Medicines and prescriptions
What Is a Drug Interaction? Medicine Labels Explained
Interaction · say it: in-ter-AK-shunAlso written: drug interaction, drug-drug interaction, medicine interaction, food interaction, drug-food interaction
Short answer
A drug interaction is when one medicine, food, drink or supplement changes how another medicine works or how strong its effects are.
What it means
An interaction happens when something changes the way a medicine behaves in the body. It could be another medicine, an herbal supplement, alcohol, or a food such as grapefruit juice. An interaction can make a medicine stronger, weaker, or more likely to cause side effects. Some happen because one substance changes how the liver breaks down the other; others because two medicines have similar effects that add together.
Labels have a 'Drug Interactions' section and leaflets list 'Taking other medicines' because many people take more than one product. The label is not saying the combination is always forbidden. Some interactions mean avoid together; others mean a dose change, spacing the doses apart, or extra monitoring.
An interaction is different from a side effect, which can happen when a medicine is taken alone. A contraindication is stronger: it means the medicine should not be used in that situation.
Where you may see it
- The 'Drug Interactions' section of prescription medicine labels
- 'Ask a doctor or pharmacist before use if you are taking' on over-the-counter labels
- Pharmacy printouts and interaction alerts
📄 How it looks on a report
Concomitant use with strong CYP3A4 inhibitors increases exposure and is not recommended.
🙅 What it does not mean
- Not every listed interaction means you cannot take the medicines together. Many are managed with timing or dose changes.
- 'Natural' products and supplements can still interact with medicines.
- An interaction warning does not mean you should stop a medicine without advice.
🗒️ Questions to ask your doctor
🧾 Reports where you will see “Interaction”
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💊 Medicines whose labels mention “Interaction”
Plain-English explanations of each medicine, from its official FDA label.
- Alprazolam
a benzodiazepine, a type of central nervous system medicine
- Atenolol
a beta-blocker (beta-adrenergic blocker). The label describes it as a beta 1-selective, or cardioselective, blocking agent.
- Bupropion Hydrochloride
an aminoketone antidepressant, a type of medicine used to treat depression
- Ceftriaxone
A broad-spectrum cephalosporin antibiotic, as described on the official FDA label
- Esomeprazole
An acid reducer. The label gives this as its purpose, and no specific drug class is listed.
- Finasteride
a 5-alpha reductase inhibitor, a medicine that blocks an enzyme involved in making a hormone called DHT
- Fluoxetine
a selective serotonin reuptake inhibitor (SSRI), a type of antidepressant medicine
- Hydroxychloroquine
an antimalarial and antirheumatic drug, which means it is used for malaria and for certain joint and immune conditions
- Isoniazid
An antibacterial medicine of the antimycobacterial type, used against tuberculosis bacteria
- Levonorgestrel and Ethinyl Estradiol
a combination birth control pill that contains a progestin and an estrogen
🔗 Read more from trusted sources
- “Interaction” on MedlinePlus ↗
US National Library of Medicine
- NCI Dictionary definition ↗
US National Cancer Institute: “drug interaction”
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