Learn how CHI St. Luke’s Health is responding to COVID-19. Read More.

Visitor Restrictions in Place. Learn More.



5 Harmful Medication Interactions You Need to Know

Sep 28, 2018

You have a headache, so you reach for the pain relievers—but did you read the label? Several medications and supplements on the market can interact with each other and result in harmful side effects. Learn about some common medication interactions and remember to always speak with your doctor before introducing a new supplement or drug into your system.

1. Medications With the Same Active Ingredient

If you begin to take a new medicine that has the same active ingredient as another medication you’re currently taking, you can be at risk of an overdose of that particular ingredient. If you experience symptoms of an overdose, such as seizures, vomiting, or confusion, call 911 or seek emergency medical care.

2. Pain Medicines  

Pain relievers, such as aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), and acetaminophen can cause severe bleeding when taken in conjunction with warfarin (an anticoagulant). This is due to their enhancing effect on anti-clotting compounds.

3. Melatonin

Some medications, such as birth control, can increase the amount of melatonin that your body produces, so taking melatonin in combination with these medications can result in an overdose. Some signs of a melatonin overdose are dizziness, nausea, and diarrhea. In the event of an overdose on melatonin, call the Poison Control Center.

Melatonin can also reduce the effectiveness of certain drugs, including SSRIs (selective serotonin reuptake inhibitors) and blood pressure medicines. If you have trouble falling or staying asleep, talk with your doctor about safe options that complement your current medications or visit a sleep center.

4. Rifampin

Rifampin is an antibiotic used to treat both tuberculosis and Neisseria meningitides, a type of bacteria that can lead to meningitis. The use of rifampin with other medications can reduce the effectiveness of those drugs. Some medicines weakened by rifampin are carbamazepine (used to control seizures) and phenobarbital (an anticonvulsant).

5. St. John’s Wort

St. John’s Wort is a supplement that some doctors prescribe to treat depression. However, St. John’s Wort can reduce the effectiveness of several medications, including antidepressants, some cancer medications, and warfarin.

Always talk to your doctor before taking any new drug or supplement, and read the label on medications to make sure you take them safely. If someone experiences any sudden symptoms of an overdose, such as dizziness, vomiting, or unconsciousness, call 911 or head to your nearest CHI St. Luke’s Health emergency room.


ScienceDirect | Drug-drug Interactions
FDA | Drug Interactions
NIH | St. John's Wort and Depression: In Depth
AAFP | Clinically Significant Drug Interactions
Healthline | Blood Thinners: Uses, Side Effects, and Drug Interactions
Healthline | Melatonin and Birth Control: Is It Safe?
Healthline | Melatonin Overdose: How Much Melatonin Should I Take?
E Medicine Health |  Drug Overdose Symptoms & Treatment
MedlinePlus | Rifampin
My Virtual Medical Centre | Blood Clotting: International Normalised Ratio (INR)
Medline Plus | Carbamazepine
Rx List | Phenobarbital