The Differences Between Metamucil and Miralax

Medically reviewed by Lindsay Cook, PharmD

Metamucil and Miralax are both over-the-counter (OTC) medicines used to treat constipation. However, Metamucil and Miralax work differently and have different side effects and safety profiles.

The following is a comparison of these medications.

Warning About Miralax in Children

The Food and Drug Administration (FDA) has received several reports of adverse events in children taking polyethylene glycol (PEG) products, such as Miralax. The FDA has conducted a review that documented several reports of neurological and psychiatric events associated with chronic (long-term) use of these medicines in children. Some of these children received an adult dose of PEG (17 grams) for an extended period.

The North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition (NASPGHAN) recommends that parents discuss Miralax use with their child's healthcare provider, who can weigh the risks and benefits of treatment with Miralax and give personalized medical advice.

What Is Metamucil?

Metamucil is a fiber laxative. The active ingredient is called psyllium husk powder. Its primary use is to relieve occasional constipation (irregularity). A dose of Metamucil usually produces a bowel movement in 12 to 72 hours. It can also be a fiber supplement to maintain regular bowel movements.

Metamucil may also reduce the following:

• Hemorrhoid pain

• Dietary cravings

Additionally, some studies show that taken regularly, Metamucil may help lower the following:

• Blood sugar

• Blood pressure

• Cholesterol

Metamucil is a bulk-forming laxative. It works by:

• Adding bulk to the stools

• Stimulating the intestines to contract and helps move stool through the digestive tract

Metamucil is available over the counter in brand-name and generic products, and it's sold in various forms like powders, granules, capsules, liquids, and wafers.

What Is Miralax?

Miralax is classified as an osmotic laxative. The active ingredient is called polyethylene glycol (PEG) 3350.

PEG works by doing the following:

• It causes water retention in the stool, helping increase the number of bowel movements.

• It softens the stool, making it easier to pass.

Miralax generally produces a bowel movement in one to three days. It is sometimes used in people with fecal impaction (stool stuck in the colon or rectum).

Some healthcare providers recommend Miralax as a bowel-cleansing agent before a procedure like a colonoscopy.

In some cases, healthcare providers also recommend Miralax for people with the following:

• Irritable bowel syndrome (IBS)

• Constipation (IBS-C)

• Other treatments

Miralax is available over the counter in brand-name and generic products. It comes in a powder form; the powder is mixed with liquids, and the individual drinks it.

Miralax is available in the following:

• Individual packets

• A large container where the individual measures each dose

Is Metamucil or Miralax More Effective?

Both OTC medications can be effective at treating constipation.

The medications have not been studied directly against each other in clinical trials.

The American Society of Colon and Rectal Surgeons' Clinical Practice Guideline for the Evaluation and Management of Constipation recommends initially managing constipation with dietary modifications, including fiber supplements like Metamucil.

The guidelines also state that an osmotic laxative like Miralax is a safe and appropriate treatment for chronic (ongoing) constipation.

Check with your healthcare provider for medical advice on whether Metamucil or Miralax would be more appropriate for you.

What Are Some Advantages of Metamucil vs. Miralax?

Advantages of Metamucil include the following:

• Various formulations to suit individual preferences

• Available without a prescription

• Inexpensive, especially the generic products

• May have other health benefits when taken regularly, like lowering blood sugar, blood pressure, and cholesterol

Advantages of Miralax include the following:

• Once-daily dosing

• Available without a prescription

• Inexpensive, especially when choosing a generic

• No taste; grit-free consistency

What Are Some Disadvantages of Metamucil vs. Miralax?

Disadvantages of Metamucil include the following:

• May take up to three days to work (but it could work quicker, within 12 hours)

• May have to take up to three times daily

• May cause choking if not taken with enough fluid

Disadvantages of Miralax include the following:

• May take one to three days to work

• Only available as a powder

Alternatives to Manage Constipation

There are some lifestyle changes you can try to help improve constipation symptoms, such as:

• Drink plenty of water or other unsweetened drinks.

• Slowly increase your fiber intake by adding high-fiber foods to your diet, like berries, pears, prunes, raisins, nuts, seeds, vegetables, and whole grains.
  

• Exercise regularly, even adding a 10–15 minute walk after each meal (consult your healthcare provider before beginning an exercise plan).

Some research supports the use of probiotics,

Talk to your healthcare provider about other options to help with constipation.

Consult a registered dietitian nutritionist (RDN) who can help you or your child find ways to incorporate more fiber into the diet.

Side Effects

Common side effects of Metamucil include the following:

• Difficulty breathing or swallowing

• Stomach pain

• Rash/itching

• Nausea and/or vomiting

Common side effects of Miralax include the following:

• Nausea

• Bloating

• Gas

• Stomach cramps

Report Side Effects

Metamucil and Miralax may cause other side effects. Call your healthcare provider if you have unusual problems while taking one of these medications. If you experience a severe side effect, you or your provider may send a report to the FDA's MedWatch Adverse Event Reporting Program or by phone (800-332-1088). If you have any urgent side effects like severe diarrhea, difficulty breathing, or swelling of the face, lips, tongue, or throat, get emergency medical help.

Precautions

Precautions for Metamucil or Miralax medications should be considered.

If you are pregnant, planning to become pregnant, or are breastfeeding, consult your healthcare provider before using Metamucil or Miralax.

Metamucil Precautions

Metamucil precautions include the following:

• Do not use it if you are allergic to psyllium.

• Avoid breathing in the powder when mixing a dose, as it can cause an allergic reaction if it is accidentally inhaled.

• To avoid choking, take Metamucil as directed with enough fluid. Not drinking enough fluid can cause blockage of the throat or esophagus, which may cause choking.

• Do not use Metamucil powder if you have difficulty swallowing.

• Get immediate medical help if you have chest pain, vomiting, or difficulty swallowing or breathing after using Metamucil powder.

• Ask your healthcare provider before using Metamucil if you have stomach pain, nausea, vomiting, or a sudden change in bowel habits for over two weeks.

• Take Metamucil two or more hours before or after other medications so it does not affect the absorption of other medications.

• Stop using Metamucil and call your healthcare provider if constipation lasts more than one week, if you have rectal bleeding, or if you do not have a bowel movement. These may indicate a severe condition.

Miralax Precautions

Miralax precautions include the following:

• Do not use Miralax if you are allergic to polyethylene glycol.

• Do not use Miralax if you have kidney problems unless advised by your healthcare provider.

• Check with a healthcare provider before using Miralax if you have IBS, nausea, vomiting, stomach pain, or a sudden change in bowel habits for over two weeks.

• Miralax may cause your stools to be loose, watery, and more frequent.

• Stop using Miralax and consult a healthcare provider if you have diarrhea, rectal bleeding, worsening symptoms, or need a laxative for more than seven days.

Who Should Avoid Metamucil or Miralax?

You should not take Metamucil if:

• You are allergic to psyllium or any ingredient in the medication.

• You may have appendicitis (inflammation of the appendix that usually requires surgery).

• You have a blockage (or possible blockage) of the stomach or intestines.

Avoid Miralax in the following circumstances:

• You are allergic to polyethylene glycol or any ingredient in the medication.

• You have a blockage (or possible blockage) of the stomach or intestines.

• Older adults (65 years and older) and individuals with kidney problems should check with a healthcare provider before using Miralax.

Interactions for Metamucil and Miralax

Metamucil

Metamucil may affect how other medications are absorbed. Therefore, take Metamucil at least two hours before or after any other oral medications.

Miralax

Miralax may affect how other medicines are absorbed. Therefore, take Miralax at least one hour before or after any other oral medications.

Drug Interactions

Consult with your healthcare provider for more information about drug interactions and how they may affect you.

Summary

Metamucil and Miralax are over-the-counter medications used to relieve constipation. Metamucil is a bulk-forming laxative that contains psyllium, a soluble fiber. It helps constipation and, taken regularly, may have other benefits, such as lowering blood sugar and cholesterol. Miralax is an osmotic laxative that contains polyethylene glycol.

If you have any questions or concerns or are unsure if one of these medications is appropriate for you, reach out to your healthcare provider.

Frequently Asked Questions

Can you take Metamucil and Miralax together?

Probably not. Although these medications do not chemically interact, it's best to check with a healthcare provider before taking more than one medication that treats constipation.

What is the difference between Metamucil and Miralax?

Metamucil and Miralax have several differences. For example, Metamucil is available in many dosage forms. It is a bulk-forming laxative that contains a fiber called psyllium. Miralax is a powder that can be dissolved in any beverage. It's an osmotic laxative that contains polyethylene glycol.

Are Metamucil and Miralax the same?

No. Although they both treat constipation, Metamucil and Miralax are not the same. They are different types of laxatives, work differently, and have different safety profiles.