Top 9 Ways to Prevent a Deadly Drug Interaction

Medically reviewed by Leigh Ann Anderson, PharmD. Last updated on July 25, 2024.

You should not be afraid to take your medication because of the possibility of a drug interaction. Drug interactions can be intimidating for anyone who regularly takes prescription medications, but you can learn how to manage and prevent them.

Drugs with a narrow therapeutic index (that is, having little difference between toxic and therapeutic doses), and certain disease states like epilepsy or depression are especially prone to serious drug interactions. In addition, multiple interactions may occur when someone is taking several drugs, as is often the case with older patients.

While most interactions are usually not life-threatening, some mixtures of medications can lead to serious - and even fatal - consequences. Pharmacists and doctors are well-trained to review and predict drug interactions, so always use them as a resource.

You can also use the drugclasses.com online Drug Interaction Checker to help gauge the risk prior to discussing with your doctor or pharmacist. As always, if you have any questions, talk to your healthcare provider.

Education and communication are key. You should consult with your health care providers, read only reliable drug information written by professionals, and empower yourself to lower your risk of drug interactions to maximize your medical treatments. Here are nine tips to achieve that goal.

1. Communicate with your healthcare providers
2. Look for possible drug interactions
3. Use the same pharmacy consistently 
4. Review for food, grapefruit juice and dietary interactions
5. Check for alcohol and caffeine drug interactions
6. Don't use medicine prescribed for someone else
7. Follow the instructions closely
8. Tell your doctor about your medical history
9. Don't buy medicines from risky websites

1. Communicate Frequently

Tell your pharmacist each time you start or stop a medication, including any over-the-counter (OTC) drug, herbal supplement, or vitamin. Keep an updated list of meds, including nonprescription drugs -- and share with your health care providers, including your doctor, pharmacist, and dentist, anytime you start or stop a medication.

• Prescription drugs are not the only medicines that can interact. Non-prescription drugs can have serious consequences, too. For example, the herbal supplement St. John’s Wort is commonly used as an OTC product for depression. If combined with other antidepressants such as the SSRIs like fluoxetine (Prozac) or sertraline (Zoloft), the risk of a rare but serious and potentially fatal condition called serotonin syndrome can occur. Symptoms of serotonin syndrome may include confusion, hallucination, seizure, extreme changes in blood pressure, and even death.

• Read your Medication Guide and prescription labeling each time you get a new prescription or refill. The FDA updates prescription drug information frequently, and there could be changes in your Medication Guide. Review your possible interactions and ask questions if you are concerned or don’t quite understand the medical jargon.

• If you discover that you are at risk for an interaction, call your doctor. It may be that the interaction is minor, and no action is needed. On the other hand, you may need to avoid the drug or have an alternative medicine prescribed. Never stop a medication without first speaking to your doctor.

2. Understand Your Medicines

• Use a reliable and consumer-friendly online drug interaction tool like the drugclasses.com Interaction Checker to become engaged in your health and learn about your medications. If you need help understanding the information, be sure to call your pharmacist. Always check for drug interactions even when you purchase OTC medications, herbal supplements or vitamins.

• The Drug Interaction Checker explains the mechanism of each drug interaction, the level of significance of the interaction, and in certain cases, can provide the recommended course of action to manage the interaction. The Drug Interaction Checker will also display any interactions between your chosen drugs, food or beverages (like alcohol or grapefruit juice, which cause common interactions) and even interactions with diseases or conditions.

• To see drug interactions in detail, just add one drug name and select “Check Interactions.” Drug interaction information is provided for that drug at both the consumer and professional level. You can also add in other drug names to check two, three or even more drugs for multiple interactions. The most frequently checked interactions for that drug are also displayed. If needed, you or your healthcare provider can find evidence-based references on drug interactions written for the professional. 

3. Keep All of Your Prescriptions at One Pharmacy

• By keeping all of your prescriptions at one pharmacy, a regular drug review and drug interaction screen can be done electronically that incorporates all of your medicines. Talk with your pharmacist and doctor and communicate new and discontinued medications with all of your health care providers. Communication is key to preventing drug interactions.

• When you buy over-the-counter medicines (OTCs) or herbal supplements, ask your pharmacist to double check for interactions and ask if they can add the agent to your regular drug profile for future drug interaction checks. If your pharmacist does not know that you are taking OTC products, they can’t check for drug interactions.

• Be sure to read the Drug Facts Label on each OTC product you use, too, paying attention to any specific drug interactions noted there.

4. Take Food and Beverage Drug Interactions Seriously

• Your pharmacist or doctor may ask about specific foods or drinks you consume depending upon which drugs you take. Common food items involved in drug interactions include foods rich in vitamin K, which can interact with certain blood thinners like warfarin and make them less effective. Certain citrus juices like grapefruit juice or pomegranate juice can change blood levels of some drugs, too. Calcium can bind with some drugs and prevent absorption.

• For example, if you take the blood thinner warfarin, increasing vitamin K levels in the body can increase clotting and reduce the effectiveness of warfarin, which could result in a stroke. Foods rich in vitamin K include beef liver, broccoli, brussel sprouts, cabbage, collard greens, endive, kale, and, mustard greens, among other foods. While there is no need to avoid products that contain vitamin K, you should maintain a consistent level of consumption of these products.

• Grapefruit or grapefruit juice consumption can also result in drug interactions that may increase the level of the medicine in your blood, possibly causing drug toxicity. For example, blood levels of some cholesterol drugs known as statins -- atorvastatin, lovastatin, or simvastatin -- can be affected by drinking grapefruit juice, and lead to severe muscle injury known as rhabdomyolysis. Not all medicines contained in a class of drugs like the statins may lead to the interaction, so your doctor might be able to prescribe a different drug. Cranberry juice, orange juice, pomegranate juice, and even garlic can lead to interactions with drugs, too.

5. Tell Your Doc About Caffeine Use, Alcohol Use, and Illegal Drug Use

• Socially-used drugs can have an especially harsh effect with other drugs. For example, some asthma drugs like the beta-2 agonist albuterol (ProAir, Proventil HFA, Ventolin HFA) can have a stimulant effect. If albuterol is combined with caffeine, this can interfere with sleep or lead to a rapid heart rate, which can be dangerous in people with heart disease. The stimulant effect from caffeine can be additive to stimulation from decongestants, too, like pseudoephedrine or phenylephrine.

• Alcohol can worsen drowsiness, especially when mixed with other drugs that cause sedation, which may put you at a higher risk for a fall or a car accident. Alcohol should never be combined with opioid painkillers or anxiety medications like benzodiazepines. Life-threatening respiratory depression can occur.

• A particularly concerning yet often unknown interaction between alcohol and cocaine has been reported. Research has found that the human liver combines cocaine and alcohol and manufactures a third substance, cocaethylene, that intensifies cocaine's euphoric effects but may increase the risk of sudden death. Experts note that the drug-drug interaction between cocaine and alcohol can result in drug-related heart toxicity and death.

• Illicit drugs combined with other illicit drugs can be particularly dangerous. Combining the opioid heroin and cocaine into one syringe, often called a “speedball”, is a mixture that is used by some injecting drug users, often with fatal results.

6. Don’t Take a Medication Prescribed for Someone Else

• Medications are prescribed specifically for an individual person, often based on their age, weight, and specific type of medical condition. In addition, when you take medications that are not prescribed for you, there is no health care provider involved to review for potential interactions or safety based on your medical conditions.

• For example, taking someone else’s antibiotic for a sore throat might not only lead to a possible drug interaction, it might worsen your infection. The antibiotic might not be the appropriate drug to treat the bacterial strain, and you probably won’t have a full course of antibiotic either, which can result in antibiotic resistance and failed treatment. Plus, if your sore throat is viral instead of bacterial (which is often the case), you may not need an antibiotic at all. Your doctor can test you for this.

7. Follow All Dosing Recommendations on Your Prescription Bottle

• Your prescription bottle will have specific directions for taking your medicine. For example, you may need to space the timing of when you take your medications. Some drug interactions involve binding of one drug to the other in the stomach. Antacids are commonly linked to this type of interaction. Your pharmacist will put a sticker on the your bottle to warn you of this interaction. To avoid the interaction you may need to space the timing of your doses, taking each drug 2 hours before or 4 hours after the other drug.

• Antacids can also raise the pH in your stomach, and may result in an early dissolution of enteric coatings -- for example, enteric-coated aspirin or ibuprofen -- which should normally dissolve in the intestine. This could lead to severe stomach bleeding or lowered absorption of the drug. Your pharmacist will provide specific instructions.

• Do not change the dose of your medication unless approved by your doctor. If your warning sticker suggests that you avoid a drug, or a certain class of drugs altogether, be sure to follow these instructions. Many patients that take blood thinners like warfarin need to avoid over-the-counter and prescription drugs that may increase the risk of bleeding; for example, NSAIDs (ibuprofen, naproxen) or aspirin.

• In addition to warfarin, ginkgo biloba (an herbal supplement) and vitamin E (a dietary supplement) can each thin the blood. Taking any of these products together may increase your potential for bleeding.

8. Tell Your Health Care Provider About Your Medical Conditions

• OTC oral decongestants like pseudoephedrine (Sudafed) or phenylephrine (Sudafed PE) can increase your blood pressure. This can occur even if you take blood pressure medicine. People with uncontrolled or severe high blood pressure (hypertension) need to avoid these medications. Talk to your doctor about this interaction if you take blood pressure treatments.

• Another common example of a disease-drug interaction is the use of the antihistamine diphenhydramine (Benadryl) in patients with acute angle-closure (narrow-angle) glaucoma. Diphenhydramine can dilate the pupil and provoke angle closure (due to its anticholinergic effects), prevent drainage and cause the pressure of the eye to rapidly increase. Antihistamines, as well as other medicines, should be avoided in people with narrow angle glaucoma or only used under the supervision of a physician. 

9. Do NOT Buy Medicine From Risky Online Pharmacies

• While it may be a tempting way to save money on medications, buying medications -- prescription or OTC -- from unreliable websites on the Internet or countries that may not fully regulate prescription drugs can be costly to your health. According to the U.S. Food and Drug Administration “the safety and effectiveness of imported drugs have not been reviewed by the FDA, and their identity and potency can't be assured.”

• You may receive the wrong drug, the wrong strength, or even outdated, expired medications. If you are not sure what’s in your medication, you can’t run a reliable drug interaction check to look for any serious problems.

See also

• Common Drug Side Effects
• Does grapefruit juice interact with my medications?
• Drug Expiration Dates - Are expired drugs still safe to take?
• Generic vs Brand Drugs: Your FAQs Answered
• How do I remember to take my medications?
• How do I stop my medication safely?
• How to Safely Dispose of Your Old Medications
• Imprint Code FAQs - For Oral Medications
• Injection Types and Sites
• Medical Conversions - How many mL in a teaspoon?
• Pill splitting - Is it safe?
• Top 150 Prescription Abbreviations & Medical Meanings
• Top 5 Ways to Avoid Drug Errors
• What are pharmaceutical salt names?
• What are the risks vs. benefits of medications?
• What is the half-life of a drug?
• What is the placebo effect?

Further information

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

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