OTC Drug Interactions

As cold and flu season approaches, many people will be flocking to the drugstore to stock up on over-the-counter (OTC) or nonprescription medications. While these medications are readily available to consumers, there are precautions customers should keep in mind to prevent consequences from drug interactions.

The U.S. Food and Drug Administration (FDA) says label comprehension is one of the most important factors to preventing an over-the-counter drug interaction. Always read medication labels before buying or ingesting a medication. The FDA says there are several different things to look for on the label of a product:

• PRODUCT NAME
• "ACTIVE INGREDIENTS": therapeutic substances in medicine
• "PURPOSE": product category (such as antihistamine, antacid, or cough suppressant)
• "USES": symptoms or diseases the product will treat or prevent
• "WARNINGS": when not to use the product, when to stop taking it, when to see a doctor, and possible side effects
• "DIRECTIONS": how much to take, how to take it, and how long to take it
• "OTHER INFORMATION": such as storage information
• "INACTIVE INGREDIENTS": substances such as binders, colors, or flavoring

Bemedwise.org posts suggestions for adults, parents and caregivers on how to get the maximum results from over-the-counter medications. Bemedwise says it is important to look for a medicine to treat ONLY the symptoms one is suffering from. This will help to prevent the mixing and matching of the wrong drugs—which could cause an undesired interaction.

The site stresses while taking over-the-counter medications, never assume anything. If in doubt, always address concerns to a pharmacist or doctor. Also, make sure to flip on a light or wear glasses when reading labels to prevent dosage mistakes. This is especially important for parents administering medications via droplets to babies and children.

The FDA says drug interactions are broken down into three categories: drug-drug, drug-food/beverage, and drug-condition. Drug-drug occurs when combining two or more drugs.

The FDA uses the example of mixing a sedative (sleep aid) with an anti-histamine (allergy medication), which would result in delayed reactions, where operating a vehicle could be a potentially dangerous activity. WebMD lists drug-drug interactions: the upcoming holiday season usually calls for overeating and a supply of acid reducers, which should not be combined with theophylline (oral asthma drug), warfarin (blood thinning drug) and phenytoin (seizure drug). Many people grab an Antitussive (cough suppressant) for the alleviation of the common cold, but WebMD suggests consulting a doctor before taking this with a sedative or tranquilizer. FamilyDoctor.org suggests not taking medications with the same active ingredients (substances that work to alleviate one's symptoms).

CVS Caremark also lists drug interactions to avoid: the Birth Control Pill can lose its effectiveness when mixed with Antibiotics. Matthew Grissinger is a pharmacist and an educator at the Institute for Safe Medication Practices says to use backup protection if you are on the pill and need to use antibiotics.

Delayed reactions can also occur from drug-food/beverage interactions. The FDA says one of the most common drug-food/beverage dangers is the mixture of alcohol with medications.

The American Association of Retired Persons (AARP) says not to mix grapefruit juice and blood-pressure lowering medications, and The Methodist Hospital System of Houston Texas, lists several of the most common drug-food/beverage interactions:

Aspirin and other OTC medications combined with a low vitamin-C intake can cause stomach bleeding; Asthma Medicines can lose effectiveness when combined with caffeine, high protein, low carbohydrate diets and charbroiled foods; Dairy intake should be limited when taking Antibiotics because it blocks the absorption of a certain class of the medication; and, the absorption of penicillin is limited when taken with food. One potentially deadly combination is Antidepressants with the following: aged cheese, Chianti wines, chicken livers, various pickled, aged and fermented foods, which can cause fever, high blood pressure and even death.

A drug-condition interaction results when consuming a certain drug will be dangerous to someone's pre-existing condition. The FDA uses the example, if one suffers from high blood pressure, refrain from using nasal decongestants. AARP.org says body changes in the elderly due to aging affect medication interactions. The absorption, metabolic, distribution and excretion processes can take longer, causing more interactions because foods and beverages are staying in one's system longer.

The Institute for Safe Medication Practices says staying an informed consumer is the way to avoid bad drug combinations. The Institute suggests keeping a list of medications you are currently taking, and update the list as new medications are incorporated into your lifestyle. The Institute stresses always taking the correct or included measuring device--do not rely on household teaspoons and tablespoons.

According to the Institute of Medicine, about 400,000 drug-related preventable injuries are reported in U.S. hospitals. According to Familydoctor.org, the effects of interactions are dizziness, nausea and bleeding in the gastrointestinal tract (GI). FamilyDoctor.org also says the most common adverse effects of drug combinations are more likely to happen when someone is taking three to four OTC medications daily. At that rate, the most likely candidates to get an adverse drug interaction are the elderly. According to AARP.org, sixty-seven percent of Americans 50 years old and over take an average of four medications every day.


The web provides many options to research specific drug combinations to ensure the drugs' compatibility. IGuard.org is a website offering a personalized alert system for patients and their health care team. The site alerts members with updates on the safety of their current medications. The site has a personalized safety scale for the medications for each of its members.



DiscoveryHealth provides a similar type of service, but focusing more on drug interactions. Users have the ability to click on several medications' names to find out if those medications will have a negative interaction with one another.

The most important advice when taking over-the-counter medications is to stay informed. Read, read, read and keep updated on each medication's effect on your body. Keep daily medications organized and take proper dosages. Do not take multiple medications that have the same active ingredients, and the FDA suggests using the same pharmacy for all of your drug needs.