Drug-Drug Interactions


Whenever a patient takes several drugs at once for one or more diseases, drug interactions could arise. Drug interactions can cause unanticipated reactions, adverse side effects, or in rare cases, a lack of therapeutic efficacy when used concurrently with other medications. Drug-drug interactions are the term used to describe these unwanted effects (DDIs). Drug manufacturers must comprehend how pharmaceuticals interact with each other since the global polypharmacy problem (people taking numerous medications at once) keeps growing. To determine if a DDI might occur and whether it might be serious enough to call for a dosage modification, precaution, or contraindication, medication developers use a variety of clinical and nonclinical investigations.

What are drug interactions?

A medicine improves your health or makes you feel better when it functions properly. But if a drug interacts poorly with another substance you take into your body, such as another medication, a particular meal, or alcohol, complications may result. A drug interaction is what is experienced in that situation. It might cause your drug to stop working, become ineffective, or become excessively potent. It could potentially have negative effects. Drug-drug interactions, drug-disease interactions, interactions with food or drink, and interactions with other drugs are all examples of "drug interactions." Both intrinsic (illness) and extrinsic (drugs, food, or alcohol) factors can affect a drug's pharmacodynamics (PD) or pharmacokinetics (PK) qualities, which can lead to a drug interaction.

What are the three types of drug interactions?

  • Drug-drug interaction − This occurs when a medicine interacts with one or more additional medications. For instance, using an antitussive to treat a cough and a sedative to aid in sleep may cause the two drugs to interact.

  • Drug-food/ beverage interaction − This occurs when a drug is impacted by anything you eat or drink. For instance, drinking alcohol while taking some drugs can be risky. Additionally, several dietary supplements and vitamins interact with medications.

  • Drug-condition interaction − This occurs when a medical condition makes it unsafe for you to use a particular medication. For instance, using a decongestant for a cold could make your high blood pressure symptoms worse if you already have the illness.

What drugs can you not take together?

While there are many different types of medications you shouldn't consume together, avoid taking combinations like the following −

  • NSAIDs and blood-thinning medications. Your chances of having a serious bleed could increase. Ibuprofen and naproxen are NSAIDs (nonsteroidal anti-inflammatory medicines), which are also used to treat pain. Ask your doctor to recommend an alternative over-the-counter pain reliever and dosage that is safer for you if you are on a blood thinner.

  • Multiple medications with the same active component. You can experience negative consequences or an overdose. The substances in medicines known as active ingredients are those that treat your ailment or its symptoms. Always check the medicine label for them.

  • Antihistamine-containing pills. Combining these can make you slower to react, making it risky for you to operate heavy machinery or operate a vehicle.

Other hazardous drug-drug combos include the following −

  • The combination of the blood pressure medication calcium channel blockers and the antibiotic clarithromycin

  • A combination of the thyroid medication levothyroxine and the proton pump inhibitor omeprazole blocks acid production

  • NSAID painkillers used with blood pressure medications

What Are Common Drug Interactions?

Some drugs don't interact well with specific foods and beverages. Here is a handful of them −

Fruit or juice of the grapefruit. Some medications, such as −

Drugs for blood pressure, Medication for anxiety, Statins and antihistamines can be harmed by too much of either.

Every drug in these drug classes interacts quite well with grapefruit juice. For any precautions about your medication, check the label or information booklet. Also, find out from your doctor or pharmacist if consuming grapefruit in any amount, including juice, is safe when using the medication in question. Ask if other berries or juices might have an impact on your medication if they advise you to stop consuming it.

Alcohol. Alcohol can have harmful side effects with a variety of medications, including ones for

Depression, High triglycerides, Depression, Infections, Pains/Allergies, Flu and cold

Medicine if a new drug may interact with alcohol before you start taking it. You should also look for alcohol warnings on medicine labels.

Foods and beverages are high in potassium, such as bananas, salt alternatives, and orange juice. These may have an impact on ACE inhibitor blood pressure medications. Your doctor will monitor your potassium levels and may advise you to limit your intake of foods containing it.

What are the Symptoms of a Drug Interaction?

Based on the drugs you're taking and how they're interacting, the signs of a specific drug might vary greatly. Sometimes an encounter may not even be immediately apparent to you.

If an interaction is present, it will typically feel like one of the following −

  • A medicine is causing more negative side effects in you.

  • Your medication doesn't appear to be functioning the same as it did previously.

Call your doctor if you notice any adverse effects that concern you or if your medication doesn't appear to be working, specifically if you've just started taking the medication or have changed doses.

Group26, Antibiotic Drugs, Contraindications, and Side Effects Chart, CC BY-SA 4.0

How can a person avoid drug interactions?

To prevent drug interactions, one can take the necessary actions −

  • All prescribed and non - prescribed medications you are now consuming or intend to take should be disclosed to your healthcare provider. Additionally, be sure to let your doctor know if you use any vitamins, dietary supplements, or herbal remedies.

  • Any additional medical issues that may have, such as diabetes or high blood pressure, should be disclosed to your healthcare professional.

  • Ask your doctor the following queries before taking a medication −

    • What is the purpose of the drug?

    • How should I administer the medication?

    • Should I exclude any certain meals or beverages, as well as other medications, while taking this medication?

    • Can I safely use this medication along with the other medications I currently take?

    • Do I need to be aware of any potential drug interactions?

    • What symptoms indicate a medication interaction?

    • What should I do if a drug interaction occurs?

Follow the advice of your doctor when using medications. Always read the written instructions and information provided with a drug. Important details concerning potential drug interactions are included on the labels and packaging inserts of medications.


By using clinical pharmacology concepts and appropriate clinical care, it is possible to identify most potential medication interactions. By being more vigilant while switching medications, doctors have a better chance of spotting unfavourable drug interactions before they have a serious negative impact. Drug interactions can be managed more successfully by being familiar with a small number of medications and using the information at hand wisely than by depending only on computerised decision support.


1. What three ways do drugs interact with each other?

Three major categories can be used to categorise the pharmacodynamic consequences of drug interactions: interference with pharmacological effects on receptor function, interaction with a physiological control mechanism, and additive or antagonistic physiological effects.

2. What is a medication interaction of Level 1?

The most severe, life-threatening interactions are classified as Level 1 interactions and are implemented as "hard stop" alerts, requiring a physician to either cancel the order they are writing or stop the pre-existing, interacting pharmaceutical order.

3. Do drug interactions ever result in death?

According to this research, 6.7% of hospitalised patients experience a major adverse medication reaction, with a 0.32 percent death rate. According to these figures, hospitalised patients experience more than 2,216,000 major adverse drug reactions (ADRs), which result in more than 106,000 fatalities per year.

4. What distinguishes a side effect from a negative reaction?

Adverse reactions and side effects are unpleasant side effects that may be brought on by a medicine. The severity of side effects might range from mild inconveniences like a runny nose to potentially fatal situations like a heart attack or liver failure.

5. What signs of a medication interaction are there?

Adverse medication responses can cause skin rashes, bruising, bleeding, and edema.


Updated on: 13-Feb-2024


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