8 Asacol HD Side Effects You Should Know About

If you have ulcerative colitis (UC), your healthcare provider may recommend a medication called mesalamine. There are many mesalamine-containing medications to choose from. One option to consider is a delayed-release tablet called Asacol HD.

Asacol HD works by reducing inflammation inside the lower gastrointestinal (GI) tract. This can help relieve UC symptoms like stomach pain, diarrhea, and rectal bleeding. But it can also cause side effects, including headache and nausea.

Some Asacol HD side effects may go away over time. But others can be more serious and need medical attention. Let’s discuss a few common and serious ones you should know about.

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1. Headache

Headache is the most common Asacol HD side effect. Around 5% of people taking the medication during clinical trials reported experiencing one. 

Studies with other forms of mesalamine suggest that headaches may be more frequent within the first few months of treatment and happen less often after that.

If your headaches are bothersome, your healthcare provider may recommend an over-the-counter (OTC) pain reliever like acetaminophen (Tylenol) for relief. 

Keep in mind that not all OTC pain relievers may be safe for you to take. For example, it’s best to avoid nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen (Motrin, Advil) and naproxen (Aleve). That’s because NSAIDs may cause a UC flare-up. 

But what about aspirin? Aspirin is an NSAID and a salicylate. And Asacol HD is a salicylate, too. Taking too much salicylate can result in toxicity that can be life-threatening. So, you may want to avoid treating your headaches with aspirin.

Let your healthcare provider know if your headaches are severe. Also, let them know if your headaches are followed by other symptoms, like fever, bloody diarrhea, and cramping. This could be a sign of a more serious problem — more on that later.

2. Nausea

Nausea was reported by about 3% of people taking Asacol HD in clinical trials. Sometimes, taking medications with food can help with nausea. But Asacol HD should be taken on an empty stomach — at least 1 hour before or 2 hours after a meal.

Let your healthcare provider if your nausea becomes bothersome. They can discuss possible options for relief. Avoid taking Pepto-Bismol (bismuth subsalicylate), since it’s also a salicylate.

Nausea can also be a symptom of salicylate toxicity. If it’s accompanied by other symptoms, like stomach pain, confusion, and rapid breathing, get medical help right away.

3. Common cold

Some people taking Asacol HD have reported common cold symptoms. This might include a stuffy or runny nose, sore throat, or headache.

Sinus infections, worsening asthma, and pneumonia have also been reported by people taking Asacol HD. Let your healthcare provider know if you experience other infections during treatment.

4. Abdominal pain

Another possible Asacol HD side effect is abdominal pain — pain you feel anywhere between your chest and groin. This is different from an upset stomach. It includes general pain in the stomach area, cramp-like pain, and pain that comes in waves.

Ulcerative colitis (UC) often causes abdominal pain and cramping. So, it might be hard to tell if your pain is due to UC or your medication. But if Asacol HD is working, it should help improve these symptoms. But, for a small number of people it may make your pain symptoms worse.

Let your healthcare provider know if your pain symptoms get worse during treatment. This could be a sign that you’re intolerant to the medication. In this case, they may have you stop taking Asacol HD.

5. Kidney problems

Before starting Asacol HD, your healthcare provider will typically check your kidneys. And they’ll likely watch them periodically during treatment as well. This is because Asacol HD can cause or worsen kidney problems like interstitial nephritis (swelling in the kidneys) and kidney failure.

Your kidney function is more likely to return to normal if these problems are caught early on. So, it’s important to keep all follow-up appointments with your healthcare provider. Report any unusual urinary symptoms, like peeing more or less often, right away.

If you have a history of kidney problems, your healthcare provider may watch you more closely during treatment. You may also be more likely to experience Asacol HD side effects. The same is true if you’re taking other medications that can harm your kidneys. Let your healthcare provider know if any side effects become bothersome or severe.

6. Acute-intolerance syndrome

Acute-intolerance syndrome can occur in some people taking Asacol HD. When this occurs, it causes UC symptoms to get worse. This typically happens soon after starting the medication. And symptoms tend to resolve after you stop taking it.

If this happens, you may experience abdominal pain, cramping, and bloody diarrhea. Fever, headache, and rash are also possible. It may seem like a UC flare-up, because the symptoms are similar.

Let your healthcare provider know if you’re experiencing worsening symptoms after starting Asacol HD. They can help you find the cause. In some cases, they may have you stop taking it. They may also see if you’re able to tolerate a different mesalamine product better.

7. Hypersensitivity reactions

Some people taking Asacol HD experience hypersensitivity reactions. These can include mild allergic reactions, severe allergic reactions (e.g., anaphylaxis), and severe skin reactions.

It’s important to get immediate medical attention if you experience a severe reaction to Asacol HD. This includes symptoms like trouble breathing and swelling of the face, tongue, or throat.

Severe skin reactions can include Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN). Both reactions involve flu-like symptoms followed by a rash. SJS can be serious and require hospitalization, and TEN can be life-threatening.

Get emergency medical help if you have flu-like symptoms followed by a rash while taking Asacol HD.

8. Photosensitivity

Photosensitivity is another skin-related side effect of mesalamine. This makes your skin more sensitive to sunlight, raising the risk of a sunburn. This side effect can be more serious in people who have existing skin problems like eczema.

It’s recommended to limit sun exposure while taking Asacol HD. If you’re going to be outdoors, make sure to wear clothing that protects your skin and a broad-spectrum sunscreen.

When should I contact my healthcare provider about side effects from Asacol HD?

When you start Asacol HD, it’s common to experience headaches and some GI symptoms. They usually get better over time as your body adjusts to the medication. But if these side effects don’t go away or get worse over time, contact your healthcare provider. The same is true if you experience symptoms of a UC flare-up.

Certain side effects need immediate medical attention. These include flu-like symptoms followed by a rash as well as allergic reactions. Your healthcare provider will watch for other side effects, like kidney problems, during treatment. Catching these early can help lessen the chance of permanent damage.

A good tool for keeping track of your side effects is a medication log. This can help you figure out if your symptoms are getting better or worse with Asacol HD. And it helps pinpoint any side effects that may be caused by it, too.

In addition to Asacol HD, several other medications contain mesalamine. A few examples include Lialda, Delzicol, and Pentasa. It’s also available as a rectal suppository (Canasa) and enema (Rowasa). If you’re unable to tolerate Asacol HD, your healthcare provider may have you try one of these medications instead.

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Written by:

Sarah Lobello Pearson, PharmD

Sarah Pearson is a practicing pharmacist with over 10 years of experience in the field. She received her doctorate in pharmacy from the University of Georgia in Athens, GA.

Edited by:

Alyssa Billingsley, PharmD

Alyssa Billingsley, PharmD, is the director of pharmacy content for GoodRx. She has over a decade of experience as a pharmacist and has worked in clinical, academic, and administrative roles.

Reviewed by:

Stacia Woodcock, PharmD

Stacia Woodcock, PharmD, is a pharmacy editor for GoodRx. She earned her Doctor of Pharmacy degree from the University of Kentucky and is licensed in New York and Massachusetts.

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