Meds Not to Mix: Your Guide to Taking OTC Drugs Safely

Jonathan Kantor/FITNESS Magazine
Jonathan Kantor/FITNESS Magazine

By Rebecca Brown

With all the meds on the market these days, it's tough to keep straight what is safe to take and what isn't unless there's an MD at the end of your name. Here, the way prescriptions, OTC pills, and even food can interact with each other.

Related: Prescription for Danger: 7 Harmful Health Shortcuts

Grapefruit Juice and OTC Antihistamine, Fexofenadine (Allegra)
A study conducted by the University of Western Ontario in Canada revealed that grapefruit products and some citrus fruits, like oranges, contain chemicals that can affect various medications in your body, often times causing the medicine to stay in your body longer. "In grapefruit juice, it is thought that naringin, a flavonoid compound naturally found in the fruit, interferes with the absorption of some drugs," says Joseph S. Bertino Jr., Pharm.D and associate professor of pharmacology at Columbia University. "Grapefruit juice turns on a pump in the small intestine that blocks some drugs from moving through and into the blood."

If you were to take Allegra with grapefruit juice, the liquid can actually decrease the amount that reaches the bloodstream, making it less -- if not completely -- ineffective. The way grapefruit juice affects drug absorption is dependent on the source of the juice (fresh, frozen, or bottled), but Bertino says that to be safe, unless told otherwise, take medications with only water.

Alcohol and Acetaminophen (Tylenol)
Tylenol has long been the go-to OTC pain and fever reliever because it doesn't irritate the stomach, but it's also the most misunderstood. Because acetaminophen is found in much more than just Tylenol -- it's an ingredient in cold remedies and prescription painkillers like Vicodin -- people can end up taking too much. "Acetaminophen overdose is the number one cause of acute liver failure in the United States," says Sandra Adamson Fryhofer, MD, MACP. "The liver damage from this is irreversible." Last year, the FDA limited prescription acetaminophen combination products to 325 mg per tablet, but even if you take the medication as prescribed, introducing alcohol can be toxic. "If you are drinking three or more drinks per day and take the recommended daily dose of acetaminophen, you are at risk for acute liver failure," adds Fryhofer. While Ibuprofen (part of the anti-inflammatory family referred to as NSAIDs) is a better choice, if you have more than three drinks, you can irritate the stomach.

Milk and Ciprofloxacin or Levofloxacin
Many women treat urinary tract infections with ciprofloxacin or levofloxacin, but taking the drug with milk, yogurt, or even calcium-fortified orange juice could result in mistreating the infection completely. Milk and other calcium-enriched liquids can bind infection-fighting Cipro in the digestive tract, preventing it from being absorbed into the bloodstream. "In terms of 'dangerous' drug-food interactions, most drug-food interactions reduce the absorption of drugs," says Bertino. Mixing these liquids can reduce the amount of drug absorbed into the blood so much that the antibiotic will not clear up the infection and the bacteria can even become resistant to those antibiotics. It's suggested that people wait a few hours between ingesting medicine and consuming dairy.

Related: What Your Gut Says About Your Health

Chocolate and Antidepressants
Before you curse your sweet tooth, let us explain. Chocolate is typically safe when consumed with a majority of antidepressants. However, there is one classification that can potentially have a bad interaction. Dr. Michael Lowenstein, co-medical director of the Waismann Method, the pioneering treatment for opiate dependency, explains that monoamine oxidase inhibitors (MAOIs) should not interact with large amounts of tyramine, a naturally occurring amino acid found in various foods. "Patients who are taking MAOIs should not consume foods with high levels of tyramine. Chocolate contains a small amount, but even so, patients taking MAOIs (such as Emsam) should be cautious," Lowenstein advises. If a large amount of chocolate is consumed along with MAOIs, there can be varying side-effects, including a sharp rise in blood pressure, increased headache, server nausea, and though rarely, death.

Licorice and Digoxin
A seemingly safe food, large amounts of the flavorful herb can actually decrease potassium levels in the body, which in turn, can increase the side effects of taking a drug like digoxin (used to treat congestive heart failure and other abnormalities in the heart). "If you mix the two it can cause digoxin toxicity which can be life threatening," says Fryhofer. Licorice has also been known to reduce the effects of blood pressure drugs. Side effects typically include irregular heart rates, diarrhea, nausea, and double vision.

St. John's Wort and Oral Contraception
A study at the University of Utah evaluating the effect of the herb on oral contraceptives found that the popular remedy is associated with breakthrough bleeding, follicle growth, and even ovulation. "People think that because it's herbal, it's safe, but that's not true either," says Fryhofer. This herb can reduce the effectiveness of medications in the blood, so women using OCs should be cautioned that St. John's Wort might not be the best bet. If you are taking birth control pills while using St. John's Wort, it's suggested that you use another form of birth control as well, like condoms.

Related: Why Little White Lies to Your Doctor Could Hurt Your Health

Xanax and Caffeine
Xanax, a benzodiazepine intended to depress the central nervous system, shouldn't be combined with other drugs that cause the same side effects. Along the same lines, people taking Xanax and other anti-anxiety medications should be careful when introducing caffeinated beverages. "Caffeine can counteract the intended effects of anti-anxiety medication," says Lowenstein. "Since drugs like Xanax and Ativan are used to reduce anxiety and have calming effects, mixing them with caffeine can cause an adverse interaction, like increased anxiety, insomnia, palpitations, agitation, and more." The amount you consume and your age and weight greatly affect interactions, but you should be careful and sip in moderation to play it safe.

More from FITNESS Magazine:
7 Recipes to Shake Up Your Snacks
9 Exercises for Strong, Sculpted Arms
10 Fit Ideas for Date Night