5 Drug Interaction Checkers

Drug Interaction Checkers

Among hundreds of available medications, some may affect or be affected by another drug, either its effectiveness or safety, when used together. The Prescribing information contains all drug interactions and provides specific recommendations. However, prescribing information is not always available at the physician’s practice or pharmacist’s desk. To address this, healthcare professionals often utilize online Drug Interaction Checkers for quick and efficient access to drug interaction information. These tools supplement, rather than replace, the detailed prescribing information and are valuable for on-the-spot consultation needs.

Luckily, today, there are Drug Interaction Checkers available online, which can help all healthcare professionals quickly access the required source of information. This easy-to-use tool on your desktop or mobile can answer your question about interactions between two or more medications in a minute.

Drug Interaction Checkers can give you relevant answers and save you time from long, detailed searches that the daily practice does not always allow you to do.

This article is about Drug Interaction Checkers, how they work, and the data they use. Find out if any can help your daily practice and save you time.

How Can I Use a Drug Interaction Checker

Drug Interaction Checkers explain the interactions that occur when one drug alters the pharmacological effect of another drug. (1) As per Britannica, the effect of one or both drugs may increase or decrease, or a new or unanticipated adverse effect may occur. Drug interactions may result from pharmacokinetic interactions (absorption, distribution, metabolism, excretion) or due to interactions on a receptor level. (1)

Many Drug Interaction Checkers (WebMD, Medscape, Drugs.com, Drugbank, RxList, and many more) are available online. The Checkers are very simple to use. Type at least two generic names that you want to check the possibility for interaction in the space dedicated to. Some checkers accept brand names, too.

Once you enter the names of the drugs you want to check, you will get the requested response after pressing the “Check for interactions” button.

Different Checkers Provide Similar Responses

Various checkers will provide a similar answer but with different depths of explanation. Let’s compare WebMD, Medscape, Drugs.com, Drugbank, and RxList and see what kind of response each provides.

For example, you want to treat a bacterial infection with doxycycline, but your patient tells you it uses an antacid containing magnesium for heartburn. You can quickly check if these two molecules interact by entering both chemicals “doxycycline” and “magnesium” and get any of the following answers:

1. WebMD


Potential for serious interaction; regular monitoring by your doctor is required, or alternate medication may be needed.

Magnesium Chloride + Doxycycline

Magnesium Chloride decreases levels of Doxycycline by reducing drug absorption from the stomach and intestine into the body when taken by mouth.” (2)

2. Medscape

SEVERITY – SERIOUS – Use Alternative

magnesium chloride + doxycycline

Magnesium chloride decreases levels of doxycycline by inhibition of GI absorption. Applies only to the oral form of both agents. Avoid or Use an Alternate Drug.” (3)

3. Drugs.com


doxycycline  magnesium chloride

Applies to: doxycycline, magnesium chloride

ADJUST DOSING INTERVAL: The administration of tetracycline with aluminum, calcium, or magnesium salts significantly decreases tetracycline serum concentrations. The proposed mechanism is the chelation of tetracycline by the cation, forming an insoluble complex that is poorly absorbed from the gastrointestinal tract. The interaction has also been reported with parenteral doxycycline and oral antacids.

MANAGEMENT: The administration of tetracyclines and preparations containing aluminum, magnesium, or calcium should be separated by two to four hours. When co-administered with Suprep Bowel Prep (magnesium/potassium/sodium sulfates), the manufacturer recommends administering tetracycline antibiotics at least 2 hours before and not less than 6 hours after Suprep Bowel Prep to avoid chelation with magnesium.” (4)

4. Drugbank


Magnesium chloride Doxycycline


The absorption of Doxycycline can be decreased when combined with Magnesium chloride.


The absorption of doxycycline is impaired by the co-administration of magnesium-containing drugs, resulting in decreased antibiotic bioavailability and efficacy.” (5)

5. RxList

SEVERITY – SERIOUS – Use Alternative

“Potential for serious interaction; regular monitoring by your doctor is required, or alternate medication may be needed.


Doxycycline hyclate oral form decreases levels of magnesium chloride by inhibiting GI absorption. Applies only to the oral form of both agents.” (6)

The Food and Drug Administration (FDA) acknowledges the interaction if taking a product containing magnesium within 2 hours of the time when doxycycline is taken, and this medicine could decrease the doxycycline’s effectiveness. (7)

You can check a possible interaction of up to five molecules at once. This is a practical option for patients with chronic diseases that use several treatment options. In addition, some checkers have developed mobile apps to be even closer to your practice (e.g., Medscape, Drugs.com, WebMD, etc.).

The best way to find out how beneficial they are is to try and test a few checkers on your own. Ensure the one you’ll start using responds fast, with an accurate answer and up-to-date information from relevant sources.

The Content Behind the Drug Interaction Checkers

Drug prescription and administration to patients is a highly responsible task. The chosen treatment should be effective but not harmful for the patient, or at least the safety profile to be manageable and not outweigh the therapeutic benefit. Therefore, despite the type of drug-drug interaction, it is essential to have relevant and up-to-date information.

Relevant Sources of Information

The content behind the checkers is carefully selected from relevant and respectful sources. The drug monographs and drug interactions are based primarily on the US FDA label approvals as a basis for each medication source of information. The dedicated staff in Medscape, RxList, and other checkers take care of their periodic updates.

You may find that WebMD relies on the latest medical findings published in The Lancet, Pediatrics, The Journal of the American Medical Association, and many more. In addition, the American Society of Health-System Pharmacists is the major supplier of Drugs.com content, where publications from Harvard Health Publications and Mayo Clinic are used as relevant resources.

Content Created by a Team of Experts

Behind the well-trusted checkers is a huge team of healthcare professionals, clinicians, practitioners, pharmacists, and other dedicated staff. Their writing and editorial role ensures all available information is relevant, independent from advertisers, fair, accurate, clinically significant, and periodically updated.

However, Drug Interaction Checkers are only tools, so you should refer to Prescribing Information approved by the FDA for more details. Double-check the interaction section, especially when you want to introduce new chemical entities in your clinical practice, because new safety data might be approved frequently in the first years of the drug life cycle.

Useful Tips

Going through various Drug Interactions Checkers and exploring their functionalities more, you may find additional benefits that some of them offer:

1. Drug Interactions Checkers categorize the severity of interaction. Yet, in some cases, you may find different categorizations among drug interaction checkers (like the example of doxycycline and magnesium shown above);

2. Some Checkers provide a Reference list of the studies and additional resources used for answering, such as WebMD, Drugs.com, Drugbank, etc.; this helps you to go further in understanding the interaction in more detail;

3. If you use Drugs.com and RxList, pay attention to which checker you use. These providers offer two checkers for consumers and professionals;

4. Aside from the interaction checking function, some checkers provide additional education and information on drug interactions;

5. Drugs.com allows viewing your previously saved lists if you sign in.


Drug Interaction Checkers are a reliable tool for quickly checking the possible interaction of two or more drugs. You need an internet connection and a minute or two to get the answer while deciding what medication to prescribe or administer.

Yet, checkers are for informational purposes only and with an attempt to provide accurate and up-to-date information, but without full guarantee. In case of uncertainty, check the interaction in the FDA-approved label and be comfortable with the decision while prescribing or administering the medication.

See Also

Amlodipine Interactions

Pantoprazole Interactions

Metronidazol Interactions

Tramadol Contraindications

Meloxicam Interactions

Lisinopril Contraindications

Acetaminophen Side Effects

Paxlovid Contraindications

Bupropion Side Effects

Current Version
June 8, 2023
Written By
Franco Cuevas, MD
June 8, 2023
Medically Reviewed By
Franco Cuevas, MD

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