Over-the-counter (OTC) medicines are medicines you can buy without a prescription from your doctor. OTC medicines can help you feel better by helping to treat or prevent health problems, such as allergies, constipation, cold and flu (influenza), and nausea. However, sometimes OTC medicines can cause unpleasant effects (also called adverse effects). These adverse effects include side effects, drug-drug interactions, food-drug interactions, and allergic reactions. It is best to be aware of the risks so you know how to avoid them.
Certain situations put you at higher risk for adverse effects. Because the possible adverse effects differ from 1 OTC medicine to another, it’s best to carefully read the drug facts label of any OTC medicine so you know what to expect.
OTC medicines have a low risk of adverse effects when used occasionally and properly by adults who are generally healthy. However, they can pose greater risks for some people, including very young children, older adults, and people taking more than 1 type of medicine. People who have the following conditions are also at a higher risk:
Even though these conditions put some people at greater risk, it is important to remember that anyone can experience an adverse effect from an OTC medicine.
When you take any type of medicine, it’s important to be aware of changes in your body and how you feel. It may be hard to know whether a certain symptom is caused by your illness or by an adverse effect from your medicine. Tell your family doctor when the symptom started and if it is different from other symptoms you have had.
Side effects are effects that medicines have on your body that don’t help your symptoms. Most side effects are unpleasant. A few examples are nausea, dizziness, or bleeding in your gastrointestinal (GI) tract. Sometimes, side effects can be useful. For example, certain antihistamines can cause sleepiness. This might be bad for people who take antihistamines during the day to treat allergies. But if you’re taking an antihistamine at nighttime, this side effect might help you get the sleep you need. Side effects are not the same thing as true drug allergies, which are much less common.
The body processes (metabolizes) every medicine differently. When medicines are used together (whether prescription or OTC) the ways they affect the body can change. This is called a drug-drug interaction. This sometimes increases the chance that you will have side effects from medicines you are taking. The following are the main interaction types:
Duplication: If you take 2 medicines that have similar active ingredients, you may get more medicine than you need. An example is when you take OTC ibuprofen (2 brand names: Advil, Motrin) along with a prescription anti-inflammatory medicine given to you by your doctor. Too much of either an anti-inflammatory medicine or acetaminophen (brand name: Tylenol) can hurt your kidneys or liver. You should know all the active ingredients in the medicines you take. Be sure to check each new medicine to avoid duplication.
Opposition (antagonism): Medicines with active ingredients that have opposite effects on your body can interact. This may reduce the effectiveness of 1 or both medicines. For example, OTC decongestants may raise your blood pressure, so they can cause opposition when taken with certain medicines intended to lower your blood pressure.
Alteration: One medicine may change the way your body absorbs, spreads, or metabolizes another medicine. For example, aspirin can change the way certain prescription blood-thinning medicines work.
If you see more than 1 doctor, tell each of them about the medicines you take, even if you take something for just a short time. Include any herbal supplements, vitamins, and minerals you take. At least once a year, bring all of your medicines and supplements with you when you see your doctor.
Food may change how your body processes some OTC or prescription medicines. This is called a drug-food (or drug-nutrient) interaction. Sometimes what you eat and drink can affect the ingredients in a medicine you’re taking and prevent the medicine from working the way it should. For example, medicines taken by mouth (orally) must be absorbed through the lining of the stomach or the small intestine. The nutrients from the food you eat are also absorbed through the lining of the stomach. So if you take a medicine with food when it’s not recommended, a possible interaction is that your body might not be able to absorb the medicine as it should.
No, but some OTC medicines can be affected by what you eat and when you eat it. This is why some medicines should be taken on an empty stomach (1 hour before eating or 2 hours after eating). On the other hand, it’s easier for your body to process other types of medicines when you take them with food.
Read the drug facts label to see if you should take your medicine with a snack or a meal, or if it should be taken on an empty stomach. If the label doesn’t give specific instructions, taking the medicine with or without food probably won’t affect the way the medicine works. If you have any questions, ask your family doctor or pharmacist. Your doctor and pharmacist can also warn you about possible interactions with your prescription medicines.
It’s not common, but some people are allergic to certain medicines. If you’ve ever had an allergic reaction to a medicine, be sure to avoid medicines that contain the same ingredients. Signs of an allergic reaction include itching, hives, and breathing problems. Call your doctor right away if you think you’re having an allergic reaction. Keep in mind that side effects are not true allergic reactions.
Older adults often use many medicines at the same time, including prescription and OTC medicines. Their bodies process medicines differently than younger adults. This is why older adults need to pay careful attention to drug-drug interactions between OTC and prescription medicines. If you are an older adult, talk with your doctor about all of the medicines, vitamins, and herbal supplements you take. Your doctor can tell you whether you are at risk of having an adverse effect from taking an OTC medicine.
If you use a nonsteroidal anti-inflammatory drug (NSAID), you may be at risk of kidney disease and GI bleeding. NSAIDs include ibuprofen, aspirin, and naproxen (brand name: Aleve). NSAIDs can interact with many different prescriptions.
Funding and support for this material have been provided by the Consumer Healthcare Products Association.
Written by familydoctor.org editorial staff