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- Blood Glucose
- Diabetes
- Diabetes and Pregnancy
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- Diabetes Medicines
- Diabetes Type 1
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- Diabetic Diet
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- How to Prevent Diabetes
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- Breast Reconstruction
- Breastfeeding
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- Cervical Cancer Screening
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- High Blood Pressure in Pregnancy
- HIV and Pregnancy
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- HPV
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- Cholesterol Levels: What You Need to Know
- Cholesterol Medicines
- DASH Eating Plan
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- How to Lower Cholesterol
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- Malabsorption Syndromes
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- Rare Diseases
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- Sciatica
- Speech and Communication Disorders
- Stuttering
Drug Reactions
Summary
Most of the time, medicines make our lives better. They reduce aches and pains, fight infections, and control problems such as high blood pressure or diabetes. But medicines can also cause unwanted reactions, such as drug interactions, side effects, and allergies.
What is a drug interaction?
A drug interaction is a change in the way a drug acts in the body when taken with certain other drugs, foods, or supplements or when taken while you have certain medical conditions. Examples include:
- Two drugs, such as aspirin and blood thinners
- Drugs and food, such as statins and grapefruit
- Drugs and supplements, such as gingko and blood thinners
- Drugs and medical conditions, such as aspirin and peptic ulcers
Interactions could cause a drug to be more or less effective, cause side effects, or change the way one or both drugs work.
What are side effects?
Side effects are unwanted, usually unpleasant, effects caused by medicines. Most are mild, such as a stomachache, dry mouth, or drowsiness, and go away after you stop taking the medicine. Others can be more serious. Sometimes a drug can interact with a disease that you have and cause a side effect. For example, if you have a heart condition, certain decongestants can cause you to have a rapid heartbeat.
What are drug allergies?
Drug allergies are another type of reaction. They can range from mild to life-threatening. Skin reactions, such as hives and rashes, are the most common type. Anaphylaxis, a serious allergic reaction, is less common.
How can I stay safe when taking medicines?
When you start a new prescription or over-the-counter medicine, make sure you understand how to take it correctly. Know which other medicines, foods, and supplements you need to avoid. Always talk to your health care provider or pharmacist if you have questions about your medicines.
Diagnosis and Tests
- Allergy Skin Test National Library of Medicine
- Anaphylaxis American Academy of Allergy, Asthma, and Immunology
- Anaphylaxis-Like Reactions National Jewish Health
- Pharmacogenetic Tests National Library of Medicine
- Therapeutic Drug Monitoring National Library of Medicine
Encyclopedia
- Anaphylaxis Medical Encyclopedia
- Erythema multiforme Medical Encyclopedia
- Hives Medical Encyclopedia
- Nausea and vomiting – adults Medical Encyclopedia
- Rashes Medical Encyclopedia
- Serum sickness Medical Encyclopedia
- Stuffy or runny nose – adult Medical Encyclopedia
- Swelling Medical Encyclopedia
- Wheezing Medical Encyclopedia
Treatments and Therapies
- Anaphylaxis: First Aid Mayo Foundation for Medical Education and Research
Patient Handouts
- Angioedema Medical Encyclopedia
- Drug allergies Medical Encyclopedia
- Drug-induced diarrhea Medical Encyclopedia
- Drug-induced tremor Medical Encyclopedia
- Taking multiple medicines safely Medical Encyclopedia
Specifics
- Aspirin Allergy: What Are the Symptoms? Mayo Foundation for Medical Education and Research
- Grapefruit Juice and Some Drugs Don’t Mix Food and Drug Administration
- Neuroleptic Malignant Syndrome National Institute of Neurological Disorders and Stroke
- Penicillin Allergy Mayo Foundation for Medical Education and Research
- Sulfa Allergy: Which Medications Should I Avoid? Mayo Foundation for Medical Education and Research
Clinical Trials
- ClinicalTrials.gov: Drug Hypersensitivity National Institutes of Health
- ClinicalTrials.gov: Drug Interactions National Institutes of Health
- ClinicalTrials.gov: Drug-Related Side Effects and Adverse Reactions National Institutes of Health
Learn More
- Drug Allergies: What to Look Out For National Institutes of Health
- Medication/Drug Allergy National Jewish Health
Start Here
- Drug Allergy Mayo Foundation for Medical Education and Research
- Drug Interactions: What You Should Know Food and Drug Administration
- Drug Reactions American Academy of Family Physicians
- Medications and Drug Allergic Reactions American Academy of Allergy, Asthma, and Immunology
Images
- Drug Eruption VisualDX
Children
- Drug Eruption (Pediatric) VisualDX
- Penicillin Allergy (For Parents) Nemours Foundation
Related Issues
- Drug-Food Interactions American Academy of Family Physicians
- Drug-Nutrient Interactions and Drug-Supplement Interactions: Examples of Dietary Supplement Interactions American Academy of Family Physicians
- FDA Pharmacists Help You Use Medicines Safely Food and Drug Administration
- Harmful Interactions: Mixing Alcohol with Medicines National Institute on Alcohol Abuse and Alcoholism
- Know the Science: How Medications and Supplements Can Interact National Center for Complementary and Integrative Health
- Medication Interactions: Food, Supplements, and Other Drugs American Heart Association
- MedWatch, the FDA Safety Information and Adverse Event Reporting Program Food and Drug Administration
- OTC Medicines: Know Your Risks and Reduce Them American Academy of Family Physicians
Find an Expert
- Food and Drug Administration Food and Drug Administration
Older Adults
- Medications Older Adults Should Avoid or Use With Caution AGS Health in Aging Foundation
Reference Desk
- MedlinePlus: Drug Information National Library of Medicine
Journal Articles
Genetics
- Stevens-Johnson syndrome/toxic epidermal necrolysis: MedlinePlus Genetics National Library of Medicine
- Thiopurine S-methyltransferase deficiency: MedlinePlus Genetics National Library of Medicine