Surprise Medication Blockers

Be aware: certain foods and beverages can block your meds.


If you’re like most people, you down your pills with juice or food, thinking you’re doing your stomach a favor by not taking the medications alone. As it turns out, you may be doing more harm than good due to food-drug interactions.

While some medications should be taken with food to increase their absorption or decrease their risk of side effects, in other cases taking with food – sometimes very specific foods or beverages – can reduce a drug’s effectiveness, or even increase their potency.

“Twenty years ago, a team of researchers and I realized that grapefruit juice could cause many medications to be as much as 10 times more powerful than they’re meant to be,” says David G. Bailey, PhD, clinical professor of pharmacology at the University of Western Ontario in Canada.

Thanks to their research, more than 50 medications now carry cautions about grapefruit juice on their labels.

Now Bailey has discovered that grapefruit, apple and orange juices can actually have the opposite effect on certain other drugs. “They block the pills’ absorption, so you get less or even no benefit from taking them,” says Bailey. “This might cause someone to think that they need to switch to a ‘better’ medication – when in fact changing what they eat, or when, would make the drug effective.”

Here are some common pill blockers to watch out for:

FOOD: Milk and yogurt
BLOCKS: Iron supplements; many antibiotics, including fluoroquinolone, ciprofloxacin and “cycline” antibiotics like tetracycline; thyroid hormone; and penicillamine (Cuprimine, Depen), a disease-modifying antirheumatic drug

FOOD: Apple, orange and grapefruit juice
BLOCKS: Disease-modifying antirheumatic drugs, including methotrexate (Rheumatrex, Trexall, Otrexup, Rasuvo); cyclosporine (Gengraf, Neoral, Sandimmune), a drug used for severe psoriasis and rheumatoid arthritis; beta blockers like acebutol (Sectral); cancer drugs like etoposide (Etopophos, Vepesid); alendronate (Fosamax), an osteoporosis drug; the allergy medicine fexofenadine (Allegra); some antibiotics including ciprofloxacin (Cipro) and levofloxacin (Levaquin)

FOOD: Coffee
BLOCKS: Alendronate; the antibiotic penicillin

FOOD: Foods rich in vitamin K, including leafy green vegetables and liver
BLOCKS: Blood thinners like warfarin (Coumadin)

FOOD: Alcohol
BLOCKS: Antidepressants, especially monoamine oxidase inhibitors (MAOIs) like tranylcypromine (Parnate). People taking SSRIs like fluoxetine (Prozac) should avoid drinking more than moderate amounts of alcohol as well, as it counteracts their benefits.

FOOD: Licorice

BLOCKS: blood pressure drugs or diuretic drugs, including hydrochlorothiazide (Hydrodiuril) and spironolactone (Aldactone) .

FOOD: Oatmeal (and other high-fiber foods)

BLOCKS: the congestive heart failure drug digoxin (Lanoxin, Cardoxin).

How long should you wait?

In most cases, you can consume an "offending" food or beverage about three to four hours after you’ve taken your meds, but it’s best to ask your pharmacist, who can tell you for sure. Plus, she can check to see if other medications or supplements you take might further affect how your body absorbs your medicines.

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