Make us your home page

Today’s top headlines delivered to you daily.

(View our Privacy Policy)

How to avoid dangerous drug interactions

Too often we don't pay attention to the fine print on our drug bottles: Take with food. Take on an empty stomach. But even the fine print may not tell you about serious drug interactions that may occur with everyday foods and beverages that can wreak serious havoc with your body. Down your blood pressure meds with a frosty glass of grapefruit juice, and you may throw off your blood pressure levels. Swallow certain antibiotics with a glass of milk and the drug's infection-fighting powers may be reduced. To better understand the relationship between what we eat and the medications we take, we consulted Glenn Whelan, who teaches pharmacology at the University of South Florida's College of Medicine. He helped us to outline the following dos and don'ts. If you notice any potentially harmful combinations that are a part of your regimen, don't quit cold turkey. Your body may have already adjusted, so a sudden change could make things worse. Instead, call your doctor. And next time you get a new prescription, ask your doctor or pharmacist about any dietary restrictions and read all accompanying literature.


Compounds in grapefruit can inhibit how some drugs are broken down in the gut, meaning you might get a stronger dose. Watch out if you are taking:

• Blood pressure medications like Procardia, Norvasc and Cardizem, known as calcium channel blockers. The juice, particularly juice made from a concentrate, could enhance the drug's impact and your blood pressure could drop beyond what is safe, leading to dizziness and unintended falls.

• Statins, including Lipitor, Zocor and lovastatin. You're at greater risk of liver injury and a condition involving the dangerous breakdown of muscle cells.

• Oral antifungals. Side effects like an upset stomach can be heightened.


Severe jitters — including shaky hands and even tremors — can result from combining too much caffeine with asthma meds like albuterol, Advair and Symbicort.

Caffeine also can amplify the effect of Ritalin, a stimulant.

Since caffeine irritates the stomach lining, you can get a double whammy with drugs that cause nausea. Consider this before taking narcotic painkillers (Vicodin, Percocet) with a morning cup of joe.

Coffee is an obvious source of caffeine, but beware of chocolate, too. Dark chocolate in particular may pack more stimulant punch than you realize.


Milk and calcium supplements may be essential to healthy bones, but they don't mix well with a class of infection-fighting antibiotics called fluoroquinolones (Cipro, Levaquin, Avelox). That's also true for tetracycline, another antibiotic often prescribed to treat women's acne.

Calcium interferes with the absorption of these antibiotics. So do the magnesium and aluminum compounds in some antacids.

But you do need calcium. If you're taking these drugs, just allow a few hours between swallowing your medication and having dairy products or taking an antacid or calcium supplement.


Broccoli, Brussels sprouts, cabbage, collard greens and spinach can be dangerous for people on the blood-thinning drug Coumadin. These leafy greens, as well as liver and beef, are rich in vitamin K, key to blood clotting.

They also have a lot of other vital nutrients, so again, you may not want to eliminate them entirely. With these foods, doctors and pharmacists typically tell patients to limit how much they eat. Consider keeping a food diary as you get started on Coumadin to share with the medical professionals monitoring your blood work.


When dealing with hypertension, a diuretic or water pill is often prescribed to help lower blood pressure. But the drug can also cause the body to lose too much potassium.

To make sure you're getting enough, add a medium-sized banana to your daily diet.

But check with your doctor before doing so. A class of diuretics spare potassium in the body, including the ACE inhibitors commonly used in patients with congestive heart failure. If you're on these drugs, you could be at risk for building up too much potassium.

Either way, take care when quenching your thirst with Gatorade, which many don't realize contains substantial potassium.


It's wise to lay off alcohol while you're on medication, as it can increase or decrease the effects of drugs.

But especially never drink alcohol while taking Valium or any other benzodiazepines or morphine — the results can range from extreme sleepiness to death.

Even something as innocuous as over-the-counter Tylenol shouldn't be mixed with alcohol. Over time, the combination can lead to liver problems.

Don't drive if you've combined alcohol with any drugs, including cold remedies. You may be fine to drive after a beer or two, but added medications can make you drowsy and dizzy.

And keep in mind that alcohol, if mixed with antidepressants or other drugs used in treatment for mental illness, can increase negative emotions of hopelessness and helplessness, especially in adolescents.


Many gourmet treats are high in tyramine, an amino acid that can invoke unpleasant reactions with two powerful antibiotics: Zyvox and isoniazid. The effects range from a flushed face and sweating to altered blood pressure.

Foods high in tyramine include aged hard cheeses, aged or cured meats, certain types of wines (Chianti and Riesling, sherry), overripe avocados, figs and sauerkraut.


Combined with Lanoxin, a drug used to treat congestive heart failure, licorice can increase the risk of palpitations, blurred vision and nausea. Licorice can also reduce the effects of diuretics used to treat high blood pressure.

How to avoid dangerous drug interactions 07/14/10 [Last modified: Wednesday, July 14, 2010 5:21pm]
Photo reprints | Article reprints

© 2017 Tampa Bay Times


Join the discussion: Click to view comments, add yours

  1. Trigaux: Amid a record turnout, regional technology group spotlights successes, desire to do more


    ST. PETERSBURG — They came. They saw. They celebrated Tampa Bay's tech momentum.

    A record turnout event by the Tampa Bay Technology Forum, held May 24 at the Mahaffey Theater in St. Petersburg, featured a panel of area tech executives talking about the challenges encountered during their respective mergers and acquisitions. Show, from left to right, are: Gerard Purcell, senior vice president of global IT integration at Tech Data Corp.; John Kuemmel, chief information officer at Triad Retail Media, and Chris Cate, chief operating officer at Valpak. [Robert Trigaux, Times]
  2. Take 2: Some fear Tampa Bay Next transportation plan is TBX redux


    TAMPA — For many, Wednesday's regional transportation meeting was a dose of deja vu.

    The Florida Department of Transportation on Monday announced that it was renaming its controversial Tampa Bay Express plan, also known as TBX. The plan will now be known as Tampa Bay Next, or TBN. But the plan remains the same: spend $60 billion to add 90 miles of toll roads to bay area interstates that are currently free of tolls. [Florida Department of Transportation]
  3. Hailed as 'pioneers,' students from St. Petersburg High's first IB class return 30 years later


    ST. PETERSBURG — The students came from all over Pinellas County, some enduring hot bus rides to a school far from home. At first, they barely knew what to call themselves. All they knew was that they were in for a challenge.

    Class of 1987 alumni Devin Brown, from left, and D.J. Wagner, world history teacher Samuel Davis and 1987 graduate Milford Chavous chat at their table.
  4. Flower boxes on Fort Harrison in Clearwater to go, traffic pattern to stay


    I travel Fort Harrison Avenue in Clearwater often and I've noticed that the travel lanes have been rerouted to allow for what looks like flower boxes that have been painted by children. There are also a few spaces that push the travel lane to the center that have no boxes. Is this a permanent travel lane now? It …

  5. Palm Harbor boat dealer facing litany of complaints of bad deals


    PALM HARBOR — With an aging father sick in the hospital and a son just graduating high school, Andrew Kashella, in between jobs, knew what he had to do.

    A sign on a front window of Gulf Coast Boat Sales, 37517 Us Highway 19 N, in Palm Harbor, notifies people they are under restructuring  The Pinellas County Sheriff's Office has received 20 complaints against Gulf Coast Boat Sales in Palm Harbor. Complainants say they sold the shop their boats and never got paid and/or paid for boats they never received. Pinellas County Consumer Protection is leading the investigation.