Drugs can interact with food in various ways. Some medications, e.g., levothyroxine, should be taken on an empty stomach as food reduces the absorption of certain drugs. Alcohol can potentiate the effects of drugs like Valium (diazepam), besides causing adverse effects.
| 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 |
Occur when a disease condition puts an individual at higher risk of adverse effects from taking certain medications. For example, hypertension and nasal decongestants could cause dangerously elevated blood pressure; beta blockers like propranolol in a patient with asthma can precipitate severe asthma; and high-dose acetaminophen in a patient with liver disease can cause toxicity.
Certain drugs can interfere with and change laboratory test results by altering the specimen or reacting with the test reagents. Examples are Biotin supplements erroneously lowering troponin levels in laboratory tests, thus interfering with the diagnosis of heart attacks; cephalosporin antibiotics causing false positive glucose and ketone tests; and PPIs like omeprazole, which interfere with the INR test (for evaluating blood clotting).
| 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 |
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