Written by Ron Gasbarro, PharmD, MS Journ. | Reviewed by Joshua Murdock, PharmD, BCBBS
Key takeaways:
– It’s possible that an oral medication may not be completely absorbed if you’re experiencing diarrhea.
– The longer you have diarrhea, the more likely a medication may not be completely absorbed.
– Talk to your healthcare provider or pharmacist for suggestions on taking your medication if you have diarrhea.
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Diarrhea — having loose, watery stools three or more times a day — can be unpleasant. The good news is that it usually only lasts a short period of time. Typically, diarrhea will resolve after a day or two.
But what if diarrhea lasts longer than a few days? If you’re experiencing diarrhea for a longer period of time, you may be concerned about whether or not your medication is being absorbed by your body the way it should.
This article will discuss some common questions you may have if you’re taking oral medications while you have diarrhea.
How are medications absorbed when they’re taken orally?
First, let’s start with the basics. Like any nutrient that comes from food or a supplement, a medication must be digested and broken down in your body — usually in your stomach and small intestine. This allows it to be absorbed through your gastrointestinal (GI) tract and into your bloodstream. In general, most medications start to work once they enter your bloodstream.
Some medications, like certain forms of aspirin, are absorbed in your stomach. But most others make their way into your bloodstream through the small intestine. At about 20 feet in length, the small intestine provides medications an opportunity to be absorbed at different points, depending on their characteristics.
And some medications are formulated in a specific way to control where they’re absorbed, too. For example, enteric-coated (EC, DR) tablets keep the medication from being absorbed until it reaches the small intestine. Extended-release (ER, XR) tablets and capsules are designed in a way that allows them to be slowly absorbed into your bloodstream over time.
What impact does diarrhea have on medication absorption?
Diarrhea puts everything on “fast forward” through your GI tract. This may cause certain medications to pass by their regular absorption sites before they have a chance to absorb into your bloodstream. So, it’s possible that your medication may not be absorbed adequately, if at all. But how bad does diarrhea have to be before this is a concern?
Acute (short-term) diarrhea usually runs its course quickly. Luckily, most cases of diarrhea resolve on their own within 48 hours. Short-term diarrhea likely won’t have a meaningful impact on oral medications that you take.
But it’s still a good idea to double check with your healthcare provider, especially if you take medications with a narrow therapeutic index, like warfarin (Coumadin, Jantoven). These are medications by which even small changes in the blood concentration can cause serious side effects or significantly impact effectiveness.
The longer you have diarrhea, the more your medications may start to be affected. If it’s been going on for over 48 hours, there may be another underlying cause that needs to be addressed. Diarrhea is considered chronic (long-lasting) when it goes on for more than 4 weeks.
If your diarrhea hasn’t resolved after 48 hours, contact your healthcare provider. Finding out the cause and treating it can help prevent potential issues with your medications from developing. But if it’s from a chronic GI condition (like Crohn’s disease), other factors can also influence how you absorb medications.
What are some examples of medications that are affected by diarrhea?
Diarrhea can potentially interfere with medication absorption, especially if it has been going on for more than a couple days. Below are two medication classes where diarrhea may have a more menacing impact.
Keep in mind: This isn’t an all-encompassing list of medications that might be affected by diarrhea. If you’re concerned that one of your medications might be less effective because of a recent spell of diarrhea, it’s recommended to reach out to your healthcare provider for guidance.
Oral contraceptives
Consider oral contraceptives (OCs). There isn’t a lot of evidence showing that OCs (birth control pills) are affected by severe diarrhea. But there’s still a theoretical risk that it could make your birth control less effective.
If you have diarrhea, recommendations look similar to what you should do if you miss taking your pill. These recommendations include:
| Duration of diarrhea | CDC recommendations |
|---|---|
| Less than 48 hours | Continue taking your pills daily at the usual time. No additional contraceptive protection is needed. You may decide to take emergency contraception, but it’s not usually required to do so. |
| 48 hours or longer | Use an additional form of contraception (like condoms) while sick and for 7 days after you feel better. During this time, keep taking your oral pills as scheduled. Your healthcare provider may recommend emergency contraception. |
| 48 hours or longer during last week of hormone-containing pills | Finish the rest of the hormone-containing pills and skip the hormone-free week. Start a new pack right away. If you can’t, use a back-up form of contraception or avoid sex until you’ve taken at least 7 days of hormone-containing pills of your new pack. |
The situations listed above may not cover all scenarios that can occur. Factors like duration of diarrhea, when you’ve last have sex, and which pills you’re taking need to be considered. Talk to your healthcare provider about any steps you should take with your specific OC.
Antibiotics
Antibiotics are usually given as a short-term regimen. Many of them are also well-known for causing diarrhea on their own.
It’s difficult to tell how your antibiotic therapy might be affected by diarrhea. That’s because you may not know if it has been in your GI tract long enough to be absorbed. But missing doses due to diarrhea can potentially open the door to antibiotic resistance and an ineffective treatment. A partial regimen can strengthen the germ and make it resistant to that antibiotic.
Infections in the GI tract are a common cause of diarrhea. When these GI infections are caused by certain bacteria, they may be intentionally treated with antibiotics like fidaxomicin (Dificid). Because fidaxomicin is specifically designed not to be absorbed, it can attack the infection as it moves through your GI tract. So, diarrhea may not be as big of an issue in this instance.
But what if you’re taking an antibiotic for an infection outside of the GI tract, like strep throat? In this case, your body will need to absorb the medication for it to be effective. And if you’re also experiencing diarrhea while treating one of these infections, you may be wondering if your treatment is being compromised.
Here are some tips:
– Ask your healthcare provider if an antibiotic is essential in your case. Sometimes a condition can be resolved just as well by using a non-antibiotic treatment.
– If an antibiotic is necessary, let them know about your situation. They may give you suggestions based on how long you need an antibiotic for, the type of antibiotic, severity of your diarrhea, and length of time you’ve had diarrhea.
– Ask your healthcare provider for tips about how to alleviate your diarrhea. This may include taking OTC medications, if appropriate.
The bottom line
If you’re experiencing diarrhea, you may be concerned about whether or not your medication is being absorbed the way it should. You’ll want to consider the timing, type of medication, and any safety concerns. Especially if diarrhea is chronic, talk to your healthcare provider about ways to optimize your oral medication therapy.
References
Centers for Disease Control and Prevention. (2021). U.S. selected practice recommendations for contraceptive use, 2016. Morbidity and Mortality Weekly Report.
Food and Drug Administration. (2019). Combating antibiotic resistance.
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