Would it occur to you not to swallow a tetracycline capsule, or the cipro-floxacin or ofloxacin antibiotic pill with a glass of milk? Or to avoid alcohol if you are taking a certain medicine for amoebiasis? Or not eat citrus fruits, pickles, and other acidic foods if you are taking erythromycin? Probably not! However, these are just some of the food-medicine interactions that you should stand guard against.

Many foods can affect the functioning of several medications. While some only hinder medications from doing their job, others can cause downright dangerous reactions triggering a sudden medical crisis.
Some foods contain natural or added chemicals that can react with certain medicines in ways that make the medicines virtually useless. For example, the calcium in dairy products can deliver a knock out punch to tetracyclines and quinolones. Acid fruit or vegetable juices can quash erythromycin and oral penicillin. Goitrogen substances in soybeans, turnips, cabbage, and Brussels sprouts can ruin the good work of thyroid medications by inhibiting the production of thyroid hormone. Liquorice (mulethi) a favourite ingredient of candy and a commonly used flavouring agent can counteract the effect of high blood pressure medications. The list could go on and on!
That’s not the only way foods affect medications. Just the simple presence of food in the digestive tract can also sometimes slow down or enhance the absorption of a medicine from the stomach. All antihistamine allergy pills, anti-hypertensive ACE inhibitor medications enalapril, lisinopril and quinapril, anti-tubercular medicine rifampicin, and many oral antibiotics find food a hindrance to their entering the bloodstream. However, the presence of certain foods also speeds up the absorption of some medications. For example, blood levels of griseofulvin, a medicine which fights ringworm, rise markedly if a fat-rich meal is taken before swallowing the medication.
If you wish to be careful of such mix-ups, here’s a list you might find handy...

w Metranidazole, an anti-amoebic pill, should not be followed by alcohol for at least three days after one stops the medication. Alcohol when taken with metronidazole can trigger a serious reaction causing nausea, abdominal cramps, vomiting and so on.
w Antibiotics such as tetracycline, doxicycline must not be taken with calcium-containing foods (milk, yoghurt, cheese, etc), vitamin-mineral supplements containing iron, and antacids. The presence of calcium, aluminium or iron interferes with the intestinal absorption of tetracycline and allows the medicine to go waste. If you have been prescribed erythromycin penicillin-V, avoid acidic foods. Increased stomach acidity can destroy these antibiotics.
w Quinolones such as ciprofloxacin, levofloxacin and ofloxacin must be taken on an empty stomach (like an hour before or two hours after a meal). Avoid calcium-containing foods (milk, yoghurt, cheese, etc), vitamin-mineral supplements containing iron, antacids, and caffeine containing drinks (coffee, cola drinks and tea). This facilitates a better absorption of the medicine. Some foods and supplements tend to decrease the useful concentration of quinolones in the body.
w Antifungal pills such as ketaconazole do not go down well with alcohol. The combination could lead to nausea, abdominal cramps, vomiting, headaches and a sudden drop in blood pressure. Avoid calcium-containing foods and antacids, as the presence of calcium, aluminium or magnesium interferes with the intestinal absorption of anti-fungal agents.
w People on blood pressure lowering pills or anti-hypertensive medications must avoid liquorice (mulethi). Regular intakes of liquorice increase the blood pressure and reduce the efficacy of these medicines.
w Anti-angina pills such as isosorbide dinitrate nitroglycerin if followed by alcohol could result in dangerously low blood pressure levels.
w If you are prescribed diuretic pills, avoid eating large amounts of potassium-rich foods such as bananas, oranges and green leafy vegetables, or salt substitutes that contain potassium. Potassium-sparing diuretics block the excretion of potassium. This can push up the potassium inside the body, and cause irregular heartbeat.
w Those taking cholesterol-lowering pills such as atorvastatin, lovastatin, simvastatin should avoid alcohol. Taking large amounts of alcohol increase risk of liver damage.
w Anticoagulant pills (blood-thinning agents) like coumadin, dicumarol etc., mustn’t be combined with foods high in vitamin K (such as green leafy vegetables, potatoes and liver), as they may counteract the blood-thinning effect.
w Soybeans, turnips, cabbage, Brussels sprouts, kale, etc contain goitrogens, substances, which inhibit production of the thyroid hormone, and so must not be taken if you are on thyroid medications.
Simple mantras to avoid the food-medication conflicts

w Never swallow a medicine with fruit juice, carbonated beverages, or caffeine drinks; instead rely on plain water.
w While taking a medicine give up alcohol.
w Seek your physician’s advice about the best timing of a medication and the foods and beverages you must avoid.

The author is Senior Specialist, Safdarjung Hospital, Professor, VM Medical College and a well-known columnist