OTC Medicines and How They Work
This information was developed as part of an educational program made possible by an unrestricted educational grant from McNeil Consumer & Specialty Pharmaceuticals.
In this section, you'll learn what you need to know to make wise choices about over-the-counter (OTC) medicines for you and your family. The following information has been adapted from the AAFP guide for physicians, "Appropriate Use of Common OTC Analgesics and Cough and Cold Medications."
In this section, you'll learn what you need to know to make wise choices about over-the-counter (OTC) medicines for you and your family. The following information has been adapted from the AAFP guide for physicians, "Appropriate Use of Common OTC Analgesics and Cough and Cold Medications."
What does OTC mean?
Do you know what's in the medicines you take?
Many OTC medicines contain the same ingredient found in prescription medicines. By combining a prescription medicine with an OTC medicine, you may be getting more than the recommended daily dose of the active ingredient. This medication chart can help you sort out what medicines have the same ingredient so you can avoid taking too much. If you have any questions, ask your pharmacist or family doctor.
A PDF version of this medication chart is available. Download PDF now (2 pages / 78 KB). About PDFs.
A PDF version of this medication chart is available. Download PDF now (2 pages / 78 KB). About PDFs.
OTC is short for over-the-counter. These are medicines you can buy without a prescription from your doctor. Chances are, you've used OTC medicines many times to relieve pain and treat symptoms of the common cold, the flu and allergies. In this section, you'll learn about four of the most common types of OTC products and how each works.
Pain Relievers
The OTC products that relieve your headache, fever or muscle aches are not all the same. That's because the pain relievers you see in the aisles of your local drug store or pharmacy are either nonsteroidal anti-inflammatory drugs (called NSAIDs, which include aspirin, ibuprofen, naproxen and ketoprofen) or acetaminophen. Each of these drugs has a different way of working:
Aspirin and NSAIDs relieve pain by stopping the production of prostaglandins, which are natural chemicals in the body. Prostaglandins irritate nerve endings, triggering the sensation of pain. Commonly used NSAIDs include:
Aspirin and NSAIDs relieve pain by stopping the production of prostaglandins, which are natural chemicals in the body. Prostaglandins irritate nerve endings, triggering the sensation of pain. Commonly used NSAIDs include:
- Aspirin, the medicine in products such as Bayer and St. Joseph
- Ibuprofen, the medicine in products such as Advil and Motrin IB
- Naproxen, the medicine in products such as Aleve
- Ketoprofen, the medicine in products such as Orudis KT
Acetaminophen relieves pain and reduces fever. We don't completely understand the way acetaminophen relieves pain. We do know that unlike aspirin and NSAIDs (which work in the skin, muscles and joints), acetaminophen blocks painful sensation in the brain and the spinal cord.
- Acetaminophen is in products such as Tylenol and Tempra.
Antihistamines
Antihistamines work by blocking the receptors that trigger itching, nasal irritation, sneezing and mucus production. The three types of antihistamines are:
- Diphenhydramine, the medicine in products such as Banophen, Benadryl Allergy and Diphenhist
- Brompheniramine, the medicine in products such as Dimetapp Allergy
- Chlorpheniramine, the medicine in products such as Aller-Chlor, Chlo-Amine and Chlor-Trimeton Allergy
Decongestants
Decongestants work by narrowing blood vessels in the lining of the nose. As a result, less blood is able to flow through the nasal area, and swollen tissue inside the nose shrinks. Pseudoephedrine is the only decongestant used in OTC products.
- Pseudoephedrine is in products such as Allermed, Genaphed and Sudafed.
Cough Medicines
Cough medicines are grouped into two types: antitussives and expectorants. Antitussives, or cough suppressants, block the cough reflex.
- Dextromethorphan is a common antitussive and is in products such as Delsym, Drixoral, Pertussin CS and Robitussin Pediatric.
Expectorants, on the other hand, are thought to thin mucus and make coughing more productive in clearing the mucus from the airway.
- Guaifenesin is the only expectorant used in OTC products and is in products such as Guiatuss, Robitussin and Tusibron.
Timeline of Symptoms Associated with the Common Cold
There is no cure for the common cold. Medicine can only make your symptoms less bothersome until your body can fight off the virus. Medicine won’t make your cold go away completely. The following are tips to help you feel better when you have a cold:
- Stay home and rest, especially while you have a fever.
- Don’t smoke and avoid secondhand smoke.
- Drink plenty of fluids like water, fruit juices and clear soups.
- Don’t drink alcohol.
- Gargle with warm salt water a few times a day to relieve a sore throat. Throat sprays or lozenges may also help relieve the pain.
- Use salt water (saline) nose drops to help loosen mucus and moisten the tender skin in your nose.
Many cold medicines are available over-the-counter. If you decide to use an OTC medicine to treat your cold symptoms, consult the chart below.
| Day | Symptoms | OTC Medicine |
|---|---|---|
| 1 | Fatigue, mild sore throat | Acetaminophen (some brand names: Panadol, Tempra, Tylenol) or nonsteroidal anti-inflammatory drug (ibuprofen [some brand names: Advil, Menadol, Motrin]) |
| 2 | Runny nose | Antihistamine (diphenhydramine [some brand names: Benadryl Allergy, Banophen, Diphenhist], chlorpheniramine [some brand names: Aller-Chlor, Chlo-Amine, Chlor-Trimeton Allergy]) |
| 3 | “Stopped up” nose | Decongestant (pseudoephedrine [some brand names: Allermed, Genaphed, Sudafed]) |
| 4 | Dry cough | Antitussive (dextromethorphan [some brand names: Drixoral, Pertussin CS, Robitussin Pediatric]) |
| 5 | Moist, productive cough | Expectorant (guiafenesin [some brand names: Guiatuss, Robitussin, Tusibron]) |
| 6 | Voice “breaks” or disappears altogether | No medicine will help your voice come back sooner. Resting it is the only thing that will help. |
How to Read an OTC Drug Label
You don't need a prescription to buy OTC medicine. But like prescription drugs, OTC medicines can also cause unwanted and sometimes dangerous side effects. Before you buy an OTC medicine, it's important to read and thoroughly understand the information on the drug label. Use the following as a guide. If you have questions about a medicine, ask your pharmacist or family doctor.
- Active Ingredient. The active ingredient is the chemical compound in the medicine that works to relieve your symptoms. It is always the first item on the label. There may be more than one active ingredient in a product. The label will clearly show this.
- Uses. This section lists the symptoms the medicine is meant to treat. The U.S. Food and Drug Administration (FDA) must approve these uses. Uses are sometimes referred to as "indications."
- Warnings. This safety information will tell you what other medicines, foods or situations (such as driving) to avoid while taking this medicine.
- Directions. Information about how much medicine you should take and how often you should take it will be listed here.
- Other Information. Any other important information, such as how to store the product, will be listed here.
- Inactive Ingredients. An inactive ingredient is a chemical compound in the medicine that isn't meant to treat a symptom. Inactive ingredients can include preservatives, binding agents and food coloring. This section is especially important for people who know they have allergies to food coloring or other chemicals.
- Questions or Comments. A toll-free number is provided to address any questions or comments you may have about the medicine.
How to Get the Most from Your Medicine
OTC medicines can help you feel better. But if they are taken the wrong way, they can actually make you feel worse. To use OTC medicines correctly, follow the guidelines below.
Talk to your family doctor
If there is something you don't understand about a medicine you're taking or are planning to take, ask your doctor or pharmacist. If you still don't understand, ask him or her to explain things more clearly. If you are taking more than 1 medicine, be sure to ask how the medicines will work together in your body. Sometimes medicines cause problems when they are taken together (called a drug interaction).
Below is a list of questions you can ask your doctor to learn how to use each medicine correctly and safely:
Talk to your family doctor
If there is something you don't understand about a medicine you're taking or are planning to take, ask your doctor or pharmacist. If you still don't understand, ask him or her to explain things more clearly. If you are taking more than 1 medicine, be sure to ask how the medicines will work together in your body. Sometimes medicines cause problems when they are taken together (called a drug interaction).
Below is a list of questions you can ask your doctor to learn how to use each medicine correctly and safely:
- What does the medicine do?
- When and how should I take the medicine?
- What are the possible side effects (reactions your body may have to the medicine)?
- Will the medicine react to any other medicines, foods or drinks?
- Should I avoid any activities while I'm taking the medicine?
- How will I know if the medicine is working?
Know about the medicine you take
You should know the following things about each medicine you take:
You should know the following things about each medicine you take:
- Name (generic name and brand name)
- Reason for taking it
- How much to take and how often to take it
- Possible side effects and what to do if you experience them
- How long to continue taking the medicine
- Special instructions (taking it at bedtime or with meals, etc.)
Know what to avoid while taking the medicine
Some foods can cause side effects, such as stomach upset, if you are taking medicine. Drinking alcohol is generally not a good idea while you are taking medicine. Some medicines cause reactions such as sun sensitivity (getting a sunburn or sun rash), so you may have to limit your outdoor activities or protect your skin from the sun.
Read the label to see what to avoid while you are taking an over-the-counter medicine. Follow the instructions just as you would with a prescription medicine. If you have questions, ask your doctor or pharmacist.
Follow these dos and don'ts:
Some foods can cause side effects, such as stomach upset, if you are taking medicine. Drinking alcohol is generally not a good idea while you are taking medicine. Some medicines cause reactions such as sun sensitivity (getting a sunburn or sun rash), so you may have to limit your outdoor activities or protect your skin from the sun.
Read the label to see what to avoid while you are taking an over-the-counter medicine. Follow the instructions just as you would with a prescription medicine. If you have questions, ask your doctor or pharmacist.
Follow these dos and don'ts:
- Do read the label carefully.
- Do take your medicine exactly as your doctor tells you to.
- Do make sure that each of your doctors (if you see more than one) has a list of all of the medicines you're currently taking.
- Do make sure everyone you live with knows what medicine you're taking and when you're supposed to take it.
- Don't combine prescription medicines and OTC medicines unless your doctor says it's okay.
- Don't stop taking a medicine, change how much you take or how often you take it without first talking to your doctor.
- Don't take someone else's medicine.
- Don't use medicine after its expiration date.
- Don't crush, break or chew tablets or capsules unless your doctor tells you to. Some medicines won't work right unless they are swallowed whole.
Understand generic vs. brand name
Just like foods, some medicines come in both brand names and generics. Generic medicines are generally cheaper. Compare the list of ingredients. If the generic has the same ingredients as the brand name, you may want to consider using it. But be careful: the generic may contain different amounts of certain medicines. Ask your doctor or pharmacist if you have questions about which medicine to choose.
Follow these tips for choosing medicines
Just like foods, some medicines come in both brand names and generics. Generic medicines are generally cheaper. Compare the list of ingredients. If the generic has the same ingredients as the brand name, you may want to consider using it. But be careful: the generic may contain different amounts of certain medicines. Ask your doctor or pharmacist if you have questions about which medicine to choose.
Follow these tips for choosing medicines
- If you have questions, ask your doctor or pharmacist.
- Although it can seem overwhelming, take the time to look at all the choices.
- Read the label carefully and note what symptoms the medicine will treat.
- Look for a medicine that will treat only the symptoms you have. For example, if you only have a runny nose, don't pick a medicine that also treats coughs and headaches.
- Note how much medicine you should take, and what side effects it may cause.
- Note what medicines or foods you should not take with the medicine.
- Check to see if the medicine causes problems for people with certain health problems (such as asthma or hypertension).
Know when to call your doctor
If you're taking an OTC medicine and it doesn't seem to be working, call your doctor. Your symptoms can get much worse if you wait too long to get treated by your doctor.
You should also call if you have side effects or any concerns about the medicine you're taking.
If you're taking an OTC medicine and it doesn't seem to be working, call your doctor. Your symptoms can get much worse if you wait too long to get treated by your doctor.
You should also call if you have side effects or any concerns about the medicine you're taking.
Potential Side Effects of OTC Medicines in Adults
While OTC medicines have a low risk of side effects when used occasionally by healthy adults, they can pose risks for very young children, the elderly, people with kidney problems and people taking more than one medicine. These people have an increased risk of side effects when they take OTC medicines. Potential side effects are described below.
Aspirin and NSAIDs
The main side effect associated with aspirin and other NSAIDs is gastrointestinal (GI) problems. These problems can range from upset stomach to GI bleeding, a serious event that is most likely to occur in older people. The chances of experiencing GI problems from NSAIDs or aspirin increase the larger the dose you take and the longer you take them.
NSAIDs can cause a variety of side effects related to kidney function. These side effects range from reversible inflammation to permanent kidney damage.
Aspirin and NSAIDs may make high blood pressure worse or interfere with blood pressure medicines.
High doses of aspirin pose a risk of liver damage for people who have liver disease, juvenile arthritis or rheumatic fever.
Acetaminophen
Although safe in the majority of users, long-term use of high doses of acetaminophen, especially in products that also contain caffeine (such as Excedrin) or codeine (such as Tylenol with Codeine), has been shown to cause a form of kidney disease called analgesic nephropathy. This serious condition may develop after years or decades of daily use.
Antihistamines
Antihistamines can cause sedation or drowsiness and, therefore, can significantly impair a person's ability to drive or operate machinery. The sedative effects of antihistamines may increase the risk of falling. Antihistamines can also cause temporary dry mouth or eyes.
Decongestants
Pseudoephedrine can temporarily cause nervousness, dizziness and sleeplessness. It can make you lose your appetite or retain urine. It can also cause heart palpitations, high blood pressure or high blood sugar levels.
Cough Medicines
Codeine, when used as a cough suppressant, can temporarily cause nausea, sedation and constipation. Dextromethorphan, the medicine in Drixoral, Pertussin CS and Robitussin, has a lower risk of sedation and GI side effects. It can, however, cause feelings of confusion, agitation, nervousness or irritability.
Drug-Drug Interactions
The body processes (metabolizes) every drug differently. If drugs are used together, their metabolism and effect on the body can change. When this happens, the chance that you will have side effects for each drug may become greater.
The main side effect associated with aspirin and other NSAIDs is gastrointestinal (GI) problems. These problems can range from upset stomach to GI bleeding, a serious event that is most likely to occur in older people. The chances of experiencing GI problems from NSAIDs or aspirin increase the larger the dose you take and the longer you take them.
NSAIDs can cause a variety of side effects related to kidney function. These side effects range from reversible inflammation to permanent kidney damage.
Aspirin and NSAIDs may make high blood pressure worse or interfere with blood pressure medicines.
High doses of aspirin pose a risk of liver damage for people who have liver disease, juvenile arthritis or rheumatic fever.
Acetaminophen
Although safe in the majority of users, long-term use of high doses of acetaminophen, especially in products that also contain caffeine (such as Excedrin) or codeine (such as Tylenol with Codeine), has been shown to cause a form of kidney disease called analgesic nephropathy. This serious condition may develop after years or decades of daily use.
Antihistamines
Antihistamines can cause sedation or drowsiness and, therefore, can significantly impair a person's ability to drive or operate machinery. The sedative effects of antihistamines may increase the risk of falling. Antihistamines can also cause temporary dry mouth or eyes.
Decongestants
Pseudoephedrine can temporarily cause nervousness, dizziness and sleeplessness. It can make you lose your appetite or retain urine. It can also cause heart palpitations, high blood pressure or high blood sugar levels.
Cough Medicines
Codeine, when used as a cough suppressant, can temporarily cause nausea, sedation and constipation. Dextromethorphan, the medicine in Drixoral, Pertussin CS and Robitussin, has a lower risk of sedation and GI side effects. It can, however, cause feelings of confusion, agitation, nervousness or irritability.
Drug-Drug Interactions
The body processes (metabolizes) every drug differently. If drugs are used together, their metabolism and effect on the body can change. When this happens, the chance that you will have side effects for each drug may become greater.
Alcohol and OTC Medicines
Pain Relievers
If you drink more than 1 alcoholic beverage per week and use NSAIDs, including aspirin, you may be at increased risk of GI bleeding. People who consume 3 or more alcoholic beverages each day should consult their physician before using any pain reliever.
Acetaminophen is much less likely than NSAIDs to be associated with GI problems, including bleeding. But to minimize the risk of serious liver injury, you should never take more than the recommended daily dose (4g per day).
Antihistamines, Decongestants and Cough Medicines
The combination of OTC antihistamines and alcohol can increase drowsiness, especially in elderly people. In addition, alcohol makes the drowsiness, sedation and impaired motor skills associated with the cough suppressants dextromethorphan (in products such as Drixoral, Robitussin) and codeine worse.
If you drink more than 1 alcoholic beverage per week and use NSAIDs, including aspirin, you may be at increased risk of GI bleeding. People who consume 3 or more alcoholic beverages each day should consult their physician before using any pain reliever.
Acetaminophen is much less likely than NSAIDs to be associated with GI problems, including bleeding. But to minimize the risk of serious liver injury, you should never take more than the recommended daily dose (4g per day).
Antihistamines, Decongestants and Cough Medicines
The combination of OTC antihistamines and alcohol can increase drowsiness, especially in elderly people. In addition, alcohol makes the drowsiness, sedation and impaired motor skills associated with the cough suppressants dextromethorphan (in products such as Drixoral, Robitussin) and codeine worse.
Special Groups
Some groups of people may be more likely to experience the side effects associated with OTC medicines. The sections below include tips for using OTC medicines in the following special populations:
Children
When used properly, OTC medications pose little risk to children. However, children metabolize drugs differently than adults. You should know how OTC drugs will affect your children before you use them. Talk with your family doctor if you have any questions about giving your child OTC medicines.
- Acetaminophen is generally considered the treatment of choice for children's pain relief.
- Do not give ibuprofen to a child younger than 6 months of age.
- Do not give aspirin to children under the age of 18 because of the risk of Reye's syndrome (a drug reaction that can lead to permanent brain injury).
- Do not use nasal decongestants, cough medicines and cold medicines in young children, especially those under 2 years of age. These medicines can produce dangerous side effects. In addition, cough and cold medicines are not effective in treating young children.
It can be helpful for parents and other caregivers to keep track of the medicine a child is taking. One way to do that is with a medication log. Using a log can help avoid giving too much medicine or giving it too often. It can also provide important information to your family doctor if there is a problem.
A PDF version of the medication log is available. Download PDF now (1 page / 15 KB). About PDFs.
A PDF version of the medication log is available. Download PDF now (1 page / 15 KB). About PDFs.
Medicine and Your Child: How to give the right dose
Here are some tips on giving the right dose:
- When your doctor says to give the medicine "every 6 hours" that generally means the medicine is taken 4 times a day (for example, at breakfast, lunch, supper and bed time). It doesn't generally mean to wake the child up in the night to take medicine. And "take every 8 hours" generally means the medicine should be taken 3 times a day.
- Pay close attention to the dosage given on the label. Labels for liquid medicines give measurements in both teaspoons (tsp) and in milliliters (mL). Your pharmacist can give you a measuring device (a spoon that's made especially for measuring medicine, a syringe or a cup) that's labeled with both tsp and mL. Your pharmacist should also show you how to use it. One tsp is not the same as 1 mL. Read the label carefully and make sure you give the right amount of medicine to your child. An ordinary kitchen teaspoon may not hold the correct amount of medicine.
- Measure the medicine carefully. If you're using a measuring cup, set it on a level surface such as a countertop and then pour the medicine in it.
- "If a little medicine is good, a lot is better (or will work quicker)" is wrong. Giving too much medicine can be harmful. Be sure you only give the recommended dose of each medicine.
- If you use a syringe-type measuring device to give liquid medicine to your child, first throw away the small cap of the syringe. Children can choke on these caps.
- If your child has a bad reaction to a medicine or is allergic to a medicine, tell your doctor right away. Also, keep a record of the following information at home: the name of the medicine, the dosage directions, the illness the medicine was used for and the side effects the medicine caused.
Older Adults
The elderly use a number of medications at the same time and therefore need to pay careful attention to drug-drug interactions between OTC medications and prescription medications. Older adults should talk with their doctor about the medicines they take and potential interactions with OTC medicines.
- There is a relatively high risk of kidney disease and GI bleeding in elderly patients who use NSAIDs. Discuss this risk with your family doctor.
- Pseudoephedrine can increase blood pressure and the pressure in your eye that can lead to glaucoma. It can also make existing blockages in the urinary tract worse. Pseudoephedrine interacts negatively with many other drugs such as beta-blockers, antidepressants, insulin and some medications that treat low blood sugar.
- If you use a monoamine oxidase inhibitor (MAOI), a type of prescription antidepressant, or take any medication for a seizure disorder, you should avoid using pseudoephedrine. Pseudoephedrine can change the way these drugs work in your system. Some common MAOIs include Marplan (generic: isocarboxazid), Nardil (generic: phenelzine sulfate) and Parnate (generic: tranylcypromine sulfate).
- If you use a MAOI, you should not use dextromethorphan. Dextromethorphan interferes with the way MAOIs work.
Pregnant or Breastfeeding Women
Pregnant or breastfeeding women should talk with their doctor before using any medicine. Some can affect your baby. The following are some general guidelines.
Pregnancy
Pregnancy
- Acetaminophen is generally considered safe for short-term pain relief during pregnancy.
- Avoid using aspirin during pregnancy. It can cause birth defects or problems during delivery.
- Avoid using other NSAIDs, especially during the third trimester of pregnancy. They can cause heart defects in the baby.
Breastfeeding
- Acetaminophen and NSAIDs such as ibuprofen provide safe pain relief for women who are breastfeeding.
- Avoid using aspirin because it is excreted in breast milk and can cause rashes and bleeding problems in nursing infants.
- Limit long-term use of antihistamines. Antihistamines are excreted in breast milk, and may cause side effects such as sedation, irritability, crying and sleep disturbances in nursing infants. Antihistamines may also interfere with the production of milk.
General Tips
These steps can help minimize the risk of side effects during pregnancy and breastfeeding:
These steps can help minimize the risk of side effects during pregnancy and breastfeeding:
- Talk to your doctor about possible alternatives to medicine.
- Avoid the use of medicines during the first trimester.
- Take oral medicines after nursing or before the infant's longest sleep period.
- Avoid the use of extra-strength, maximum-strength or long-acting medicines.
- Avoid "combination" products.
- Watch your infant for possible side effects, such as a rash, difficulty breathing, headache or other symptoms that your child didn't have before you took the medicine and then breastfed.
Other Groups
People with health problems such as kidney disease, heart disease, diabetes, asthma, blood clotting disorders or gout may be at increased risk of side effects associated with OTC medicines.
This chart contains detailed information on use of OTC pain relievers in patients with these and other medical conditions.
This chart contains detailed information on use of OTC pain relievers in patients with these and other medical conditions.
Bibliography
- OTC Labeling Questions and Answers. FDA Web Site. Available at: www.fda.gov/cder/otc/label/quesanswers.htm. Accessed February 27, 2002.
- Aspirin PI (RxList). Available at: www.rxlist.com/cgi/generic/asa_wcp.htm. Accessed March 18, 2002.
- Dextromethorphan drug information. Available at: www.nlm.nih.gov/medlineplus/druginfo/medmaster/a682492.html. Accessed October 20, 2003.
- Diphenhydramine PI (RxList). Available at: www.rxlist.com/cgi/generic/dihydram_wcp.htm. Accessed March 18, 2002.
- Guaifenesin PI (RxList). Available at: www.rxlist.com/cgi/generic2/guaifen_wcp.htm. Accessed March 18, 2002.
- Ibuprofen PI (RxList). Available at: www.rxlist.com/cgi/generic/ibup_wcp.htm. Accessed March 18, 2002.
- Naproxen sodium PI (RxList). Available at: www.rxlist.com/cgi/generic/naproxsod_wcp.htm. Accessed March 18, 2002.
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Written by familydoctor.org editorial staff.
This information was developed as part of an educational program made possible by an unrestricted educational grant from McNeil Consumer & Specialty Pharmaceuticals.
Reviewed/Updated: 03/08
Created: 10/03










