Adverse Reactions to Medicines

Topic Overview

Adverse reactions to medicines include side effects, reactions between two or more medicines or herbal supplements, reactions between a food and a medicine, overmedication, and addiction. A reaction can range from mild to severe. Most adverse reactions are not serious.

A drug allergy is a serious type of adverse reaction, because it involves the body's defense system (immune system). It is important for your doctor to find out whether you have a drug allergy or another type of adverse reaction. You have more treatment options if your reaction is not because of an allergy.

Symptoms of adverse reactions are often the same as a drug allergy. Symptoms of an adverse reaction include:

• Feeling sick to the stomach and vomiting.
• Constipation or diarrhea.
• Trouble breathing.
• Rashes or bruising.
• Bleeding problems.
• Being confused, forgetful, sleepy, or depressed.
• Feeling irritable or nervous.
• Headache, dizziness, or ringing in the ears.
• Problems with urination.
• Blurred or double vision.

Don't assume any symptom is a normal side effect of a medicine. Call your doctor or pharmacist anytime you suspect that your medicines are making you sick. Make sure that your doctor and pharmacist have a complete list of all the prescription and nonprescription medicines and herbal supplements you are taking.

For more information, see the topic Dealing With Medicine Side Effects and Interactions.