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Drug Interactions: What You Should Know
Drug Interactions
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.
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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
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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. |
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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.
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:
|
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
|
Bronchodilators
(drugs for the temporary relief of shortness of breath, tightness of chest
and wheezing due to bronchial asthma) |
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
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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.
To order one copy of this booklet, write:
Federal Citizen Information Center
Item #527M
Pueblo, CO 81009
www.pueblo.gsa.gov
Consumer Education: Ensuring Safe Use
of Medicine
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Date created: March 03, 2003; Updated March 24, 2006 |
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