimes food changes how much of a drug your body absorbs. For example, levothyroxine is typically taken on an empty stomach because food can reduce its absorption. Alcohol is another common interaction: it can intensify (potentiate) the effects of drugs such as Valium (diazepam) and can also increase the risk of adverse effects.

Common drug-food interactions

Drug-food combination	Effect
MAO inhibitors + high tyramine foods (cheese, wine, cured meats, bananas, etc.)	Potentially fatal increase in blood pressure, headache
Warfarin + Vit K-rich foods (kale, broccoli, etc.)	Reduced effect of warfarin causing blood clots
Digoxin + oatmeal	Decreased absorption due to high fiber
Bisphosphonates + any food	Decreased absorption and effect
Tetracycline + milk/dairy products	Decreased absorption from forming calcium complexes

Drug-condition/disease interactions

Drug-condition (or drug-disease) interactions happen when a medical condition increases the risk of adverse effects from a medication.

For example:

• Hypertension + nasal decongestants can lead to dangerously elevated blood pressure.
• Beta blockers such as propranolol in a patient with asthma can precipitate severe asthma.
• High-dose acetaminophen in a patient with liver disease can cause toxicity.

Drug-laboratory interactions

Some drugs interfere with laboratory test results. They can do this by altering the specimen or by reacting with test reagents.

Examples include:

• Biotin supplements can erroneously lower troponin levels in laboratory tests, interfering with the diagnosis of heart attacks.
• Cephalosporin antibiotics can cause false-positive glucose and ketone tests.
• PPIs such as omeprazole can interfere with the INR test (used to evaluate blood clotting).

Drug interactions with herbal supplements

Herbal supplement	Drug involved	Effect
CoQ-10	Warfarin \ Blood pressure medications	Risk of clotting \ Decreased blood pressure
Danshen	Warfarin, clopidogrel, aspirin \ Digoxin	Risk of bleeding \ Digoxin toxicity
Evening primrose; Saw palmetto	Warfarin, clopidogrel, aspirin	Risk of bleeding
Ginkgo biloba	Warfarin, clopidogrel, aspirin	Risk of bleeding
Hawthorn	Digoxin and other cardiac medications	Risk of toxicity like bradycardia, hypotension, arrhythmias, cardiac arrest
Licorice	Warfarin \ Digoxin	Risk of clotting \ Digoxin toxicity
St.John’s wort	Warfarin \ Multiple interactions with cardiac drugs, statins, immunosuppressants, antidepressants, benzodiazepines, anti-epileptics, birth control pills, anti-HIV drugs	Risk of clotting \ Decreased effect, increased toxicity