Drug Interactions: What You Should Know

There are more opportunities today than ever before to learn about your health and to take better care of yourself. It is also more important than ever to know about the medicines you take. If you take several different medicines, see more than one doctor, or have certain health conditions, you and your doctors need to be aware of all the medicines you take. Doing so will help you to avoid potential problems such as drug interactions.

Drug interactions may make your drug less effective, cause unexpected side effects, or increase the action of a particular drug. Some drug interactions can even be harmful to you. Reading the label every time you use a nonprescription or prescription drug and taking the time to learn about drug interactions may be critical to your health. You can reduce the risk of potentially harmful drug interactions and side effects with a little bit of knowledge and common sense. Drug interactions fall into three broad categories:

Drug-drug interactions occur when two or more drugs react with each other. This drug-drug interaction may cause you to experience an unexpected side effect. For example, mixing a drug you take to help you sleep (a sedative) and a drug you take for allergies (an antihistamine) can slow your reactions and make driving a car or operating machinery dangerous.
Drug-food/beverage interactions result from drugs reacting with foods or beverages. For example, mixing alcohol with some drugs may cause you to feel tired or slow your reactions.
Drug-condition interactions may occur when an existing medical condition makes certain drugs potentially harmful. For example, if you have high blood pressure you could experience an unwanted reaction if you take a nasal decongestant.

Drug Interactions and Over-the-Counter Medicines

Over-the-counter (OTC) drug labels contain information about ingredients, uses, warnings and directions that is important to read and understand. The label also includes important information about possible drug interactions. Further, drug labels may change as new information becomes known. That's why it's especially important to read the label every time you use a drug.

The "Active Ingredients" and "Purpose" sections list:
- the name and amount of each active ingredient
- the purpose of each active ingredient

The "Uses" section of the label:
- tells you what the drug is used for
- helps you find the best drug for your specific symptoms

The "Warnings" section of the label provides important drug interaction and precaution information such as
- when to talk to a doctor or pharmacist before use
- the medical conditions that may make the drug less effective or not safe
- under what circumstances the drug should not be used
- when to stop taking the drug

The "Directions" section of the label tells you:
- the length of time and the amount of the product that you may safely use
- any special instructions on how to use the product

The "Other Information" section of the label tells you:
- required information about certain ingredients, such as sodium content, for people with dietary restrictions or allergies

The "Inactive Ingredients" section of the label tells you:
- the name of each inactive ingredient (such as colorings, binders, etc.)

The "Questions?" or "Questions or Comments?" section of the label (if included):
- provides telephone numbers of a source to answer questions about the product

Learning More About Drug Interactions

Talk to your doctor or pharmacist about the drugs you take. When your doctor prescribes a new drug, discuss all OTC and prescription drugs, dietary supplements, vitamins, botanicals, minerals and herbals you take, as well as the foods you eat. Ask your pharmacist for the package insert for each prescription drug you take. The package insert provides more information about potential drug interactions.

Before taking a drug, ask your doctor or pharmacist the following questions:

Can I take it with other drugs?
Should I avoid certain foods, beverages or other products?
What are possible drug interaction signs I should know about?
How will the drug work in my body?
Is there more information available about the drug or my condition (on the Internet or in
health and medical literature)?

Know how to take drugs safely and responsibly. Remember, the drug label will tell you:

what the drug is used for
how to take the drug
how to reduce the risk of drug interactions and unwanted side effects

If you still have questions after reading the drug product label, ask your doctor or pharmacist for more information

Remember that different OTC drugs may contain the same active ingredient. If you are taking more than one OTC drug, pay attention to the active ingredients used in the products to avoid taking too much of a particular ingredient. Under certain circumstances — such as if you are pregnant or breast-feeding — you should talk to your doctor before you take any medicine. Also, make sure you know what ingredients are contained in the medicines you take. Doing so will help you to avoid possible allergic reactions.

Examples of Drug Interaction Warnings

The following are examples of drug interaction warnings that you may see on certain OTC drug products. These examples do not include all of the warnings for the listed types of products and should not take the place of reading the actual product label.

Drug Interaction Information
Category	Drug Interaction Information
Acid Reducers H2 Receptor Antagonists (drugs that prevent or relieve heartburn associated with acid indigestion and sour stomach)	For products containing cimetidine, ask a doctor or pharmacist before use if you are: taking theophylline (oral asthma drug), warfarin (blood thinning drug), or phenytoin (seizure drug)
Antacids (drugs for relief of acid indigestion, heartburn, and/or sour stomach)	Ask a doctor or pharmacist before use if you are: allergic to milk or milk products if the product contains more than 5 grams lactose in a maximum daily dose taking a prescription drug Ask a doctor before use if you have: kidney disease
Antiemetics (drugs for prevention or treatment of nausea, vomiting, or dizziness associated with motion sickness)	Ask a doctor or pharmacist before use if you are: taking sedatives or tranquilizers Ask a doctor before use if you have: a breathing problem, such as emphysema or chronic bronchitis glaucoma difficulty in urination due to an enlarged prostate gland When using this product: avoid alcoholic beverages
Antihistamines (drugs that temporarily relieve runny nose or reduce sneezing, itching of the nose or throat, and itchy watery eyes due to hay fever or other upper respiratory problems)	Ask a doctor or pharmacist before use if you are taking: sedatives or tranquilizers a prescription drug for high blood pressure or depression Ask a doctor before use if you have: glaucoma or difficulty in urination due to an enlarged prostate gland breathing problems, such as emphysema, chronic bronchitis, or asthma When using this product: alcohol, sedatives, and tranquilizers may increase drowsiness avoid alcoholic beverages
Antitussives Cough Medicine (drugs that temporarily reduce cough due to minor throat and bronchial irritation as may occur with a cold)	Ask a doctor or pharmacist before use if you are: taking sedatives or tranquilizers Ask a doctor before use if you have: glaucoma or difficulty in urination due to an enlarged prostate gland
Ask a doctor before use if you: have heart disease, high blood pressure, thyroid disease, diabetes, or difficulty in urination due to an enlarged prostate gland have ever been hospitalized for asthma or are taking a prescription drug for asthma
Laxatives (drugs for the temporary relief of constipation)	Ask a doctor before use if you have: kidney disease and the laxative contains phosphates, potassium, or magnesium stomach pain, nausea, or vomiting
Nasal Decongestants (drugs for the temporary relief of nasal congestion due to a cold, hay fever, or other upper respiratory allergies)	Ask a doctor before use if you: have heart disease, high blood pressure, thyroid disease, diabetes, or difficulty in urination due to an enlarged prostate gland
Nicotine Replacement Products (drugs that reduce withdrawal symptoms associated with quitting smoking, including nicotine craving)	Ask a doctor before use if you: have high blood pressure not controlled by medication have heart disease or have had a recent heart attack or irregular heartbeat, since nicotine can increase your heart rate Ask a doctor or pharmacist before use if you are: taking a prescription drug for depression or asthma (your dose may need to be adjusted) using a prescription non-nicotine stop smoking drug Do not use: if you continue to smoke, chew tobacco, use snuff, or use other nicotine-containing products
Nighttime Sleep Aids (drugs for relief of occasional sleeplessness)	Ask a doctor or pharmacist before use if you are: taking sedatives or tranquilizers Ask a doctor before use if you have: a breathing problem such as emphysema or chronic bronchitis glaucoma difficulty in urination due to an enlarged prostate gland When using this product: avoid alcoholic beverages
Pain Relievers (drugs for the temporary relief of minor body aches, pains, and headaches)	Ask a doctor before taking if you: consume three or more alcohol-containing drinks per day (The following ingredients are found in different OTC pain relievers: acetaminophen, aspirin, ibuprofen, ketoprofen, magnesium salicylate, and naproxen. It is important to read the label of pain reliever products to learn about different drug interaction warnings for each ingredient.)
Stimulants (drugs that help restore mental alertness or wakefulness during fatigue or drowsines)	When using this product: limit the use of foods, beverages, and other drugs that have caffeine. Too much caffeine can cause nervousness, irritability, sleeplessness, and occasional rapid heart beat be aware that the recommended dose of this product contains about as much caffeine as a cup of coffee
Topical Acne (drugs for the treatment of acne)	When using this product: increased dryness or irritation of the skin may occur immediately following use of this product or if you are using other topical acne drugs at the same time. If this occurs, only one drug should be used unless directed by your doctor

This information is brought to you by the Council on Family Health in cooperation with the National Consumers League and the U.S. Food and Drug Administration.