Online Drug Interaction Checkers

When it comes to needs inside our hospital, we have expensive professional tools available on our intranet that allow clinicians to check for drug interactions. In preparation for our library’s eventual internet presence, I wanted to see if there was a free, consumer-oriented tool that we might feel okay recommending.

I decided to try out several of them to see what they had to say about Ketorolac and Ibuprofen, a combination that one of our hospital’s PharmDsThis PharmD, Kathleen LaParne is wonderful. She’s smart, she’s generous with her expertise and time, she’s awfully nice and the way that she so clearly and strongly *cares* about doing what is best for patients makes her one of my favorite people in the hospital where I am employed. tells me any interaction checker should absolutely, positively catch as a Very Bad Idea.


    I had tried DoubleCheckMD previously, but went back to try it again. I find the look and layout of site aesthetically appealling and I really like how it’ll suggest complete drug names after the user enters the first three letters.

    I find it interesting how the report is split into three parts. First it gives the basic answer in English, then more detail in English, then a short statement in what we might call “MedSpeak.” This could perhaps help make the danger understood to a greater number of users.

    However: immediately above the information in the screen capture above, DoubleCheckMD says

    “Below is a list of your drug combinations that can cause problems. Note that these problems are RARE. In most cases, these drugs are safe to take together.’

    That’s a bit confusing, isn’t it? It seems to contradict the content that immediately follows (“This medication combination is not recommended and should be avoided”).

    Another minor annoyance is that one must register in order to use this tool and log in the next time one wants to use it.

  • PDRHealth Drug Interaction Tool

    Having played with DoubleCheckMD first, I found that I missed the convenience of the way DoubleCheckMD auto-completed drug names.

    Also, the results seem…I don’t know…less than clear, somehow. For me, they suggest that taking these drugs together might be a bad idea rather than saying clearly that one simply should not do it.

  • Express Scripts’ Drug Digest

    Huh. Looks like I’m not going to be recommending this one. It failed to see a problem with taking Ketorolac and Ibuprofen together:
  • Drug Interaction Checker

    This one has a pleasant auto-complete function and the results seem pretty unambiguous:
  • DiscoveryHealth Drug Interaction Checker

    I won’t be recommending this one either because of its horrible interface for entering drug names. Rather than searching for a drug or having drug names suggested as you type, you have to select the first letter of the drug’s name, then scroll to the drug you want. Awful, awful interface. The results were okay:

  • CVS/Caremark Drug Interactions

    I really like the clear, straight-forward wording of the results in this one:

    Also, this checker also offers to check for interactions with foods, alcohol and tobacco:

Are there others I should try? Are there particular features of these that you like or dislike? Do you recommend any of these or similar tools to patients? Please leave a comment and let me know!

13 thoughts on “Online Drug Interaction Checkers

  1. Thanks, Jon! I tried several times to get to MedScape, but can’t seem to get it to load this morning. I’ll try it again later and hopefully add it to this post. 🙂

  2. Hi David,

    I’m curious if you compared any of these free tools to what is offered in a pay-for-use product (e.g. Lexi-Comp). I think it might be easier to judge the quality of the information the free tools provide in that context. For example, this is what Lexi-Comp says about Ibuprofen interacting with other NSAIDs:

    Title Nonsteroidal Anti-Inflammatory Agents / Nonsteroidal Anti-Inflammatory Agents

    Risk Rating C: Monitor therapy

    Summary Nonsteroidal Anti-Inflammatory Agents may enhance the adverse/toxic effect of other Nonsteroidal Anti-Inflammatory Agents. Severity Moderate Reliability Rating Fair

    Patient Management Monitor for increased incidence of nonsteroidal anti-inflammatory agents (NSAID)-associated adverse events if two or more such agents are concurrently used.

    Nonsteroidal Anti-Inflammatory Agents Interacting Members Celecoxib; Diclofenac; Diflunisal; Etodolac; Fenoprofen; Flurbiprofen; Ibuprofen; Indomethacin; Ketoprofen; Ketorolac; Lumiracoxib; Meclofenamate; Mefenamic Acid; Meloxicam; Nabumetone; Naproxen; Oxaprozin; Piroxicam; Sulindac; Tiaprofenic Acid; Tolmetin

    Discussion The concomitant use of multiple NSAIDs would seem to increase the risk of adverse events, particularly those associated with inhibited platelet aggregation or renal toxicity.

    So maybe not things you want to take together, but also maybe not the worst choice you could make, as some of the examples above suggest.

  3. Hi Jeff-

    No, I did not consider comparing these to professional tools built for healthcare professionals (like Lexi-Interact or MicroMedex).

    I think it is almost always a bad idea to attempt to compare tools built for healthcare professionals and tools built for healthcare consumers.

    The information as written for professionals is usually for use in a clinical setting where, as the monograph from Lexi-Interact states, the advisement to “Monitor therapy” can be followed. Renal failure, for instance, is somewhat dificult to monitor at home.

    A healthcare consumer lacks the resources to respond appropriately should an interaction appear. For instance, it may be difficult to monitor for renal failure at home.

    A healthcare consumer also usually lacks the education to judge from the information provided by a tool like Lexi-Interact how much danger this interaction may represent. I have (I think and hope) a greater level of health information literacy than the average healthcare consumer- but I wouldn’t know what to make of the Lexi-Interact information if I accessed it for free from home.

    A healthcare consumer using an interaction checker from home needs, I believe, simpler information along the lines of: “Am I potentially putting myself in danger if I take these drugs together?” or “Is this something I need to discuss with my doctor?”

    Jeff wrote:

    So maybe not things you want to take together, but also maybe not the worst choice you could make, as some of the examples above suggest.

    As to the degree of danger posed by the potential interaction between these two drugs, I defer to the expertise (and Doctorate in Pharmacy) of the PharmDs over my reading of a response from this one tool.

    I’m an unusually well-informed healthcare consumer with access to professional health information tools and the skills to use them- but I don’t fool myself for a second into thinking that this makes me the equal of a physician or a pharmacist.

    This long comment perhaps indicates I should write a post on the topic…?

    Thanks for the comment, Jeff!


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  5. I agree with the consumer health POV you take in your response. I guess where I stand is that, for the average person, these resources really need to stress the importance of speaking with your doctor or pharmacist and I’m not sure they all do that equally, or in a meaningful way (e.g. burying that tidbit of info in a paragraph).

    Something that says “Do not take these two drugs together” seems to black and white. Maybe something along the lines of “Do not take these two drugs together unless you are being closely monitored by …”. And while I’m at it, wouldn’t it just be nice if consumer health resources used plain language when it suffices (e.g. what does contraindicated mean to your average person?).

  6. Hi David,

    Great post. I felt pretty confident of the drug checker we use, Drug Digest
    from Express Scripts. We link to it from the homepage. Confident that is until I checked the drugs in your example and the results show no interaction or warning. Thanks for the example.

  7. Jeff-

    I think we generally agree and you noticed, I’m sure, that the post notes where the responses are clear and where they are confusing.

    Where we differ is that I think something that is (as you say) “black and white” is exactly what is called for.


    Yeah, that surprised me too!

  8. I was just looking at your blog and found it fairly interesting. Being in the medical profession it was interesting to see what you found. I also noticed that medications you have chose are from the same class of drugs. They are both non-steriodal anti inflammatory drugs. Technically there is no interaction but there is a therapeutic duplication. Some sites are information based and base their information on clinical evidence. That maybe why they do not place this as an interaction. I myself see why the information seems like an interaction but using two medications from the same class will increase the risk of a side effect like GI bleeds to occur. It does not mean that these two medications are actually interacting. I know that many of these sites are reputable and while looking at them the people that have put the site together are very knowledgeable especially based on their backgrounds. Anyways I still enjoyed the blog, but think it is inaccurate until you find out how these companies decide to put information up.

  9. knowledgeispower, would you like to suggest some alternate drugs that could be used to test these sites in the same manner?

    I’m not sure “accurate” is a useful term here. I tried an set of variables to compare what each tool would do with them and faithfully reported the results along with my comments and preferences.

    I’m going to operate on the assumption that what you mean to say is that any comparison of such tools should include mention of what data each tool uses to look for interactions. This would be a fair point…if each of these sites made such information clear.

  10. Hola David
    From Spain, as Jon Brassey first said,
    I have just read this from Medscape
    Multi-Drug Interaction Checker

    Patient Regimen



    Contraindicated Drug Combination
    Ketorolac Tromethamine Oral and Ibuprofen Oral may interact based on the potential interaction between KETOROLAC and NSAID;ASPIRIN.


    This information is generalized and not intended as specific medical advice. Consult your healthcare professional before taking or discontinuing any drug or commencing any course of treatment.

    MONOGRAPH TITLE: Ketorolac/NSAID;Aspirin

    SEVERITY LEVEL: 1-Contraindicated Drug Combination: This drug combination is contraindicated and generally should not be dispensed or administered to the same patient.

    MECHANISM OF ACTION: Possible additive or synergistic side effects.(1)

    CLINICAL EFFECTS: Concurrent use of ketorolac and other non-steroidal antiinflammatory agents (NSAIDs) or aspirin may result in an increase in NSAID-related side effects.(1)

    PREDISPOSING FACTORS: None determined.

    PATIENT MANAGEMENT: The manufacturer of ketorolac states that concurrent use of ketorolac with either other NSAIDs or aspirin is contraindicated.(1)

    DISCUSSION: There is no clinical documentation to support this interaction. The manufacturer of ketorolac states that as a result of the cumulative risks of inducing serious NSAID-related adverse events, the concurrent administration of ketorolac with other NSAIDs or aspirin is contraindicated.(1)


    1.Toradol (ketorolac tromethamine) US prescribing information. Roche Pharmaceuticals January, 2007.
    So, Good enough

    I can hardly write english, but I can understand quite well medical information.
    I like your blog a lot.

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  12. I had a very bad reaction bd 180+ pulse 120+ with 100 mg provigil and 7 hours later 1/4 tab of 5.4 mg yohimbine. I couldn’t find any drug interaction information that said it was dangerous(that’s why I only took 1/4 tab). I submitted an FDA report.