Patient education: Side effects from medicines (The Basics)

What are side effects? — These are unintended or unwanted effects that medicines can cause. A side effect might also be called an "adverse reaction" or "adverse effect."

Most people take medicines without having side effects, or have only mild side effects that go away. But sometimes, side effects do happen.

Almost any medicine can cause side effects in some people. This includes prescription medicines and those sold over the counter ("OTC"). Even vitamins and supplements can cause side effects. Prescription medicines are studied to make sure that the benefit of taking them (like treating a symptom or curing an illness) is more likely than a serious side effect.

What are some common side effects? — Side effects can be different depending on what medicine or medicines you take. Your doctor, nurse, or pharmacist can talk to you about common side effects of the specific medicine, vitamin, or supplement you will take.

Examples of some common side effects include:

●Upset stomach or nausea

●Dry mouth

●Drowsiness

●Minor headache

Read the information that comes with your medicine to understand the possible side effects.

Can side effects be dangerous? — Yes. In rare cases, side effects can be dangerous or even life-threatening. These might include:

●Severe bleeding

●Liver or kidney damage

●Heart problems

●Trouble breathing

●Allergic reactions

Some medicines are not safe to take during pregnancy. They can cause serious problems in a fetus (developing baby).

When should I call the doctor? — Call for an ambulance (in the US and Canada, call 9-1-1) or have someone bring you to the emergency department if you start a new medicine and have any of these symptoms:

●Wheezing, or trouble breathing or talking

●Chest pain or tightness

●Passing out, or feeling like you might pass out

●Swelling of your face, lips, tongue, or throat

●Blisters or rash around your eyes, lips, mouth, or genitals

●Seizures

●Thinking about hurting or killing yourself

These symptoms require emergency treatment.

Call for advice if you start a new medicine and have any of these symptoms:

●Hives or rash (raised bumps on the skin that can be itchy)

●Confusion

●Severe stomach ache, vomiting, or diarrhea

●Not wanting to eat

●Aches, pain, fever, weakness, or no energy

●Dark-colored urine, black stools (bowel movements), or yellow skin or eyes

●Other symptoms that worry you

When can side effects start? — If side effects are going to happen, they usually start soon after you begin a new medicine or when your dose is increased. Some side effects happen in the first hours after taking a medicine, such as an allergic reaction or upset stomach. Others might not start for a week or even months, such as rashes or a dry cough.

What should I do if I have minor side effects? — If you think that they might be related to your medicine, talk to your doctor. Do not simply stop taking the medicine without talking to your doctor. The medicine might be very important for your health, and stopping it could cause other problems.

Your doctor can help you figure out if the symptoms you are having are really side effects of your medicines or are caused by something else. If your symptoms are actually side effects, your doctor might be able to adjust your dose or switch you to a different medicine.

In some cases, there might be simple things you can do to make side effects less bothersome. For example:

●Some medicines can make your skin sensitive to the sun. Stay in the shade, and wear sunscreen and protective clothing to help you avoid a sunburn.

●Some medicines can make you feel sleepy. But if you take them just before bed, this is not a problem.

●Other medicines can make you constipated. You can reduce constipation by eating more fruits and vegetables, drinking more water, and using a laxative when needed.

●If a blood pressure medicine or antidepressant causes problems with sex, you might be able to take another medicine to help with this.

The important thing is to talk to your doctor about any side effects that bother you. That way, they can offer solutions. Not everyone has the same side effects, so your doctor won't know what's happening unless you tell them.

How can I prevent having side effects?

●Take the medicine correctly – Take the dose that is written on the prescription label (figure 1). This dose considers your age, weight, and specific health problems as well as the other medicines you take. Carefully follow all of the instructions on the label and printed patient education that comes with the medicine. (For example, some medicine labels say "take with food," "avoid alcohol," or "may cause drowsiness.") Also, follow the instructions your doctor gives you. They might tell you to start at a low dose and increase the dose slowly, so you don't have side effects. If you are not sure how much medicine to take or when to take it, do not guess. Ask your doctor, nurse, or pharmacist.

You can also use a pill box that has a section for each day of the week. This can help you avoid taking too much or too little of your medicines (picture 1).

●Have your medicines checked to make sure that you are taking them correctly – Bring a bag with all of your medicines to your doctor's office. Have your doctor or nurse go over them with you.

●Be careful about mixing medicines – Some medicines do not mix well with other medicines, alcohol, or herbal products. Tell your doctor and pharmacist about all of the medicines you take, including nonprescription (OTC) medicines, herbs, and any other drugs. Have them check for drug interactions.

●Never take someone else's medicine – When medicine is prescribed for you, the doctor considers your health problem and health history. Someone else's problem and history are likely different from yours.

●If you take acetaminophen, do NOT take too much – Acetaminophen (known as paracetamol outside of the US) is in many different medicines. Taking too much is dangerous. Check the labels of all medicines you take. Make sure that you do not take more than 3000 mg of acetaminophen a day in total from all of your medicines.

●Remember that some side effects go away over time – As your body gets used to the medicine, the side effect might go away. For example, medicines to treat depression can sometimes bother your stomach for a while. But that side effect usually goes away after 1 week.

How can I find out the known side effects of my medicines? — There are a few different ways you can find this out:

●For detailed information about your medicines, ask your doctor or nurse for the patient drug information handout from UpToDate Lexidrug. It explains how to use and store your medicines. It also lists possible side effects and warns you if your medicines should not be taken with certain other medicines or foods.

●Ask your doctor or nurse what side effects to expect when they prescribe the medicines. Ask your pharmacist about side effects when you get your prescriptions filled. Always read the printed information that comes with each medicine.

●Many medicines come with a Medication Guide approved by the US Food and Drug Administration ("FDA"). More information about Medication Guides, including a link to search for information about specific medicines, can be found online at www.fda.gov/drugs/fdas-labeling-resources-human-prescription-drugs/patient-labeling-resources#medication-guides.

●Check online at www.medlineplus.gov for information about the medicine.

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