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Preventing Drug Interactions

Being aware of the potential dangers can help keep you safe

Medications can help ease pains and cure diseases. But sometimes, mixing medications with other drugs, foods or supplements can result in unwanted side effects.

"A drug interaction is when after taking two medications, the body reacts in a way that would not be expected if each of the drugs was taken alone," says Daniel Dunham, MD, a primary care physician at Rush University Medical Center.

Sometimes, the interactions make the medications more potent, and other times less. Occasionally, these changes can be life threatening. Knowing about potential interactions — and how to prevent them — can keep you and your family safe.

What you need to know*

1. In some cases, taking two medications together can change how the drugs work.

For instance, simultaneously taking an aspirin to minimize blood clotting along with a non-steroidal anti-inflammatory drug (e.g., ibuprofen) for inflammation can reduce the aspirin's effectiveness.

2. Certain foods or beverages can increase or reduce a drug's effectiveness.

For example, grapefruit juice acts on an enzyme responsible for breaking down cholesterol-lowering statins. This makes the statins too strong and can increase potential side effects, ranging from joint pain to kidney failure.

And be aware that some medications — like beta blockers — work more steadily with a full stomach while others work best on an empty stomach. Check your labels before your first dose.

Here are some common food/medication combinations to avoid:

  • Grapefruit juice and statins
  • Dairy and certain antibiotics
  • Leafy greens and blood thinners
  • Natural black licorice and certain heart and blood pressure medications
  • Chocolate, processed meats or aged cheese and MAOI inhibitors

3. Sometimes, a medication for one condition can make another condition worse.

For instance, some antidepressants, like amitriptyline, can affect your heart rate.

4. Certain over-the-counter medications are more likely to cause interactions.

Note that these types of medications often have drug interaction warnings:

  • Antacids
  • Antihistamines
  • Laxatives
  • Decongestants
  • Nicotine replacements
  • Pain relievers
  • Sleep aids

Not only can it make driving dangerous, but sometimes mixing medication with alcohol — such as codeine and alcohol — can lead to coma.

5. Vitamins and herbal supplements can interact with medications.

For instance, studies show that St. John's wort — commonly taken for depression — decreases the effectiveness of several medications including oral contraceptives.

"Since supplements are not regulated by the Food & Drug Administration, we are not sure of what is in each dosage, making them unpredictable," Dunham says. "There is not much data saying vitamins and supplements make a big difference. So it's probably better to skip them." 

The best way to get megadoses of vitamins? Eat more fresh fruits and vegetables.

6. Mixing alcohol with medications can be dangerous.

Not only can it make driving dangerous, but sometimes mixing medication with alcohol — such as codeine and alcohol — can lead to coma.

Heart medications and antidepressant should never be mixed with alcohol, either.

Keep yourself safe

Given that so many things can cause potentially harmful interactions, Dunham says it's important to always do the following:

  • Read the labels. You will learn what the medication is used for, its active and inactive ingredients (which might interfere with other medications), how to take the medication and how to limit unwanted interactions. Call the phone number on the label if you have other questions.
  • Ask your doctor questions. "We like it when you come to appointments with questions," Dunham says. "When you get a new prescription or take a new over-the-counter medication, look up information on the Web, then bring in your questions. Your doctor will make sure the information you found online applies to you."

Just make sure to use a reliable source, such as the National Institutes of Health or Centers for Disease Control, since the Internet houses some bad information.

  • Talk to your pharmacist. The pharmacist is another great resource, according to Dunham. "He or she can answer questions on site, before you buy an over-the-counter medication or supplement," Dunham says. "This is really important when you're taking a prescription drug as well."

Even if you get the information you need from the pharmacist, follow up with your doctor to make sure he or she is aware you're taking something new that could affect your care or your health down the road.

  • Use the same doctor and pharmacist. "Go to the professionals who know you and your family well," Dunham says. "That way, they will have the most comprehensive list of your conditions and medications, and there is far less risk of information falling through the cracks."

Sign documents at your doctors' offices or from their websites allowing information to be exchanged between your primary care doctor and your specialists. Often, electronic medical records alert the physician or pharmacist when there are potentially dangerous interactions, but that only works if the documents are signed. 

  • Make a list. Carry a list of all the prescriptions (including topical medicines), over-the-counter drugs, vitamins, supplements and herbal remedies that you use. Show the list to any medical professionals you visit — doctors, pharmacist, nurse practitioner, etc. And be sure to give a copy of your list to your emergency contact(s).

Keep separate lists (on paper or on your phone) of any medications your spouse, children and elderly parents are taking.

"Also, don't forget to update your list every time you start or stop taking something," Dunham advises. "If there's an emergency and you can't communicate, you want health care providers and your family to have accurate information."

 Bottom line: Although there are risks to some medications, you should always take your prescriptions as directed by your doctor.

"Overall, just be mindful of what you're taking," Dunham says. "And be sure to keep your entire medical team informed."

*This is not mean to be a comprehensive list of all potential interactions. Talk to your doctor or pharmacist before starting any new medication (prescription or over-the-counter), vitamin or supplement to make sure it does not interact with anything you are currently taking.

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